United States Office of Atmospheric EPA-430-R-93-007

Environmental Protection

Agency

and Indoor Air

Programs

June1993

 EE-RM-93-801 COMMENT OR2

United States 

Environmental Protection 

Agency 

II erslo 

Office of Atmospheric 

and Indoor Air 

Programs 

serfs a 

EPA-430-R-93-007 

June 1993 

( 

at 
User's

Version 1.0

Prepared for

U.S. Environmental Protection Agency

Global Change Division

by

Richard Merriam

Anthony Verone

He Feng

Arthur D. Little, Inc.

Cambridge, Massachusetts

02140

March 1993

ADL Ref. 67895

 EE-RM-93-801 COMMENT OR2

( 

erator 

ram 

User's anual 

Version 1.0 

Prepared for 

U.S. Environmental Protection Agency 

Global Change Division 

by 

Richard Merriam 

Anthony Verone 

He Feng 

Arthur D. Little, Inc. 

Cambridge, Massachusetts 

02140 

March 1993 

is 

ADL Ref. 67895 
NOTICE

Installation Instructions for the User in a Hurry

Section 2 of the ERA User's Manual contains full instructions for installation of ERA. The new

user is advised to read this material.

For the user in a hurry to try out the program, and who will then read the manual, please pay attention

to the information summarized here.

Program Diskettes. Disk 1 contains the program and the basic data files. Disk 2 contains files

used to carry out the EPA Multiple Pathways analyses. The user is advised to work initially with

the files supplied on Diskette 1.

Virus Checking. The diskettes have been checked using a commercial product. An additional

check by the user, prior to installation, is recommended.

Install on. Create a directory \ERA on a hard disk and copy all the files on Diskette 1 to this

directory. It is not necessary to make any path assignments.

COMMA ND.C®M. The root directory of the disk containing the \ERA directory must have a copy

of COMMAND.COM, otherwise ERA will not work.

README.DOC. Type out or print file README.DOC. The file gives important information

relating to the computer hardware requirements and to methods of configuring ERA to work with

it.

SETUP.D)AT. This file contains information relating to the default hardware expected by ERA.

After reading README.DOC (and Section 2 of the manual), make any necessary changes to

SETUP.DAT with an ASCII text editor. If you don't do so, the program might not work properly

on your computer.

Math Co-Processor. ERA uses some very intensive calculation methods. The machine must have

a math co-processor to run ERA.

Help Menus. Extensive Help menus are built into ERA at all levels. Press the Fl function key to

request the menu. The program manual assumes that the user accesses the Help menu as the primary

means of resolving program data questions.

Starting the Program. Type ERA and press the <Enter> key.

 EE-RM-93-801 COMMENT OR2

NOTICE 

Installation Instructions for the User in a Hurry 

Section 2 of the ERA User's Manual contains full instructions for installation of ERA. The new 

user is advised to read this material. 

For the user in a hurry to try out the program, and who will then read the manual, please pay attention 

to the information summarized here. 

Program Diskettes. Disk 1 contains the program and the basic data fIles. Disk 2 contains fIles 

used to carry out the EPA Multiple Pathways analyses. The user is advised to work initially with 

the fIles supplied on Diskette 1. 

Virus Checking. The diskettes have been checked using a commercial product. An additional 

check by the user, prior to installation, is recommended. 

Installation. Create a directory \ERA on a hard disk and copy all the fIles on Diskette 1 to this 

directory. It is not necessary to make any path assignments. 

COMMAND.COM. The root directory of the disk containing the \ERA directory must have a copy 

of COMMAND.COM, otherwise ERA will not work. 

README.DOC. Type out or print fIle README. DOC. The me gives important information 

relating to the computer hardware requirements and to methods of configuring ERA to work with 

it. 

SETUP.DAT. This me contains information relating to the default hardware expected by ERA. 

Mter reading README. DOC (and Section 2 of the manual), make any necessary changes to 

SETUP.DAT with an ASCn text editor. If you don't do so, the program might not work properly 

on your computer. 

Math Co-Processor. ERA uses some very intensive calculation methods. The machine must have 

a math co-processor to run ERA. 

Help Menus. Extensive Help menus are built into ERA at all levels. Press the Fl function key to 

request the menu. The program manual assumes that the user accesses the Help menu as the primary 

means of resolving program data questions. 

Starting the Program. Type ERA and press the <Enter> key. 
Table of Contents

LO INTRODUCTION 1-1

1.1 Background 1-1

1.2 Capabilities and Limitations 1-2

1.3 Microcomputer Requirements 1-2

1.4 How to Read This Manual 1-3

2.0 PROGRAM INSTALLATION 2-1

2.1 Initial Steps 2-1

2.2 Program Data and Execution Files 2-2

2.3 Customizing ERA to Your Computer Environment 2-6

2.4 Solution Tolerances 2-7

2.5 Running ERA 2-7

2.6 Display of Results 2-8

3.0 MODEL OVERVIEW 3-1

3.1 Basic Structure of the ERA Program 3-1

3.2 E.BAT 3-3

3.3 Input Data Processor ( .E ) 3-4

3.4 Cabinet Loads Model (CAB.E ) 3-4

3.5 Refrigeration Cycle Analysis and Energy Use (ERACYC.EXE) 3-5

4.0 DATA INPUT PROCESSOR 4-1

4.1 Menu Structure 4-1

4.2 Retrieving and Saving Input Data Files 4-3

4.3 Data File Management 4-3

4.4 Editing Data 4-5

4.5 GettingHelp 4-5

4.6 Default Data 4-9

4.7 Calculation Assists 4-9

4.8 Input Data Error Trapping and Correction 4-11

4.9 Using DOS Within ERA 4-11

4.10 Printing Input Data Files 4-12

4.11 Program Execution 4-12

500 CABINET LOADS INPUT DATA REFERENCE 5-1

5.1 Title of Analysis 5-1

5.2 Cabinet Type and Dimensions 5-1

5.3 Refrigerated Volumes 5-2

5.4 Freezer and Fresh Food Cabinets 5-2

5.5 Mullion 5-4

5.6 Air and Cabinet Temperatures 5-4

5.7 Door Opening Schedules 5-4

5.8 Gasket Heat Leaks 5-5

5.9 Defrost and Controls Energy Use 5-5

i

 EE-RM-93-801 COMMENT OR2

Table of Contents 

1.0 INTRODUCTION 

1.1 Background 

1.2 Capabilities and Limitations 

1.3 Microcomputer Requirements 

1.4 How to Read This Manual 

2.0 PROGRAM INSTALLATION 

1·1 

1-1 

1-2 

1-2 

1-3 

2·1 

2.1 Initial Steps 2-1 

2.2 Program Data and Execution Files 2-2 

2.3 Customizing ERA to Your Computer Environment 2-6 

2.4 Solution Tolerances 2-7 

2.5 Running ERA 2-7 

2.6 Display of Results 2-8 

3.0 MODEL OVERVIEW 3-1 

3.1 Basic Structure of the ERA Program 3-1 

3.2 ERA. BAT 3-3 

3.3 Input Data Processor (MENU.EXE) 3-4 

3.4 Cabinet Loads Model (CAB.EXE) 3-4 

3.5 Refrigeration Cycle Analysis and Energy Use (ERACYC.EXE) 3-5 

4.0 DATA INPUT PROCESSOR 

4.1 Menu Structure 

4.2 Retrieving and Saving Input Data Files 

4.3 Data File Management 

4.4 Editing Data 

4.5 Getting Help 

4.6 Default Data 

4.7 Calculation Assists 

4.8 Input Data Error Trapping and Correction 

4.9 Using DOS Within ERA 

4.10 Printing Input Data Files 

4.11 Program Execution 

5.0 CABINET LOADS INPUT DATA REFERENCE 

5.1 Title of Analysis 

5.2 Cabinet Type and Dimensions 

5.3 Refrigerated Volumes 

5.4 Freezer and Fresh Food Cabinets 

5.5 Mullion 

5.6 Air and Cabinet Temperatures 

5.7 Door Opening Schedules 

5.8 Gasket Heat Leaks 

5.9 Defrost and Controls Energy Use 

1 

4·1 

4-1 

4-3 

4-3 

4-5 

4-5 

4-9 

4-9 

4-11 

4-11 

4-12 

4-12 

5·1 

5-1 

5-1 

5-2 

5-2 

5-4 

5-4 

5-4 

5-5 

5-5 
Table of Contents (Continued)

5.10 Electrical Anti-Sweat Heat 5-5

5.11 Refrigerant Line Anti-Sweat Heat 5-6

5.12 Penetration Heat Input 5-7

6.0 REFRIGERATION CYCLE INPUT DATA REFERENCE 6-1

6.1 Cycle Type 6-1

6.2 Refrigerants 6-2

6.3 Evaporator Design 6-3

6.4 Condenser sign 6-5

6.5 Calculation Assist Menus for Evaporator

and Condenser UA Values

6-5

6.6 Compressor Design 6-5

6.7 Cycling Losses 6-7

6.8 Interchangers 6-8

7.0 SAMPLE PROBLEM 7-1

7.1 Multiple Pathway "Model D" Prototype Design 7-1

7.2 Input Data Menus (MODEL_D.INP) 7-1

7.3 Intermediate Cabinet Loads Data File (CABINET.DAT) 7-1

7.4 Cabinet Loads Results (CABINET.OUT) 7-13

7.5 Intermediate Cycle Data File (CYCLE.DAT) 7-13

7.6 Cycle Analysis Results (CYCLE.OUT) 7-18

7.7 Energy Consumption Results (ERA.OUT) 7-21

8.0 SUGGESTIONS FOR USING ERA 8-1

8.1 File Naming Conventions 8-1

8.2 Internal Documentation of the Case 8-1

8.3 Summary Output Form 8-2

9.0 REFERENCES 9-1

Appendix A: Overview of Cabinet Loads Analysis Technical Approach A-1

Appendix B: Overview of Cycle Analysis Technical Approach E-1

Appendix C: Sample Data Files: Multiple Pathways Data Input C-1

ii

 EE-RM-93-801 COMMENT OR2

Table of Contents (Continued) 

5.10 Electrical Anti-Sweat Heat 5-5 

5.11 Refrigerant Line Anti-Sweat Heat 5-6 

5.12 Penetration Heat Input 5-7 

6.0 REFRIGERATION CYCLE INPUT DATA REFERENCE 6-1 

6.1 Cycle Type 6-1 

6.2 Refrigerants 6-2 

6.3 Evaporator Design 6-3 

6.4 Condenser Design 6-5 

6.5 Calculation Assist Menus for Evaporator 6-5 

and Condenser U A Values 

6.6 Compressor Design 6-5 

6.7 Cycling Losses 6-7 

6.8 Interchangers 6-8 

7.0 SAMPLE PROBLEM 7-1 

7.1 Multiple Pathway "Model D" Prototype Design 7-1 

7.2 Input Data Menus (MODEL_D.lNP) 7-1 

7.3 Intermediate Cabinet Loads Data File (CABINET.DA T) 7-1 

7.4 Cabinet Loads Results (CABINET. OUT) 7-13 

7.5 Intermediate Cycle Data File (CYCLE.DAT) 7-13 

7.6 Cycle Analysis Results (CYCLE.OUT) 7-18 

7.7 Energy Consumption Results (ERA.OUT) 7-21 

8.0 SUGGESTIONS FOR USING ERA 8-1 

8.1 File Naming Conventions 8-1 

8.2 Internal Documentation of the Case 8-1 

8.3 Summary Output Form 8-2 

9.0 REFERENCES 9·1 

Appendix A: Overview of Cabinet Loads Analysis Technical Approach A-I 

Appendix B: Overview of Cycle Analysis Technical Approach B-1 

Appendix C: Sample Data Files: Multiple Pathways Data Input C-l 

ii 
List of Figures

Figure No.

3-1 Overall Data and Program Flow 3-2

3-2 J-orenz-Meutzner Refrigerator/Freezer Cycle 3-5

4-1 Main Menu 4-2

4-2 File Selection Menu Example 4-4

4-3 Cycle Data Edit Menu 4-6

4-4 Data Edit Menu Example 4-7

4-5 Help Menu Example 4-8

4-6 Calculation Assist Menu Example 4-10

7-1 Vertical Section - 18Ft3 Prototype Model 7-3

7-2 Front View, Cabinet Only - 18 Ft3 Prototype Model 7-4

7-3 Heat Exchanger Designs 7-5

7-4 Input Data Menus 7-6

7-5 Intermediate Data: Cabinet Loads Analysis 7-11

7-6 Cabinet Loads Output 7-14

7-7 Intermediate Data: Cycle Analysis 7-16

7-8 Cycle Analysis Output 7-19

7-9 Energy Consumption Results 7-22

8-1 Summary Output Form 8-3

111

 EE-RM-93-801 COMMENT OR2

List of Figures 

Figure No. 

3-1 Overall Data and Program Flow 3-2 

3-2 Lorenz-Meutzner Refrigerator!Freezer Cycle 3-5 

4-1 Main Menu 4-2 

4-2 File Selection Menu Example 4-4 

4-3 Cycle Data Edit Menu 4-6 

4-4 Data Edit Menu Example 4-7 

4-5 Help Menu Example 4-8 

4-6 Calculation Assist Menu Example 4-10 

7-1 Vertical Section - 18Fe Prototype Model 7-3 

7-2 Front View, Cabinet Only - 18 Fe Prototype Model 7-4 

I 

7-3 Heat Exchanger Designs 7-5 

7-4 Input Data Menus 7-6 

7-5 Intermediate Data: Cabinet Loads Analysis 7-11 

7-6 Cabinet Loads Output 7-14 

7-7 Intermediate Data: Cycle Analysis 7-16 

7-8 Cycle Analysis Output 7-19 

7-9 Energy Consumption Results 7-22 

8-1 Summary Output Form 8-3 

iii 
List of Tables

Table No.

1-1 Refrigerator/Freezer Design/Performance Parameters 1-4

2-1 ERA Data and Execution Files 2-4

7-1 Characteristics of Model D Prototype Refrigerator 7-2

iv

 EE-RM-93-801 COMMENT OR2

List of Tables 

Table No. 

1-1 

2-1 

7-1 

Refrigerator/Freezer Design/Perfonnance Parameters 

ERA Data and Execution Files 

Characteristics of Model D Prototype Refrigerator 

iv 

1-4 

2-4 

7-2 
1.0 INTRODUCTION

1.1 Background

Substantial advances have been made in the energy efficiency of refrigerators and

freezers in the past four decades since the introduction of CFCs. Prior to concerns over

the environmental impacts of ozone depletion, these fluids were felt to have ideal properties for this application. The ban on the use of these chemicals requires rapid product

redesign which must not only eliminate the use of CFCs but also meet tightened energy

efficiency standards.

Development of improved refrigerators and freezers has been primarily by evolutionary improvement of the product, largely by component design. Because of the simultaneous needs for refrigerant replacement, new foam blowing methods (or alternate

insulation concepts) and significant reductions from current energy consumption

levels, the industry must now look at a wide range of refrigerant possibilities and alternative cycle concepts. Refrigerant options include pure FIFCs, HCFCs, and mixtures

of fluids.

The EPA Refrigerator Analysis Program (ERA) was designed to enable a comparison

of the performance potential of alternate cabinet and cycle designs of current and nearterm interest. A goal of the program is to allow evaluations of the various design

options on a common analytical basis and to enable a consistent means of determining

the performance and economic tradeoffs between these options. It is recognized that

the use of such a model is only one step towards improving the appliance design.

ERA combines an analysis of the refrigeration load requirements of the cabinet with a

simulation of the capacity and efficiency of the refrigeration cycle. The cabinet loads

programs is an enhancement of a program developed for the U.S. Department of

Energy during the late 1970s [ 1]. Model enhancements include addition of door opening effects, additional flexibility in describing the cabinet geometry, and an ability to

deal with complex insulation systems.

The cycle model is a derivative of the NIST CYCLE 7 program [2] which uses the

CSD equation of state to represent the thermodynamic properties of pure and mixed

refrigerants [3]. Routines for calculating properties, and refrigerant property coefficients, are similar to those in the REFPROP3 program, available from NIST [4].

Changes in the cycle model include 1) incorporation of an ability to deal with refrigerator/freezer cycle design, 2) addition of interchangers, 3) specification of the heat

exchanger parameters in terms of its design details, and 4) determination of mass flow

and motor power consumption from a compressor model. The refrigerant cycle options

added to the model are 1) standard single evaporator refrigerator/freezer, 2) Lorenz

cycle with refrigerant mixture, 3) dual-loop system employing two independent refrigeration cycles, one for each compartment, and 4) dual evaporator cycle, with two evaporators connected in series, normally employing a pure refrigerant.

 EE-RM-93-801 COMMENT OR2

1.0 INTRODUCTION 

1.1 Background 

Substantial advances have been made in the energy efficiency of refrigerators and 

freezers in the past four decades since the introduction of CFCs. Prior to concerns over 

the environmental impacts of ozone depletion, these fluids were felt to have ideal properties for this application. The ban on the use of these chemicals requires rapid product 

redesign which must not only eliminate the use of CFCs but also meet tightened energy 

efficiency standards. 

Development of improved refrigerators and freezers has been primarily by evolutionary improvement of the product, largely by component design. Because of the simultaneous needs for refrigerant replacement, new foam blowing methods (or alternate 

insulation concepts) and significant reductions from current energy consumption 

levels, the industry must now look at a wide range of refrigerant possibilities and alternative cycle concepts. Refrigerant options include pure HFCs, HCFCs, and mixtures 

of fluids. 

The EPA Refrigerator Analysis Program (ERA) was designed to enable a comparison 

of the performance potential of alternate cabinet and cycle designs of current and nearterm interest. A goal of the program is to allow evaluations of the various design 

options on a common analytical basis and to enable a consistent means of determining 

the performance and economic tradeoffs between these options. It is recognized that 

the use of such a model is only one step towards improving the appliance design. 

ERA combines an analysis of the refrigeration load requirements of the cabinet with a 

simulation of the capacity and efficiency of the refrigeration cycle. The cabinet loads 

programs is an enhancement of a program developed for the U.S. Department of 

Energy during the late 1970s [1]. Model enhancements include addition of door opening effects, additional flexibility in describing the cabinet geometry, and an ability to 

deal with complex insulation systems. 

The cycle model is a derivative of the NIST CYCLE 7 program [2] which uses the 

CSD equation of state to represent the thermodynamic properties of pure and mixed 

refrigerants [3]. Routines for calculating properties, and refrigerant property coefficients, are similar to those in the REFPROP3 program, available from NIST [4]. 

Changes in the cycle model include 1) incorporation of an ability to deal with refrigerator/freezer cycle design, 2) addition of interchangers, 3) specification of the heat 

exchanger parameters in terms of its design details, and 4) determination of mass flow 

and motor power consumption from a compressor model. The refrigerant cycle options 

added to the model are 1) standard single evaporator refrigerator/freezer, 2) Lorenz 

cycle with refrigerant mixture, 3) dual-loop system employing two independent refrigeration cycles, one for each compartment, and 4) dual evaporator cycle, with two evaporators connected in series, normally employing a pure refrigerant. 

1-1 
1.2 Capabilities and Limitations

ERA determines the daily energy projection assuming quasi-steady cabinet heat flow

and cycle-averaged operating efficiencies. The underlying assumption is that the

effects of cabinet load dynamics and the uncertainties associated with corrections to

describe refrigeration system cycling behavior, are small in relation to the difference

between alternative cabinet and cycle designs.

Most, but not all, of the common refrigerator classes are represented within ERA. Version 1.0 of the program is not capable of directly modelling a single door refrigerator/freezer, such as found in compact units.

The program is best thought as a design tool, intended to provide a means of sorting

though the consequences of alternative design concepts and/or component characteristics on potential energy savings. As such, the model calculates what is theoretically

possible, not what may be achieved in actual practice. For example, various design

approaches may or may not be acceptable from a customer standpoint (e.g., impact on

moisture level control). The refrigerator designer must consider the practicality, potential reliability , and costs of all design options. ERA is a tool that can be used as part of

the design process to determine the energy potential performance benefits of a

candidate option.

Table 1 summarizes the refrigerator/freezer design and performance factors considered

by the program. In most instances, the individual heat flow and cycle parameters can

be treated on the basis of physical principles. In certain instances basic assumptions

must be provided by the user (for example, the temperature of the air under the refrigerator cabinet must be specified). In all instances, certain idealizations must be

accepted as a starting point for describing the physical or model parameter.

For this reason, proper use of the model requires an adequate understanding of its capabilities and inherent limitations. Descriptions of each of the input and output parameters is provided throughout this manual and in the Help menus found in the program.

1.3 Microcomputer Requirements

ERA runs in the MS-DOS environment. A minimum computer configuration will

include:

® 640 K on-board memory

® 4 Meg hard disk storage available

® math compressor (80X87 chip)

Because of the extensive computational requirements for the thermodynamic property

determination, it is highly recommended that a 386 or 486 class machine be utilized.

Although not required, a color monitor of high resolution is also recommended to take

advantage of the use of various color attributes by the program as a means of conveying information.

 EE-RM-93-801 COMMENT OR2

1.2 Capabilities and Limitations 

ERA determines the daily energy projection assuming quasi-steady cabinet heat flow 

and cycle-averaged operating efficiencies. The underlying assumption is that the 

effects of cabinet load dynamics and the uncertainties associated with corrections to 

describe refrigeration system cycling behavior, are small in relation to the difference 

between alternative cabinet and cycle designs. 

Most, but not all, of the common refrigerator classes are represented within ERA. Version 1.0 of the program is not capable of directly modelling a single door refrigerator/freezer, such as found in compact units. 

The program is best thought as a design tool, intended to provide a means of sorting 

though the consequences of alternative design concepts and/or component characteristics on potential energy savings. As such, the model calculates what is theoretically 

possible, not what may be achieved in actual practice. For example, various design 

approaches mayor may not be acceptable from a customer standpoint (e.g., impact on 

moisture level control). The refrigerator designer must consider the practicality, potential reliability, and costs of all design options. ERA is a tool that can be used as part of 

the design process to determine the energy potential performance benefits of a 

candidate option. 

Table 1 summarizes the refrigerator/freezer design and performance factors considered 

by the program. In most instances, the individual heat flow and cycle parameters can 

be treated on the basis of physical principles. In certain instances basic assumptions 

must be provided by the user (for example, the temperature of the air under the refrigerator cabinet must be specified). In all instances, certain idealizations must be 

accepted as a starting point for describing the physical or model parameter. 

For this reason, proper use of the model requires an adequate understanding of its capabilities and inherent limitations. Descriptions of each of the input and output parameters is provided throughout this manual and in the Help menus found in the program. 

1.3 Microcomputer Requirements 

ERA runs in the MS-DOS environment. A minimum computer configuration will 

include: 

" 640 K on-board memory 

It 4 Meg hard disk storage available 

.. math compressor (80X87 chip) 

Because of the extensive computational requirements for the thermodynamic property 

determination, it is highly recommended that a 386 or 486 class machine be utilized. 

Although not required, a color monitor of high resolution is also recommended to take 

advantage of the use of various color attributes by the program as a means of conveying information. 

1-2 
1.4 How to Use this Manual

The structure of this manual attempts to follow the ERA input data processor program

to the greatest degree possible. For the user in a hurry, the most important sections to

read are: Section 2 (Program Installation), Section 4 (Data Input Processor) and Section 7 (Sample Problem). Various Help Menus within the program are available to

provide on-line information as needed. Section 3 (Model Overview) provides a

description of the overall structure of ERA and the relationships between the three

executable files comprising ERA. Summary discussions of the engineering algorithms

used in these sub-programs appear in Appendices A (Cabinet Loads) and B (Cycle

Analysis). These sections can be read as required to answer specific questions or to

gain a deeper understanding of what ERA can and cannot do.

Sections 5 and 6 are reference chapters which define the input data requirements for

each data menu in ERA. They supplement material found in the on-line Help Menu. If

additional information is desired about an input data, the program user should turn to

these sections.

Suggestions for file naming conventions and for documenting the program input/output

are contained in Section 8. They may prove helpful in managing the large amount of

output from making multiple ERA analyses.

 EE-RM-93-801 COMMENT OR2

1.4 How to Use this Manual 

The structure of this manual attempts to follow the ERA input data processor program 

to the greatest degree possible. For the user in a hurry, the most important sections to 

read are: Section 2 (Program Installation), Section 4 (Data Input Processor) and Section 7 (Sample Problem). Various Help Menus within the program are available to 

provide on-line infonnation as needed. Section 3 (Model Overview) provides a 

description of the overall structure of ERA and the relationships between the three 

executable files comprising ERA. Summary discussions of the engineering algorithms 

used in these sub-programs appear in Appendices A (Cabinet Loads) and B (Cycle 

Analysis). These sections can be read as required to answer specific questions or to 

gain a deeper understanding of what ERA can and cannot do. 

Sections 5 and 6 are reference chapters which define the input data requirements for 

each data menu in ERA. They supplement material found in the on-line Help Menu. If 

additional infonnation is desired about an input data, the program user should tum to 

these sections. 

Suggestions for file naming conventions and for documenting the program input/output 

are contained in Section 8. They may prove helpful in managing the large amount of 

output from making multiple ERA analyses. 

1-3 
Table 1-1 Refri 1e.

Category

--/Freezer Design/Performance Parameters

Parameter How Treated

Cabinet Loads Configurations Top-Mount R/F, Bottom-Mount R/F, Sideby-Side R/F, Chest Freezer, Upright

Freezer

External Dimensions

Internal Dimensions

Control Temperatures

Ambient Conditions

Insulation System

- Edge Losses

- Construction

- Penetrations

Heat Conduction from

Environment

Internal Heat Conduction

Gasket Heat Leaks

Heaters

Ancillary Heat Input

Mullion and Cabinet Flange

Heat

Door Openings Effects

Number of doors

Moisture

- Open Door

- Condensation

Defrost

Specified

Calculated

Specified for each cabinet section

Assumed constant

Specify temperature and relative humidity

of the environment

Calculated analytically within program

Foam, advanced insulation, or composite

panels treated

User-specified heat leaks

Wedge, wall panel, door, top, bottom, back

panel, mullion edges

Across mullion between compartments

Conduction loss related to door perimeter

Anti-sweat heater

Fan heat determined by compressor runtime; controls heat input considered constant and/or run-time dependent

Electric

Hot gas from compressor

Condenser liquid line

Latent and sensible loads

Time dependent openings

1 or 2

Calculated moisture input

Mass balance , with all moisture

condensing

Determined from moisture balance and

temperature of evaporator. Defrost energy

equal to heat of freezing

 EE-RM-93-801 COMMENT OR2

Table 1-1 Refrigerator/Freezer Design/Performance Parameters 

category 

Cabinet Loads 

Parameter 

Configurations 

External Dimensions 

Internal Dimensions 

Control Temperatures 

Ambient Conditions 

Insulation System 

- Edge Losses 

- Construction 

- Penetrations 

Heat Conduction from 

Environment 

Internal Heat Conduction 

Gasket Heat Leaks 

Heaters 

Ancillary Heat Input 

Mullion and Cabinet Flange 

Heat 

Door Openings Effects 

Number of doors 

Moisture 

- Open Door 

- Condensation 

Defrost 

1-4 

How Treated 

Top-Mount RlF, Bottom-Mount RlF, Sideby-Side RlF, Chest Freezer, Upright 

Freezer 

Specified 

Calculated 

Specified for each cabinet section 

Assumed constant 

Specify temperature and relative humidity 

of the environment 

Calculated analytically within program 

Foam, advanced insulation, or composite 

panels treated 

User-specified heat leaks 

Wedge, wall panel, door, top, bottom, back 

panel, mullion edges 

Across mullion between compartments 

Conduction loss related to door perimeter 

Anti-sweat heater 

Fan heat determined by compressor runtime; controls heat input considered constant and/or run-time dependent 

Electric 

Hot gas from compressor 

Condenser liquid line 

Latent and sensible loads 

Time dependent openings 

10r2 

Calculated moisture input 

Mass balance, with aU moisture 

condenSing 

Determined from moisture balance and 

temperature of evaporator. Defrost energy 

equal to heat of freezing 
Table 1-1 F ' _ Drtor/Freezer Design/Performance Parameters (continued)

Refrigeration Cycle

Parameter How Treated

Cycle Types

Refrigerants

Heat Exchanger Types

Heat Exchange Parameters

Heat Transfer Rates

Heat Exchanger Model

Pressure Drops

Refrigerant Flow Control

Compressor Model

Compressor Design

Details of Compressor Mass Flow

Model

Volumetric Efficiency

Energy Consumptions Cabinet

Cycle

Standard ( 1 evap/1 cond)

Dual Loop (2 units)

Lorenz Cycle

Dual evaporator

34 Pure refrigerants

Binary or ternary blends

Static or fan-forced

Cross-flow or counter-flow

In-cabinet space or hot-wall/cold-wall

Specify or calculate overall U by regime

Specify or calculate total area

Specify fan air flow

Specify fan powers

Specify or calculate. Effect of degradation due to mixtures not considered

Effectiveness - NTU Model

Specify or calculate

Specify subcooling and superheat

Independent of refrigerant charge or

type of expansion device

Built-in model determines power and

mass flow. Control options include

single speed and variable speed. Compressor map option available

Single stage reciprocating design or

rotary

Speed, displacement specified. Suction

gas density calculated

Determined by clearance volume, pressure ratio, temperature.

Heaters

Defrost

Ancillary (lights, controls)

Fan Power

Compressor power

Electronics

 EE-RM-93-801 COMMENT OR2

Table 1-1 Refrigerator/Freezer Design/Performance Parameters (continued) 

category Parameter How Treated 

Refrigeration Cycle Cycle Types Standard (1 evap/1 cond) 

Dual Loop (2 units) 

Lorenz Cycle 

Dual evaporator 

Refrigerants 34 Pure refrigerants 

Binary or ternary blends 

Heat Exchanger Types Static or fan-forced 

Cross-flow or counter-flow 

In-cabinet space or hot-waillcold-wall 

Heat Exchange Parame- Specify or calculate overall U by regime 

tel's Specify or calculate total area 

Specify fan air flow 

Specify fan powers 

Heat Transfer Rates Specify or calculate. Effect of degradation due to mixtures not considered 

Heat Exchanger Model Effectiveness - NTU Model 

Pressure Drops Specify or calculate 

Refrigerant Flow Control Specify subcooling and superheat 

Independent of refrigerant charge or 

type of expansion device 

Compressor Model Built-in model determines power and 

mass flow. Control options include 

single speed and variable speed. Compressor map option available 

Compressor Design Single stage reciprocating design or 

rotary 

Details of Compressor Mass Flow Speed, displacement specified. Suction 

Model gas density calculated 

Volumetric Efficiency Determined by clearance volume, pressure ratio, temperature. 

Energy Consumptions Cabinet Heaters 

Defrost 

Ancillary (lights, controls) 

Cycle Fan Power 

Compressor power 

Electronics 

1-5 
2.0 PROGRAM INSTALLATION

2.1 Initial Steps

ERA uses a simple file structure. All files should be loaded in a single hard-drive

directory (e.g., \ERA) The root directory of the drive should contain COMMAND.COM. If a virtual drive is set up or if an auxiliary hard-card type drive is used

the root directory might not contain COMMAND.COM. The absence of this file in the

root directory even if a path is defined to another drive or directory, will result in

incomplete operation of ERA, since the program must have access to a secondary command processor for some of its functions.

ERA and its files are supplied on a single high-density diskette. The diskette has been

virus-checked; however, the user should perform a secondary virus check before loading the disk contents onto the hard disk.

Program installation consists of the following steps, where it is assumed that the program is to installed on hard drive C: from the program diskette in drive A:

Step 1: Create a directory named ERA on the hard drive and then change

to the directory.

C:

SERA

CD\ERA

Step 2: Copy the contents of the ERA 1 disk to the ERA directory on the

hard drive.

COPY A: C:

Step 3: Create a subdirectory DATA to contain the data files and

change to the subdirectory.

MD DATA

CD DATA

Step 4: Copy the data files from the program diskette to the FILES

subdirectory.

COPY A: *.ERA C:\ERA\DATA

ERA is supplied with two additional diskettes that contain the input files created for the

EPA Multiple Pathways analysis [5]. The data is grouped according to the refrigerator/freezer. For example, all pathways starting with Model A refrigerator/freezer are

contained in directory \MODEL_A on one of the two data disks.

 EE-RM-93-801 COMMENT OR2

2.0 PROGRAM INSTALLATION 

2.1 Initial Steps 

ERA uses a simple file structure. All files should be loaded in a single hard-drive 

directory (e.g., \ERA) The root directory of the drive should contain COMMAND.COM. If a virtual drive is set up or if an auxiliary hard-card type drive is used 

the root directory might not contain COMMAND.COM. The absence of this file in the 

root directory even if a path is defined to another drive or directory, will result in 

incomplete operation of ERA, since the program must have access to a secondary command processor for some of its functions. 

ERA and its files are supplied on a single high-density diskette. The diskette has been 

virus-checked; however, the user should perform a secondary virus check before loading the disk contents onto the hard disk. 

Program installation consists of the following steps, where it is assumed that the program is to installed on hard drive C: from the program diskette in drive A: 

Step I: Create a directory named ERA on the hard drive and then change 

to the directory. 

C: 

MD\ERA 

CD\ERA 

Step 2: Copy the contents of the ERA 1 disk to the ERA directory on the 

hard drive. 

COpy A:C: 

Step 3: Create a subdirectory \DATA to contain the data files and 

change to the subdirectory. 

MDDATA 

CD DATA 

Step 4: Copy the data files from the program diskette to the FILES 

subdirectory. 

COpy A:*.ERA C:\ERA\DATA 

ERA is supplied with two additional diskettes that contain the input files created for the 

EPA Multiple Pathways analysis [5]. The data is grouped according to the refrigerator/freezer. For example, all pathways starting with Model A refrigerator/freezer are 

contained in directory \MODEL_A on one of the two data disks. 

2-1 
The following DOS commands will create a subdirectory \E ODEL_A and copy

the corresponding files from the data disk:

CD\ERA

MODEL_A

MODEL_A

COPY A: ODEL_A\*.E

Similar commands could be used to create subdirectories \E ODEL_B through

\ERA ODEL_F and to copy the contents of the two data disks, where it is assumed

that the source diskette is in drive A:.

Following completion of the file transfers, the supplied diskettes should be stored in a

safe place with the write protection tab set.

2.2 Program Data and Execution Files

ERA consists of 6 executable files (programs), a batch file (E .BAT), and approximately 80 data files. Most of the data files are either static (not changed by the user) or

are modified under the control of an interactive menu - driven input data processor.

Several, optional, files are used to control the assumptions used by ERA relating to the

computer configuration, to control the solution tolerances, or to define compressor performance by a map. Default files are supplied with ERA. They may be modified by

using an ASCII editor.

Although not required, it is recommended that a full screen scientific (ASCII) editor be

utilized with the program. All output is in ASCII form, which can be read with an

ASCII editor. In addition, several intermediate files are prepared by the interactive

menu-driven processor, as inputs to the executable programs. ERA has been designed

to pass data between the various programs using formatted ASCII files to facilitate an

understanding of the workings of the program.

These intermediate files may be printed out and stored with each run as part of the run

documentation. In rare circumstances the user may choose to edit these intermediate

data files directly and execute the cabinet loads (CAB) or cycle performance (ERACYC) program directly. This option is discussed further in Section 3.

Table 2.1 lists the files supplied with ERA. A brief discussion of each follows.

ERA The overall program and data flow is controlled by this batch file. This file

should not be modified.

BI,OCKOI.DAT to BLCCK72.DAT. ERA uses 72 data and help menus. They must not

be changed.

CABINET.DAT. ERA creates this intermediate file as input to the cabinet loads program. Under most circumstances this file is not modified by the user, but is available

as an ASCII file describing the input data to the cabinet loads model.

CABINET.FRM. This is a static file used to create the intermediate file CABINET.DAT. This file must not be changed.

2-2

 EE-RM-93-801 COMMENT OR2

The following DOS commands will create a subdirectory \ERA \MODEL_A and copy 

the corresponding files from the data disk: 

CD\ERA 

l\ID MODEL_A 

CD MODEL_A 

COpy A:\MODEL_A \*.ERA 

Similar commands could be used to create subdirectories \ERA \MODEL_B through 

\ERA \MODEL_F and to copy the contents of the two data disks, where it is assumed 

that the source diskette is in drive A:. 

Following completion of the file transfers, the supplied diskettes should be stored in a 

safe place with the write protection tab set. 

2.2 Program Data and Execution Files 

ERA consists of 6 executable files (programs), a batch file (ERA.BAT), and approximately 80 data meso Most of the data files are either static (not changed by the user) or 

are modified under the control of an interactive menu - driven input data processor. 

Several, optional, files are used to control the assumptions used by ERA relating to the 

computer configuration, to control the solution tolerances, or to define compressor performance by a map. Default files are supplied with ERA. They may be modified by 

using an ASCII editor. 

Although not required, it is recommended that a full screen scientific (ASCII) editor be 

utilized with the program. All output is in ASCII form, which can be read with an 

ASCII editor. In addition, several intermediate files are prepared by the interactive 

menu-driven processor, as inputs to the executable programs. ERA has been designed 

to pass data between the various programs using formatted ASCII files to facilitate an 

understanding of the workings of the program. 

These intermediate files may be printed out and stored with each run as part of the run 

documentation. In rare circumstances the user may choose to edit these intermediate 

data files directly and execute the cabinet loads (CAB) or cycle performance (ERACYC) program directly. This option is discussed further in Section 3. 

Table 2.1 lists the files supplied with ERA. A brief discussion of each follows. 

ERA BAT. The overall program and data flow is controlled by this batch file. This file 

should not be modified. 

BWCKOI,DAT to BWCK72,DAT. ERA uses 72 data and help menus. They must not 

be changed. 

CABINEI,DAT. ERA creates this intermediate file as input to the cabinet loads program. Under most circumstances this me is not modified by the user, but is available 

as an ASCII me describing the input data to the cabinet loads model. 

CABINET.FRM. This is a static file used to create the intermediate me CABINET.DA T. This file must not be changed. 

2-2 
*,LM

a

If the compressor map option is selected , the performance data of the compressor must be defined using a file with this extension. The file is prepared using

external editor. A sample file, CO .TAE is supplied. The structure of this file

should be evident, and should not be m odified. Compressor map files can be prepared

for as many compressors as desired, and may be given any legal DOS file name (e.g.,

ROTARYl.TAE). Ordinarily the na should indicate the compressor t ype. It is

assumed that the compressor map files are stored in the directory containing ERA.

CYCLE.DAT. ERA creates this intermediate file as input to the cycle program. Under

most circumstances this file is not modified by the user, but is available as an ASCII

file describing the input data to the cycle model.

CLE.'RM. This is a static file used to create the interm ediate file CYCLE.DAT.

This file must not be changed.

ERAC®ND R and ERACOND.DAT. ERA provides the facility to determine heat

transfer rates and press ure drops from various condenser designs. E CO .DAT is

an intermediate file prepared by ERA as part of this process. A readable copy of this

intermediate file is given by file ERACOND.BAK. Neither of these files should be

modified.

E EV .R and E EV .DAT. These files are prepared for the evaporator heat

transfer and pressure drop analysis. They should not be modified.

SETUP.DAT. ERA assumes the presence of a color monitor, and printer port L 1.

These assumptions, and other program options, may be changed by editing

SETUP.DAT using an external editor. A full discussion of this option is given below

(see "Customizing ERA to your Computer Environment").

README.DOC. This file is intended to catch the attention of users who do not take

the time to read this Manual. It contains important summary information about ERA.

Each of the input data files describing the cabinet and cycle design have the

extension ERA. The name of the file may have up to 8 characters (e.g.,

MODEL_D.E ). Creation and modification of these files is done within the ERA

menu system. All files are in binary format. The user must not attempt to edit these

files directly since the file structure may be inadvertently changed.

CABLM Cabinet loads analyses are performed, using CABINET.DAT as input,

under control of the ERA batch command.

ERACOND.EXE. Calculation of condenser heat transfer coefficients and pressure

drops is carried out for specified design data. Operation of the program is under control of the ERA Menu-driven data processor.

E CYC.EXE. Refrigeration cycle performance and energy use is calculated by this

program, which is called by the ERA batch command.

ERAEVAP.EXE. Calculation of evaporator heat transfer coefficients and pressure

drops is carried out for specified design data. Operation of the program is under control of the ERA menu-driven data processor.

2-3

 EE-RM-93-801 COMMENT OR2

* IT AB. If the compressor map option is selected, the performance data of the compressor must be defined using a file with this extension. The file is prepared using an 

external editor. A sample file, COMPMAP.TAB is supplied. The structure of this file 

should be evident, and should not be modified. Compressor map files can be prepared 

for as many compressors as desired, and may be given any legal DOS file name (e.g., 

ROTARYl.TAB). Ordinarily the name should indicate the compressor type. It is 

assumed that the compressor map files are stored in the directory containing ERA. 

CYCLEDAT, ERA creates this intermediate file as input to the cycle program. Under 

most circumstances this file is not modified by the user, but is available as an ASCII 

file describing the input data to the cycle model. 

CYCLE.FRM, This is a static file used to create the intermediate file CYCLE.DAT. 

This file must not be changed. 

ERACOND.BAK and ERACONDDAT. ERA provides the facility to determine heat 

transfer rates and pressure drops from various condenser designs. ERACOND.DAT is 

an intermediate file prepared by ERA as part of this process. A readable copy of this 

intermediate file is given by file ERACOND.BAK. Neither of these files should be 

modified. 

ERAEV AP .BAK and ERAEV AP DAT. These files are prepared for the evaporator heat 

transfer and pressure drop analysis. They should not be modified. 

SETUP DAT. ERA assumes the presence of a color monitor, and printer port LPTI. 

These assumptions, and other program options, may be changed by editing 

SETUP.DAT using an external editor. A full discussion of this option is given below 

(see "Customizing ERA to your Computer Environment"). 

READMEDOC. This file is intended to catch the attention of users who do not take 

the time to read this Manual. It contains important summary information about ERA. 

* .ERA. Each of the input data files describing the cabinet and cycle design have the 

extension .ERA. The name of the file may have up to 8 characters (e.g., 

MODEL_D.ERA). Creation and modification of these files is done within the ERA 

menu system. All files are in binary formal The user must not attempt to edit these 

files directly since the file structure may be inadvertently changed. 

CAB.EXE. Cabinet loads analyses are performed, using CABINET.DAT as input, 

under control of the ERA batch command. 

ERACOND .EXE. Calculation of condenser heat transfer coefficients and pressure 

drops is carried out for specified design data. Operation of the program is under control of the ERA Menu-driven data processor. 

ERA Cyc.EXE. Refrigeration cycle performance and energy use is calculated by this 

program, which is called by the ERA batch command. 

ERAEV AP .EXE. Calculation of evaporator heat transfer coefficients and pressure 

drops is carried out for specified design data. Operation of the program is under control of the ERA menu-driven data processor. 

2-3 
ER -, F; nd Execution Sues

ERAZAT Batch file that controls processing of input data ASCII

and program execution

BLOCK011MAT Data menus and Help menus (72) Binary

to and

BLOCK 72MAT ASCII

C I ET. T Intermediate file, input to cabinet loads program ASCII

C I ET.F Template for input data to cabinet loads program ASCII

*.TAB Compressor map files ASCII

CYCLE. AT Intermediate file, input to cycle program ASCII

CYCLE.FRM Template for input data to cycle program ASCII

E C . AT° Intermediate file, input to condenser heat ASCII

E AC . AK exchanger analysis program

ERAEVAPMAT Intermediate file, input to evaporator heat ASCII

ERAEVAP.BAK exchanger analysis program

SETUP. AT Configuration data. Used to select options for ASCII

ERA

READMEMOC Notes on ERA. Documentation file ASCII

*.ERA Input data files (see Appendix C) Binary

CAB.EXE Cabinet loads analysis program Binary

E AC .EXE Condenser heat exchanger analysis program Binary

ERACYC.EXE Cycle analysis program and energy use calcula- Binary

tion

ERAEVAP.EXE Evaporator heat exchanger analysis program Binary

 EE-RM-93-801 COMMENT OR2

Table 2.1 ERA Data and Execution Flies 

ERA,BAT 

BLOCK01.DAT 

to 

BLOCK 72.DAT 

CABINET.DAT 

CABINET.FRM 

*.TAB 

CYCLE.DAT 

CYCLE.FRM 

ERACOND.DAT 

ERACOND.BAK 

ERAEVAP.DAT 

ERAEVAP .BAK 

SETUP.DAT 

README.DOC 

".ERA 

CAB.EXE 

ERACOND.EXE 

ERACYC.EXE 

ERAEVAP .EXE 

Batch file that controls processing of input data ASCII 

and program execution 

Data menus and Help menus (72) Binary 

and 

ASCII 

Intermediate file, input to cabinet loads program ASCii 

Template for input data to cabinet loads program ASCII 

Compressor map files ASCII 

Intermediate file, input to cycle program ASCII 

Template for input data to cycle program ASCII 

Intermediate file, input to condenser heat ASCii 

exchanger analysis program 

Intermediate file, input to evaporator heat ASCII 

exchanger analysis program 

Configuration data. Used to select options for ASCII 

ERA 

Notes on ERA. Documentation file ASCII 

Input data files (see Appendix C) Binary 

Cabinet loads analysis program Binary 

Condenser heat exchanger analysis program Binary 

Cycle analysis program and energy use calcula- Binary 

tion 

Evaporator heat exchanger analysis program Binary 

2-4 
Tale 2.1 ERA and Execution Files (continued)

MENU.EXE Input data processor Binary

S E .E Automated program output display Binary

*.FIG Drawings of cycles (4) Binary

*.P RP Thermophysical proprietary data files (7) ASCII

CYCLE.TOL Optional file for specifying solution tolerances ASCII

SUMMARY Blank form for summarizing results of analysis. ASCII

Notes:

Files, SETUP.DAT, CYCLE.TOL, and *.TAB may be changed using an external

ASCII editor. They are read by the executable files (program).

The intermediate files CABINET.DAT and CYCLE.DAT are prepared by ERA.

Normally they should not be changed by the user. However, if desired they may be

edited by an external editor and the corresponding files (CAB.EXE and ERACYC.EXE) run separately.

 EE-RM-93-801 COMMENT OR2

Table 2.1 ERA Data and Execution Flies (continued) 

MENU.EXE Input data processor Binary 

SHOWERA.EXE Automated program output display Binary 

*.FIG Drawings of cycles (4) Binary 

*.PRP Thermophysical proprietary data files (7) ASCII 

CYClE.TOl Optional file for specifying solution tolerances ASCII 

SUMMARY Blank form for summarizing results of analysis. ASCII 

Notes: 

Files, SETUP.DAT, CYCLE.TOL, and *.TAB may be changed using an external 

ASCII editor. They are read by the executable f:tles (program). 

The intermediate f:tles CABINET.DAT and CYCLE.DAT are prepared by ERA. 

Normally they should not be changed by the user. However, if desired they may be 

edited by an external editor and the corresponding f:tles (CAB.EXE and ERACYC.EXE) run separately. 

2-5 
MENfL.E%E. ERA processes all input data through a menu-driven, interaction program. prepares the input files for subsequent cabinet loads and cycle analyses.

SHAH ERA.EXE. Display summary results for cabinet loads and daily energy consumption. ERA.BAT calls SHOWERA at the completion of the cycle analysis.

* FI Sketches of the refrigeration cycles are contained within these four files, which

are used by the cycle analysis program. They must not be modified.

*,89P. Tables of thermophysical properties are available for CFC-12, HCFC-22,

C- 152a, HC-270 (cyclopropane), HC-290 (propane) and C-134a in these files.

They are used in the analysis of evaporator and condenser heat transfer and pressure

drops. ERA will estimate the properties of other refrigerants, or refrigerant mixtures,

and store them in file REFRIG.PRP. These files must not be modified.

CYCLE.? ®L. Solution tolerances are contained in this file , which may be modified

using an external ASCII editor. The structure of the file is self-explanatory. Additional information in given below ("Solution tolerances").

SUMMARY. A blank form is provided to summarize the results of the analysis. If

desired, this form may be modified with an external editor. Copies of the form are

obtained by multiple print outs of the file.

2.3 Customizing ERA to Your Computer Environment

ERA assumes the following: 1) presence of a color monitor, 2) print output sent to parallel print port LPT1:, 3) data limits within the program must be obeyed, 4) a page

eject will not be sent at the beginning of an output file (only at the end), 5) ASCII

character 12 serves as the form feed character, and 6) the ERA data files (*.ERA) are

contained in directory \ERA. To change these assumptions, a file SETUP.DAT must

be present. A sample of this file is shown below:

mono screen=no

print_port=lptl

form-feed=no

page_feed=no

i ore limits=no

path=\ERAATA

If your computer setup does not include a color graphics monitor, then change the

command in SETUP.DAT to read "mono-screen=yes".

The program assumes that the printer is connected to LPT1 (or to a COM port using

the MODE L1:=C®M? command in the autoexec file). If the printer is connected to

LPT2, insert a line reading "print_port=lpt2" into the SETUP.DAT file (the program is

supplied with a default setting of "print_port=lptl").

Depending upon the printer setup, page ejects are controlled by issuing a "1" or a form

feed character (ASCII character 12) in column one. ERA assumes that all files written

to a disk use ASCII character 12 for print control, and that those written directly to a

printer also use this character . To Utilize "1" in column 1 as the print form feed charac2-6

 EE-RM-93-801 COMMENT OR2

MENU.EXE. ERA processes aU input data through a menu-driven, interaction program. MENU prepares the input files for subsequent cabinet loads and cycle analyses. 

SHOWERA.EXE. Display summary results for cabinet loads and daily energy consumption. ERA.BA T calls SHOWERA at the completion of the cycle analysis. 

* .FIG. Sketches of the refrigeration cycles are contained within these four files, which 

are used by the cycle analysis program. They must not be modified. 

*.PRP. Tables of thermophysical properties are available for CFC-12, HCFC-22, 

HFC-152a, HC-270 (cyclopropane), HC-290 (propane) and HFC-134a in these files. 

They are used in the analysis of evaporator and condenser heat transfer and pressure 

drops. ERA will estimate the properties of other refrigerants, or refrigerant mixtures, 

and store them in file REFRIG.PRP. These files must not be modified. 

CYCLE.TOL. Solution tolerances are contained in this file, which may be modified 

using an external ASCII editor. The structure of the file is self-explanatory. Additional information in given below ("Solution tolerances"). 

SUMMARY. A blank form is provided to summarize the results of the analysis. If 

desired, this form may be modified with an external editor. Copies of the form are 

obtained by multiple print outs of the file. 

2.3 Customizing ERA to Your Computer Environment 

ERA assumes the following: 1) presence of a color monitor, 2) print output sent to parallel print port LPTl:, 3) data limits within the program must be obeyed, 4) a page 

eject will not be sent at the beginning of an output file (only at the end), 5) ASCII 

character 12 serves as the form feed character, and 6) the ERA data files (*.ERA) are 

contained in directory \ERA. To change these assumptions, a file SETUP.DAT must 

be present. A sample of this file is shown below: 

mono screen=no 

print port=lptl 

form -feed=no 

page ~feed=no 

ignore _limits=no 

path=\ERA \DAT A 

If your computer setup does not include a color graphics monitor, then change the 

command in SETUP.DA T to read "mono_screen=yes". 

The program assumes that the printer is connected to LPT 1 (or to a COM port using 

the MODE LPTl:=COM? command in the autoexec file). If the printer is connected to 

LPT2, insert a line reading "prinCport=lpt2" into the SETUP.DAT file (the program is 

supplied with a default setting of "prinCport=lptl "). 

Depending upon the printer setup, page ejects are controlled by issuing a "1" or a form 

feed character (ASCII character 12) in column one. ERA assumes that all files written 

to a disk use ASCII character 12 for print control, and that those written directly to a 

printer also use this character. To Utilize "1" in column 1 as the print form feed charac2-6 
ter insert a line reading "form_feed=yes" into the SETUP.DAT file. To issue a page

eject prior to the printout of the first data file enter the command "page_feed=yes" in

SE P.DAT.

Every data value entered into ERA is checked against upper and lower limits to prevent

running a problem with obvious errors. However, in some instances the user may wish

to over-ride this capability to force the program to look at some unusual conditions. To

allow the program to attempt to run for all data values supplied, enter the command

"ignore-limits=yes" in the SE P.DAT file. The user should note that the program

may not work for all data values entered.

It is assumed that the data files (which have extension ERA) are on the same directory

as the program. However, the user may define a path towards another directory or

drive where the data files are kept. This is accomplished by inserting the "path="

directive followed by the drive and directory. The example shown above assumes that

the files are on the C: drive in sub directory \ERA\DATA. In order for the command to

work, it must be left justified in the SETUP.DAT file. If it is not present, ERA will

assume all files are found in the directory containing ERA.

Two additional statements appear at the end of the SETUP.DAT file supplied with the

program: "expand" and "shadow." These commands control the display of the program

title screen. With both present, the title ERA is shown using an exploding windowing

method and appears to cast a shadow on the screen. These effects can be removed, if

desired, by eliminating these last two commands in SE P.DAT.

2.4 Solution Tolerances

Because of the many, highly non-linear equations utilized to describe the refrigerator

cycle, an iterative solution technique is employed. That is, sets of equations are solved

sequentially until the differences between two succeeding solutions fall within some

tolerance.

The first five data lines in CYCLE.TOL relate to solution for refrigerant temperatures

and mass flow. Of these, the most sensitive are the condenser temperature tolerances

(set to 0. 01F) and the mass flow rate tolerance (set to 0.001). The user may wish to

experiment with different values for these tolerances to determine an acceptable tradeoff between computer execution time and refrigerator cycle performance prediction.

The program is capable of dividing the two -phase heat transfer region in the evaporator

or condenser into an arbitrary number of nodes. In most instances the choice of only

one node will yield nearly the same predicted cycle performance as the choice of 5 or

10 nodes. To speed computation it is recommended that the specified number of subdivisions remain at one . In unusual cases, where a refrigerant blend is used which has a

highly non-linear relationship between temperature and quality over the evaporation or

condensation process, a larger number of subdivisions can be used (3 is recommended).

2.5 Running ERA

To run the program type ERA and press the <Enter> key.

2-7

 EE-RM-93-801 COMMENT OR2

ter insert a line reading "fonn_feed=yes" into the SETUP.DAT file. To issue a page 

eject prior to the printout of the first data file enter the command "page_feed=yes" in 

SETUP.DAT. 

Every data value entered into ERA is checked against upper and lower limits to prevent 

running a problem with obvious errors. However, in some instances the user may wish 

to over-ride this capability to force the program to look at some unusual conditions. To 

allow the program to attempt to run for all data values supplied, enter the command 

"ignore_limits=yes" in the SETUP.DAT file. The user should note that the program 

may not work for all data values entered. 

It is assumed that the data files (which have extension .ERA) are on the same directory 

as the program. However, the user may define a path towards another directory or 

drive where the data files are kept. This is accomplished by inserting the "path=" 

directive followed by the drive and directory. The example shown above assumes that 

the files are on the C: drive in subdirectory \ERA \DATA. In order for the command to 

work, it must be left justified in the SETUP.DAT file. If it is not present, ERA will 

assume all files are found in the directory containing ERA. 

Two additional statements appear at the end of the SETUP.DAT file supplied with the 

program: "expand" and "shadow." These commands control the display of the program 

title screen. With both present, the title ERA is shown using an exploding windowing 

method and appears to cast a shadow on the screen. These effects can be removed, if 

desired, by eliminating these last two commands in SETUP.DAT. 

2.4 Solution Tolerances 

Because of the many, highly non-linear equations utilized to describe the refrigerator 

cycle, an iterative solution technique is employed. That is, sets of equations are solved 

sequentially until the differences between two succeeding solutions fall within some 

tolerance. 

The first five data lines in CYCLE. TaL relate to solution for refrigerant temperatures 

and mass flow. Of these, the most sensitive are the condenser temperature tolerances 

(set to 0.01F) and the mass flow rate tolerance (set to 0.001). The user may wish to 

experiment with different values for these tolerances to detennine an acceptable tradeoff between computer execution time and refrigerator cycle performance prediction. 

The program is capable of dividing the two-phase heat transfer region in the evaporator 

or condenser into an arbitrary number of nodes. In most instances the choice of only 

one node will yield nearly the same predicted cycle perfonnance as the choice of 5 or 

10 nodes. To speed computation it is recommended that the specified number of subdivisions remain at one. In unusual cases, where a refrigerant blend is used which has a 

highly non-linear relationship between temperature and quality over the evaporation or 

condensation process, a larger number of subdivisions can be used (3 is recommended). 

2.5 Running ERA 

To run the program type ERA and press the <Enter> key. 

2-7 
2.6 Display of Results

Following completion of an analysis under control of the ERA batch command, an

automatic display of the results will occur. If a complete analysis is done, including

the cycle and energy calculations, the summary results for cabinet loads and daily

energy consumption are displayed; if a only a cabinet loads analysis has been

requested the cabinet loads output will be displayed.

Ordinarily, three output files are available for display: 1) the summary output (ERA.-

OUT); 2) the cabinet loads output (CABI T.OU T)); and 3) the cycle analysis results

(CYCLE.OUT). Any of these may be requested during the output display by pressing

the <Fl> key (summary output), <F2> key (cabinet loads), or the <F3> key (cycle output). If only a cabinet loads analysis has been requested, the only available output will

be the calculated cabinet loads. Request of another output from within execution of the

display program, will cause a return to DOS with an error message.

A print of any of the files displayed may be requested by simultaneously pressing the

<Alt> and <P> keys. It is assumed that the print port is LPT1:.

To return to the menu program and perform another analysis press the <FlO> key.

To make a normal return to DOS from the display of the output results press the <Esc>

key.

 EE-RM-93-801 COMMENT OR2

2.6 Display of Results 

Following completion of an analysis under control of the ERA batch command, an 

automatic display of the results will occur. If a complete analysis is done, including 

the cycle and energy calculations, the summary results for cabinet loads and daily 

energy consumption are displayed; if a only a cabinet loads analysis has been 

requested the cabinet loads output will be displayed. 

Ordinarily, three output files are available for display: 1) the summary output (ERA.-

OUT); 2) the cabinet loads output (CABINET. OUT); and 3) the cycle analysis results 

(CYCLE.OUT). Any of these may be requested during the output display by pressing 

the <FI> key (summary output), <F2> key (cabinet loads), or the <F3> key (cycle output). If only a cabinet loads analysis has been requested, the only available output will 

be the calculated cabinet loads. Request of another output from within execution of the 

display program, will cause a return to DOS with an error message. 

A print of any of the files displayed may be requested by simultaneously pressing the 

<Alt> and <I» keys. It is assumed that the print port is LPTI:. 

To return to the menu program and perform another analysis press the <FlO> key. 

To make a normal return to DOS from the display of the output results press the <Esc> 

key. 

2-8 
3.0 MODEL OVERVIEW

3.1 Basic Structure of the ERA Program

ERA consists of a batch command file (E .EAT'), and three major modules:

® MENU - a menu driven interaction input processor and analysis flow control prograrn. The program interacts with the user during the program input sification

phase and prepares the data files needed for the subsequent program modules;

® CAB - analyses of the cabinet loads. The steady-state heat inputs to the cabinet section are determined for various types of refrigerator/freezers, alternative insulation

system designs, and specified environment and usage conditions;

® ERACYC - determination of the steady-state, instantaneous, refrigeration cycle

capacity and power draws. The hourly average cabinet loads and instantaneous

refrigeration capacities determine the compressor duty cycle and the corresponding

fan powers. Corrections are made to the compressor energy to account for cycling

effects. ERACYC establishes the net duty energy consumption and prepares a summary of the results.

Data input to both the cabinet loads and cycle models are in the form of ASCII files

that can be edited off-line from the main calculation stream if desired.

The overall data and program flow is illustrated in Figure 3-1. The program is under

the control of the batch file ERA.BAT. Operations specified by ERA.BAT will depend

upon choices selected by the user from the Main Menu of the overall control program,

MENU. However, because of the modularity of the program structure, and the design

of the intermediate files, the program user can elect to run only a portion of the analysis, either from the menu driven program, or external to it using a data editor.

Figure 3-1 differentiates these different types of files: program (executable files), data

(output from one or more programs which serve as input to another program), and output (given the extension .OUT). The cycle data intermediate file, CYCLE.DAT,

receives cycle parameters from the menu program, and has a summary of the cabinet

loads results added at the end. The cabinet loads are used by ERACYC to determine

the compressor and fan run times.

Operation of the heat exchanger analysis programs, ERACOND and ERAEVAP, is

completely under the control of the menu program. MENU prepares the required input

data, calls the executable files using a secondary command processor, reads the output

files, and updates the heat exchanger data values (UA, area, pressure drop).

Following completion of an analysis, the ERA batch command calls a file display program (SHOWERA.EXE). Any of the three output files (E .OUT, CABINET.OUT,

CYCLE.OUT) may be selected within the display program by pressing a function key.

In addition, a return to the menu program for another analysis can be requested by

pressing a function key.

 EE-RM-93-801 COMMENT OR2

3.0 MODEL OVERVIEW 

3.1 Basic Structure of the ERA Program 

ERA consists of a batch command file (ERA.BAT), and three major modules: 

e MENU - a menu driven interaction input processor and analysis flow control program. The program interacts with the user during the program input specification 

phase and prepares the data files needed for the subsequent program modules; 

.. CAB - analyses of the cabinet loads. The steady-state heat inputs to the cabinet section are detennined for various types of refrigerator/freezers, alternative insulation 

system designs, and specified environment and usage conditions; 

e ERACYC - determination of the steady-state, instantaneous, refrigeration cycle 

capacity and power draws. The hourly average cabinet loads and instantaneous 

refrigeration capacities detennine the compressor duty cycle and the corresponding 

fan powers. Corrections are made to the compressor energy to account for cycling 

effects. ERACYC establishes the net duty energy consumption and prepares a summary of the results. 

Data input to both the cabinet loads and cycle models are in the fonn of ASCn files 

that can be edited off-line from the main calculation stream if desired. 

The overall data and program flow is illustrated in Figure 3-1. The program is under 

the control of the batch file ERA.BAT. Operations specified by ERA.BAT will depend 

upon choices selected by the user from the Main Menu of the overall control program, 

MENU. However, because of the modularity of the program structure, and the design 

of the intermediate files, the program user can elect to run only a portion of the analysis, either from the menu driven program, or external to it using a data editor. 

Figure 3-1 differentiates these different types of files: program (executable files), data 

(output from one or more programs which serve as input to another program), and output (given the extension .OUT). The cycle data intermediate file, CYCLE.DAT, 

receives cycle parameters from the menu program, and has a summary of the cabinet 

loads results added at the end. The cabinet loads are used by ERACYC to determine 

the compressor and fan run times. 

Operation of the heat exchanger analysis programs, ERACOND and ERAEV AP, is 

completely under the control of the menu program. MENU prepares the required input 

data, calls the executable files using a secondary command processor, reads the output 

files, and updates the heat exchanger data values (VA, area, pressure drop). 

Following completion of an analysis, the ERA batch command calls a file display program (SHOWERA.EXE). Any of the three output files (ERA.OUT, CABINET. OUT, 

CYCLE.OUT) may be selected within the display program by pressing a function key. 

In addition, a return to the menu program for another analysis can be requested by 

pressing a function key. 

3-1 
E A. T

MENU.EXE

CYCLE.DAT

® Cycle Parameters

® Cabinet Loads

Program

o Process Input Data

o Analyze Heat Exc.

o Prepare Cycle Data

o Prepare Cabinet Data

Data Program

ERACYC.EXE

* Cycle Performance

o Energy Use

o Process Output Files

Display

SHO ERA.EXE

o ERA.OUT

o CA INET.OUT

o CYCLE.OUT

Figure 3®1: Overall Data and Program Flow

Program

ER?, EV '.EYE

ERA Cc: J.EXE

Data

CAINET.DAT

Outpu

Output Results:

CAI ET.OUT

Output

Output Results:

CYCLE.OUT

ERA.OUT

 EE-RM-93-801 COMMENT OR2

CYCLE.DAT 

" Cycle Parameters 

" Cabinet Loads 

Data 

-

ERA.BAT 

Program 

MENU.EXE 

II Process Input Data 

II Analyze Heat Exchanger 

II Prepare Cycle Data 

II Prepare Cabinet Data 

Progl'llllll 

CAB.EXE 

II Calculate Cabinet Loads 

II Add Loads to Cycle Data 

ERACYC.EXE 

II Cycle Performance 

II Energy Us. 

Progl'llllll 

II Process Outpu,t Files 

SHOWERA.EXE 

II ERA.OUT 

" CABINET.OUT 

" CYCLE.OUT 

DIsplay 

Figure 3-1: Overall Data and Program Flow 

3-2 

Program 

ERA EVAP .EXE 

ERA COND.EXE 

Data 

CABINET.DAT 

Output 

Output Results: 

CABINET.OUT 

Output 

Output Results: 

CYCLE.OUT 

ERA. OUT 
3.2 T

As illustrated in Figure 3-1, the overall data and program execution flow is controlled

by the ERA batch file. The file is reproduced below:

@Echo off

:START

if exist cabinet.dat erase cabinet.dat

if exist cycle.dat erase cycle.dat

if exist era.out erase era.out

NU

if not exist cabinet.dat goto DO NE

CAB

if not exist cycle.dat goto SHOW-CAB

ERACYC

if not exist era.out goto done

goto SHOW-ERA

:DISPLAY

if errorlevel 5 goto NO-FILE

if errorlevel 4 goto START

if errorlevel 3 goto SHOW-CYCLE

if errorlevel 2 goto SHOW-CAB

if errorlevel 1 goto SHOW-ERA

goto DONE

:NO-FILE

cis

echo Requested File is not Present

goto STOP

:SHOW CYCLE

showera cycle.out

goto DISPLAY

:SHOW CAB

showera cabinet.out

goto DISPLAY

:SHOW ERA

showera era.out

goto DISPLAY

:DONE

cis

:STOP

echo on

The analysis programs (CAB and ERACYC) will be executed only if the intermediate

data files (CABINET.DAT and CYCLE.DAT) have been prepared by MENU.

 EE-RM-93-801 COMMENT OR2

3.2 ERA.BAT 

As illustrated in Figure 3-1, the overall data and program execution flow is controlled 

by the ERA batch file. The file is reproduced below: 

@Echooff 

: START 

if exist cabinet.dat erase cabinet.dat 

if exist cycle.dat erase cycle.dat 

if exist era. out erase era. out 

MENU 

if not exist cabinet.dat goto DONE 

CAB 

if not exist cycle.dat goto SHOW_CAB 

ERACYC 

if not exist era.out goto done 

goto SHOW_ERA 

:DISPLAY 

if errorleve15 gOlo NO_FILE 

if errorleve14 gOlO START 

if errorlevel 3 goto SHOW_CYCLE 

if errorleve12 goto SHOW_CAB 

if errorlevel 1 goto SHOW_ERA 

gotoDONE 

: NO_FILE 

cls 

echo Requested File is not Present 

goto STOP 

: SHOW _CYCLE 

showera cycle.out 

goto DISPLA Y 

: SHOW_CAB 

showera cabinet.out 

goto DISPLAY 

: SHOW_ERA 

showera era.out 

goto DISPLA Y 

: DONE 

cls 

:STOP 

echo on 

The analysis programs (CAB and ERACYC) will be executed only if the intermediate 

data files (CABINET.DAT and CYCLE.DAT) have been prepared by MENU. 

3-3 
3.3 Input Data Processor ( E U.EX )

allows the following basic options: 1) retrieve and edit the cabinet loads input

data, 2) retrieve and edit the refrigeration cycle data, 3) delete a data file, 4) write out

the data input file in readable form to a file or directly to the printer, 5) run the cabinet

loads program only, and 6) run both the cabinet loads and cycle models and determine

the total daily energy consumption and load components.

Every menu has associated Help menu. A logical tree sc e is utilized to group

the data and to provide a means of specifying the data in a fashion similar to the evolution of the overall design. Every data value is screened to ensure that it lies within an

allowable range and to guarantee logical consistency with other data.

Data specification help routines are available for: 1) determination of the net resistivity

of an insulation panel, 2) calculation of evaporator and condenser heat exchanger

parameters and pressure drops, and 3) calculation of variable speed fan air flow and fan

energy.

Input data to the MENU program is a user selected ERA data file. The output files

from MENU are CABINET.DAT and CYCLE.DAT.

3.4 Cabinet Loads Model (CAB.EXE)

Five basic R/F configurations are described: 1) top-mount refrigerator/freezer, 2) sideby-side refrigerator/freezer, 3) bottom-mount refrigerator/freezer, 4) chest freezer, and

5) upright freezer. Design parameters considered are: external dimensions, internal

volumes, insulation system geometry and resistivities, mullion dimensions and resistivity, compressor cabinet dimensions and insulation design, gasket heat leaks, cabinet

section control temperatures, environmental conditions, door opening schedules, and

ancillary electrical energies.

The cabinet loads program breaks down the steady-state heat loads by component as

well as by compartment. Note that the fan heat inputs are not yet considered in the

thermal loads budget. They are treated as a correction to the refrigeration capacity, by

the cycle program, and are related to the compressor run time.

The major heat flows present in the cabinet are considered, including the effects of edge

losses associated with vacuum insulation panels. The most significant uncertainties in the

modeled loads are associated with the gaskets (conduction and an unknown infiltration),

penetrations of the insulation system, and moisture input.

A door opening model has been included. Based on some limited research data [7] and

a simple description of time-dependent air exchanges, both the sensible and latent heat

loads are estimated for user-specified door opening schedules. The moisture exchange

may result in additional defrost loads, depending on the temperature of the evaporator.

 EE-RM-93-801 COMMENT OR2

3.3 Input Data Processor (MENU.EXE) 

MENU allows the following basic options: 1) retrieve and edit the cabinet loads input 

data, 2) retrieve and edit the refrigeration cycle data, 3) delete a data file, 4) write out 

the data input file in readable form to a file or direcdy to the printer, 5) run the cabinet 

loads program only, and 6) run both the cabinet loads and cycle models and determine 

the total daily energy consumption and load components. 

Every menu has an associated Help menu. A logical tree structure is utilized to group 

the data and to provide a means of specifying the data in a fashion similar to the evolution of the overall design. Every data value is screened to ensure that it lies within an 

allowable range and to guarantee logical consistency with other data. 

Data specification help routines are available for: 1) determination of the net resistivity 

of an insulation panel, 2) calculation of evaporator and condenser heat exchanger 

parameters and pressure drops, and 3) calculation of variable speed fan air flow and fan 

energy. 

Input data to the MENU program is a user selected .ERA data file. The output files 

from MENU are CABINET.DAT and CYCLE.DAT. 

3.4 Cabinet Loads Model (CAB.EXE) 

Five basic R/F configurations are described: 1) top-mount refrigerator/freezer, 2) sideby-side refrigerator/freezer, 3) bottom-mount refrigerator/freezer, 4) chest freezer, and 

5) upright freezer. Design parameters considered are: external dimensions, internal 

volumes, insulation system geometry and resistivities, mullion dimensions and resistivity, compressor cabinet dimensions and insulation design, gasket heat leaks, cabinet 

section control temperatures, environmental conditions, door opening schedules, and 

ancillary electrical energies. 

The cabinet loads program breaks down the steady-state heat loads by component as 

well as by compartment. Note that the fan heat inputs are not yet considered in the 

thermal loads budget. They are treated as a correction to the refrigeration capacity, by 

the cycle program, and are related to the compressor run time. 

The major heat flows present in the cabinet are considered, including the effects of edge 

losses associated with vacuum insulation panels. The most significant uncertainties in the 

modeled loads are associated with the gaskets (conduction and an unknown infIltration), 

penetrations of the insulation system, and moisture input. 

A door opening model has been included. Based on some limited research data [7] and 

a simple description of time-dependent air exchanges, both the sensible and latent heat 

loads are estimated for user-specified door opening schedules. The moisture exchange 

may result in additional defrost loads, depending on the temperature of the evaporator. 

3-4 
3.5 Refrigeration Cycle Analysis and Energy Use (ERACYC.EXE)

Four cycle configurations are descri : 1) standard single evaporator refrigerator/freezer, 2) Lorenz cycle with refrigerant mixtures, 3) dual-loop system employing

two independent refrigeration cycles, one for each compartment, and 4) dual

evaporator cycle, with two evaporators connected in series, normally employing a pure

refrigerant.

Figure 3-2 illustrates one of the cycles (Lorenz) described by ERA. ERACYC will

establish the refrigerant pressures and enthalpies around the cycle and the mass flow

that satisfies the heat and mass balances at each location in the cycle. Note that the

single evaporator cycle and dual evaporator cycle are derivatives of the Lorenz cycle.

9

MM

m

Tmnp

Figure 3-2. Lorenz-Meutzner Refrigerator/Freezer Cycle

The following control methods are adopted by the program:

® Standard Single Evaporator Cycle - The fresh food section and freezer section

temperatures are specified. Air damper control is assumed to achieve these temperatures. The analysis involves calculation of the temperature of the air mixing from

the two compartments as it approaches the evaporator. For example, if cabinet

temperatures of 38F and 5F are specified for the two compartments, the mixed air

temperature inlet to the evaporator will be about 12F, depending on the ratio of the

cabinet loads and the evaporator refrigerant temperature.

 EE-RM-93-801 COMMENT OR2

3.5 Refrigeration Cycle Analysis and Energy Use (ERACYC.EXE) 

Four cycle configurations are described: 1) standard single evaporator refrigerator/freezer, 2) Lorenz cycle with refrigerant mixtures, 3) dual-loop system employing 

two independent refrigeration cycles, one for each compartment, and 4) dual 

evaporator cycle, with two evaporators connected in series, normally employing a pure 

refrigerant. 

Figure 3-2 illustrates one of the cycles (Lorenz) described by ERA. ERACYC will 

establish the refrigerant pressures and enthalpies around the cycle and the mass flow 

that satisfies the heat and mass balances at each location in the cycle. Note that the 

single evaporator cycle and dual evaporator cycle are derivatives of the Lorenz cycle. 

2 

Temp 

Figure 3-2. Lorenz-Meutzner Refrigerator/Freezer Cycle 

The fonowing control methods are adopted by the program: 

Standard Single Evaporator Cycle - The fresh food section and freezer section 

temperatures are specified. Air damper control is assumed to achieve these temperatures. The analysis involves calculation of the temperature of the air mixing from 

the two compartments as it approaches the evaporator. For example, if cabinet 

temperatures of 38F and 5F are specified for the two compartments, the mixed air 

temperature inlet to the evaporator will be about 12F, depending on the ratio of the 

cabinet loads and the evaporator refrigerant temperature. 

3-5 
® Dual Loop Cycle - Each refrigeration loop, which contains its own evaporator,

compressor, and condenser, acts independently to achieve the average temperatures specified for the individual compartments. The model simulates each l oop

separately.

® Lorenz Cycle - The air temperatures approaching the two evaporators are assumed

to be at the specified control points. Normally the evaporator loads will be unbalanced, requiring additional refrigeration to be delivered to one of the compartments during off-cycle period for the other compartment. The control options

are: 1) adjust the fresh food section temperat ; 2) adjust the freezer temperature;

3) adjust the evaporator areas; 4) use a means to bypass the refrigerant cooling of

one evaporators during a portion of the cycle to enable the other evaporator to

meet its cabinet load; 5) allow imbalance to occur. Control option 4 is intended

to represent the use of a solenoid valve for refrigerant bypass, or the effects of

turning off the fan in a fan-forced evaporator. The energy consumption from a

solenoid valve can be specified.

® Dual Evaporator Cycle - The control logic is similar to the Lorenz cycle, with the

exception that an interchanger is not present between the evaporators, and that

pure refrigerants are normally used with this cycle. An additional control option

provided is alternately circuiting the refrigerant to one evaporator and then to

another. This would be accomplished by a switching valve. The energy consumption from such a valve can be specified.

Energy Consumption Model

The relationship between the hourly total cabinet heat loads (the refrigeration requirement at the evaporators), and the instantaneous capacity of the refrigeration cycle establishes the compressor run time (duty cycle = fraction of the hour that the compressor

operates to meet the load):

Duty = Cabinet-Load/(Evaporator-Capacity - Fan_Power)

Cabinet-Load = Duty*Fan_On_Cabinet_Load + (1.0 - Duty)*Fan_Off Cabinet Load

where,

Duty = Calculated duty cycle (0 to 1)

Fan_On_Cabinet_Load = Cabinet load during compressor operation

Fan_Off Cabinet_Load = Cabinet load during compressor off-cycle

The underlying assumption is that the thermal transients in the cabinet and in the

refrigeration cycle are small. That is, it is assumed that the cabinet temperature is

either relatively constant over the complete cycle, or that the sensible heat corresponding to temperature swings between the compressor on-cycle and off-cycle conditions is

small. The equations above link the time averaged cabinet loads to the instantaneous

capacity of the refrigeration system.

 EE-RM-93-801 COMMENT OR2

e Dual Loop Cycle - Each refrigeration loop, which contains its own evaporator, 

compressor, and condenser, acts independently to achieve the average temperatures specified for the individual compartments. The model simulates each loop 

separately. 

e Lorenz Cycle - The air temperatures approaching the two evaporators are assumed 

to be at the specified control points. Normally the evaporator loads will be unbalanced, requiring additional refrigeration to be delivered to one of the compartments during an off-cycle period for the other compartment. The control options 

are: 1) adjust the fresh food section temperature; 2) adjust the freezer temperature; 

3) adjust the evaporator areas; 4) use a means to bypass the refrigerant cooling of 

one evaporators during a portion of the cycle to enable the other evaporator to 

meet its cabinet load; 5) allow an imbalance to occur. Control option 4 is intended 

to represent the use of a solenoid valve for refrigerant bypass, or the effects of 

turning off the fan in a fan-forced evaporator. The energy consumption from a 

solenoid valve can be specified. 

" Dual Evaporator Cycle - The control logic is similar to the Lorenz cycle, with the 

exception that an interchanger is not present between the evaporators, and that 

pure refrigerants are normally used with this cycle. An additional control option 

provided is alternately circuiting the refrigerant to one evaporator and then to 

another. This would be accomplished by a switching valve. The energy consumption from such a valve can be specified. 

Energy Consumption Model 

The relationship between the hourly total cabinet heat loads (the refrigeration requirement at the evaporators), and the instantaneous capacity of the refrigeration cycle establishes the compressor run time (duty cycle = fraction of the hour that the compressor 

operates to meet the load): 

where, 

Duty = CabinecLoad!(Evaporator_Capacity - Fan_Power) 

CabineCLoad = Duty*Fan_On_CabineCLoad + (1.0 - Duty)*Fan_OfCCabinet_Load 

Duty = Calculated duty cycle (0 to 1) 

Fan_On_CabinecLoad = Cabinet load during compressor operation 

Fan_Off_CabinecLoad = Cabinet load during compressor off-cycle 

The underlying assumption is that the thermal transients in the cabinet and in the 

refrigeration cycle are small. That is, it is assumed that the cabinet temperature is 

either relatively constant over the complete cycle, or that the sensible heat corresponding to temperature swings between the compressor on-cycle and off-cycle conditions is 

small. The equations above link the time averaged cabinet loads to the instantaneous 

capacity of the refrigeration system. 

3-6 
Once the duty cycle is determined, the energy consumption terms are easily calculated:

Compressor energy use = Compressor power times the duty cycle

Fan energy use = Fan power times the duty cycle

Electronics (variable speed motor) = Electronics losses times the duty cycle

Heaters and controls = Specified hourly total values

frost energy = Net electrical input corresponding to

heat of fusion of the moisture condensing on the cold evaporator. (Note that it

is assumed that moisture will not freeze

on a fresh food evaporator in the dual

loop cycle, the Lorenz cycle, or the dual

evaporator cycle.)

Total Electrical Energy Use = Sum of above components

CYCLE.DAT is the input data file to ERACYC. Output files are ERA.OUT and

CYCLE.OUT.

Full documentation of a single run would consist of the following files:

ERA.OUT -- summary of energy use and cabinet loads

CAEINET.DAT -- input to CAB

CABINET.OUT -- output from CAB

CYCLE.DAT -- input to ERACYC

CYCLE.OUT -- results of cycle analysis

Sample data input and output files are given in Section.7.

 EE-RM-93-801 COMMENT OR2

Once the duty cycle is detenuined, the energy consumption tenus are easily calculated: 

Compressor energy use = Compressor power times the duty cycle 

Fan energy use = Fan power times the duty cycle 

Electronics (variable speed motor) = Electronics losses times the duty cycle 

Heaters and controls = Specified hourly total values 

Defrost energy = Net electrical input corresponding to 

heat of fusion of the moisture condensing on the cold evaporator. (Note that it 

is assumed that moisture will not freeze 

on a fresh food evaporator in the dual 

loop cycle, the Lorenz cycle, or the dual 

evaporator cycle.) 

Total Electrical Energy Use = Sum of above components 

CYCLE.OAT is the input data file to ERACYC. Output files are ERA.OUT and 

CYCLE.OUT. 

Full documentation of a single run would consist of the following files: 

ERA.OUT -- summary of energy use and cabinet loads 

CABINET.OAT -- input to CAB 

CABINET.OUT -- output from CAB 

CYCLE.OAT -- input to ERACYC 

CYCLE. OUT -- results of cycle analysis 

Sample data input and output files are given in Section 7. 

3-7 
4.0 PUT PROCESSOR

4.1 Menu Structure

ERA uses an iterative, menu driven input processor. Menus, or instructions, are used

at all levels of the input processing. For the most part, the appropriate response is a

cursor movement, or a data entry, followed by use of the <Enter> key or <Pg Dn> key.

The menu sc e has been developed to be as intuitive as feasible. Standard key

stroke interpretations apply throughout the program:

• <Esc> escape back to previous process or terminate current

process

• <Pg Up go back to previous menu

• <Pg Dn> : go to next menu

• <Enter> enter value or select option

• <Home> move cursor to start of list

• <End> move cursor to end of list

In addition, a common menu structure has been designed for most of the functions of

the input data processor.

The program begins at the Main Menu, illustrated in Figure 4-1. Eleven specific

actions are grouped into 4 sets. The first set deals with data file editing and manipulation (read data, edit cabinet data, edit cycle data, save data, delete data). A second set

provides two means to return to DOS (temporary exit to DOS, quit program). A third

set relates to the type of analysis to be performed (calculate cabinet loads, calculate

energy). The last set provides a permanent, off-line copy of the input data (print data

menus, write data menus to a file). An action is selected by moving the cursor to the

desired option and pressing the <Enter> key.

As illustrated in Figure 4-1, available help keys are shown at the top of each menu.

Function key Fl always leads to a Help menu which explains the intent of the menu;

function key F9 always provides an explanation of the use of special keys.

As also illustrated in Figure 4- 1, the bottom line of each menu normally lists important

keys. For example , at the Main Menu level, touching the <Esc> key will move the cursor to the "Quit Program" option; pressing the <Pg Dn> key, or the <Enter> key will

select the highlighted option.

The Main Menu contains a two line description for the highlighted function. A new

message will appear each time the cursor is moved.

 EE-RM-93-801 COMMENT OR2

4.0 INPUT PROCESSOR 

4.1 Menu Structure 

ERA uses an iterative, menu driven input processor. Menus, or instructions, are used 

at all levels of the input processing. For the most part, the appropriate response is a 

cursor movement, or a data entry, followed by use of the <Enter> key or <Pg Dn> key. 

The menu structure has been developed to be as intuitive as feasible. Standard key 

stroke interpretations apply throughout the program: 

.. <Esc> 

.. <PgUp> 

.. <PgDn> 

" <Enter> 

" <Home> 

.. <End> 

escape back to previous process or terminate current 

process 

go back to previous menu 

go to next menu 

enter value or select option 

move cursor to start of list 

move cursor to end of list 

In addition, a common menu structure has been designed for most of the functions of 

the input data processor. 

The program begins at the Main Menu, illustrated in Figure 4-1. Eleven specific 

actions are grouped into 4 sets. The first set deals with data file editing and manipulation (read data, edit cabinet data, edit cycle data, save data, delete data). A second set 

provides two means to return to DOS (temporary exit to DOS, quit program). A third 

set relates to the type of analysis to be performed (calculate cabinet loads, calculate 

energy). The last set provides a permanent, off-line copy of the input data (print data 

menus, write data menus to a file). An action is selected by moving the cursor to the 

desired option and pressing the <Enter> key. 

As illustrated in Figure 4-1, available help keys are shown at the top of each menu. 

Function key Fl always leads to a Help menu which explains the intent of the menu; 

function key F9 always provides an explanation of the use of special keys. 

As also illustrated in Figure 4-1, the bottom line of each menu normally lists important 

keys. For example, at the Main Menu level, touching the <Esc> key will move the cursor to the "Quit Program" option; pressing the <Pg Dn> key, or the <Enter> key will 

select the highlighted option. 

The Main Menu contains a two line description for the highlighted function. A new 

message will appear each time the cursor is moved. 

4-1 
F1 = Help ERA F9 = Keys - Help Keys

Main Menu

Read in a to File

Edit Cabinet Data

Edit Cycle Data

Save Data to File

Delete Data File

Temporary Exit to DOS

Quit Program

2 lane help menu goes here

e of Menu

Functions

Descriptions o

options

<Esc> = Quit <Pg Dn> ® Select Key Strokes

Calculate Cabinet Loads

Calculate Energy

Print Menus

Write Data Menus to a File

Figure 4®1: Main Menu

 EE-RM-93-801 COMMENT OR2

..,.. 

I 

N 

F1 = Help IERA I F9 = Keys 

I Main Menu I 

I 

Read in a Data File Calculate Cabinet loads 

Edit Cabinet Data Calculate Energy 

Edit Cycle Data 

Save Data to File 

Delete Data File 

Temporary Exit to DOS Print Menus 

Quit Program Write Data Menus to a File 

2 line help menu goes here 

<Esc> = Quit <Pg Dn> = Select 

Figure 4-1: Main Menu 

Help Keys 

Name of Menu 

Functions 

Descriptions of 

options 

Key Strokes 
4.2 Retrieving and Saving Input Data Files

The first step in preparing an analysis is to create the input required for the analysis

programs (CAB and ERACYC). This is accomplished by selecting a data file and then

using the menu-driven editor.

All data files have the extension ERA. When a request is made to retrieve data, ERA

performs a search for all files (up to 200 in a sub-directory) with this extension and

lists them in alphabetical order in the File Selection Menu, illustrated by Figure 4-2.

To select an existing file move the cursor to highlight the name and press the <Enter>

key. An automatic return to the next menu will then occur.

If more than 40 data files are available for selection, pressing the <Pg Dn> key will

scroll the screen forward to display the next 40 (or fewer) files. The <Pg Up> key will

scroll backwards to the previous display of files.

The File Selection Menu shows the name of the current data sub-directory (called the

"Current Path"). To change to a different sub-directory, press the <Fl0> key and enter

the data path (e.g., "\E \C ST"). If the data path is valid, a list of the available

*.ERA data files will be displayed.

Once a file is selected, it is read into the data "buffer" where it is available for editing

or for analysis. The file name will appear in a window on the File Selection Menu (see

Figure 4-2). If a new file is read in, this new name will be shown the next time the File

Selection Menu is called.

Two methods of creating a data file with a new name are provided. One method

involves selecting a file, as described above, editing the data values, and then saving it

under a new name. The process of saving the data creates a file with the desired name,

but does not change the name of the file in the buffer. A second, more direct method,

involves pressing the <F5> key first (see Figure 4-2) and then entering the (new) name

of the file to be created as requested. The new name will automatically be entered into

the buffer when the data is saved. The data in the new file will be same as those in the

highlighted file. Hence, using the cursor, the highlight should be moved to the file

most similar to the new file to be created. Once the data is edited it will be assigned

the new file name.

The procedure for saving a file is similar to the process of selecting a file. If a file

name is the same as that shown in the buffer area (see Figure 4-2), the changed file can

be saved simply by pressing the <F5> key. Otherwise, the name of the file must be

typed where requested. The extension ERA is always assumed. Up to 8 characters

may be entered.

4.3 Data File Management

In some instances the user may wish to create and store more than 200 data files. ERA

allows the definition of any valid DOS path for designating the location of the data

files. This can be accomplished using the "path=" command in the SETUP.DAT file as

discussed in Section 2 where a sample data file sub-directory \ERA\DATA was

defined.

4-3

 EE-RM-93-801 COMMENT OR2

4.2 Retrieving and Saving Input Data Flies 

The fIrst step in preparing an analysis is to create the input required for the analysis 

programs (CAB and ERACYC). This is accomplished by selecting a data fIle and then 

using the menu-driven editor. 

All data fIles have the extension .ERA. When a request is made to retrieve data, ERA 

performs a search for all fIles (up to 200 in a sub-directory) with this extension and 

lists them in alphabetical order in the File Selection Menu, illustrated by Figure 4-2. 

To select an existing fIle move the cursor to highlight the name and press the <Enter> 

key. An automatic return to the next menu will then occur. 

If more than 40 data fIles are available for selection, pressing the <Pg Dn> key will 

scroll the screen forward to display the next 40 (or fewer) fIles. The <Pg Up> key will 

scron backwards to the previous display of files. 

The File Selection Menu shows the name of the current data sub-directory (called the 

"Current Path"). To change to a different sub-directory, press the <FlO> key and enter 

the data path (e.g., H\ERA\CHEST"). If the data path is valid, a list of the available 

* .ERA data files will be displayed. 

Once a file is selected, it is read into the data "buffer" where it is available for editing 

or for analysis. The file name will appear in a window on the File Selection Menu (see 

Figure 4-2). If a new file is read in, this new name will be shown the next time the File 

Selection Menu is called. 

Two methods of creating a data file with a new name are provided. One method 

involves selecting a file, as described above, editing the data values, and then saving it 

under a new name. The process of saving the data creates a file with the desired name, 

but does not change the name of the file in the buffer. A second, more direct method, 

involves pressing the <F5> key fIrst (see Figure 4-2) and then entering the (new) name 

of the file to be created as requested. The new name will automatically be entered into 

the buffer when the data is saved. The data in the new file will be same as those in the 

highlighted file. Hence, using the cursor, the highlight should be moved to the file 

most similar to the new file to be created. Once the data is edited it will be assigned 

the new file name. 

The procedure for saving a file is similar to the process of selecting a file. If a file 

name is the same as that shown in the buffer area (see Figure 4-2), the changed file can 

be saved simply by pressing the <F5> key. Otherwise, the name of the file must be 

typed where requested. The extension .ERA is always assumed. Up to 8 characters 

may be entered. 

4.3 Data File Management 

In some instances the user may wish to create and store more than 200 data fIles. ERA 

allows the defInition of any valid DOS path for designating the location of the data 

fIles. This can be accomplished using the "path=" command in the SETUP.DAT file as 

discussed in Section 2 where a sample data file sub-directory \ERA \DATA was 

defIned. 

4-3 
F1 = Help I ERA I F9 = Keys Help Keys

Buffer File:

MODEL-D File Selection Menu Name of Menu

MODEL-A

MODEL-B

MODEL-C

MODEL-D

Press <F5> to Create a New File

<Esc> = Main Menu <Pg Dn> ® roll

Available files

Up to 40 per screen

Special Instruction

Key Strokes

Figure 4-2: File Selection Menu Example

 EE-RM-93-801 COMMENT OR2

F1 = Help IERA I F9 = Keys Help Keys 

Buffer File: 

MODEl_D I File SelectilOn Menu I 

I Name lOf Menu 

MODEl_A 

MODEl_B 

MODEl_C 

Available fiies 

MODEl_D Up to 40 per screen 

I Press <F5> tc Create a New File : Special InstructilOn 

<Esc> = Main Menu <Pg Dn> = ScrlOll Key StrlOkes 

Figure 4-2: File Selection Menu Example 
The "path=" command might also be used to define sub-directories that are specific to

the type of refrigerating unit. For example, top-mount units might be stored in subdirectory \ERA\TOP, chest freezers in sub-directory \E \C ST, and so on. The

limit of 200 data files will apply to each sub-directory defined. An external editor must

be used to change the path command in SE P.DAT.

An alternate means of creating additional file space in a sub-directory is to request the

"Delete Data File" command from the Main Menu (see Figure 4-1). This function

changes the file extension to EAK rather than actually erasing it. Hence if the file has

been accidentally "deleted" it can be retrieved. The function allows additional file

name space, but does not result in a reduction in the hard disk memory usage.

4.4 Editing

Once a file has been read into the buffer, editing proceeds by selecting the type of data

(cabinet loads or cycle data). As an example, Figure 4-3 illustrates the Cycle Data Edit

Menu. The data set to be edited is selected by moving the cursor to highlight the item

(e.g., Evaporator Design) and pressing the <Enter> or <Pg Dn> key.

Figure 4-4 illustrates an example of a data edit menu for freezer insulation resistivities.

Each data set is comprised of 1 to 14 values, which are displayed in the menu. They

are edited by moving the cursor key to highlight the parameter, and then typing the

new value, followed by pressing the <Enter> key.

A moving "data entry box", with an arrow pointing to the current value, identifies the

parameter to be changed. As the new data is entered it appears in this box until it is

entered (by pressing the <Enter> key, or any other key that will move the cursor). The

simplest way to enter a new value is to type the data into the box and then press a cursor key to move the box to a new location.

4.5 Getting Help

As shown in Figure 4-4, an explanation of the data menu and the parameters to be

edited can be obtained by pressing the <Fl> key. Figure 4-5 illustrates the structure of

the Help menu. Each Help menu shows the name of the data menu, and provides text

and simple line drawings, as needed, to explain the data requirements. If the information requires more than 17 lines, the text may be scrolled within the window by using

the cursor or the <Pg Up> and <Pg Dn> keys. A bar indicator to either side of the text

window symbolizes what portion of the Help menu appears on the screen.

As noted in the top line of the Help menu (Figure 4-5), a return to the edit menu is

made using the <Esc> key.

A print out of the Help menu may be obtained by simultaneously pressing the <Alt>

and <P> keys. The print port called is that defined in the SETUP.DAT file (see Section 2). If the program does not provide a print out or it hangs up at this point, the

information in SETUP.DAT is probably incorrect for the particular computer hardware

configuration. Options relating to printing from within ERA are explained in Section 2

and in the README.DOC file supplied with the program.

 EE-RM-93-801 COMMENT OR2

The "path=" command might also be used to define sub-directories that are specific to 

the type of refrigerating unit. For example, top-mount units might be stored in subdirectory \ERA \TOP, chest freezers in sub-directory \ERA \CHEST, and so on. The 

limit of 200 data files will apply to each sub-directory defined. An external editor must 

be used to change the path command in SETUP.DAT. 

An alternate means of creating additional file space in a sub-directory is to request the 

"Delete Data File" command from the Main Menu (see Figure 4-1). This function 

changes the file extension to .BAK rather than actually erasing it. Hence if the fIle has 

been accidentally "deleted" it can be retrieved. The function allows additional file 

name space, but does not result in a reduction in the hard disk memory usage. 

4.4 Editing Data 

Once a file has been read into the buffer, editing proceeds by selecting the type of data 

(cabinet loads or cycle data). As an example, Figure 4-3 illustrates the Cycle Data Edit 

Menu. The data set to be edited is selected by moving the cursor to highlight the item 

(e.g., Evaporator Design) and pressing the <Enter> or <Pg On> key. 

Figure 4-4 illustrates an example of a data edit menu for freezer insulation resistivities. 

Each data set is comprised of 1 to 14 values, which are displayed in the menu. They 

are edited by moving the cursor key to highlight the parameter, and then typing the 

new value, followed by pressing the <Enter> key. 

A moving "data entry box", with an arrow pointing to the current value, identifies the 

parameter to be changed. As the new data is entered it appears in this box until it is 

entered (by pressing the <Enter> key, or any other key that will move the cursor). The 

simplest way to enter a new value is to type the data into the box and then press a cursor key to move the box to a new location. 

4.5 Getting Help 

As shown in Figure 4-4, an explanation of the data menu and the parameters to be 

edited can be obtained by pressing the <PI> key. Figure 4-5 illustrates the structure of 

the Help menu. Each Help menu shows the name of the data menu, and provides text 

and simple line drawings, as needed, to explain the data requirements. If the information requires more than 17 lines, the text may be scrolled within the window by using 

the cursor or the <Pg Up> and <Pg On> keys. A bar indicator to either side of the text 

window symbolizes what portion of the Help menu appears on the screen. 

As noted in the top line of the Help menu (Figure 4-5), a return to the edit menu is 

made using the <Esc> key. 

A print out of the Help menu may be obtained by simultaneously pressing the <Alt> 

and <P> keys. The print port called is that defined in the SETUP.DAT file (see Section 2). If the program does not provide a print out or it hangs up at this point, the 

information in SETUP.DAT is probably incorrect for the particular computer hardware 

configuration. Options relating to printing from within ERA are explained in Section 2 

and in the README.DOC file supplied with the program. 

4-5 
F1 ® Help ERA F9® Keys , ; Sys

Cycle Data Edit Menu

Cycle Type Condenser Design

Refrigerants Compressor Design

Evaporator sin Interchanger(s)

2 line help menu goes here

<Esc> = Main Menu <Pg n> = Select

f Menu

tins

Descriptions

options

Key Strokes

Figure -3: Cycle Data it Menu

 EE-RM-93-801 COMMENT OR2

F1 = Help IERA I F9 = Keys 

I Cycle Data Edit Menu I 

I 

Cycle Type Condenser Design 

Refrigerants Compressor Design 

Evaporator Design Interchanger( s) 

2 line help menu goes here 

<Esc> = Main Menu <Pg Dn> = Select 

Figure 4-3: Cycle Data Edit Menu 

Help Keys 

Name of Menu 

Options 

Descriptions of 

options 

Key Strokes 
F1 = Hell! I ERA I F9 = Keys Help Keys

Freezer Insulation Resistivities

Resistivity ( 2- -cm)

* Top Wall 0.544

* Side Wall 0.544

* Back all 0.544

* Door 0.544

Wedge 0.544

Data Error Message

* Press <F5> to Calculate Data

<Esc> = Main Menu <Pg Dn> = Next Menu

Name of data group

Data `} o nU location

(Enter n value)

Cursor

Special instruction

Key Strokes

Figure 4-4: Data Edit Menu Example

 EE-RM-93-801 COMMENT OR2

F1 = Help IERA I F9 = Keys 

I Freezer Insulation Resistivities : 

iResistivity (m2-clw-cm) 

• Top Wall 0.544 """'-

• Side Wall 0.544 

---------- '" Back Wall 0.544 

---

'" Door 0.544 

Wedge 0.544 

Data Error Message / 

'" Press <FS> to Calculate Data 

<Esc> = Main Menu <Pg On> = Next Menu 

Figure 4-4: Data Edit Menu Example 

------

Help Keys 

Name of data group 

Data editing location 

(Enter new value) 

Cursor 

Special instruction 

Key Strokes 
<Esc>: Return I Help Menu

er Insulation Resistivitles

Text of Help nu

ERA

< It®P>: Print Key strokes

Name of help menu

Up cursor to scroll up

Indicator

Down cursor to scroll

down

Figure ®5® Help Menu ample

 EE-RM-93-801 COMMENT OR2

~<S!E!:.:s~C~>~: ....!R~e:=.!t~u!!rn!.-_____ -1I-!!H!!el!.Elp!...!M~e~n~u~L 1 _____ ~<A~it-:!P~>:.:.: ..!P:.!:r~in~t..r---- Key strokes 

x 

xx 

I Freezer Insulation Resistivities 11--___ -+ ___ Name of help menu 

~~----------------------------------_--~I~ 

Text of Help Menu 

I ERA T 

figure 4-5: Help Menu Example 

-

t 1----+---- Up cursor to scroil up 

~ ~V'0\.J---+---lndicator »« 0-

1----+---- Down cursor to scroll 

down 
The Keys Menu, accessed by pressing the <F9> key, defines the actions specific to

individual keys.

A considerable amount of information has been collected in the Help and Keys menus.

It is highly recommended that these menus be read at each level of the progr until

the user is very familiar with ERA.

4.6 Default I"'- '

Preparation of input data file involves editing, or selecting, current data. That is, the

data preparation process always begins with the data file last read into the data buffer.

By definition, therefore, the current data values in the selected file are default data.

Suggestions for values, or ranges of values, for data parameters are found in the Help

menus.

4.7 Calculation Assists

In certain instances the requested data value may be difficult to assign without additional analysis. Examples include: the effective resistivity of a cabinet wall containing

foam and vacuum insulation in a sandwich arrangement, evaporator UA value, and fan

power in a variable-speed fan configuration.

ERA provides a calculation assist to determine these values by calling secondary

menus. Data values that can be estimated in this manner are indicated by an asterisk

(*) next to the name of the parameter and a message at the bottom of the data window

(see Figure 4-4).

To call the calculation assist menu, position the highlight to the variable of interest

using a cursor key and press the <F5> key.

The structure of the calculation assist menu is shown in Figure 4-6 for the example of a

variable speed fan. As with data edit menus, a Help menu is available by using the

<Fl> key. A return to the calling menu is made by pressing the <Pg Dn> key or the

<Esc> key. If the <Pg Dn> key is pressed, the calculation is performed and the results

are automatically entered into the calling menu. To avoid making the calculation and

to return directly to the calling menu, press the <Esc> key.

In some instances, the data appearing in the calculation assist menu may appear not to

be retained when the file is saved. This is because the assist facilities are considered to

be only a means of calculating some data value that is saved in the menu from which

the calculation assist function is called. This approach reduces the size of the data

files, thereby speeding the file read and write functions and freeing up disk space.

 EE-RM-93-801 COMMENT OR2

The Keys Menu, accessed by pressing the <P9> key, defmes the actions specific to 

individual keys. 

A considerable amount olin/ormation has been collected in the Help and Keys menus. 

It is highly recommended that these menus be read at each level o/the program until 

the user is very familiar with ERA. 

4.6 Default Data 

Preparation of an input data me involves editing, or selecting, current data. That is, the 

data preparation process always begins with the data file last read into the data buffer. 

By definition, therefore, the current data values in the selected file are default data. 

Suggestions for values, or ranges of values, for data parameters are found in the Help 

menus. 

4.7 Calculation Assists 

In certain instances the requested data value may be difficult to assign without additional analysis. Examples include: the effective resistivity of a cabinet wall containing 

foam and vacuum insulation in a sandwich arrangement, evaporator VA value, and fan 

power in a variable-speed fan configuration. 

ERA provides a calculation assist to determine these values by calling secondary 

menus. Data values that can be estimated in this manner are indicated by an asterisk 

(*) next to the name of the parameter and a message at the bottom of the data window 

(see Figure 4-4). 

To call the calculation assist menu, position the highlight to the variable of interest 

using a cursor key and press the <P5> key. 

The structure of the calculation assist menu is shown in Figure 4-6 for the example of a 

variable speed fan. As with data edit menus, a Help menu is available by using the 

<PI> key. A return to the calling menu is made by pressing the <Pg Dn> key or the 

<Esc> key. If the <Pg Dn> key is pressed, the calculation is performed and the results 

are automatically entered into the calling menu. To avoid making the calculation and 

to return directly to the calling menu, press the <Esc> key. 

In some instances, the data appearing in the calculation assist menu may appear not to 

be retained when the file is saved. This is because the assist facilities are considered to 

be only a means of calculating some data value that is saved in the menu from which 

the calculation assist junction is called. This approach reduces the size of the data 

files, thereby speeding the file read and write junctions andfreeing up disk space. 

4-9 
F1 =He

Calculated Fan Power (w): 900

Calculated Air Flow ( ): 15.5

Data editing location

(Enter new value)

Cursor

< c> ® Cancel <Pg n> ® Calculate Strokes

ERA ®evs

Variable Speed Fan acne of variable

Rated Conditions

9.00

Air Flow Rate (US) 15.57

Power (w)

Fan Speed (rpm) 3600.00

VSD Control

Fan Speed (rpm) 3600.00

Figure Calculation Assist u Example

 EE-RM-93-801 COMMENT OR2

F1 = Help I ERA I F9 = Keys 

I Variable Speed Fan: 

Rated Conditions 

Fan Speed (rpm) 3600.00 -.:::.. 

Power (w) 9.00 

Air Flow Rate (US) 15.57 

------------ VSD Control 

Fan Speed (rpm) 3600.00 

Calculated Fan Power (w): 9.0 

Calculated Air Flow (US): 15.5 

<Esc> = Cancel <Pg Dn> = Calculate 

Figure 4 .. 6: Calculation Assist Menu Example 

r------

Help Keys 

Name of variable 

Data editing location 

(Enter new value) 

Cursor 

Key Strokes 
4.8 input Data Error Trapping and Correction

All input data are checked against high and low limits whenever they are entered in a

data edit menu. If the data value lies outside the expected range, an error message is

written at the bottom of the data window (Figure 4-4). Depending on the nature of the

parameters, one of three actions is taken:

® The data will not be accepted since it must lie within the limits. An example would

be the code for the type of compressor (only 1 and 2 are allowed).

® The data must be above a minimum value but may exceed the upper limit. If the

data is above the expected upper limit it may be accepted by pressing the <Esc> key

(the menu will display this message).

® Data below the expected range may be accepted by pressing the <Esc> key.

In certain instances the user may wish to exceed the upper and lower limits , no matter

what type of parameter is being edited. This can be allowed by entering the statement

"ignore-limits = yes" in the SETUP.DAT file. The user should be cautioned that violation of expected limits may lead to erroneous answers or even a computer crash if an

illogical request is made.

Prior to executing the cabinet loads analysis, a check of the consistency of the data is

made. Obvious errors, such as a door flange wider than the wall insulation, are caught

and an error message is displayed. The user m resolve the error before execution of

the analysis is allowed.

4.9 Using DOS Within ERA

In some instances the user may wish to call a DOS function or some other program

(such as a data editor) without leaving ERA. An example situation might be the need

to look at an ASCII file using an external editor to determine a data value to be entered

into one of the ERA menus.

This is accomplished by returning to the Main Menu and then choosing the "Temporary Exit to DOS" function (see Figure 4-1). A second version of COM MAND .COM

will be executed, while leaving the ERA MENU program resident in memory. After

all DOS requests have been completed a return to ERA will be made if the command

"EXIT" is entered. The return will be made to the drive and directory containing the

ERA program.

Because ERA remains as a memory resident program during this temporary return to

DOS, the available memory will be smaller (ERA requires about 390 K of memory).

As a consequence, programs or DOS functions that require a large amount of memory

may not work.

In all instances the user should avoid loading another memory resident program during

a temporary exit to DOS since this second memory resident program may prevent the

release of the memory used by ERA upon exiting the program. In such a case the only

recourse would be to reboot the computer.

4-11

 EE-RM-93-801 COMMENT OR2

4.8 Input Data Error Trapping and Correction 

All input data are checked against high and low limits whenever they are entered in a 

data edit menu. If the data value lies outside the expected range, an error message is 

written at the bottom of the data window (Figure 4-4). Depending on the nature of the 

parameters, one of three actions is taken: 

" The data will not be accepted since it must lie within the limits. An example would 

be the code for the type of compressor (only 1 and 2 are allowed). 

.. The data must be above a minimum value but may exceed the upper limit. If the 

data is above the expected upper limit it may be accepted by pressing the <Esc> key 

(the menu will display this message). 

" Data below the expected range may be accepted by pressing the <Esc> key. 

In certain instances the user may wish to exceed the upper and lower limits, no matter 

what type of parameter is being edited. This can be allowed by entering the statement 

"ignore_limits = yes" in the SETUP.DAT file. The user should be cautioned that violation of expected limits may lead to erroneous answers or even a computer crash if an 

illogical request is made. 

Prior to executing the cabinet loads analysis, a check of the consistency of the data is 

made. Obvious errors, such as a door flange wider than the wall insulation, are caught 

and an error message is displayed. The user ~ resolve the error before execution of 

the analysis is allowed. 

4.9 Using DOS Within ERA 

In some instances the user may wish to call a DOS function or some other program 

(such as a data editor) without leaving ERA. An example situation might be the need 

to look at an ASCII file using an external editor to determine a data value to be entered 

into one of the ERA menus. 

This is accomplished by returning to the Main Menu and then choosing the "Temporary Exit to DOS" function (see Figure 4-1). A second version of COMMAND.COM 

will be executed, while leaving the ERA MENU program resident in memory. After 

all DOS requests have been completed a return to ERA will be made if the command 

"EXIT" is entered. The return will be made to the drive and directory containing the 

ERA program. 

Because ERA remains as a memory resident program during this temporary return to 

DOS, the available memory will be smaller (ERA requires about 390 K of memory). 

As a consequence, programs or DOS functions that require a large amount of memory 

may not work. 

In all instances the user should avoid loading another memory resident program during 

a temporary exit to DOS since this second memory resident program may prevent the 

release of the memory used by ERA upon exiting the program. In such a case the only 

recourse would be to reboot the computer. 

4-11 
4.10 Printing Input Data Files

A permanent copy of the data appearing in the data menus may be obtained by selecting the "Print Data Menus" or "Write Data Menus to a File" options from the Main

Menu (see Figure 4-1). If the data are printed directly, the user must ensure that a

printer is connected and that the correct print port is defined in the SE P.DAT file.

Otherwise the printout may not occur or the computer may hang-up.

A safer procedure is to write the data to a file and print it after leaving the ERA program. Data written to a file are stored with extension .INP. The name of the file,

which contains the data as ASCII text, will be the same as the file in the buffer.

4.11 Program Execution

As shown in Figure 3-1 (Section 3.2), a cabinet loads analysis and cycle analysis may

be requested. This request occurs at the Main Menu where the user selects "Calculate

Cabinet Loads" or "Calculate energy". The first request results in a calculation of the

cabinet loads only. The second request results in both the loads and cycle analysis.

The selected program will run to completion unless aborted by pressing the <Esc> key.

Time requirements for the cabinet loads program are very small. The cycle model may

require a small or large computational time, depending on the refrigeration cycle

defined and the refrigerant characteristics. The most time consuming calculations will

occur for a ternary refrigerant mixture in a two-evaporator cycle (such as the Lorenz or

dual evaporator cycles which use a single compressor) where some adjustments to the

cabinet set points or to the evaporator areas may be required to balance the loads and

the evaporator capacities.

As discussed earlier, ERACYC uses an iterative solution technique to solve the many

coupled, non-linear equation. A screen display of the estimated temperatures and the

refrigerant mass flow is made throughout the iteration process. Although not indicated

on the screen, a solution may be "forced" by hitting the <F10> key. This will result in

an assumed satisfaction of the solution tolerances following a condenser analysis and

lead to termination of the analysis. A note will appear in the output that the solution

was forced.

As long as execution is not terminated by pressing the <Esc> key, a display of the output files will automatically occur. However, a direct return to DOS, without display of

any files, will occur if the <Esc> key is pressed.

 EE-RM-93-801 COMMENT OR2

4.10 Printing Input Data Flies 

A permanent copy of the data appearing in the data menus may be obtained by selecting the "Print Data Menus" or "Write Data Menus to a File" options from the Main 

Menu (see Figure 4-1). If the data are printed directly, the user must ensure that a 

printer is connected and that the correct print port is defined in the SETUP.DAT file. 

Otherwise the printout may not occur or the computer may hang-up. 

A safer procedure is to write the data to a file and print it after leaving the ERA program. Data written to a file are stored with extension .INP. The name of the file, 

which contains the data as ASCII text, will be the same as the file in the buffer. 

4.11 Program Execution 

As shown in Figure 3-1 (Section 3.2), a cabinet loads analysis and cycle analysis may 

be requested. This request occurs at the Main Menu where the user selects "Calculate 

Cabinet Loads" or "Calculate energy". The first request results in a calculation of the 

cabinet loads only. The second request results in both the loads and cycle analysis. 

The selected program will run to completion unless aborted by pressing the <Esc> key. 

Time requirements for the cabinet loads program are very small. The cycle model may 

require a small or large computational time, depending on the refrigeration cycle 

defined and the refrigerant characteristics. The most time consuming calculations will 

occur for a ternary refrigerant mixture in a two-evaporator cycle (such as the Lorenz or 

dual evaporator cycles which use a single compressor) where some adjustments to the 

cabinet set points or to the evaporator areas may be required to balance the loads and 

the evaporator capacities. 

As discussed earlier, ERACYC uses an iterative solution technique to solve the many 

coupled, non-linear equation. A screen display of the estimated temperatures and the 

refrigerant mass flow is made throughout the iteration process. Although not indicated 

on the screen, a solution may be "forced" by hitting the <FlO> key. This will result in 

an assumed satisfaction of the solution tolerances following a condenser analysis and 

lead to termination of the analysis. A note will appear in the output that the solution 

was forced. 

As long as execution is not terminated by pressing the <Esc> key, a display of the output files will automatically occur. However, a direct return to DOS, without display of 

any files, will occur if the <Esc> key is pressed. 

4-12 
5.0 CABINET LOADS I PUT° DATA REFERENCE

The material within the present and following chapters are meant to supplement information provided within the ERA menu program.

During the first run of the program and when questions arises concerning some data

requirement the Help menu should be used (press the <Fl> key). A printed copy of

each Help menu may obtained by pressing the <Alt-P> key from within the Help

menu. Over 60 pages of Help menus can be printed out and assembled in a separate

note book if desired.

5.1 Title of Analysis

Five lines of information may be entered as a description of the design analysis. The

entered title will appear on the summary output.

A full screen editor is built into the menu program. The Help or Keys screen describes

the editing keys.

5.2 Cabinet Type and Di mension

Five basic designs are described: 1) top-mount refrigerator/freezer, 2) bottom-mount

refrigerator/freezer, 3) side-by-side refrigerator/freezer, 4) chest fteezer, and 5) upright

freezer. Specific design variables (such as the presence or absence of automatic defrost)

are requested later in the menu structure. For the purposes of the analysis select the

configuration that most closely represents the design under study.

Not all refrigeration cycles are consistent with each cabinet configuration. To enable

the user to edit portions of the input data in an arbitrary order, a consistency check

between the specified cabinet data and cycle data is made only prior to the program

execution step.

The Help menu illustrates the definition of height, width and depth. The following

conventions are adopted:

® Cabinet height is measured from the bottom to top of the cabinet, not from the floor.

Hence, space below the cabinet that may contain a fan-forced condenser and compressor is not included in this parameter.

® Depth includes the cabinet doors. This dimension measures the distance from the

outside (front) surface of the doors to the back of the cabinet. Protrusions such as a

handle on the front of the cabinet or a cover over a wire harness on the back of the

unit are NOT included in this value.

To facilitate an understanding of the data request, the width of the gasket and the

door edge thickness are requested. ERA interprets the depth of the refrigerated box,

not containing the door, as the total depth minus the sum of the door edge thickness

and the gasket width. Later data requests for the door thickness refer to the center

thickness, thereby allowing the specification of doors that are thicker in the middle

than at the edges. The effects of door thickness on the internal volume are taken

into account.

5-1

 EE-RM-93-801 COMMENT OR2

5.0 CABINET LOADS INPUT DATA REFERENCE 

The material within the present and following chapters are meant to supplement information provided within the ERA menu program. 

During the first run of the program and when questions arises concerning some data 

requirement the Help menu should be used (press the <PI> key). A printed copy of 

each Help menu may be obtained by pressing the <Alt-I» key from within the Help 

menu. Over 60 pages of Help menus can be printed out and assembled in a separate 

note book if desired. 

5.1 Title of Analysis 

Five lines of infonnation may be entered as a description of the design analysis. The 

entered title will appear on the summary output 

A full screen editor is built into the menu program. The Help or Keys screen describes 

the editing keys. 

5.2 Cabinet Type and Dimension 

Five basic designs are described: 1) top-mount refrigerator/freezer, 2) bottom-mount 

refrigerator/freezer, 3) side-by-side refrigerator/freezer, 4) chest freezer, and 5) upright 

freezer. Specific design variables (such as the presence or absence of automatic defrost) 

are requested later in the menu structure. For the purposes of the analysis select the 

configuration that most closely represents the design under study. 

Not all refrigeration cycles are consistent with each cabinet configuration. To enable 

the user to edit portions of the input data in an arbitrary order, a consistency check 

between the specified cabinet data and cycle data is made only prior to the program 

execution step. 

The Help menu illustrates the definition of height, width and depth. The following 

conventions are adopted: 

.. Cabinet height is measured from the bottom to top of the cabinet, not from the floor. 

Hence, space below the cabinet that may contain a fan-forced condenser and compressor is not included in this parameter. 

e Depth includes the cabinet doors. This dimension measures the distance from the 

outside (front) surface of the doors to the back of the cabinet. Protrusions such as a 

handle on the front of the cabinet or a cover over a wire harness on the back of the 

unit are NOT included in this value. 

To facilitate an understanding of the data request, the width of the gasket and the 

door edge thickness are requested. ERA interprets the depth of the refrigerated box, 

not containing the door, as the total depth minus the sum of the door edge thickness 

and the gasket width. Later data requests for the door thickness refer to the center 

thickness, thereby allowing the specification of doors that are thicker in the middle 

than at the edges. The effects of door thickness on the internal volume are taken 

into account. 

5-1 
Wedge dimensions are requested in a separate menu. The cabinet wedge is the section

of the cabinet near the door. In all cabinet types, except the chest freezer, the thickness

of the insulation is reduced near the door to accommodate the door geometry. Dimensions are assumed to be the same within each cabinet section (i.e., the side and top

wedges of the freezer compartment in a top-mount unit are taken to be the same)

although they may be different in one compartment from another.

It is assumed that a freezer compartment in a refrigerator/freezer will always have a

wedge with a taper; a wedge is often present in the fresh food section, but may be set to

zero (typical of Chinese designs). An upright freezer will also have a wedge. The

chest freezer is assumed to not have a wedge.

An illustration of the wedge geometry is given in the Help screen. The wedge depth is

the length of the taper from the front towards the back. Wedge width is the thickness

of the cabinet at the front.

5.3 Refrigerated Volumes

ERA will calculate internal volumes of the cabinet compartments based on the input

data for the cabinet dimensions. The calculated volume is used in the simulation of the

contribution to the cabinet loads from door openings. If the calculated volumes are significantly different from the manufacturer's specifications then the input data is probably faulty. For example, the location of the mullion at the wrong position within the

cabinet will result in an incorrect calculation of the individual compartment volumes.

See Help screen for additional information.

Normally, the compressor will be located in a space at the rear, bottom of the cabinet,

where it is cooled by air blown over the condenser or by natural convection. This

space requirement will reduce the food storage volume of the cabinet located above,

and will also affect the net external surface area available for heat exchange with the

room. A separate menu is provided to describe the compressor compartment.

Three cases are described: 1) the compressor is located outside the dimensions of the

cabinet, requiring no reduction in food storage volume; 2) the bottom portion of the

back wall is slanted; and 3) the bottom portion of the cabinet contains a compressor

space with a horizontal wall. If the compressor is located outside the envelope of a

rectangular cabinet box enter 0 for the three data values requested. Otherwise enter

data values as directed by the Help menu.

5.4 Freezer and Fresh Food Cabinets

Two menus request the data input for each cabinet section: 1) the wall and door thicknesses, and 2) insulation resistivity for each wall element and door. The net resistance

of each cabinet element is determined by the resistivity and the thickness. Drawings of

the cabinets showing the requested data are given in the Help screens.

In most instances, interpretation of the wall thickness requests should be straight forward. If the thickness varies over the element, such as the floor of a fresh food cabinet

that may have thicker insulation over the compressor, use an averaged thickness value.

5-2

 EE-RM-93-801 COMMENT OR2

Wedge dimensions are requested in a separate menu. The cabinet wedge is the section 

of the cabinet near the door. In all cabinet types, except the chest freezer, the thickness 

of the insulation is reduced near the door to accommodate the door geometry. Dimensions are assumed to be the same within each cabinet section (i.e., the side and top 

wedges of the freezer compartment in a top-mount unit are taken to be the same) 

although they may be different in one compartment from another. 

It is assumed that a freezer compartment in a refrigerator/freezer will always have a 

wedge with a taper; a wedge is often present in the fresh food section, but may be set to 

zero (typical of Chinese designs). An upright freezer will also have a wedge. The 

chest freezer is assumed to not have a wedge. 

An illustration of the wedge geometry is given in the Help screen. The wedge depth is 

the length of the taper from the front towards the back. Wedge width is the thickness 

of the cabinet at the front. 

5.3 Refrigerated Volumes 

ERA will calculate internal volumes of the cabinet compartments based on the input 

data for the cabinet dimensions. The calculated volume is used in the simulation of the 

contribution to the cabinet loads from door openings. If the calculated volumes are significantly different from the manufacturer's specifications then the input data is probably faulty. For example, the location of the mullion at the wrong position within the 

cabinet will result in an incorrect calculation of the individual compartment volumes. 

See Help screen for additional information. 

Normally, the compressor will be located in a space at the rear, bottom of the cabinet, 

where it is cooled by air blown over the condenser or by natural convection. This 

space requirement will reduce the food storage volume of the cabinet located above, 

and will also affect the net external surface area available for heat exchange with the 

room. A separate menu is provided to describe the compressor compartment. 

Three cases are described: 1) the compressor is located outside the dimensions of the 

cabinet, requiring no reduction in food storage volume; 2) the bottom portion of the 

back wall is slanted; and 3) the bottom portion of the cabinet contains a compressor 

space with a horizontal wall. If the compressor is located outside the envelope of a 

rectangular cabinet box enter 0 for the three data values requested Otherwise enter 

data values as directed by the Help menu. 

5.4 Freezer and Fresh Food Cabinets 

Two menus request the data input for each cabinet section: 1) the wall and door thicknesses, and 2) insulation resistivity for each wall element and door. The net resistance 

of each cabinet element is determined by the resistivity and the thickness. Drawings of 

the cabinets showing the requested data are given in the Help screens. 

In most instances, interpretation of the wall thickness requests should be straight forward. If the thickness varies over the element, such as the floor of a fresh food cabinet 

that may have thicker insulation over the compressor, use an averaged thickness value. 

5-2 
The specified thickness of a wall containing a sandwich of fo am and a vacuum insulation panel should be the total thickness (neglecting the thickness of the liner).

The thermal resistivities are properties of the materials of construction and the construction methods. For example, typical CFC- 11 blown polyurethane foams have a

resistivity of 0.55 m2-C -cm. Some vacuum insulation panels may have resistivities

of greater than 1.5. Default values for many of the insulation strategies under consideration are available to the user by using the <F5> function key.

Some example insulation values are:

HCFC Blown Foam 0.48 m2- C/W -cm 7 hr-ft2-F/Rtu-in

CFC- Blown Foam 0.55 m2-C -cm 8 hr-ft2-F/Rtu-in

Water Blown Foam 0.42 m2-C/W-cm 6 hr-ft2-F/Ptu-in

Evacuated Powder 1.73 m2-C -cm 25 hr-ft2-F/Rtu-in

Evacuated Aerogel 1.39 m2-C -cm 20 hr-ft2-F/Rtu-in

The corresponding thermal conductivity of the HCFC blown foam is (typically):

Metric units: 0.0206 W/m-C

Calory units: 0.0177 kCal/m-hr-C

English units: 0.0119 Bth/hr-ft-F

When a composite insulation system is used, an average resistivity for the wall should

be specified. ERA provides a method of estimating the average resistivity of a composite consisting of a foam sandwich containing a vacuum insulation panel (see

Appendix A). The general case assumes a vacuum insulation panel located between

inner and outer foam panels and surrounded by foam along all four edges.

This calculational assist is reached by pressing the <F5> key within the Insulation

Resistivity menu. This will cause an additional menu to be displayed which requests

information on the design of the insulation system. A Help menu is available which

shows the geometry and describes each of the required input parameters . Typical

material property values are also given in the Help menu.

Once within the calculational assist menu, two additional editing assists are provided:

1) the fraction of the refrigerator wall consisting of foam may be determined by pressing the <F4> key and entering the vacuum panel thickness; and 2) the amount of foam

along the four edges of the panel may be determined by pressing the <F5> key and

entering the fractional coverage of the wall by the panel. These functions are explained

in further depth in the Help menu.

The user should note that the data displayed in this calculational assist menu will be

the last entered and will be carriedforth to the next set of calculations. Hence, the

user should always be sure that the entire set of data shown in the menu applies to the

specific configuration being analyzed.

After leaving the calculation assist menu (press <Pg Dn> key), the calculated net

resistivity for the insulation system is directly entered into the Insulation Resistivity

menu. Note that different constructions can be used at various locations of the cabinet.

5-3

 EE-RM-93-801 COMMENT OR2

The specified thickness of a wall containing a sandwich of foam and a vacuum insulation panel should be the total thickness (neglecting the thickness of the liner). 

The thermal resistivities are properties of the materials of construction and the construction methods. For example, typical CFC-ll blown polyurethane foams have a 

resistivity of 0.55 m2

-C/W-cm. Some vacuum insulation panels may have resistivities 

of greater than 1.5. Default values for many of the insulation strategies under consideration are available to the user by using the <F5> function key. 

Some example insulation values are: 

HCFC Blown Foam 

CFC-ll Blown Foam 

Water Blown Foam 

Evacuated Powder 

Evacuated Aerogel 

0.48 m2 -CIW -cm 

0.55 m2

-C/W-cm 

0.42 m2 -C/W -cm 

1.73 m

2

-C/W-cm 

1.39 m

2

-C/W-cm 

7 hr-ff-FlBtu-in 

8 hr-fr-FlBtu-in 

6 hr-ff-FlBtu-in 

25 hr-ff-FlBtu-in 

20 hr-fr-FlBtu-in 

The corresponding thermal conductivity of the HCFC blown foam is (typically): 

Metric units: 

Calory units: 

English units: 

0.0206 W /m-C 

0.0177 kCaVm-hr-C 

0.0119 Bth/hr-ft-F 

When a composite insulation system is used, an average resistivity for the wall should 

be specified. ERA provides a method of estimating "the average resistivity of a composite consisting of a foam sandwich containing a vacuum insulation panel (see 

Appendix A). The general case assumes a vacuum insulation panel located between 

inner and outer foam panels and surrounded by foam along all four edges. 

This calculational assist is reached by pressing the <F5> key within the Insulation 

Resistivity menu. This will cause an additional menu to be displayed which requests 

information on the design of the insulation system. A Help menu is available which 

shows the geometry and describes each of the required input parameters. Typical 

material property values are also given in the Help menu. 

Once within the calculational assist menu, two additional editing assists are provided: 

I) the fraction of the refrigerator wall consisting of foam may be determined by pressing the <F4> key and entering the vacuum panel thickness; and 2) the amount of foam 

along the four edges of the panel may be determined by pressing the <F5> key and 

entering the fractional coverage of the wall by the panel. These functions are explained 

in further depth in the Help menu. 

The user should note that the data displayed in this calculational assist menu will be 

the last entered and will be carriedforth to the next set of calculations. Hence, the 

user should always be sure that the entire set of data shown in the menu applies to the 

specific configuration being analyzed. 

After leaving the calculation assist menu (press <Pg Dn> key), the calculated net 

resistivity for the insulation system is directly entered into the Insulation Resistivity 

menu. Note that different constructions can be used at various locations of the cabinet. 

5-3 
5.5 Mullion

The mullion is the wall between the fresh food and freezer sections of the refrigerator.

One is found in configuration type 1 (top-mount: horizontal mullion), type 2 (bottommount: horizontal mullion) and in type 3 (side-by-side: vertical mullion). By definition,

there is no mullion in a chest freezer or upright freezer.

Typically the resistivity of the mullion insulation is less than that of the foam walls

since a removable insulation is often installed in this area. The resistivity is normally

about half that of the walls.

5.6 Air and Cabinet Temperatures

The room air and cabinet temperatures establish the heat loads of each compartment on

the refrigeration system. For a DOE closed door test simulation a room air temperature

of 32.2 C (90 F) is ordinarily specified, along with a freezer temperature of -15 C (5 F)

and a fresh food cabinet temperature of 3.3 C (38 F). Temperatures must also be specified for under the cabinet (where the compressor is normally located) and for "air

entering the condenser". There will be some uncertainty in these temperatures, since a

heat balance is not modeled for the space under the cabinet. Both the compressor and

condenser release considerable heat to this compartment. As a rule of thumb, the air

temperature in this region should be 10 to 15 F (5 to 10 C) higher than the room temperature.

ERA also contains algorithms for estimating the effects of open door loads on energy

consumption. For these analyses (which require door opening schedules) a typical

room temperature will be 18 to 24 C (64 to 75 F).

5.7 Door Opening Schedules

The schedule of door openings is defined here to establish the net sensible and latent load

heat inputs to the cabinet during the hour. The model assumes an initial complete spilling

of the cold air and replacement with warm, relatively more humid, room air, followed by

a longer term free convective driven air exchange. The controlling parameters are: the

room relative humidity, the number of times each door is opened during the hour, and the

average duration of each opening.

Parameters controlling the sensible and latent loads are: room temperature, cabinet

temperature, room relative humidity, number of openings/hour,' average duration of

each door opening, and type of defrost (manual or automatic). A typical schedule for

door openings might be:

Fresh Food Door - Opening/hr. 2.5

- Duration (sec) 20

Freezer Door - Opening/hr. 1

- Duration (sec) 15

 EE-RM-93-801 COMMENT OR2

5.5 Mullion 

The mullion is the wall between the fresh food and freezer sections of the refrigerator. 

One is found in configuration type 1 (top-mount: horizontal mullion), type 2 (bottommount: horizontal mullion) and in type 3 (side-by-side: vertical mullion). By definition, 

there is no mullion in a chest freezer or upright freezer. 

Typically the resistivity of the mullion insulation is less than that of the foam walls 

since a removable insulation is often installed in this area. The resistivity is normally 

about half that of the walls. 

5.15 Air and cabinet Temperatures 

The room air and cabinet temperatures establish the heat loads of each compartment on 

the refrigeration system. For a DOE closed door test simulation a room air temperature 

of 32.2 C (90 F) is ordinarily specified, along with a freezer temperature of -15 C (5 F) 

and a fresh food cabinet temperature of 3.3 C (38 F). Temperatures must also be specified for under the cabinet (where the compressor is normally located) and for "air 

entering the condenser". There will be some uncertainty in these temperatures, since a 

heat balance is not modeled for the space under the cabinet. Both the compressor and 

condenser release considerable heat to this compartment As a rule of thumb, the air 

temperature in this region should be 10 to 15 F (5 to 10 C) higher than the room temperature. 

ERA also contains algorithms for estimating the effects of open door loads on energy 

consumption. For these analyses (which require door opening schedules) a typical 

room temperature will be 18 to 24 C (64 to 75 F). 

5.7 Door Opening Schedules 

The schedule of door openings is defined here to establish the net sensible and latent load 

heat inputs to the cabinet during the hour. The model assumes an initial complete spilling 

of the cold air and replacement with warm, relatively more humid, room air, followed by 

a longer term free convective driven air exchange. The controlling parameters are: the 

room relative humidity, the number of times each door is opened during the hour, and the 

average duration of each opening. 

Parameters controlling the sensible and latent loads are: room temperature, cabinet 

temperature, room relative humidity, number of openings/hour,' average duration of 

each door opening, and type of defrost (manual or automatic). A typical schedule for 

door openings might be: 

Fresh Food Door - Opening/hr. 

- Duration (sec) 

Freezer Door - Opening/hr. 

- Duration (sec) 

5-4 

2.5 

20 

1 

15 
Moisture exchange with the room will result in condensation in both cabinets and frost

build-up in the fi-eezer section. It is assumed that all moisture entering the fresh food

section will end up as frost on the evaporator of a single evaporator system. Frost

buildup is not assumed to occur in the fresh food cabinet of a two evaporator system.

Defrost energy may result from use of a resistance heating element in the evaporator.

This energy is added to the defrost energy specified for the closed door condition, and

is reported as "Defrost" in the summary output.

5.8 Gasket Heat Leaks

The gasket areas around the cabinet doors are sources of heat due to conduction loads

from the room air along the cabinet and door flanges, and through the gasket itself.

Correct estimates of the heat leaks must take into consideration the geometry and materials used in the wall panels and doors. Reference values for the gasket heat leaks may

be obtained from the Help menu by pressing the <Fl> function key.

All gasket heat leaks are expressed in units of conductance per length of the gasket.

The net leak is determined by the program from the total door perimeter and from the

outside-inside air temperature difference.

Because of the low values of the conductance, enter the data in units of W/m-1000. A

typical value is 10 W/m-100 C temperature difference.

5.9 Defrost and Controls Energy Use

Electrical energy consumption consists of compressor energy, fan energy, anti-sweat

energy, and other (ancillary) sources. Such ancillary energy includes automatic defrost

and controls. It is assumed that any electrical energy consumed within the cabinet is

converted to an equivalent heat load that must be removed by the refrigeration system.

The data menu defines constant and cycle-dependent electrical energy uses, not including fan energy or anti-sweat energy.

Automatic defrost energy usage is a cycle-dependent load, which is normally triggered

by a controller that keeps track of compressor operation. Under closed-door test conditions, a typical defrost system might use a 450 watt heater, activated for 10 minutes

once every 10 hours of compressor run-time. Additional defrost energy will be

required under normal usage conditions. ERA assumes that the additional defrost loads

resulting from door openings are additive to the defined closed-door automatic defrost

energy.

Energy use from timers and other sources may be defined as being cycle-dependent

(related to the compressor run-time) or constant. The locations of these loads determine their effects on the cabinet heat loads. For example, a defrost timer located in the

space below the fresh food section will not add to the cabinet heat load, whereas

electric defrost heat will add to the load.

5.10 Electric Anti-Sweat Heat

Moisture control on the outside of the cabinet may be accomplished by the use of electric heaters in the area of the cabinet flanges and the mullion. Ordinarily an "energysaver" switch is supplied with the refrigerator to allow these heaters to be disabled.

 EE-RM-93-801 COMMENT OR2

Moisture exchange with the room will result in condensation in both cabinets and frost 

build-up in the freezer section. It is assumed that all moisture entering the fresh food 

section will end up as frost on the evaporator of a single evaporator system. Frost 

buildup is not assumed to occur in the fresh food cabinet of a two evaporator system. 

Defrost energy may result from use of a resistance heating element in the evaporator. 

This energy is added to the defrost energy specified for the closed door condition, and 

is reported as "Defrost" in the summary output. 

5.8 Gasket Heat leaks 

The gasket areas around the cabinet doors are sources of heat due to conduction loads 

from the room air along the cabinet and door flanges, and through the gasket itself. 

Correct estimates of the heat leaks must take into consideration the geometry and materials used in the wall panels and doors. Reference values for the gasket heat leaks may 

be obtained from the Help menu by pressing the <PI> function key. 

All gasket heat leaks are expressed in units of conductance per length of the gasket. 

The net leak is determined by the program from the total door perimeter and from the 

outside-inside air temperature difference. 

Because of the low values of the conductance, enter the data in units of W /m-lOOC. A 

typical value is 10 W/m-lOO C temperature difference. 

5.9 Defrost and Controls Energy Use 

Electrical energy consumption consists of compressor energy, fan energy, anti-sweat 

energy, and other (ancillary) sources. Such ancillary energy includes automatic defrost 

and controls. It is assumed that any electrical energy consumed within the cabinet is 

converted to an equivalent heat load that must be removed by the refrigeration system. 

The data menu defines constant and cycle-dependent electrical energy uses, not including fan energy or anti-sweat energy. 

Automatic defrost energy usage is a cycle-dependent load, which is normally triggered 

by a controller that keeps track of compressor operation. Under closed-door test conditions, a typical defrost system might use a 450 watt heater, activated for 10 minutes 

once every 10 hours of compressor run-time. Additional defrost energy will be 

required under normal usage conditions. ERA assumes that the additional defrost loads 

resulting from door openings are additive to the defined closed-door automatic defrost 

energy. 

Energy use from timers and other sources may be defined as being cycle-dependent 

(related to the compressor run-time) or constant. The locations of these loads determine their effects on the cabinet heat loads. For example, a defrost timer located in the 

space below the fresh food section will not add to the cabinet heat load, whereas 

electric defrost heat will add to the load. 

5.1 0 Electric Anti-Sweat Heat 

Moisture control on the outside of the cabinet may be accomplished by the use of electric heaters in the area of the cabinet flanges and the mullion. Ordinarily an "energysaver" switch is supplied with the refrigerator to allow these heaters to be disabled. 

5-5 
Under a 0 E closed-door test, the refrigerator is operated under both conditions --

with the heaters on and with the heaters off. ERA can be run for both cases, and the

results then averaged to simulate the test conditions. A simple approximation that can

be employed is to run ERA once using one half of the heater power to represent an

average condition.

Since the heaters are normally installed immediately under the cabinet flanges and/or

the mullion, a portion of the heat will leak into the cabinet. A typical fractional heat

leak is 20% - 40% in the cabinet flange region, and 40% - 80% in the mullion region.

Electrical heat applied in the mullion region will contribute to heat loads in both compartments. Because of the lower freezer temperature, more of the heat will likely flow

to this compartment.

5.11 Refrigerant Line Anti-Sweat Heat

Moisture control on the outside of the cabinet may be accomplished by the use of

refrigerant lines in the area of the cabinet door flanges and the mullion. To simplify

construction, a combination of refrigerant lines around the cabinet flanges and electrical heaters in the mullion region might also be used.

Either a refrigerant vapor line (containing superheated vapor leaving the compressor)

or a refrigerant liquid line (containing refrigerant leaving the condenser) may be used

for this function. An advantage resulting from using a liquid line is that additional subcooling occurs prior to entering the capillary tube.

In actual practice, the refrigerant entering a liquid line around the door flange or across

the mullion may be in two-phase, with condensation completed within the liquid line.

This may be desirable to limit the total refrigerant charge. ERA cannot model this situation, since it assumes completion of condensation in the condenser. The condenser

subcooling should be set to zero when a liquid line is represented.

The refrigerant enthalpy decrease from the use of a vapor or liquid line is dependent on

the compressor run time. File CYCLE.OUT (the cycle analysis output file) should be

reviewed to ensure that the specified cycle-average refrigerant line heating has not

resulted in an excessive enthalpy drop (e.g., liquid subcooling to below ambient conditions). A warning message indicating excessive heat withdrawal from the liquid line

will appear in the summary output file (ERA.OUT) whenever the refrigerant is cooled

below room temperature. In this instance, the degree of refrigerant line heat should be

reduced and replaced with an equivalent amount of electric anti-sweat heat. Since the

electric anti-sweat heat is switchable, only one-half of the heat deficit should be

entered as electric anti-sweat heat to represent average conditions for the DOE closed

door test.

(For example, assume that a 6 watt switchable anti-sweat heater is to replaced by a liquid line. Under the closed door test condition, the average condition is represented by

3 watts electrical anti-sweat heat. Since the liquid line heat is not switchable, the 3

watts electrical heat should be replaced by 6 watts liquid line heat. If only 4 watts of

liquid line heat can be withdrawn without cooling the refrigerant below room temperature, enter 4 watts liquid line heat and supplement it with 1 watt average electrical antisweat heat.)

5-6

 EE-RM-93-801 COMMENT OR2

Under a DOE closed-door test, the refrigerator is operated under both conditions --

with the heaters on and with the heaters off. ERA can be run for both cases, and the 

results then averaged to simulate the test conditions. A simple approximation that can 

be employed is to run ERA once using one half of the heater power to represent an 

average condition. 

Since the heaters are normally installed immediately under the cabinet flanges and/or 

the mullion, a portion of the heat will leak into the cabinet. A typical fractional heat 

leak is 20% - 40% in the cabinet flange region, and 40% - 80% in the mullion region. 

Electrical heat applied in the mullion region will contribute to heat loads in both compartments. Because of the lower freezer temperature, more of the heat will likely flow 

to this compartment. 

5.11 Refrigerant line Anti-Sweat Heat 

Moisture control on the outside of the cabinet may be accomplished by the use of 

refrigerant lines in the area of the cabinet door flanges and the mullion. To simplify 

construction, a combination of refrigerant lines around the cabinet flanges and electrical heaters in the mullion region might also be used. 

Either a refrigerant vapor line (containing superheated vapor leaving the compressor) 

or a refrigerant liquid line (containing refrigerant leaving the condenser) may be used 

for this function. An advantage resulting from using a liquid line is that additional subcooling occurs prior to entering the capillary tube. 

In actual practice, the refrigerant entering a liquid line around the door flange or across 

the mullion may be in two-phase, with condensation completed within the liquid line. 

This may be desirable to limit the total refrigerant charge. ERA cannot model this situation, since it assumes completion of condensation in the condenser. The condenser 

subcooling should be set to zero when a liquid line is represented. 

The refrigerant enthalpy decrease from the use of a vapor or liquid line is dependent on 

the compressor run time. File CYCLE.OUT (the cycle analysis output file) should be 

reviewed to ensure that the specified cycle-average refrigerant line heating has not 

resulted in an excessive enthalpy drop (e.g., liquid subcooling to below ambient conditions). A warning message indicating excessive heat withdrawal from the liquid line 

will appear in the summary output me (ERA. OUT) whenever the refrigerant is cooled 

below room temperature. In this instance, the degree of refrigerant line heat should be 

reduced and replaced with an equivalent amount of electric anti-sweat heat. Since the 

electric anti-sweat heat is switchable, only one-half of the heat deficit should be 

entered as electric anti-sweat heat to represent average conditions for the DOE closed 

door test. 

(For example, assume that a 6 watt switchable anti-sweat heater is to replaced by a liquid line. Under the closed door test condition, the average condition is represented by 

3 watts electrical anti-sweat heat. Since the liquid line heat is not switchable, the 3 

watts electrical heat should be replaced by 6 watts liquid line heat. If only 4 watts of 

liquid line heat can be withdrawn without cooling the refrigerant below room temperature, enter 4 watts liquid line heat and supplement it with 1 watt average electrical antisweat heat.) 

5-6 
For the dual loop cycle, ERA assumes that the refrigerant line used for anti-sweat

and/or mullion heating is associated with the freezer loop.

5.12 Penetratic ' 1 ut

Heat inputs to the cabinet not associated with electrical sources can be specified as

"penetration heat inputs." One such heat source would be associated with through-thedoor ice service. In this instance, estimate of the additional heat leak due to the

presence of themechanism in the door can be made and included as a direct heat leak.

This menu can used for all heat inputs that cannot be directly associated with electrical energy usage.

 EE-RM-93-801 COMMENT OR2

For the dual loop cycle, ERA assumes that the refrigerant line used for anti-sweat 

and/or mullion heating is associated with the freezer loop. 

5.12 Penetration Heat Input 

Heat inputs to the cabinet not associated with electrical sources can be specified as 

"penetration heat inputs." One such heat source would be associated with through-thedoor ice service. In this instance, an estimate of the additional heat leak due to the 

presence of the mechanism in the door can be made and included as a direct heat leak. 

This menu can be used for all heat inputs that cannot be directly associated with electrical energy usage. 

5-7 
6.0 REFRIGERATION CYCLE INPUT DATA REFERENCE

6.1 Cycle Type

Four generic cycle types are described: 1) standard single evaporator and single compressor configuration; 2) Lorenz cycle; 3) dual loop cycle, and 4) dual evaporator

cycle.

The standard cycle (type 1) uses a baffle arrangement to mix the airs from the freezer

and fresh food cabinets before entering the evaporator. Two evaporators are employed

in the Lorenz cycle (type 2), with two interchangers used to promote additional subcooling of the refrigerant leaving the condenser. Two independent refrigeration loops

are used in the dual loop cycle (type 3) to cool the fresh food and freezer sections; each

loop has its own components.

The dual evaporator cycle (type 4) is similar to the Lorenz cycle, except that pure

refrigerants are normally used. The evaporators are in series, with little interchange

between the lines connecting the two evaporators and the liquid line leaving the condenser.

Pure refrigerants or refrigerant mixtures can be used with any of the cycles. Normally

a binary or ternary non-azeotropic mixture (NARM) is used with the Lorenz cycle, and

a pure refrigerant or a near-azeotropic mixture will be used with the standard single

evaporator cycle and with the dual loop cycle.

Not all of the cycle types apply to each of the cabinet designs. The table below illustrates the allowable cycles for the five cabinet designs:

Top Mount Bottom Side-by- Chest Upright

Mount Side Freezer Freezer

1: Single Evap

2: Lorenz

3: Dual Loop

4: Dual Evap

* * *

* * *

* * *

* *

A check of the consistency between the cabinet design and refrigeration cycle is made

prior to execution of an energy analysis.

Control of the evaporator loads in the Lorenz cycle or the dual evaporator cycle is difficult if fans are not used. Without some active control method, the cabinet temperatures

will change until the loads and evaporator capacities are in balance.

ERA provides six analysis options for the Lorenz and dual evaporator cycles: 0) no

control (allow an imbalance in the loads); 1) "mathematically" adjust the relative sizes

of the evaporators in the two compartments to obtain balanced loads; 2) adjust the fresh

food cabinet temperature to balance the loads; 3) adjust the freezer cabinet temperature

to balance the loads; 4) use a flow control valve to alternately direct the refrigerant to

one evaporator at a time; and 5) activate a solenoid valve to isolate one of the evaporators during part of the cycle, while allowing refrigerant to flow to the other evaporator

whenever the compressor operates.

6-1

 EE-RM-93-801 COMMENT OR2

6.0 REFRIGERATION CYCLE INPUT DATA REFERENCE 

6.1 Cycle Type 

Four generic cycle types are described: 1) standard single evaporator and single compressor configuration; 2) Lorenz cycle; 3) dual loop cycle, and 4) dual evaporator 

cycle. 

The standard cycle (type 1) uses a baffle arrangement to mix the airs from the freezer 

and fresh food cabinets before entering the evaporator. Two evaporators are employed 

in the Lorenz cycle (type 2), with two interchangers used to promote additional subcooling of the refrigerant leaving the condenser. Two independent refrigeration loops 

are used in the dual loop cycle (type 3) to cool the fresh food and freezer sections; each 

loop has its own components. 

The dual evaporator cycle (type 4) is similar to the Lorenz cycle, except that pure 

refrigerants are normally used. The evaporators are in series, with little interchange 

between the lines connecting the two evaporators and the liquid line leaving the condenser. 

Pure refrigerants or refrigerant mixtures can be used with any of the cycles. Normally 

a binary or ternary non-azeotropic mixture (NARM) is used with the Lorenz cycle, and 

a pure refrigerant or a near-azeotropic mixture will be used with the standard single 

evaporator cycle and with the dual loop cycle. 

Not all of the cycle types apply to each of the cabinet designs. The table below illustrates the allowable cycles for the five cabinet designs: 

Top Mount Bottom Side-by- Chest Upright 

Mount Side Freezer Freezer 

1 : Single Evap * * * * * 

2: Lorenz * * * 

3: Dual Loop * * * 

4: Dual Evap * * * 

A check of the consistency between the cabinet design and refrigeration cycle is made 

prior to execution of an energy analysis. 

Control of the evaporator loads in the Lorenz cycle or the dual evaporator cycle is difficult if fans are not used. Without some active control method, the cabinet temperatures 

will change until the loads and evaporator capacities are in balance. 

ERA provides six analysis options for the Lorenz and dual evaporator cycles: 0) no 

control (allow an imbalance in the loads); 1) "mathematically" adjust the relative sizes 

of the evaporators in the two compartments to obtain balanced loads; 2) adjust the fresh 

food cabinet temperature to balance the loads; 3) adjust the freezer cabinet temperature 

to balance the loads; 4) use a flow control valve to alternately direct the refrigerant to 

one evaporator at a time; and 5) activate a solenoid valve to isolate one of the evaporators during part of the cycle, while allowing refrigerant to flow to the other evaporator 

whenever the compressor operates. 

6-1 
Option 0 allows an imbalance to occur; it provides the user maximum control over the

analysis. Option 1 assumes that the total heat exchanger area is held constant; it is provided as a "design analysis" tool, to determine the necessary distribution of evaporator

areas to achieve balanced loads.

Options 2 and 3 result in a change in'the cabinet temperatures until the loads in each

cabinet are met by the individual evaporators.

Option 4 assumes that the flow control valve will sequentially divert the refrigerant to

one and then to the other of the two evaporators over a portion of the cycle. At any

given time in the cycle, only one evaporator receives refrigerant.

Option 5 assumes that the refrigerant flows through both evaporators during the major

portion of the cycle, and then diverts it past one of the evaporators during the remainder of the cycle. This can be accomplished by a solenoid valve (requiring some

energy use). In concept, the use of active fan control accomplishes the same objective;

deactivation of an evaporator fan during a portion of the cycle effectively removes the

fan-forced heat exchanger from the circuit by substantially reducing its heat transfer

capacity.

6.2 Refrigerants

Thirty-four refrigerants, whose data values are stored in a built-in data base, can be utilized as either pure refrigerants or as components of a mixture:

01 = R11 , 02 = R12, 03 = R13, 04 = R13B1,

05 = R K 06 = R22, 07 = R23, 08 = R1 13,

09 = R114, 10 = R1 42b, 11 = R152a, 12 = R216a,

13 = R125, 14 = R1 43a, 15 = R134a, 16 = R123,

17=RC318, 18=8134, 19=RC270, 20=R141b

21 = S02, 22 = R290, 23 = R600, 24 = R600a,

25 = R32, 26 = R1270, 27 = R124, 28 = 8115,

29 = CE216, 30 = El 25, 31 = R21, 32 = R143,

33=R218, 34=E134.

The refrigerant data menu references two function keys:

® <P4>: pressing this key results in display of the refrigerant properties and chemical

formulas. This may be valuable when selecting one refrigerant in favor of another

or when putting together candidate refrigerant mixtures.

® <F5>: pressing this key results in selection of default interaction parameters for

mixture pairs.

 EE-RM-93-801 COMMENT OR2

Option 0 allows an imbalance to occur; it provides the user maximum control over the 

analysis. Option 1 assumes that the total heat exchanger area is held constant; it is provided as a "design analysis" tool, to determine the necessary distribution of evaporator 

areas to achieve balanced loads. 

Options 2 and 3 result in a change in 'the cabinet temperatures until the loads in each 

cabinet are met by the individual evaporators. 

Option 4 assumes that the flow control valve will sequentially divert the refrigerant to 

one and then to the other of the two evaporators over a portion of the cycle. At any 

given time in the cycle, only one evaporator receives refrigerant. 

Option 5 assumes that the refrigerant flows through both evaporators during the major 

portion of the cycle, and then diverts it past one of the evaporators during the remainder of the cycle. This can be accomplished by a solenoid valve (requiring some 

energy use). In concept, the use of active fan control accomplishes the same objective; 

deactivation of an evaporator fan during a portion of the cycle effectively removes the 

fan-forced heat exchanger from the circuit by substantially reducing its heat transfer 

capacity. 

6.2 Refrigerants 

Thirty-four refrigerants, whose data values are stored in a built-in data base, can be utilized as either pure refrigerants or as components of a mixture: 

01=R11, 

05 = R14, 

09=R114, 

13=R125, 

17 = RC318, 

21 = S02, 

25 = R32, 

29= CE216, 

33 = R218, 

02 = R12, 

06= R22, 

10 = R142b, 

14 = R143a, 

18 = R134, 

22 = R290, 

26 = R1270, 

30 = E125, 

34= E134. 

03 = R13, 

07= R23, 

11 = R152a, 

15 = R134a, 

19= RC270, 

23= R600, 

27= R124, 

31 = R21, 

The refrigerant data menu references two function keys: 

04 = R13B1, 

08= R113, 

12 = R216a, 

16 = R123, 

20 = R141b 

24 = R600a, 

28=R115, 

32 = R143, 

• <F4>: pressing this key results in display of the refrigerant properties and chemical 

formulas. This may be valuable when selecting one refrigerant in favor of another 

or when putting together candidate refrigerant mixtures. 

• <F5>: pressing this key results in selection of default interaction parameters for 

mixture pairs. 

6-2 
6.3 Evaporator Design

The options for evaporator design are:

® type: fan forced or natural convection

® air flow pattern: cross-flow or counter-flow

® location of natural convection evaporator: in cabinet space, cold-plate (mounted on

the cabinet wall with one side facing the cabinet space), or directly behind the plastic liner.

The state of the refrigerant leaving the evaporator is determined by specification of. 1)

the superheat (C) at the exit of the evaporator, 2) the superheat (C) at the exit of the

interchanger between the evaporator and the compressor, or 3) the refrigerant quality

(less than 1.0) at the exit of the evaporator.

Specification of the evaporator exit condition (quality or superheat) avoids the necessity to model the flow control device (cap-tube). The superheat condition at the evaporator exit actually corresponds to a design goal. Normally, the selection of cap-tube

diameter and length will depend on the amount of superheat desired.

The heat transfer from a fan-forced evaporator will depend on the overall U-values in

the two-phase (evaporating) and single-phase (superheating) regimes. These values,

along with the refrigerant pressure drop, may be estimated by pressing the <F5> key

where noted in the evaporator menu and by inputting the requested heat exchanger

design information. For computational purposes, the heat exchanger is assumed to be

composed of circular tubes containing refrigerant in cross-flow with air. The face area

is determined from the number and spacing of the tubes in the transverse direction

(perpendicular to the air flow) and the tube length. The depth of the heat exchanger is

determined from the number and spacing of the tubes in the direction of the air flow.

A "deep" heat exchanger (more than 3 - 5 tubes deep) will behave like a counter-flow

design.

The user may also elect to enter an overall UA value for the evaporator. This may be

useful if a measured value is available. In this instance, ERA will assume a constant

U-value along the length of the heat exchanger.

If fan-forced, the evaporator may be considered as being in cross-flow or in counterflow. For a pure refrigerant, in the absence of a significant pressure drop, there is

essentially no difference between the two. However, with a refrigerant mixture that

results in a large temperature glide from the entrance to the exit of the evaporator, a

counter-flow design may be more efficient.

Solution of counter-flow heat transfer in the evaporator is more difficult and time consuming than cross-flow. Because of this, the following recommendations are made:

® select the cross-flow model unless a large temperature glide is expected. Set the

number of two-phase nodes equal to 1 in file CYCLE.TOL;

 EE-RM-93-801 COMMENT OR2

6.3 Evaporator Design 

The options for evaporator design are: 

" type: fan forced or natural convection 

.. air flow pattern: cross-flow or counter-flow 

o location of natural convection evaporator: in cabinet space, cold-plate (mounted on 

the cabinet wall with one side facing the cabinet space), or directly behind the plastic liner. 

The state of the refrigerant leaving the evaporator is determined by specification of: 1) 

the superheat (C) at the exit of the evaporator, 2) the superheat (C) at the exit of the 

interchanger between the evaporator and the compressor, or 3) the refrigerant quality 

(less than 1.0) at the exit of the evaporator. 

Specification of the evaporator exit condition (quality or superheat) avoids the necessity to model the flow control device (cap-tube). The superheat condition at the evaporator exit actually corresponds to a design goal. Normally, the selection of cap-tube 

diameter and length will depend on the amount of superheat desired. 

The heat transfer from a fan-forced evaporator will depend on the overall V-values in 

the two-phase (evaporating) and single-phase (superheating) regimes. These values, 

along with the refrigerant pressure drop, may be estimated by pressing the <F5> key 

where noted in the evaporator menu and by inputting the requested heat exchanger 

design information. For computational purposes, the heat exchanger is assumed to be 

composed of circular tubes containing refrigerant in cross-flow with air. The face area 

is determined from the number and spacing of the tubes in the transverse direction 

(perpendicular to the air flow) and the tube length. The depth of the heat exchanger is 

determined from the number and spacing of the tubes in the direction of the air flow. 

A "deep" heat exchanger (more than 3 - 5 tubes deep) will behave like a counter-flow 

design. 

The user may also elect to enter an overall VA value for the evaporator. This may be 

useful if a measured value is available. In this instance, ERA will assume a constant 

V-value along the length of the heat exchanger. 

If fan-forced, the evaporator may be considered as being in cross-flow or in counterflow. For a pure refrigerant, in the absence of a significant pressure drop, there is 

essentially no difference between the two. However, with a refrigerant mixture that 

results in a large temperature glide from the entrance to the exit of the evaporator, a 

counter-flow design may be more efficient. 

Solution of counter-flow heat transfer in the evaporator is more difficult and time consuming than cross-flow. Because of this, the following recommendations are made: 

" select the cross-flow model unless a large temperature glide is expected. Set the 

number of two-phase nodes equal to 1 in file CYCLE.TOL; 

6-3 
® explore the effects of counter-flow heat transfer if the temperature glide is larger

than 10 C. Set the number of nodes in the two-phase regime equal to 3 in file

CYCLE.TOL.

ERA uses a built-in natural convection model to establish the rate of natural convection

heat exchange between the evaporator plate and the cabinet air. Both radiative and free

convective heat transfer contribute to the net cooling accomplished by the evaporator.

A data menu requests information relating to the geometry of the evaporator to calculate the refrigerant pressure drop. Evaporation and sensible heat exchange will determine the two-phase and vapor velocities, which will in turn establish the refrigerant

pressure loss across the evaporator.

Three generic types of natural convection evaporators are modeled: 1) a flat plate

located within the cabinet space, 2) a cold-plate configuration, and 3) a behind-theliner configuration. If the evaporator is mounted behind the plastic liner, an additional

heat transfer resistance will be encountered, with a typical reduction in the cooling

capacity of 10 to 15 %. ERA assumes an added resistance equal to 2.5 mm polystyrene

(0.9 cal/hr-cm-C thermal conductivity).

A higher cooling capacity will be achieved from a plate of a given size that is located

within the cooled space since both sides of the plate will be available for heat convection and since the wall temperature will not be significantly affected by the plate. A

cold-plate evaporator or a behind-the-liner (mounted directly under the liner) type of

evaporator provides more internal volume , but will result in an increased refrigeration

load due to the cooling of the wall by the evaporator and a reduced foam thickness.

An ERA data menu requests information on the evaporator heat transfer area . This is

the total effective area available for heat transfer. For a free convective evaporator

located within the cabinet space, the total area of both sides of the evaporator should be

entered; for a cold-plate evaporator, only the area of the plate facing the cabinet space

should be entered.

ERA was not intended to substitute for a detailed heat exchanger design program. For

instance, if a roll-bond type free convective evaporator design is employed, some estimate of the effects of thermal bond resistance on the effective heat transfer area must

be made by the user. Normally, the level of uncertainty in the net effective area will

not have a large impact on the cycle performance calculations.

For the refrigerator/freezer configurations, a portion of a natural convection freezer

evaporator may be located in the mullion area between the two cabinet sections. The

evaporator thickness determines the volume occupied in the cabinet wall and/or mullion that would otherwise be occupied by insulation.

Specification of this geometry, which satisfies the definition of a cold-plate evaporator,

will be requested only for a natural convection design. A fan-forced freezer evaporator

of a refrigerator/freezer is always assumed to be located in the back of the freezer section (vertical orientation).

 EE-RM-93-801 COMMENT OR2

" explore the effects of counter-flow heat transfer if the temperature glide is larger 

than 10 C. Set the number of nodes in the two-phase regime equal to 3 in me 

CYCLE.TOL. 

ERA uses a built-in natural convection model to establish the rate of natural convection 

heat exchange between the evaporator plate and the cabinet air. Both radiative and free 

convective heat transfer contribute to the net cooling accomplished by the evaporator. 

A data menu requests information relating to the geometry of the evaporator to calculate the refrigerant pressure drop. Evaporation and sensible heat exchange will determine the two-phase and vapor velocities, which will in turn establish the refrigerant 

pressure loss across the evaporator. 

Three generic types of natural convection evaporators are modeled: 1) a flat plate 

located within the cabinet space, 2) a cold-plate configuration, and 3) a behind-theliner configuration. If the evaporator is mounted behind the plastic liner, an additional 

heat transfer resistance will be encountered, with a typical reduction in the cooling 

capacity of 10 to 15%. ERA assumes an added resistance equal to 2.5 mm polystyrene 

(0.9 cal/hr-cm-C thermal conductivity). 

A higher cooling capacity will be achieved from a plate of a given size that is located 

within the cooled space since both sides of the plate will be available for heat convection and since the wall temperature will not be significantly affected by the plate. A 

cold-plate evaporator or a behind-the-liner (mounted directly under the liner) type of 

evaporator provides more internal volume, but will result in an increased refrigeration 

load due to the cooling of the wall by the evaporator and a reduced foam thickness. 

An ERA data menu requests information on the evaporator heat transfer area. This is 

the total effective area available for heat transfer. For a free convective evaporator 

located within the cabinet space, the total area of both sides of the evaporator should be 

entered; for a cold-plate evaporator, only the area of the plate facing the cabinet space 

should be entered. 

ERA was not intended to substitute for a detailed heat exchanger design program. For 

instance, if a roll-bond type free convective evaporator design is employed, some estimate of the effects of thermal bond resistance on the effective heat transfer area must 

be made by the user. Normally, the level of uncertainty in the net effective area will 

not have a large impact on the cycle performance calculations. 

For the refrigerator/freezer configurations, a portion of a natural convection freezer 

evaporator may be located in the mullion area between the two cabinet sections. The 

evaporator thickness determines the volume occupied in the cabinet wall and/or mullion that would otherwise be occupied by insulation. 

Specification of this geometry, which satisfies the definition of a cold-plate evaporator, 

will be requested only for a natural convection design. A fan-forced freezer evaporator 

of a refrigerator/freezer is always assumed to be located in the back of the freezer section (vertical orientation). 

6-4 
6.4 Condenser Design

As with the evaporator, the condenser may employ a fan-forced or natural convection

design; if fan-forced it may be cross-flow or counter flow. Liquid subcooling is specified as a design goal (this replaces need for a mass inventory balance about the

refrigerator loop to calculate the subs ling).

Hot-wall condensers (tubes attached to the underside of the outer skin of the cabinet)

may be specified for any of the refrigerator/freezer or freezer designs other than the

side-by-side unit. Free convection (static) condensers may be used for all designs.

Fan-forced condensers are assumed to be located under the cabinet. The increase in air

temperature under the cabinet from condenser (and compressor shell) heat losses must

be estimated andspecified by the program user.

It is assumed that most of a static or fan-forced heat exchanger has flat or wire fins to

increase the effective heat transfer area. The condenser fins provide extended heat

transfer area to increase the overall effectiveness of the heat exchanger. Wire fins will

act to break up the air flow (promote turbulence) as well as to provide additional heat

transfer area.

The issues relating to cross-flow versus counter-flow heat transfer are essentially the

same as discussed above for the evaporator.

Heat losses will occur along the line from the compressor discharge port to the condenser inlet. These may be uncontrolled, as in a bare or partially insulated line, or may

result from cabinet flange heating. A hot gas loop used for cabinet flange heating will

normally lose a fraction of its heat to both of the cabinet sections as well as to the environment.

6.5 Calculation Assist Menus for Evaporator and Condenser UA Values

If the analysis involves alternate refrigerants or various compressor designs, use of the

calculation assist menus to calculate the heat exchanger UAs is recommended. The

UA analysis algorithms take into consideration the influence of refrigerant thermopyhisical properties and the refrigerant mass flow rate on the refrigerant-side heat transfer

(see Appendix B).

It is noted that the calculation of UA values is done within the data input program,

rather than during the cycle simulation. The required inputs for the refrigerant mass

flow rate and evaporator inlet quality may not be known until the cycle analysis has

been completed. Once the cycle analysis has been run, the output file (CYCLE.OUT)

should be reviewed to ensure that the calculated mass flow rate and inlet quality agree

with those used to determine the heat exchanger UAs. If the values differ significantly,

the analysis should be rerun using updated values for these parameters in the heat

exchanger calculation assist menus.

6.6 Compressor Design

Separate models are provided for a reciprocating compressor and a rotary compressor.

The models differ in the treatment of suction gas heating within the shell and in the

volumetric efficiency algorithm (see Appendix B).

6-5

 EE-RM-93-801 COMMENT OR2

6.4 Condenser Design 

As with the evaporator, the condenser may employ a fan-forced or natural convection 

design; if fan-forced it may be cross-flow or counter flow. Liquid subcooling is specified as a design goal (this replaces the need for a mass inventory balance about the 

refrigerator loop to calculate the subcooling). 

Hot-wall condensers (tubes attached to the underside of the outer skin of the cabinet) 

may be specified for any of the refrigerator/freezer or freezer designs other than the 

side-by-side unit. Free convection (static) condensers may be used for all designs. 

Fan-forced condensers are assumed to be located under the cabinet. The increase in air 

temperature under the cabinet from condenser (and compressor shell) heat losses must 

be estimated and specified by the program user. 

It is assumed that most of a static or fan-forced heat exchanger has flat or wire fins to 

increase the effective heat transfer area. The condenser fins provide extended heat 

transfer area to increase the overall effectiveness of the heat exchanger. Wire fins will 

act to break up the air flow (promote turbulence) as well as to provide additional heat 

transfer area. 

The issues relating to cross-flow versus counter-flow heat transfer are essentially the 

same as discussed above for the evaporator. 

Heat losses will occur along the line from the compressor discharge port to the condenser inlet. These may be uncontrolled, as in a bare or partially insulated line, or may 

result from cabinet flange heating. A hot gas loop used for cabinet flange heating will 

normally lose a fraction of its heat to both of the cabinet sections as well as to the environment. 

6.5 Calculation Assist Menus for Evaporator and Condenser UA Values 

If the analysis involves alternate refrigerants or various compressor designs, use of the 

calculation assist menus to calculate the heat exchanger UAs is recommended. The 

U A analysis algorithms take into consideration the influence of refrigerant thermopyhisical properties and the refrigerant mass flow rate on the refrigerant-side heat transfer 

(see Appendix B). 

It is noted that the calculation of U A values is done within the data input program, 

rather than during the cycle simulation. The required inputs for the refrigerant mass 

flow rate and evaporator inlet quality may not be known until the cycle analysis has 

been completed. Once the cycle analysis has been run, the output file (CYCLE. OUT) 

should be reviewed to ensure that the calculated mass flow rate and inlet quality agree 

with those used to determine the heat exchanger UAs. If the values differ significantly, 

the analysis should be rerun using updated values for these parameters in the heat 

exchanger calculation assist menus. 

6.6 Compressor Design 

Separate models are provided for a reciprocating compressor and a rotary compressor. 

The models differ in the treatment of suction gas heating within the shell and in the 

volumetric efficiency algorithm (see Appendix B). 

6-5 
A compressor map based model, an EER and capacity model, or an efficiency model

may be selected to describe compressor performance.

The compressor map approach utilizes a table of performance data (supplied by the

user) for the specific refrigerant. A sample performance map table (a file, which may

have any valid 8 character name with the extension TAE) is shown below:

Sample Compressor Map Data Table (*.TAB)

Name of Compressor

12.3 Mass flow at standard rating point (lb/hr or k )

3 Number of data points along evaporating temperature axis

3 Number of data points along condensing temperature axis

1 Compressor type (1 - reciprocating; 2 - rotary)

1 Units for capacity, temperature data, and mass flow

(1 - btu/hr, deg F, lb/hr; 2 - kcal/hr, deg C, kg/hr)

Capacity Data

Cond Temp Evaporating Temperature

-30 -10 10

110 441 837 1428

120 419 794 1384

130 397 762 1340

Cond Temp

Compressor Power, Watts

Evaporating Temperature

-30 -10 10

110 107 160 210

120 108 160 214

130 108 162 218

The EER and capacity model requests a single calorimeter data point at the standard

test condition with CFC-12 refrigerant. Correlations for the suction gas superheat and

shell heat loss (discussed in APPENDIX B) are use to determine values for the

clearance volume and the compression efficiency. A correction for the thermodynamic

characteristics of the circulating refrigerant is made.

 EE-RM-93-801 COMMENT OR2

A compressor map based model, an EER and capacity model, or an efficiency model 

may be selected to describe compressor performance. 

The compressor map approach utilizes a table of performance data (supplied by the 

user) for the specific refrigerant. A sample performance map table (a me, which may 

have any valid 8 character name with the extension .TAB) is shown below: 

Sample Compressor Map Data Table (* .TAB) 

Name of Compressor 

12.3 Mass flow at standard rating point (lb/hr or kg/hr) 

3 Number of data points along evaporating temperature axis 

3 Number of data points along condensing temperature axis 

1 Compressor type (1 - reciprocating; 2 - rotary) 

1 Units for capacity, temperature data, and mass flow 

(1 - btu/hr, deg F, Ib/hr; 2 - kcal/hr, deg C, kg/hr) 

Capacity Data 

Cond Temp Evaporating Temperature 

-30 -10 10 

110 441 837 1428 

120 419 794 1384 

130 397 762 1340 

Compressor Power, Watts 

Cond Temp Evaporating Temperature 

-30 -10 10 

110 107 160 210 

120 108 160 214 

130 108 162 218 

The EER and capacity model requests a single calorimeter data point at the standard 

test condition with CFC-12 refrigerant. Correlations for the suction gas superheat and 

shell heat loss (discussed in APPENDIX B) are use to determine values for the 

clearance volume and the compression efficiency. A correction for the thermodynamic 

characteristics of the circulating refrigerant is made. 

6-6 
To extend the performance data to other conditions and other refrigerants , it is necessary to know the conditions under which the data were obtained. These parameters are

the displacement and the method of compressor can cooling during the calorimeter test.

The efficiency model requests information concerning the compressor components and

the piston displacement. Approximate values for the shell losses and internal tubing

losses must be supplied as well. Specific instructions for defining these data are pro

-vided in the Help menu for the physically based model.

The efficiency model may only be used for a reciprocating compressor. However, the

analysis approach allows the evaluation of v ariable speed drive options, an investigation of the effects of motor efficiency on perfo rmance, and the direct specification of

size as measured by the displacement.

The cycle model (ERACYC) calculates the mass flow of the refrigerant pumped by the

compressor, based on the estimated conditions at the suction port of the pump and the

volumetric efficiency. Suction gas superheat at the suction port is determined from the

heat exchange internal to the compressor can. The can loss parameter , which defines

the rate of shell cooling , directly affects the internal heating.

Additional details about the input data requirements for the compressor models are provided by the Help menu (press <Fl> key). Appendix B summarizes the algorithms

employed for the various models.

6.7 Cycling Losses

Cycling losses are caused by thermal transient effects in the evaporator and condenser

as well as by migration of refrigerant from the condenser to the evaporator during the

off-cycle.

Some system designs with a rotary compressor employ a shut-off valve between the

condenser and evaporator to reduce the off-cycle refrigerant flow. In those designs, it

is may be advantageous to maintain tight temperature control in the cabinets to force

more frequent cycling, thereby maintaining a higher average temperature evaporator

and a lower average temperature condenser. For the standard design, without a shutoff valve, it will be advantageous to minimize the compressor stop/starts, thereby minimizing the losses associated with refrigerant migration (a typical cycle time might be

20 minutes on and 30 minutes off).

ERA provides two options relative to cycling losses: 1) ignore losses on compressor

energy use; or 2) adjust the calculated steady-state compressor power for losses using

an algorithm based on the cycling rate. At a cycling rate of 2 cycles per hour, the estimated cycling loss would be 2.2%. The cycling model is described in Appendix E.

There are indications that a shut-off valve can actually increase the cycle-average compressor performance above the steady-state level [6]. At a cycling rate of 2 cpm, the

"cycle loss model" predicts an efficiency gain of about 3%. Hence the overall

efficiency increase from using a shut-off valve (with a rotary compressor) may be

about 5%. This is discussed in further detail in Appendix B.

 EE-RM-93-801 COMMENT OR2

To extend the performance data to other conditions and other refrigerants, it is necessary to know the conditions under which the data were obtained. These parameters are 

the displacement and the method of compressor can cooling during the calorimeter test. 

The efficiency model requests information concerning the compressor components and 

the piston displacement. Approximate values for the shell losses and internal tubing 

losses must be supplied as well. Specific instructions for defining these data are provided in the Help menu for the physically based model. 

The efficiency model may only be used for a reciprocating compressor. However, the 

analysis approach allows the evaluation of variable speed drive options, an investigation of the effects of motor efficiency on performance, and the direct specification of 

size as measured by the displacement 

The cycle model (ERACYC) calculates the mass flow of the refrigerant pumped by the 

compressor, based on the estimated conditions at the suction port of the pump and the 

volumetric efficiency. Suction gas superheat at the suction port is determined from the 

heat exchange internal to the compressor can. The can loss parameter, which defines 

the rate of shell cooling, directly affects the internal heating. 

Additional details about the input data requirements for the compressor models are provided by the Help menu (press <P1> key). Appendix B summarizes the algorithms 

employed for the various models. 

6.7 Cycling Losses 

Cycling losses are caused by thermal transient effects in the evaporator and condenser 

as well as by migration of refrigerant from the condenser to the evaporator during the 

off-cycle. 

Some system designs with a rotary compressor employ a shut-off valve between the 

condenser and evaporator to reduce the off-cycle refrigerant flow. In those designs, it 

is may be advantageous to maintain tight temperature control in the cabinets to force 

more frequent cycling, thereby maintaining a higher average temperature evaporator 

and a lower average temperature condenser. For the standard design, without a shutoff valve, it will be advantageous to minimize the compressor stop/starts, thereby minimizing the losses associated with refrigerant migration (a typical cycle time might be 

20 minutes on and 30 minutes off). 

ERA provides two options relative to cycling losses: 1) ignore losses on compressor 

energy use; or 2) adjust the calculated steady-state compressor power for losses using 

an algorithm based on the cycling rate. At a cycling rate of 2 cycles per hour, the estimated cycling loss would be 2.2%. The cycling model is described in Appendix B. 

There are indications that a shut-off valve can actually increase the cycle-average compressor performance above the steady-state level [6]. At a cycling rate of 2 cpm, the 

"cycle loss model" predicts an efficiency gain of about 3%. Hence the overall 

efficiency increase from using a shut-off valve (with a rotary compressor) may be 

about 5%. This is discussed in further detail in Appendix B. 

6-7 
6.8 Interchangers

The line leaving the condenser is normally in thermal contact with the line leaving the

evaporator on its way to the compressor. This line contact provides liquid subcooling

at the expense of additional superheat in the suction line. ERA requests information

relating to the effectiveness of the interchanger (and of the interchanger between the

fresh food and freezer evaporators in the Lorenz cycle). Additional heat transfer may

also take place in the refrigeration line between the interchanger and compressor shell

inlet (normally heating of the refrigerant by the room air).

 EE-RM-93-801 COMMENT OR2

6.8 Interchangers 

The line leaving the condenser is normally in thermal contact with the line leaving the 

evaporator on its way to the compressor. This line contact provides liquid subcooling 

at the expense of additional superheat in the suction line. ERA requests information 

relating to the effectiveness of the interchanger (and of the interchanger between the 

fresh food and freezer evaporators in the Lorenz cycle). Additional heat transfer may 

also take place in the refrigeration line between the interchanger and compressor shell 

inlet (normally heating of the refrigerant by the room air). 

6-8 
7.0 SAMPLE PROBLEM

7.1 Multiple Pathway "Model D" Prototype Design

Use of the ERA model for loads and energy use analysis is illustrated for the Multiple

Pathway Model D refrigerator [5]. This design is intended to be a composite of design

features for a prototype 18 cu-ft top-mount refrigerator/freezer that would meet the

1993 energy standard by a comfortable margin using off-the-shelf technology. The

specific design approach adopted provides an outer shell 76 cm (30 inches) wide, amenable to thicker wall insulation without exceeding normal width constraints. Figures

7-1 through 7-3 illustrate design features (where the dimensions are in units of inches

to facilitate comparison with typical designs of current model refrigerators). The overall characteristics of the prototype model are summarized in Table 7-1, where data are

shown in both English and metric units.

Most of the parameters in Table 7-1 are well defined (e.g., dimensions, temperatures,

compressor characteristics). Others are either estimates (e.g., temperature under fresh

food cabinet) or "typical" (e.g., gasket heat loss). The model user can easily adopt

alternate assumptions and investigate the effects of uncertainties in these parameters on

the predicted cabinet loads and energy use.

7.2 Input Data Menus (MODEL _ .I P)

The data file for the sample problem is MODEL_D.ERA.

Figure 7-4 shows the input data menus for the sample problem. Individual data menus

and values are shown for each data block defining the sample problem, exactly as displayed during the input data processing phase of the analysis. The specific menus are

consistent with the type of cabinet (top-mount, refrigerator/freezer) and the type of

refrigerator cycle (single evaporator, fan-forced). Only data relevant to the particular

problem are shown.

This data is not normally output for each analysis. However, the user may choose to

create and save the menu data as part of the documentation for an analysis. The output

(MODEL_D.INP) is obtained from the Main Menu of ERA using the "Print Data

Menus" or "Write Data Menus to a File" function.

7.3 Intermediate Cabinet Loads Data File (C INET.DAT)

The first executable module of ERA (MENU.EXE) creates an intermediate data file

which serves as the input to the cabinet loads program (see Figure 3-1 for the relationship between the executable program modules and the data transfers). As illustrated in

Figure 7-5, the structure of the intermediate file is designed to facilitate interpretation

by the program user.

Because of the overall structure of ERA, the intermediate data file is not meant to be

modified. Program module CAB.EXE will read the file, whose structure will be different for each cabinet type, and perform the cabinet loads analysis. The user may choose

to print out this file for documentation purposes.

 EE-RM-93-801 COMMENT OR2

7.0 SAMPLE PROBLEM 

7.1 Multiple Pathway "Model D" Prototype Design 

Use of the ERA model for loads and energy use analysis is illustrated for the Multiple 

Pathway Model D refrigerator [5]. This design is intended to be a composite of design 

features for a prototype 18 cu-ft top-mount refrigerator/freezer that would meet the 

1993 energy standard by a comfortable margin using off-the-shelf technology. The 

specific design approach adopted provides an outer shell 76 cm (30 inches) wide, amenable to thicker wall insulation without exceeding normal width constraints. Figures 

7-1 through 7-3 illustrate design features (where the dimensions are in units of inches 

to facilitate comparison with typical designs of current model refrigerators). The overall characteristics of the prototype model are summarized in Table 7-1, where data are 

shown in both English and metric units. 

Most of the parameters in Table 7-1 are well defined (e.g., dimensions, temperatures, 

compressor characteristics). Others are either estimates (e.g., temperature under fresh 

food cabinet) or "typical" (e.g., gasket heat loss). The model user can easily adopt 

alternate assumptions and investigate the effects of uncertainties in these parameters on 

the predicted cabinet loads and energy use. 

7.2 Input Data Menus (MODEL_D.lNP) 

The data file for the sample problem is MODEL_D.ERA. 

Figure 7-4 shows the input data menus for the sample problem. Individual data menus 

and values are shown for each data block defining the sample problem, exactly as displayed during the input data processing phase of the analysis. The specific menus are 

consistent with the type of cabinet (top-mount, refrigerator/freezer) and the type of 

refrigerator cycle (single evaporator, fan-forced). Only data relevant to the particular 

problem are shown. 

This data is not normally output for each analysis. However, the user may choose to 

create and save the menu data as part of the documentation for an analysis. The output 

(MODEL_D.INP) is obtained from the Main Menu of ERA using the "Print Data 

Menus" or "Write Data Menus to a File" function. 

7.3 Intermediate Cabinet Loads Data File (CABINET.DAT) 

The first executable module of ERA (MENU.EXE) creates an intermediate data file 

which serves as the input to the cabinet loads program (see Figure 3-1 for the relationship between the executable program modules and the data transfers). As illustrated in 

Figure 7-5, the structure of the intermediate file is designed to facilitate interpretation 

by the program user. 

Because of the overall structure of ERA, the intermediate data file is not meant to be 

modified. Program module CAB.EXE will read the file, whose structure will be different for each cabinet type, and perform the cabinet loads analysis. The user may choose 

to print out this file for documentation purposes. 

7-1 
Table 7-1. Characteristics cf ®®_

i scio i®nz

Height

Prototype Refrigerator

61.50 in 156.21 cm

Width

Depth

30.01 in 76.20 cm

28.25 in 71.76 cm

Freezer Volume (approx.)

Fresh Food Volume (approx.)

4.60 cu-ft

13.40 cu-ft

130.30 liter

379.50 liter

Door Thickness

Freezer Wall Thickness

Fresh Food Thickness

1.75 in

2.38 in

1.88 in

4.45 cm

6.03 cm

4.76 cm

Gasket Heat Loss

Air Temperatures

0. Btu/hr-in-F 0.0900 w/m-C

Room

Freezer

Fresh Food

Under Cabinet/Condenser

90.0 F

5.0 F

38.0 F

100.0 F

32.2 C

-15.0 C

3.3 C

37.8 C

Auxiliary Energy (Cycle Average)

Door Flange Heater Liquid Line Liquid Line

Mullion Heater 2.75 w 2.75 w

Defrost Heat 2.81 w 2.81 w

Defrost Timer 1.50 w 1.50 w

Refrigeration Cycle Single Evaporator

Com pressor

Type Reciprocating

EER 5.28

Capacity 865 Btuh 218 kcal/hr

Evaporator

Area (Air side) 25.2 ft2 2.34 m2

Air Flow 50.0 cfm 23.6 liter/sec.

Fan Energy 9.4 w 9.4 w

Condenser

Area (Air side) 9.15 ft2 0.85 m2

Air Flow 90.0 cfm 42.48 liter/sec.

Fan Energy 12.0 w 12.0 w

 EE-RM-93-801 COMMENT OR2

Table 7-1. Characteristics of Model D Prototype Refrigerator 

Dimensions 

Height 

Width 

Depth 

Freezer Volume (approx.) 

Fresh Food Volume (approx.) 

Door Thickness 

Freezer Wall Thickness 

Fresh Food Thickness 

Gasket Heat Loss 

Air Temperatures 

Room 

Freezer 

Fresh Food 

Under Cabinet/Condenser 

Auxiliary Energy (Cycle Average) 

Door Flange Heater 

Mullion Heater 

Defrost Heat 

Defrost Timer 

Refrigeration Cycle 

Com pressor 

Type 

EER 

Capacity 

Evaporator 

Area (Air side) 

Airflow 

Fan Energy 

Condenser 

Area (Air side) 

Airflow 

Fan Energy 

61.50 in 

30.01 in 

28.25 in 

4.60 cu-ft 

13.40 eu-ft 

1.75 in 

2.38 in 

1.88 in 

0.004 Btu/hr-in-F 

90.0F 

5.0F 

38.0F 

100.0 F 

Liquid Line 

2.75 w 

2.81 w 

1.50w 

156.21 em 

76.20 em 

71.76 cm 

130.30 liter 

379.50 liter 

4.45 em 

6.03 cm 

4.76 em 

0.0900 w/m-C 

32.2C 

-15.0 C 

3.3 C 

37.8 C 

Liquid Line 

2.75 w 

2.81 w 

1.50w 

Single Evaporator 

Reciprocating 

5.28 

865 Btuh 218 kcallhr 

25.2 fr 

50.0 cfm 

9.4 w 

9.15 fr 

9O.0cfm 

12.0w 

7-2 

2.34 m2 

23.6 liter/sec. 

9.4 w 

0.85 m2 

42.48 liter/sec. 

12.0w 
28.25

26.00

k---.625 r- 2.375

19.00

.75 1

Cabinet Width

30.00"

66.00

24.625

39.00

41.75

2.00

T

4.50

A1.875 -->

FIGURE 7-1

VERTICAL SECTI O N - 18 FT3 PROTOTYPE M O DEL

(APPR O X. 1/8 SCALE)

Evaporator

3 x 8 x 22

7-3

 EE-RM-93-801 COMMENT OR2

r

-------- 28.

25 --------:1 II-E--I< -26.00------?l 

~ I<-.625 2.375 

~--- ----~--

1.75 i-E------ 20.875---+---»\ 

19.00 15.625 

"L 

Cabinet Width 

30.00" 

2.50 

66.00 

~-------+-24.625 --------7:;.1 

39.00 

1.875 

41.75 

4.50 

t 

FIGURE 7-1 

VERTICAL SECTION - 18 FT3 PROTOTYPE MODEL 

(APPROX. 1/8 SCALE) 

7-3 

Evaporator 

3x8x22 
30.00

2.375

18.125

2.375

---------------------- ;

2.375

1.875

56.00

s.oo

Evap. Fan - 4.5" dia

Orifice - 4.75" I.D.

Evaporator

3 x 8 x 22

Finned Lgth.

Cabinet Flange

1.00 - 3 Sides

Condenser Air

Inlet/Exhaust

Approx 24.50 x 2.75

FIGURE 7-2

FRONT VIEW, CABINET ONLY - 18 FT3 PROTOTYPE MODEL

(APPROX. 1/8 SCALE)

7-4

 EE-RM-93-801 COMMENT OR2

r

E ----30.00-------:;.;"'1 

-r 2

.

375 

--.------,r--

66.00 

~ ~2.375 

/ " I \ 

I 

Evap. Fan - 4.5" dia 

___ ---., Orifice - 4.75" 1.0. 

c::...,- --- \ I 

\ I 

" '" r~:-------------------~~I 

Evaporator 

3 x 8 x 22 

Finned Lgth. 

r-z---- I -- , , I -- , , I -- , , 

I 

I 

, , , --

, 

- ~ - -- I , I , , --- I , , -- ~ 

, --I " 

18.125 I - - _ ~ ~ , I 

~/~~ 2.375 OJ 

1.875~ <E- _,.. IE- Cabinet Flange 

1.00 - 3 Sides 

~------------------------------~/ 

~ Conde nser Air 

/ " Inlet! Exhaust I Approx 2 4.50 x 2.75 

r----\ -z-----

6r 

_L...J '--

FIGURE 7-2 

FRONT VIEW, CABINET ONLY - 18 FT3 PROTOTYPE MODEL 

(APPROX. 1/8 SCALE) 

7-4 
r- Inlet

> Outlet (to Accumulator)

1.

8.00

2

3.00

Air Flow

22.00" [111 Fins Spaced .20]

24.50

EVAPORATOR DETAIL

Fin & Tube: 24 Tubes - 5/16 OD x .028 Wall Al.

111 Fins - 3 x 8 x Mfrs. Recommended Thickness

Note: Circuitry shown is compatible with Peerless mfg. techniques. Other circuitry possible.

Defrost Drain Tray

Rests Here

----------

U Gas ..

In (Rear)

Machine Compartment Divider Panel Located Here

i C^ x

J

0----0----0----0----0

D----Q----O----O !G "- I

Q---- Q---- O ----0-- 2.75

---U

23.50

CONDENSER DETAIL (WIRE & TUBE - FAN COOLED)

Specs: Tubing-1/40D x .028 Wall Steel

Serpentine - 36 Tubes - 16" Overall Width

Wires -.046 Dia. - 60 per Side (120 total) - Spaced .200"

FIGURE 7-3

HEAT EXCHANGER DESIGNS

I

Tubes marked "X"

are not welded.

7-5

 EE-RM-93-801 COMMENT OR2

t Inlet 

~ __ ----,- Outlet (to Accumulator) 

8.00 

~ 3.00--l L UAirFlow 

22.00" [111 Fins Spaced .20J ---------?j 

I-E-------- 24.50 -----------~ 

EVAPORATOR DETAIL 

Fin & Tube: 24 Tubes - 5/16 00 x .028 Wall AI. 

111 Fins - 3 x 8 x Mfrs. Recommended Thickness 

Note: Circuitry shown is compatible with Peerless mfg. techniques. Other circuitry possible. 

(

Machine Compartment Divider Panel Located Here 

Defrost Drain Tray 

Rests Here ~ ; (X 

'\ - - - - ~ - - - - - 7 "C)""-----;-C)=---~--C)=------C)= X t 

Hot Gas.../'\ \ .Jf C)----C)----C)----C)--D~ 2.75 In (Rear) - If '- - - - - - - - - , 

C)-... C) .... C) .... C)---.C) .. : C)----C)----C)----C)-- i 

~IE ----- 23.50 _L_x -----7-1>1 

CONDENSER DETAIL (WIRE & TUBE - FAN COOLED) 

Specs: Tubing - 1/400 x .028 Wall Steel 

Serpentine - 36 Tubes - 16" Overall Width 

Wires - .046 Dia. - 60 per Side (120 total) - Spaced .200" 

FIGURE 7-3 

HEAT EXCHANGER DESIGNS 

7-5 

Tubes marked "X" 

are not welded. 
Multiple Pathways Baseline Protot : Model -D (Top-Mount)

CABINET TYPE AND OVERALL DIMENSIONS

Configuration Type (1-5) 1

Cabinet Height (c) 156.21

Cabinet Width (cm) 76.20

Cabinet Depth* (cm) 71.75

Gasket Width (cm) 1.59

Door Edge Thickness (cm) 4.45

* including door and gasket

CABINET WEDGE DIMENSIONS

Freezer Section

Wedge Depth (cm)

Flange Width (cm)

Fresh Food section

Wedge Depth (cm)

Flange Width (cm)

7.62

3.87

7.62

3.87

REFRIGERATED VOLUME

Freezer Section

Volume Used by Evap (L) 21.01

Vol Used by Food (L) .00

volume Used by Shelf (L) .00

Net Storage Volume (L) 135.07

Fresh Food Section

Vol Used by Evap (L) .00

Volume Used by Food (L) .00

Volume Used by Shelf (L) 18.34

Net Storage Volume (L) 394.74

COMPRESSOR COMPARTMENT DIMENSIONS

Top Depth (cm) .00

Bottom Depth (cm) .00

Height (cm) .00

FREEZER INSULATION THICKNESS

Top Wall Thickness (cm) 6.03

Side Wall Thickness (cm) 6.03

Back Wall Thickness (cm) 6.03

Door Thickness (cm) 4.45

Figure 7-4. Input Data Menus

7-6

 EE-RM-93-801 COMMENT OR2

Multiple Pathways Baseline Prototype: Model_D (Top-Mount) 

CABINET TYPE AND OVERALL DIMENSIONS 

Configuration Type (1-5) 

Cabinet Height (em) 

Cabinet width (em) 

Cabinet Depth 1< (em) 

Gasket Width 

Door Edge Thickness 

(em) 

(em) 

1< including door and gasket 

CABINET WEDGE DIMENSIONS 

Freezer Section 

Wedge Depth (em) 

Flange Width (em) 

Fresh Food section 

Wedge Depth (em) 

Flange Width (em) 

REFRIGERATED VOLUME 

Freezer Section 

volume Used by Evap (L) 

Volume Used by Food (L) 

Volume Used by Shelf (L) 

Net Storage Volume (L) 

Fresh Food Section 

volume Used by Evap (L) 

Volume Used by Food (L) 

Volume Used by Shelf (L) 

Net Storage Volume (L) 

COMPRESSOR COMPARTMENT DIMENSIONS 

TOp Depth (em) 

Bottom Depth (em) 

Height (em) 

FREEZER INSULATION THICKNESS 

Top Wall Thickness (em) 

Side Wall Thickness (em) 

Back Wall Thickness (em) 

Door Thickness (em) 

Figure 7-4. Input Data Menus 

7-6 

1 

156.21 

76.20 

71. 75 

1.59 

4.45 

7.62 

3.87 

7.62 

3.87 

21.01 

.00 

.00 

135.07 

.00 

.00 

18.34 

394.74 

.00 

.00 

.00 

6.03 

6.03 

6.03 

4.45 
FREEZER INSULATION RESISTIVITIES

Resistivity ( m2-C/W-cm)

Top Wall .555

Side Wall .555

Back Wall .555

Wedge .555

Door .555

FRESH FOOD INSULATION THICKNESS

Side Wall Thickness ( cm) 4.76

Back Wall Thickness (cm) 4.76

Bottom Wall Thickness ( cm) 5.08

Door Thickness ( cm) 4.45

FRESH FOOD INSULATION RESISTIVITIES

Resistivity ( m2-C/W-cm)

Side Wall .555

Back Wall .555

Bottom .555

Door .555

Wedge .555

MULLION

Distance to Top ( cm) 45.72

Thickness ( cm) 6.35

Resistivity ( m2-C/W-cm) .31

AIR AND CABINET TEMPERATURES

Room Air ( C) 32.22

Freezer Section (C) -15.00

Fresh Food Section ( C) 3.33

Air Under Cabinet ( C) 37.80

Air Entering Condenser (C) 35.00

DOOR OPENING SCHEDULE

Room Relative Humidity ( %) 50.00

Fresh Food Door - #/Hr .00

Fresh Food Door - Sec Open 15.00

Freezer Door - #/Hr .00

Freezer Door - Sec Open 20.00

Manual Defrost ( O=N, 1=Y) 0

GASKET HEAT LEAKS ( W/M-100C)

Fresh Food Section 9.00

Freezer Section 9.00

Figure 7-4. Input Data Menus (continued)

7-7

 EE-RM-93-801 COMMENT OR2

FREEZER INSULATION RESISTIVITIES 

Resistivity (m2-C/W-em) 

Top Wall 

Side Wall 

Back Wall 

Door 

Wedge 

FRESH FOOD INSULATION 

Side Wall Thickness 

Back Wall Thickness 

Bottom Wall Thickness 

Door Thickness 

THICKNESS 

(em) 

(em) 

(em) 

(em) 

FRESH FOOD INSULATION RESISTIVITIES 

Resistivity (m2-C/W-em) 

.555 

.555 

.555 

.555 

.555 

4.76 

4.76 

5.08 

4.45 

Side Wall .555 

Back Wall .555 

Bottom .555 

Door .555 

Wedge .555 

MULLION 

Distance to Top (em) 

Thickness (em) 

Resistivity (m2-C/W-em) 

AIR AND CABINET TEMPERATURES 

Room Air (C) 

Freezer Section (C) 

Fresh Food Section (C) 

Air Under Cabinet (C) 

Air Entering Condenser (C) 

DOOR OPENING SCHEDULE 

Room Relative Humidity (%) 

Fresh Food Door - #/Hr 

Fresh Food Door - Sec Open 

Freezer Door - #/Hr 

Freezer Door - Sec Open 

Manual Defrost (O=N, l=Y) 

GASKET HEAT LEAKS (W/M-100C) 

Fresh Food Section 

Freezer Section 

Figure 7-4. Input Data Menus (continued) 

7-7 

45.72 

6.35 

.31 

32.22 

-15.00 

3.33 

37.80 

35.00 

50.00 

.00 

15.00 

.00 

20.00 

o 

9.00 

9.00 
DEFROST AND CONTROLS ENERGY USE

Automatic Defrost Load

Timer Interval (Hr)

Heater On-Time (Min)

Defrost Heater Energy (W)

Other Cycle-Dependent Loads

Freezer Section (W)

Fresh Food Section (W)

Outside Cabinet (W)

Constant Electrical Loads*

Freezer Section (W)

Fresh Food Section (W)

Outside Cabinet (W)

* See Help Menu <Fl>

ELECTRIC ANTI-SWEAT HEAT

Freezer Door Flange

Cycle Average Energy (W)

Fraction Heat Leak (0-1)

Fresh Food Door Flange

Cycle Average Energy (W)

Fraction Heat Leak (0-1)

Mullion

Cycle Average Energy (W)

Heat Leak to FZ (0-1)

Heat Leak to FF (0-1)

REFRIGERANT LINE ANTI -SWEAT HEAT

Type (1=Vapor, 2=Liquid)

Freezer Door Flange

Cycle Average Energy (W)

Fraction Heat Leak (0-1)

Fresh Food Door Flange

Cycle Average Energy (W)

Fraction Heat Leak (0-1)

Mullion

Cycle Average Energy (W)

Heat Leak to FZ (0-1)

Heat Leak to FF (0-1)

PENETRATION HEAT INPUT

Penetration Heat to FZ (W)

Penetration Heat to FF (W)

Figure 7-4. Input Data Menus (continued)

10.00

10.00

450.00

.00

.00

1.50

.00

.00

.00

.00

.00

.00

.00

2.75

.50

.25

2

4.00

.30

.00

.00

.00

.00

.00

.00

.00

7-8

 EE-RM-93-801 COMMENT OR2

DEFROST AND CONTROLS ENERGY USE 

Automatic Defrost Load 

Timer Interval (Hr) 

Heater On-Time (~n) 

Defrost Heater Energy (W) 

Other Cycle-Dependent Loads 

Freezer Section (W) 

Fresh Food Section (W) 

Outside Cabinet (W) 

Constant Electrical Loads* 

Freezer Section (W) 

Fresh Food Section (W) 

Outside Cabinet (W) 

* See Help Menu <F1> 

ELECTRIC ANTI-SWEAT HEAT 

Freezer Door Flange 

Cyc1e Average Energy (W) 

Fraction Heat Leak (0-1) 

Fresh Food Door Flange 

Cycle Average Energy (W) 

Fraction Heat Leak (0-1) 

Mullion 

Cycle Average Energy (W) 

Heat Leak to FZ (0-1) 

Heat Leak to FF (0-1) 

REFRIGERANT LINE ANTI-SWEAT HEAT 

Type (1=Vapor, 2=Liquid) 

Freezer Door Flange 

Cycle Average Energy (W) 

Fraction Heat Leak (0-1) 

Fresh Food Door Flange 

Cycle Average Energy (W) 

Fraction Heat Leak (0-1) 

Mullion 

Cycle Average Energy (W) 

Heat Leak to FZ (0-1) 

Heat Leak to FF (0-1) 

PENETRATION HEAT INPUT 

Penetration Heat to FZ (W) 

Penetration Heat to FF (W) 

Figure 7-4. Input Data Menus (continued) 

7-8 

10.00 

10.00 

450.00 

.00 

.00 

1.50 

.00 

.00 

.00 

.00 

.00 

.00 

.00 

2.75 

.50 

.25 

2 

4.00 

.30 

.00 

.00 

.00 

.00 

.00 

.00 

.00 
CYCLE DEFINITION

Cycle Type (1-4)

1 = Single Evap

2 = Lorenz Cycle

3 = Dual Loop Cycle

4 = Dual Evap Cycle

Number Refrigerants (1-3)

1

1

1 = Pure Refrigerant

2 = Binary Mixture

3 = Ternary Mixture

REFRIGERANT CODES

Refrigerant Code (1-34) 2

EVAPORATOR DATA

Ref Control Option (1-3) 1

1: Evaporator Superheat

2: Interchanger Superheat

3: Evap Exit Quality

Refrigerant Superheat (C) .00

Heat Exchanger Type (1-2) 1

1: Cross-Flow

2: Counter-Flow

Heat Transfer Type (1-2) 1

1: Forced Convection

2: Free Convection

Fan Motor Power ( w) 9.40

EVAPORATOR DATA, CONTINUED

Heat Transfer Area (m2) 2.338

Air Flow Rate (L/s) 23.600

Two-Phase U (W/m2 -C) 13.787

Superheat U (W/m2 -C) 5.633

Refr Pressure Drop ( kPa) 7.200

CONDENSER DATA

Refrigerant Subcooling (C) .00

Heat Exchanger Type (1,2) 1

1 = Cross-Flow

2 = Counter-Flow

Heat Transfer Type (1,2) 1

1 = Forced Convection

2 = Free Convection

Fan Motor Power (w) 12.00

Figure 7-4. Input Data Menus (continued)

7-9

 EE-RM-93-801 COMMENT OR2

CYCLE DEFINITION 

Cycle Type (1-4) 

1 = Single Evap 

2 = Lorenz Cycle 

3 = Dual Loop Cycle 

4 = Dual Evap Cycle 

Number Refrigerants (1-3) 

1 = Pure Refrigerant 

2 = Binary Mixture 

3 = Ternary Mixture 

REFRIGERANT CODES 

Refrigerant Code (1-34) 

EVAPORATOR DATA 

Ref Control Option (1-3) 

1: Evaporator Superheat 

2: Interchanger Superheat 

3: Evap Exit Quality 

Refrigerant Superheat (C) 

Heat Exchanger Type (1-2) 

1: Cross-Flow 

2: Counter-Flow 

Heat Transfer Type (1-2) 

1: Forced Convection 

2: Free Convection 

Fan Motor Power (w) 

EVAPORATOR DATA, CONTINUED 

Heat Transfer Area (m2) 

Air Flow Rate (LIs) 

Two-Phase U (W/m2-C) 

Superheat U (W/m2-C) 

Refr Pressure Drop (kJ?a) 

CONDENSER DATA 

Refrigerant Subcooling (C) 

Heat Exchanger Type (1,2) 

1 ;: Cross-Flow 

2 = Counter-Flow 

Heat Transfer Type (1,2) 

1 = Forced Convection 

2 = Free Convection 

Fan Motor Power (w) 

Figure 7-4. Input Data Menus (continued) 

7-9 

1 

1 

2 

1 

3.00 

1 

1 

9.40 

2.338 

23.600 

13.787 

5.633 

7.200 

.00 

1 

1 

12.00 
CONDENSER DATA, CONTINUED

Heat Transfer Area (m2) .85

Air Flow Rate (L/s) 42.48

Sub-Cool U (W/m2-C) 15.43

Two-Phase U (W/m2-C) 19.23

superheat U (W/m2-C) 15.17

Refr Pressure Drop (kPa) 4.72

COMPRESSOR MODEL OPTIONS

Compressor Type (1,2) 1

1: Reciprocating

2: Rotary

Compressor Model (0,1,2) 1

0: Compressor Map

1: EER and Capacity

2: Efficiency Model

Cycling Loss Analysis (0,1) 1

0: No, 1: Yes

Cycles per Hour 2.00

Typical: 1.5 to 4.0

Shut-off Valve (0, 1) 0

0: No, 1: Yes

COMPRESSOR DATA

Displacement (cc) 6.57

Rated Capacity (kcal/hr) 218.00

Nominal Speed (rpm) 3450.00

Rated EER 5.28

Type of Can Cooling (0, 1) 1

0: Static, 1: Fan-Forced

Fractional Speed (0.2-1.0) 1.00

Mass Flow Guess (kg/hr) 5.80

INTERCHANGER DATA

Comer Shell Inlet Temp (C) -1.00

(-1 Means Unspecified)

Interchanges Effect (0 - 1)

Condenser Subcooler .80

Figure 7-4. Input Data Menus (continued)

7-10

 EE-RM-93-801 COMMENT OR2

CONDENSER DATA, COdTlNUED 

Heat Transfer Area (m2) 

Air Flow Rate (L/s) 

Sub-Cool U (W/m2-C) 

Two-Phase U (W/m2-C) 

Superheat U (W/m2-C) 

Refr Pressure Drop (kPa) 

COMPRESSOR MODEL OPTIONS 

Compressor Type (1,2) 

1: Reciprocating 

2: Rotary 

Compressor Model (0,1,2) 

0: Compressor Map 

1: EER and Capacity 

2: Efficiency Model 

Cycling Loss Analysis (0,1) 

0: No, 1: Yes 

Cycles per Hour 

Typical: 1.5 to 4.0 

Shut-off Valve (0, 1) 

0: No, 1: Yes 

COMPRESSOR DATA 

Displacement (cc) 

Rated Capacity (kcal/hr) 

Nominal Speed (rpm) 

Rated EER 

Type of Can Cooling (0, 1) 

0: Static, 1: Fan-Forced 

Fractional Speed (0.2-1.0) 

Mass Flow Guess (kg/hr) 

INTERCHANGER DATA 

Compr Shell Inlet Temp (C) 

(-1 Means Unspecified) 

Interchanger Effect (0 - 1) 

Condenser Subcooler 

Figure 7-4. Input Data Menus (continued) 

7-10 

.85 

42.48 

15.43 

19.23 

15.17 

4.72 

1 

1 

1 

2.00 

o 

6.57 

218.00 

3450.00 

5.28 

1 

1.00 

5.80 

-1.00 

.80 
Multiple Pathways Baseline Protot : Model -D (Top-Mount)

*

* CABINET TYPE

1 TOP-MOUNT REFRIGERATOR/FREEZER

*

CABINET D IMENSIONS

156.2100 CABINET HEIGHT (CM)

76.2000 CABINET WIDTH (CM)

71.7500 CABINET DEPTH (CH)

7.6200 FREEZER WEDGE (CH)

3.8700 FREEZER FLANGE (CM)

7.6200 FRESH FOOD WEDGE (CM)

3.8700 FRESH FOOD FLANGE (04)

4.4450 DOOR EDGE THICKNESS (CH)

1.5900 GASKET THICKNESS (CM)

.0000 COMPRESSOR 'C TOP DEPTH (CM)

.0000 COMPRESSOR COMPARTMENT BOTTOM DEPTH (CM)

.0000 COMPRESSOR COMPARTMENT HEIGHT (CM)

* MULLION DATA

45.7200 DISTANCE TO TOP (CM)

6.3500 THICKNESS OF MULLION (CM)

*

* FREEZER INSULATION THICKNESS

6.0300 THICKNESS OF INSULATION ON TOP OF FREEZER (CM)

6.0300 THICKNESS OF INSULATION ON LEFT SIDE OF FREEZER (CM)

6.0300 THICKNESS OF INSULATION ON RIGHT SIDE OF FREEZER (CM)

4.4450 THICKNESS OF INSULATION ON FRONT OF FREEZER (CM)

6.0300 THICKNESS OF INSULATION ON BACK OF FREEZER (CM)

* FRESH FOOD INSULATION THICKNESS

4.7600 THICKNESS OF INSULATION ON LEFT SIDE OF FRESH FOOD (CM)

4.7600 THICKNESS OF INSULATION ON RIGHT SIDE OF FRESH FOOD (CM)

4.4450 THICKNESS OF INSULATION ON FRONT OF FRESH FOOD (CM)

4.7600 THICKNESS OF INSULATION ON BACK OF FRESH FOOD (CM)

*

* COMPRESSOR CABINET INSULATION THICKNESS

5.0800 MAXIMUM THICKNESS OF BOTTOM INSULATION FRESH FOOD (CM)

5.0800 THICKNESS OF INSULATION OVER COMPRESSOR (CM)

* REFRIGERATED VOLUMES

21.0100 FREEZER VOLUME USED FOR HEAT EXCHANGERS (L)

135.0700 ADJUSTED FREEZER VOLUME (L)

18.3400 FRESH FOOD VOLUME USED FOR HEAT EXCHANGERS (L)

394.7400 ADJUSTED GENERAL REFRIGERATED VOLUME (L)

*

* AIR AND CABINET TEMPERATURES

32.2200 ROOM TEMPERATURE (C)

-15.0000 FREEZER TEMPERATURE (C)

3.3300 FRESH FOOD COMPARTMENT TEMPERATURE (C)

37.8000 UNDERSIDE AIR TEMPERATURE (C)

Figure 7-5. Intermediate Data: Cabinet Loads Analysis

7-11

 EE-RM-93-801 COMMENT OR2

Multiple Pathways Baseline Prototype: Model D (Top-Mount) 

1< 

1< CABINET TYPE 

1< 

'* 

1 TOP-MOUNT REFRIGERATOR/FREEZER 

CABINET 

156.2100 

76.2000 

71.7500 

7.6200 

3.8700 

7.6200 

3.8700 

4.4450 

1.5900 

.0000 

.0000 

.0000 

DIMENSIONS 

CABINET HEIGHT (CM) 

CABINET WIDTH (CM) 

CABINET DEPTH (CM) 

FREEZER WEDGE (CM) 

FREEZER FLANGE (CM) 

FRESH FOOD WEDGE (CM) 

FRESH FOOD FLANGE (CM) 

DOOR EDGE THICKNESS (CM) 

GASKET THICKNESS (CM) 

COMPRESSOR ~OMPARTMENT TOP DEPTH (CM) 

COMPRESSOR COMPARTMENT BOTTOM DEPTH (CM) 

COMPRESSOR COMPARTMENT HEIGHT (CM) 

1< MULLION DATA 

1< 

1< 

1< 

1< 

'* 

45.7200 DISTANCE TO TOP (CM) 

6.3500 THICKNESS OF MULLION (CM) 

FREEZER 

6.0300 

6.0300 

6.0300 

4.4450 

6.0300 

INSULATION THICKNESS 

FRESH FOOD 

4.7600 

4.7600 

4.4450 

4.7600 

THICKNESS OF INSULATION ON TOP OF FREEZER (CM) 

THICKNESS OF INSULATION ON LEFT SIDE OF FREEZER (CM) 

THICKNESS OF INSULATION ON RIGHT SIDE OF FREEZER (CM) 

THICKNESS OF INSULATION ON FRONT OF FREEZER (CM) 

THICKNESS OF INSULATION ON BACK OF FREEZER (eM) 

INSULATION THICKNESS 

THICKNESS OF INSULATION ON LEFT SIDE OF FRESH FOOD (CM) 

THICKNESS OF INSULATION ON RIGHT SIDE OF FRESH FOOD (CM) 

THICKNESS OF INSULATION ON FRONT OF FRESH FOOD (CM) 

THICKNESS OF INSULATION ON BACK OF FRESH FOOD (CM) 

'* COMPRESSOR CABINET INSULATION THICKNESS 

'* '* 

'* '* 

5.0800 MAXLMUM THICKNESS OF BOTTOM INSULATION FRESH FOOD (CM) 

5.0800 THICKNESS OF INSULATION OVER COMPRESSOR (CM) 

REFRIGERATED 

21. 0100 

135.0700 

18.3400 

394.7400 

VOLUMES 

FREEZER VOLUME USED FOR HEAT EXCHANGERS (L) 

AD.roSTED FREEZER VOLUME (L) 

FRESH FOOD VOLUME USED FOR HEAT EXCHANGERS (L) 

AD.roSTED GENERAL REFRIGERATED VOLUME (L) 

AIR AND 

32.2200 

-15.0000 

3.3300 

37.8000 

CABINET TEMPERATURES 

ROOM TEMPERATURE (C) 

FREEZER TEMPERATURE (C) 

FRESH FOOD COMPARTMENT TEMPERATURE 

UNDERSIDE AIR TEMPERATURE (C) 

(C) 

Figure 7-5. Intermediate Data: Cabinet Loads Analysis 

7-11 
*

* INSULATION RESISTIVITIES

.5550 RESISTIVITY OF REFRIGERATOR INSULATION

.5550

.5550

.5550

.5550

.5550

.3150

*

GASKET

.0900

.0900

*

RESISTIVITY OF FREEZER INSULATION

RESISTIVITY OF REFRIGERATOR WEDGE INSULATION

RESISTIVITY OF FREEZER WEDGE INSULATION

RESISTIVITY OF REFRIGERATOR DOOR

RESISTIVITY OF FREEZER DOOR

RESISTIVITY OF THE MULLION INSULATION

S

GASEET HEAT LEAK FOR FREEZER COMPARTMENT

GASKET HEAT LEAK FOR FRESH FOOD COMPARTMENT

* DOOR OPENING SCHEDULES

32.2200

50.0000

.0000

15.0000

.0000

20.0000

*

ROOM TEMPERATURE (C)

ROOM RELATIVE HUMIDITY

FRESH FOOD DOOR - OPEN /HR

FRESH FOOD DOOR - SEC OR

FREEZER DOOR - OPEN #/HR.

FREEZER DOOR - SEC OPEN

* AUXILIARY ENERGY USE (CONSTANT)

.9167 FRESH FOOD ANTI-SWEAT HEATER (W)

1.8333 FREEZER ANTI-SWEAT HEATER (W)

.0000 FRESH FOOD OTHER ENERGY (W)

.0000 FREEZER OTHER ENERGY (W)

.0000 OUTSIDE CABINET (W)

*

* PENETRATIONS

.0000 FRESH FOOD (W)

.0000 FREEZER (W)

*

* AUXILIARY THERMAL HEAT INPUTS

.6575 FRESH FOOD ELECTRIC ANTI-SWEAT (W)

1.3750 FREEZER ELECTRIC ANTI-SWEAT (W)

.0000 FRESH FOOD REFRIGERANT LINE ANTI-SWEAT (W)

1.2000 FREEZER REFRIGERANT LINE ANTI-SWEAT (W)

.0000 FRESH FOOD OTHER HEAT SOURCES (W)

.0000 FREEZER OTHER HEAT SOURCES (W)

Figure 7-5. Intermediate Data: Cabinet Loads Analysis (continued)

7-12

 EE-RM-93-801 COMMENT OR2

1< 

1< INSULATION RESISTIVITIES 

.5550 RESISTIVITY OF REFRIGERATOR INSULATION 

.5550 RESISTIVITY OF FREEZER INSULATION 

.5550 RESISTIVITY OF REFRIGERATOR WEDGE INSULATION 

.5550 RESISTIVITY OF FREEZER WEDGE INSULATION 

.5550 RESISTIVITY OF REFRIGERATOR DOOR 

.5550 RESISTIVITY OF FREEZER DOOR 

.3150 RESISTIVITY OF THE MULLION INSULATION 1< 

1< GASKET HEAT LEAltS 

.0900 GASKET HEAT LEAlt FOR FREEZER COMPARTMENT 

.0900 GASKET HEAT LEAlt FOR FRESH FOOD COMPARTMENT 1< 

1< DOOR OPENING SCHEDULES 

1< 

1< 

1< 

32.2200 

50.0000 

.0000 

15.0000 

.0000 

20.0000 

AUXILIARY 

.9167 

1.8333 

.0000 

.0000 

.0000 

ROOM TEMPERATURE (C) 

ROOM RELATIVE HUMIDITY (%) 

FRESH FOOD DOOR - OPEN I/HR 

FRESH FOOD 'DooR - SEC OPEN 

FREEZER DOOR - OPEN I/HR 

FREEZER DOOR - SEC OPEN 

ENERGY USE (CONSTANT) 

FRESH FOOD ANTI-SWEAT HEATER (W) 

FREEZER ANTI-SWEAT HEATER (W) 

FRESH FOOD OTHER ENERGY (W) 

FREEZER OTHl!;R ENERGY (W) 

OUTSIDE CABINET (W) 

1< PENETRATIONS 

1< 

1< 

.0000 FRESH FOOD (W) 

.0000 FREEZER (W) 

AUXILIARY 

.6875 

1.3750 

.0000 

1.2000 

.0000 

.0000 

THERMAL HEAT INPUTS 

FRESH FOOD ELECTRIC ANTI-SWEAT (W) 

FREEZER ELECTRIC ANTI-SWEAT (W) 

FRESH FOOD REFRIGERANT LINE ANTI-SWEAT (W) 

FREEZER REFRIGERANT LINE ANTI-SWEAT (W) 

FRESH FOOD OTHER HEAT SOURCES (W) 

FREEZER OTHER HEAT SOURCES (W) 

Figure 7-5. Intennediate Data: Cabinet Loads Analysis (continued) 

7-12 
7.4 Cabinet Loads Results (CABINET.OUT)

The cabinet loads program creates an output file (CAEI T.OUT) which summarizes

the input data and the calculated loads . Figure 7-6 illustrates the output for the sample

problem.

Interpretation of most of the input data is straight forward. The freezer and general

refrigerated (fresh food section) volumes are shown to provide a check on the accuracy

of the specified input. (A large difference between the calculated and specified net volumes may indicate an input error.)

Most of the file CABINET.OUT summarizes the individual cabinet design parameters.

Results of the steady state analysis are listed under the heading " HEAT LEAK

BREAKDOWN", where components of the net heat load are shown. As discussed earlier, the listed quantities do not yet include the effects of fan heat and of a cold-plate

evaporator or hot-wall condenser.

The gasket heat loss is a product of the heat leak per unit perimeter, the calculated door

perimeter and the room to cabinet temperature difference. The fresh food section

always has a negative heat leak across the mullion, since heat flows from the fresh food

section to the freezer section.

7.5 Intermediate Cycle Data File (CYCLE. AT)

An ASCII file containing inputs to the cycle model is also created by the menu-driven

input processor. An example of the file (CYCLE.DAT) for the sample problem is

shown in Figure 7-7. As with the cabinet loads intermediate data file, CYCLE.DAT is

not meant to be edited directly, but is written in a formatted style for ease of interpretation. The actual format will differ with the cycle type and according to the types of

evaporator and condenser. Hence, the user should not attempt to run the cycle model

directly without using the ERA overall program facilities.

Most of the data listed in Figure 7-7 are self explanatory. The section of data entitled

"In-wall Evaporator Data" contains correction factors to the cabinet loads that are made

in the cycle model to account for the presence of a cold-plate evaporator, or a hot-wall

condenser, or both. A code (0, 1) indicates if the evaporator is behind the inner plastic

liner.

Summary cabined loads output data are appended to the CYCLE.DAT file for use by

the cycle model. These parameters enable calculation of the compressor run time, fan

energy, and the daily energy consumption. Each of the cabinet loads data found in Figure 7-7, for the sample problem, can be found in the cabinet loads output report, Figure

7-6.

File CYCLE.DAT is essential to run the final executable program, ERACYC.EXE.

The ERA program user may wish to print the file out as part of the run documentation.

 EE-RM-93-801 COMMENT OR2

1.4 cabinet Loads Results (CABINET. OUT} 

The cabinet loads program creates an output file (CABINET.OUn which summarizes 

the input data and the calculated loads. Figure 7-6 illustrates the output for the sample 

problem. 

Interpretation of most of the input data is straight forward. The freezer and general 

refrigerated (fresh food section) volumes are shown to provide a check on the accuracy 

of the specified input. (A large difference between the calculated and specified net volumes may indicate an input error.) 

Most of the file CABINET. OUT summarizes the individual cabinet design parameters. 

Results of the steady state analysis are listed under the heading "HEAT LEAK 

BREAKDOWN", where components of the net heat load are shown. As discussed earlier, the listed quantities do not yet include the effects of fan heat and of a cold-plate 

evaporator or hot-wall condenser. 

The gasket heat loss is a product of the heat leak per unit perimeter, the calculated door 

perimeter and the room to cabinet temperature difference. The fresh food section 

always has a negative heat leak across the mullion, since heat flows from the fresh food 

section to the freezer section. 

1.5 Intermediate Cycle Data File (CYCLE.DAT) 

An ASCII file containing inputs to the cycle model is also created by the menu-driven 

input processor. An example of the file (CYCLE.DA T) for the sample problem is 

shown in Figure 7-7. As with the cabinet loads intermediate data file, CYCLE.DAT is 

not meant to be edited directly, but is written in a formatted style for ease of interpretation. The actual format will differ with the cycle type and according to the types of 

evaporator and condenser. Hence, the user should not attempt to run the cycle model 

directly without using the ERA overall program facilities. 

Most of the data listed in Figure 7 -7 are self explanatory. The section of data entitled 

"In-wall Evaporator Data" contains correction factors to the cabinet loads that are made 

in the cycle model to account for the presence of a cold-plate evaporator, or a hot-wall 

condenser, or both. A code (0, 1) indicates if the evaporator is behind the inner plastic 

liner. 

Summary cabined loads output data are appended to the CYCLE.DAT file for use by 

the cycle model. These parameters enable calculation of the compressor run time, fan 

energy, and the daily energy consumption. Each of the cabinet loads data found in figure 7-7, for the sample problem, can be found in the cabinet loads output report, Figure 

7-6. 

File CYCLE.DAT is essential to run the final executable program, ERACYC.EXE. 

The ERA program user may wish to print the file out as part of the run documentation. 

7-13 
Multiple Pathways Baseline Protot : Model -D (Top-Mount)

THERMAL ANALYSIS OF A TOP-MOUNT REFRIGERATOR/FREEZES.

CONFIGURATION TYPE: 1

DIMENSIONAL SPECIFICATIONS

OVERALL: 156.21 HIGH X 76.20 WIDE X 71.75 DEEP

FREEZER:

THE WEDGE IS 7.62 DEEP

THE FLANGES ARE 3.87 WIDE

FRESH FDCOMPARTMENT:

THE WEDGE IS 7 . 62 DEEP

THE FLANGES AliZ, 3 . 87 WIDE

THE TOP OF THE MULLION IS 45.72 FROM THE TOP OF THE CABINET

THE MULLION IS 6.35 THICK

COMPRESSOR COMPARTMENT D IMENSIONS:

TOP DEPTH: .00 CM BOTTOM DEPTH: .00 CM HEIGHT: .00

INSULATION THICKNESS

FREEZER

TOP 6.03 CM

LEFT SIDE 6.03

RIGHT SIDE 6.03

FRONT (DOOR) 4.45 CM

BACK 6.03

INSULATION THICKNESS

FRESH FOOD

LEFT SIDE 4.76

RIGHT SIDE 4.76

FRONT (DOOR) 4.45

BACK 4.76

BOTTOM 5.08

M

CM

VOLUMES

FREEZER REFRIGERATED VOLUME

CALCULATED 134.98 LITER

SPECIFIED

SHELF/EVAP 21.01 LITER

NET VOLUME 135.07 LITER

GENERAL REFRIGERATED VOLUME

CALCULATED 394.79 LITER

SPECIFIED

SHELF/EVAP 18.34 LITER

NET VOLUME 394.74 LITER

TEMPERATURES

ROOM 32.22 DEG C

FREEZER CABINET -15.00 DEG C

FRESH FOOD CABINET 3.33 DEG C

AIR UNDER REFRIGERATOR 37.80 DEG C

Figure 7-6. Cabinet Loads Output

7-14

 EE-RM-93-801 COMMENT OR2

Mu1tiple pathways Baseline Prototype: Model D (Top-Mount) 

THERMAL ANALYSIS OF A TOP-MOUNT REFRIGERATOR/FREEZER 

CONFIGURATION TYPE: 1 

DIMENSIONAL SPECIFICATIONS 

OVERALL: 156.21 eM HIGH X 76.20 eM WIDE X 71.75 eM DEEP 

FREEZER: 

THE WEDGE IS 7 . 62 eM DEEP 

THE FLANGES ARE 3.87 eM WIDE 

FRESH FOOD COMPARTMENT: 

THE WEDGE IS 7 . 62 eM DEEP 

THE FLANGES ARE· 3. 87 eM WIDE 

THE TOP OF THE MULLION IS 45 .72 eM FROM THE TOP OF THE CABINET 

THE MULLION IS 6 . 35 eM THICK 

COMPRESSOR COMPARTMENT DIMENSIONS: 

TOP DEPTH: .00 eM BOTTOM DEPTH: .00 eM HEIGHT: .00 eM 

INSULATION THICKNESS 

FREEZER 

TOP 

LEFT SIDE 

RIGHT SIDE 

FRONT (DOOR) 

BACK 

INSULATION THICKNESS 

VOLUMES 

FRESH FOOD 

LEFT SIDE 

RIGHT SIDE 

FRONT (DOOR) 

BACK 

BOTTOM 

FREEZER REFRIGERATED VOLUME 

CALCULATED 

SPECIFIED 

SHELF/EVAP 

NET VOLUME 

GENERAL REFRIGERATED VOLUME 

CALCULATED 

SPECIFIED 

TEMPERATURES 

ROOM 

SHELF/EVAP 

NET VOLUME 

FREEZER CABINET 

FRESH FOOD CABINET 

AIR UNDER REFRIGERATOR 

6.03 eM 

6.03 eM 

6.03 eM 

4.45 eM 

6.03 eM 

4.76 eM 

4.76 eM 

4.45 eM 

4.76 eM 

5.08 eM 

134.98 LITER 

21.01 LITER 

135.07 LITER 

394.79 LITER 

18.34 LITER 

394.74 LITER 

32.22 DEG C 

-15.00 DEG C 

3.33 DEG C 

37.80 DEG C 

Figure 7-6. Cabinet Loads Output 

7-14 
THERMAL CHARACTERISTICS

THERMAL RESISTIVITY

FRESH FOOD CABINET .5550 m2 -C/W-cm

FREEZER CABINET .5550 m2-C/W-cm

FRESH FOOD WEDGE .5550 x2-C/W-c

FREEZER WEDGE .5550 m2-C/W-cm

FRESH FOOD DOOR .5550 m2 -C/W-cm

FREEZER DOOR .5550 m2-C/W-cm

LION .3150 m2-C/W-cm

GASKET HEAT LEAK

FREEZER

REFRIGERATOR

.0900 W/m-C

.0900 W/ffi-C

DOOR OPENINGS

AIR TEMPERATURE

RELATIVE HUMIDITY

FRESH FOOD COMPARTMENT

OPENINGS/HR

DURATION OF 1 OPENING

FREEZER COMPARTMENT

OPENINGS/HR

DURATION OF 1 OPENING

32.2 Deg C

50.0 (%)

. 0 /HR

15.0 SECONDS

. 0 /HR

20.0 SECONDS

ANTI-SWEAT HEATERS

FRESH FOOD CABINET .92 W

FREEZER CABINET 1.83 W

AUXILIARY ENERGY

FRESH FOOD CABINET .00 W

FREEZER CABINET .00

OUTSIDE CABINET .00 W

HEAT LEAK BREAKDOWN

FRESH FOOD

(W)

FREEZER

(W)

RIGHT WALL 5.53 2.97

LEFT WALL 5.53 2.97

BACK WALL 6.86 3.62

FRONT (DOOR) 7.27 4.69

TOP WALL .00 4.84

BOTTOM 4.31 .00

MULLION -2.60 2.60

WEDGE 2.45 1.94

GASKET 9.12 10.37

OPEN DOOR SENSIBLE LOAD .00 .00

MOISTURE LOAD - CONDENSE .00 .00

MOISTURE LOAD - FROST .00 .00

ANTI-SWEAT HEATER .69 1.38

REFRIGERANT LINE HEAT .00 1.20

PENETRATIONS .00 .00

OTHER THERMAL INPUT .00 .00

TOTAL, 39.16 36.57

Figure 7-6. Cabinet Loads Output (continued)

7-15

 EE-RM-93-801 COMMENT OR2

THERMAL CHARACTERISTICS 

THERMAL RESISTIVITY 

FRESH FOOD CABINET 

FREEZER CABINET 

FRESH FOOD WEDGE 

FREEZER WEDGE 

FRESH FOOD DOOR 

FREEZER DOOR 

.MULLION 

GASKET HEAT LEAK 

FREEZER 

REFRIGERATOR 

DOOR OPENINGS 

AIR TEMPERATURE 

RELATIVE HUMIDITY 

FRESH FOOD COMPARTMENT 

OPENINGS/HR 

DURATION OF 1 OPENING 

FREEZER COMPARTMENT 

OPENINGS/HR 

DURATION OF 1 OPENING 

ANTI-SWEAT HEATERS 

FRESH FOOD CABI;NET 

FREEZER CABINET 

AUXILIARY ENERGY 

FRESH FOOD CABINET 

FREEZER CABINET 

OUTSIDE CABINET 

HEAT LEAK BREAKDOWN 

RIGHT WALL 

LEFT WALL 

BACK WALL 

FRONT (DOOR) 

TOP WALL 

BOTTOM 

MULLION 

WEDGE 

GASKET 

OPEN DOOR SENSIBLE LOAD 

MOISTURE LOAD - CONDENSE 

MOISTURE LOAD - FROST 

ANTI-SWEAT HEATER 

REFRIGERANT LINE HEAT 

PENETRATIONS 

OTHER THERMAL INPUT 

TOTAL 

.5550 m2-C/W-cm 

.5550 m2-C/W-cm 

.5550 m2-C/W-cm 

.5550 m2-C/W-cm 

.5550 m2-C/W-cm 

.5550 m2-C/w-cm 

.3150 m2-C/W-cm 

.0900 W/m-C 

.0900 W/m-C 

32.2 Deg C 

50.0 (%) 

.0 I/HR 

15.0 SECONDS 

.0 I/HR 

20.0 SECONDS 

.92 W 

1.83 W 

.00 W 

.00 W 

.00 W 

FRESH FOOD 

(W) 

5.53 

5.53 

6.86 

7.27 

.00 

4.31 

-2.60 

2.45 

9.12 

.00 

.00 

.00 

.69 

.00 

.00 

.00 

39.16 

Figure 7-6. Cabinet Loads Output (continued) 

7-15 

FREEZER 

(W) 

2.97 

2.97 

3.62 

4.69 

4.84 

.00 

2.60 

1.94 

10.37 

.00 

.00 

.00 

1.38 

1.20 

.00 

.00 

36.57 
Multiple Pathways Baseline Prototype: Model-D (Top-Mount)

FILE N : MODELD.ERA.

REFRIGERATOR/FREEZER CONFIGURATION

1

1

REFRIGERATION TYPE (1-5)

CYCLE TYPE ( 1=STANDARD, 2=L0 Z, 3=DUAL LOOP, 4=DUAL EVAP )

MOISTURE CONTROL

0 MANUAL DEFROST : 0=NO, 1=YES

COMPRESSOR OPTIONS

1 COMPRESSOR TYPE (I=RECIPROCATING, 2=ROTARY)

1 COMPRESSOR ANALYSIS (O=MAP , 1=EER, 2=EFFICIENCY MODEL)

1 CYCLING LOSS ANALYSIS ( 0=NO, 1= S)

2.000 CYCLES PER HOUR

0 SHUT-OFF V .(O=NO, 1= S)

REFRIGERANT CODES (1 - 34):

1 = R11, 2 = R12, 3 = R13, 4 = R13B1,

5 = R14, 6 = R22, 7 = R23, 8 = R113,

9 = R114, 10 = R142b, 11 = R152a, 12 = R216a,

13 = 8125, 14 = R143a, 15 = R134a, 16 = 8123,

17 = C-318, 18 = 8134, 19 = C-C3H6, 20 = R141b

21 = SO2, 22 = 8290, 23 = R600, 24 = R600a,

25 = R32, 26 = R1270, 27 = 8124, 28 = 8115,

29 = CE-216 30 = E-125, 31 = R21, 32 = R143,

33=8218, 34 = E-134

REFRIGERANT DATA

2 CODE ( IR(1)) FOR 1ST REFRIGERANT

0 CODE ( IR(2)) FOR 2ND REFRIGERANT

0 CODE ( IR(3)) FOR 3RD REFRIGERANT

1 NUMBER OF COMPONENTS (MAXIMUM OF THREE)

0.0 MIXTURE INTERACTION PARAMETER- COMPONENT 1-2

0.0 MIXTURE INTERACTION PARAMETER.- COMPONENT 1-3

0.0 MIXTURE INTERACTION PARAMETER- COMPONENT 2-3

1.000 MASS FRACTION OF 1ST REFRIGERANT

0.0 MASS FRACTION OF 2ND REFRIGERANT

0.0 MASS FRACTION OF 3RD REFRIGERANT

CONDENSER PARAMETERS

1 HEAT EXCHANGER CONFIGURATION (0=NATURAL CONVECTION,

1=CROSS -FLOW, 2=COUNTER-FLOW)

35.000 TEMP OF AIR ENTERING CONDENSER (C)

42.476 AIR FLOW RATE ACROSS COIL (L/s)

12.000 FAN POWER (W)

4.720 PRESSURE DROP THROUGH CONDENSER (kPa)

15.167 DESUPERHEATING HEAT TRANSFER CONDUCTANCE, W/m2-C

19.227 TWO-PHASE HEAT TRANSFER CONDUCTANCE , W/m2-C

15.434 SUBCOOLING HEAT TRANSFER CONDUCTANCE, W/m2-C

.849 TOTAL HEAT TRANSFER SURFACE AREA, m2

.000 REFRIGERANT EXIT SUBCOOLING, DEG C

4.000 LIQUID-LINE ANTI-SWEAT HEAT (W)

.000 VAPOR-LINE ANTI -SWEAT HEAT (W)

EVAPORATOR PARAMETERS

1 EVAPORATOR SPECIFICATION (1=EVAP EXIT SUPERHEAT,

2=INTERCHANGER EXIT SUPERHEAT, 3=EVAP EXIT QUALITY

1 HEAT EXCHANGER CONFIGURATION ( 0=NATURAL CONVECTION,

1=CROSS-FLOW, 2=COUNTER-FLOW)

-11.334 TEMP OF AIR ENTERING FRESH FOOD SECTION EVAPORATOR (C)

Figure 7-7. Intermediate Data: Cycle Analysis

7-16

Multiple Pathways 

 EE-RM-93-801 COMMENT OR2

Baseline Prototype: Model_D (Top-Mount) 

FILE NAME: M.ODEL D. ERA 

REFRIGERATOR/FREEZER CONFIGURATION 

1 REFRIGERATION TYPE (1-5) 

1 CYCLE TYPE (1=STANDARD, 2=LORENZ, 3=DUAL LOOP, 4=DUAL EVAP) 

MOISTURE CONTROL 

o MANUAL DEFROST: O=NO, 1=YES 

COMPRESSOR 

1 

1 

1 

OPTIONS 

2.000 

o 

REFRIGERANT CODES 

1 = R11, 

5 = R14, 

9 = R114, 

13 = R125, 

17 = C-318, 

21 = S02, 

25 = R32, 

29 = CE-216 

33 = R218, 

COMPRESSOR TYPE (1=RECIPROCATING, 2=ROTARY) 

COMPRESSOR ANALYSIS (O=MAP, 1=EER, 2=EFFICIENCY MODEL) 

CYCLING LOSS ANALYSIS (O=NO, 1=YES) 

CYCLES PER HOUR 

SHUT-OFF VALVE. (O=NO, l=YES) 

(1 - 34) : 

2 = R12, 3 = R13, 4 = R13B1, 

6 = R22, 7 = R23, 8 = R113, 

10 = R142h, 11 = R152a, 12 = R216a, 

14 = R143a, 15 = R134a, 16 = R123, 

18 = R134, 19 = C-C3H6, 20 = R141h 

22 = R290, 23 = R600, 24 = R600a, 

26 = R1270, 27 = R124, 28 = R115, 

30 = E-125, 31 = R21, 32 = R143, 

34 = E-134 

INPUT DATA FOR THE REFRIGERATION SYSTEM 

REFRIGERANT DATA 

2 CODE (IR(1» FOR 1ST REFRIGERANT 

o CODE (IR (2» FOR 2ND REFRIGERANT 

o CODE (IR (3» FOR 3RD REFRIGERANT 

1 NUMBER OF COMPONENTS (MAXIMUM OF THREE) 

0.0 MIXTURE INTERACTION PARAMETER- COMPONENT 

0.0 MIXTURE INTERACTION PARAMETER- COMPONENT 

0.0 M.IXTURE INTERACTION PARAMETER- COMPONENT 

1.000 MASS FRACTION OF 1ST REFRIGERANT 

0.0 MASS FRACTION OF 2ND REFRIGERANT 

0.0 MASS FRACTION OF 3RD REFRIGERANT 

CONDENSER PARAMETERS 

1-2 

1-3 

2-3 

1 HEAT EXCHANGER CONFIGURATION (O=NATURAL CONVECTION, 

1=CROSS-FLOW, 2 =COUNTER-FLOW) 

35.000 

42.476 

12.000 

4.720 

15.167 

19.227 

15.434 

.849 

.000 

4.000 

.000 

EVAPORATOR 

1 

1 

-11.334 

TEMP OF AIR ENTERING CONDENSER (C) 

AIR FLOW RATE ACROSS COIL (LIs) 

FAN POWER (W) 

PRESSURE DROP THROUGH CONDENSER (kPa) 

DESUPERHEATING HEAT TRANSFER CONDUCTANCE, W/m2-C 

TWO-PHASE HEAT TRANSFER CONDUCTANCE, W/m2-C 

SUBCooLING HEAT TRANSFER CONDUCTANCE, W/m2-C 

TOTAL HEAT TRANSFER SURFACE AREA, m2 

REFRIGERANT EXIT SUBCooLING, DEG C 

LIQUID-LINE ANTI-SWEAT HEAT (W) 

VAPOR-LINE ANTI-SWEAT HEAT (W) 

PARAMETERS 

EVAPORATOR SPECIFICATION (1=EVAP EXIT SUPERHEAT, 

2=INTERCHANGER EXIT SUPERHEAT, 3=EVAP EXIT QUALITY 

HEAT EXCHANGER CONFIGURATION (O=NATURAL CONVECTION, 

1=CROSS-FLOW, 2=COUNTER-FLOW) 

TEMP OF AIR ENTERING FRESH FOOD SECTION EVAPORATOR (C) 

Figure 7-7. Intermediate Data: Cycle Analysis 

7-16 
23.600 AIR FLOW RATE ACROSS COIL (L/s)

9.400 FAN POWER (W)

7.200 PRESSURE DROP THROUGH FRESH FOOD EVAPORATOR (kPa)

13.787 TWO-PHASE HEAT TRANSFER CONDUCTANCE, W/m2-C

5.633 SUPERHEAT REGION CO t. T CE, W/an2-C

2.338 TOTAL HEAT TRANSFER SURFACE AREA, m2

3.000 REFRIGERANT EXIT SUPERHEAT (C) OR QUALITY (0-1)

COMPRESSOR PARAMETERS

5.800 INITIAL GUESS FOR REFRIGERANT MASS FLOW RATE (kg/hr)

6.570 COMPRESSOR DISPLACEMENT , (cc)

218.000 RATED CAPACITY ( kcal/hr)

3450 . 000 NOMINAL SPEED ( rpm)

5.280 RATED EER

1 TYPE OF CAN COOLING (0: STATIC, 1: FAN-FORCED)

1.000 FRACTIONAL SPEED (-)

-1.000 TEMP. AT COMP. INLET (C) (-1 IF UNSPECIFIED]

% ER GER.S

.000 I E GER EXIT SUPERHEAT (C)

.800 EFFECTIVENESS OF HIGH TEMP INTERCHANGER

IN-WALL EVAPORATOR DATA

.000 EV : A/R IN FRESH FOOD SECTION ( OR CABINET WALLS)

.000 EV : A/R IN FREEZER SECTION WALLS (IF SEP ARATE SECTION)

.000 EVAP : A/R IN MULLION SECTION ( IF PRESENT)

.000 COND : A/R IN FRESH FOOD SECTION ( OR CABINET WALLS)

.000 COND: A/R IN FREEZER SECTION WALLS ( IF SEPARATE SECTION)

.000 BOTH : A/R IN FRESH FOOD SECTION ( OR CABINET WALLS)

.000 BOTH : A/R IN FREEZER SECTION WALLS ( IF SEPARATE SECTION)

.000 FRACTION OF FRESH FOOD SECTION (OR CABINET WALLS)

.000 FRACTION OF FREEZER SECTION WALLS ( INCLUDING MULLION)

0 FF (OR CABINET) EVAPORATOR BEHIND LINER (O:NO, 1:YES)

0 FZ EVAPORATOR BEHIND LINER ( 0:NO, 1:YES)

CYCLE-DEPENDENT ELECTRICAL ENERGY DATA

7.500 CLOSED-DOOR AUTOMATIC DEFROST (W)

.000 FRESH FOOD SECTION

.000 FREEZER SECTION

1.500 OUTSIDE CABINET

CABINET LOADS DATA

.92 FRESH FOOD ANTISWEAT HEATER (W)

.00 FRESH FOOD AUXILIARY POWER (W)

1.83 FREEZER ANTISWEAT HEATER (W)

.00 FREEZER AUXILIARY POWER (W)

.00 OUTSIDE CABINET POWER (W)

32.22 ROOM TEMPERATURE (C)

3.33 FRESH FOOD TEMPERATURE (C)

-15.00 FREEZER TEMPERATURE (C)

39.16 FRESH FOOD NET LOAD (W)

36.57 FREEZER LOAD (W)

.00 FRESH FOOD DOOR SENSIBLE LOAD (W)

.00 FRESH FOOD DOOR CONDENSATION LOAD (W)

.00 FRESH FOOD DOOR FROST LOAD (W)

.00 FREEZER DOOR SENSIBLE LOAD (W)

.00 FREEZER DOOR CONDENSATION LOAD (W)

.00 FREEZER DOOR FROST LOAD (N)

.00 FRESH FOOD PENETRATIONS (W)

.00 FREEZER PENETRATIONS (W)

.69 FRESH FOOD HEATERS AND CONTROLS (W)

1.38 FREEZER HEATERS AND CONTROLS (W)

.00 FRESH FOOD REFRIGERANT LINE (W)

1.20 FREEZER REFRIGERANT LINE (W)

2.60 MULLION HEAT LOAD (W)

Figure 7-7. Intermediate Data: Cycle Analysis (continued)

7-17

 EE-RM-93-801 COMMENT OR2

23.600 

9.400 

7.200 

13.787 

5.633 

2.338 

3.000 

AIR FLOW RATE ACROSS COIL (Lis) 

FAN POWER (W) 

PRESSURE DROP THROUGH FRESH FOOD EVAPORATOR (kPa) 

TWO-PHASE HEAT TRANSFER CONDUCTANCE, W/m2-C 

SUPERHEAT REGION COND~~TANCE, W/m2-C 

TOTAL HEAT TRANSFER SURFACE AREA, m2 

REFRIGERANT EXIT SUPERHEAT (C) OR QUALITY (0-1) 

COMPRESSOR 

5.800 

6.570 

218.000 

3450.000 

5.280 

PARAMETERS 

1 

1.000 

-1.000 

INTERCHANGERS 

INITIAL GUESS FOR REFRIGERANT MASS FLOW RATE (kg/hr) 

COMPRESSOR DISPLACEMENT, (cc) 

RATED CAPACITY (kcal/hr) 

NOMINAL SPEED (rpm) 

RATED EER 

TYPE OF CAN COOLING (0: STATIC, 1: FAN-FORCED) 

FRACTIONAL SPEED (-) 

TEMP. AT COMPo INLET (C) [-1 IF UNSPECIFIED] 

.000 INTERCHANGER EXIT SUPERHEAT (C) 

.800 EFFECTIVENESS OF HIGH TEMP INTERCHANGER 

IN-WALL EVAPORATOR DATA 

.000 EVAP: AIR IN FRESH FOOD SECTION (OR CABINET WALLS) 

.000 EVAP: AIR IN FREEZER SECTION WALLS (IF SEPARATE SECTION) 

.000 EVAP: AIR IN MULLION SECTION (IF PRESENT) 

.000 COND: AIR IN FRESH FOOD SECTION (OR CABINET WALLS) 

.000 COND: AIR IN FREEZER SECTION WALLS (IF SEPARATE SECTION) 

.000 BOTH: AIR IN FRESH FOOD SECTION (OR CABINET WALLS) 

.000 BOTH: AIR IN FREEZER SECTION WALLS (IF SEPARATE SECTION) 

.000 FRACTION OF FRESH FOOD SECTION (OR CABINET WALLS) 

.000 FRACTION OF FREEZER SECTION WALLS (INCLUDING MULLION) 

o FF (OR CABINET) EVAPORATOR BEHIND LINER (0 :NO, 1 :YES) 

o FZ EVAPORATOR BEHIND LINER (O:NO, l:YES) 

CYCLE-DEPENDENT ELECTRICAL ENERGY DATA 

7.500 CLOSED-DOOR AUTOMATIC DEFROST (W) 

.000 FRESH FOOD SECTION 

.000 FREEZER SECTION 

1.500 OUTSIDE CABINET 

CABINET LOADS 

.92 

.00 

1.83 

.00 

.00 

32.22 

3.33 

-15.00 

39.16 

36.57 

.00 

.00 

.00 

.00 

.00 

.00 

.00 

.00 

.69 

1.38 

.00 

1.20 

2.60 

DATA 

FRESH FOOD ANT I SWEAT HEATER (W) 

FRESH FOOD AUXILIARY POWER (W) 

FREEZER ANTISWEAT HEATER (W) 

FREEZER AUXILIARY POWER (W) 

OUTSIDE CABINET POWER (W) 

ROOM TEMPERATURE (C) 

FRESH FOOD TEMPERATURE (C) 

FREEZER TEMPERATURE (C) 

FRESH FOOD NET LOAD (W) 

FREEZER LOAD (W) 

FRESH FOOD DOOR SENSIBLE LOAD (W) 

FRESH FOOD DOOR CONDENSATION LOAD (W) 

FRESH FOOD DOOR FROST LOAD (W) 

FREEZER DOOR SENSIBLE LOAD (W) 

FREEZER DOOR CONDENSATION LOAD (W) 

FREEZER DOOR FROST LOAD (W) 

FRESH FOOD PENETRATIONS (W) 

FREEZER PENETRATIONS (W) 

FRESH FOOD HEATERS AND CONTROLS (W) 

FREEZER HEATERS AND CONTROLS (W) 

FRESH FOOD REFRIGERANT LINE (W) 

FREEZER REFRIGERANT LINE (W) 

MULLION HEAT LOAD (W) 

Figure 7-7. Intennediate Data: Cycle Analysis (continued) 

7-17 
7.6 Cycle Analysis Results (CYCLE. U

Program ERACYC.EXE reads the cycle data, CYCLE.DAT, and then simulates the

steady state thermodynamic cycle. The calculations assume constant operation of the

compressor. Transient effects are, by definition, missing, From the evaporator capacity, the fan power, and the cabinet loads, the compressor run time is estimated. A correction to the net compressor power to account for cycle transients is estimated and

utilized when determining the daily energy consumption (see Appendix A).

Figure 7-8 lists the output from the cycle program (CYCLE.OUT). Thermodynamic

state points are shown for 12 locations about the circuit. In the instance of the single

evaporator cycle only one subcooling heat exchanger and one evaporator are present.

Temperatures and thermodynamic data are shown for the refrigerant at each state point.

Temperature data are also shown for the air in the instance of a fan forced heat

exchanger. The air temperatures are shown as if counter-flow heat exchangers were

used, even if the flow is cross-flow. The important parameter is the product of the air

flow rate, specific heat, and air temperature change across the heat exchanger. This

product must agree with the mass flow - enthalpy difference product of the refrigerant

across the heat exchanger.

The listed evaporator capacity ignores the effects of fan heat, which are taken into

account in another manner. Capacities and power are shown in units of kJ/hr and

watts.

The data listed in the cycle output will be dependent on the type of compressor model

selected. For the sample case, the compressor was described in terms of the capacity,

EER and displacement in a standard calorimeter test configuration. ERA estimates the

values for the adiabatic compression efficiency, combined motor-pump efficiency and

shell loss from built-in algorithms (see Appendix B). The estimated clearance volume

is determined from the calorimeter data for capacity (and, hence, refrigerant mass

flow). These are printed, followed by "(Compressor EER Model)," to indicate the

source of the compressor model data. The data values may be used for a subsequent

analysis using the compressor efficiency model option, if desired.

The output also lists the calculated air flow distribution between the fresh food and

freezer sections. A change in the cabinet or cycle design may result in significant

changes in the required distribution of refrigerated air. For example, use of a variable

capacity compressor may require a means of active baffle control to ensure that both

cabinet temperatures are maintained.

The second page of CYCLE.OUT gives a simple diagram of the cycle, with calculated

refrigerant temperatures.

 EE-RM-93-801 COMMENT OR2

7.6 Cycle Analysis Results (CYCLE. OUT) 

Program ERACYC.EXE reads the cycle data, CYCLE.DAT, and then simulates the 

steady state thermodynamic cycle. The calculations assume constant operation of the 

compressor. Transient effects are, by definition, missing, From the evaporator capacity, the fan power, and the cabinet loads, the compressor run time is estimated. A correction to the net compressor power to account for cycle transients is estimated and 

utilized when determining the daily energy consumption (see Appendix A). 

Figure 7-8 lists the output from the cycle program (CYCLE.OUT). Thermodynamic 

state points are shown for 12 locations about the circuit. In the instance of the single 

evaporator cycle only one subcooling heat exchanger and one evaporator are present. 

Temperatures and thermodynamic data are shown for the refrigerant at each state point. 

Temperature data are also shown for the air in the instance of a fan forced heat 

exchanger. The air temperatures are shown as if counter-flow heat exchangers were 

used, even if the flow is cross-flow. The important parameter is the product of the air 

flow rate, specific heat, and air temperature change across the heat exchanger. This 

product must agree with the mass flow - enthalpy difference product of the refrigerant 

across the heat exchanger. 

The listed evaporator capacity ignores the effects of fan heat, which are taken into 

account in another manner. Capacities and power are shown in units of kJ/hr and 

watts. 

The data listed in the cycle output will be dependent on the type of compressor model 

selected. For the sample case, the compressor was described in terms of the capacity, 

EER and displacement in a standard calorimeter test configuration. ERA estimates the 

values for the adiabatic compression efficiency, combined motor-pump efficiency and 

shell loss from built-in algorithms (see Appendix B). The estimated clearance volume 

is determined from the calorimeter data for capacity (and, hence, refrigerant mass 

flow). These are printed, followed by "(Compressor EER Model)," to indicate the 

source of the compressor model data. The data values may be used for a subsequent 

analysis using the compressor efficiency model option, if desired. 

The output also lists the calculated air flow distribution between the fresh food and 

freezer sections. A change in the cabinet or cycle design may result in significant 

changes in the required distribution of refrigerated air. For example, use of a variable 

capacity compressor may require a means of active baffle control to ensure that both 

cabinet temperatures are maintained. 

The second page of CYCLE.OUT gives a simple diagram of the cycle, with calculated 

refrigerant temperatures. 

7-18 
RUN AT 10:51:13 ON 18 MAR 1993

STANDARD ONE EVAPORATOR CYCLE

THE REFRIGERANT MIXTURE CONSISTS OF 100.% R12

OUTPUT RESULTS

STATE T ( C) P H V S XL XV XQ

AIR REF (KPA) ( / ) (M3/KG) (KJ/KG-C) (MASS FRAC)

1 COMP IN N/A 32.4 125.2 202.0 .1639 .799 .000 1.000 1.000

2 COMP DIS N/A 77.8 1258.9 218.3 .0160 .702 .000 1.000 1.000

3 COND IN 39 . 8 77.9 1259.1 218.3 .0186 .715 .000 1.000 1.000

4 COND DEW N/A 51 . 5 1258.3 198.1 .0137 .643 .000 1.000 1.000

5 COND BUB N/A 51.3 1254.4 77.8 .0008 .272 1.000 .000 .000

6 COND OUT 35.0 51.3 1254.1 77.8 .0008 .272 1.000 .000 .000

7 LIQ LINE N/A 45.2 1254.1 71.4 .0008 .252 1 . 000 .000 .000

8 SUBCOOL N/A 12.9 1254.1 39.5 .0007 .146 1.000 .000 .000

9 EVAP IN -19 . 1 -23.2 132.4 39.5 .0262 .190 1.000 1.000 .206

10 EVAP DEW N/A -24 . 5 125.4 168.5 .1301 .678 .000 1.000 1.000

11 EVAP OUT -12.3 -21.6 125.2 170.1 .1321 .685 .000 1.000 1.000

12 HX OUT N/A 32.4 125.2 202.0 .1639 .799 .000 1.000 1.000

CYCLE PERFORMANCE SUMMARY

EVAPORATOR CAPACITY--------------- 788.9 KJ/HR (219.1 W)

CONDENSER HEAT REJECTION RATE ---- 848.8 KJ/HR (235.8 W)

COMPRESSOR POWER REQUIREMENT ----- 563 . 0 KJ/HR ( 156.4 W)

COEFFICIENT OF PERFORMANCE ------- 1 . 401

FRACTION AIR TO FRESH FOOD ------- . 150 (SINGLE EVAPORATOR CYCLE)

ESTIMATED COMPRESSION EFFICIENCY - 1.348 (COMPRESSOR EER MODEL)

ESTIMATED MOTOR.-PUMP EFFICIENCY - . 449 (COMPRESSOR EER MODEL)

ESTIMATED CLEARANCE VOLUME - .022 (COMPRESSOR EER MODEL)

ESTIMATED SHELL LOSS - . 825 (COMPRESSOR EER MODEL)

ESTIMATED DISC TUBE HEAT LOSS - . 387 (COMPRESSOR EER MODEL)

HEAT EXCHANGER PERFORMANCE SUMMARY

EXCHANGER EFFECTIVENESS , % SUBCOOLED FRACTION, % SUPERHEATED FRACTION, %

EVAPORATOR --------- 96.2

CONDENSER ---------- 89.4

N/A 2.5

.0 11.0

COMPRESSOR PERFORMANCE SUMMARY

REFRIGERANT MASS FLOW RATE ----- 6.040 KG/HR

VOLUMETRIC EFFICIENCY ---------- .772

PRESSURE RATIO ----------------- 10.05

SUCTION PORT TEMPERATURE ------- 49.9 C

DISCHARGE PORT TEMPERATURE ----- 126.2 C

DISCHARGE SUPERHEAT ------------ 26.4 C

Figure 7-8. Cycle Analysis Output

7-19

 EE-RM-93-801 COMMENT OR2

RUN AT 10:51:13 ON 18 MAR 1993 

STANDARD ONE EVAPORATOR CYCLE 

THE REFRIGERANT MIXTURE CONSISTS OF 100.% R12 

STATE T 

AIR 

1 COMP IN N/A 

2 COMP DIS N/A 

3 COND IN 39.8 

4 COND DEW N/A 

5 COND BUB N/A 

6 COND OUT 35.0 

7 LIQ LINE N/A 

8 SUBCOOL N/A 

9 EVAP IN -19.1 

10 EVAP DEW N/A 

11 EVAP OUT -12.3 

12 ax OUT N/A 

OUTPUT RESULTS 

(C) P H V 

REF (KPA) (KJ/KG) (M3/KG) 

32.4 125.2 202.0 .1639 

17.8 1258.9 218.3 .0160 

17.9 1259.1 218.3 .0186 

51.5 1258.3 198.1 .0137 

51.3 1254:4 77 .8 .0008 

51.3 1254.1 77.S .0008 

45.2 1254.1 71.4 .0008 

12.9 1254.1 39.5 .0007 

-23.2 132.4 39.5 .0262 

-24.5 125.4 168.5 .1301 

-21.6 125.2 170.1 .1321 

32.4 125.2 202.0 .1639 

CYCLE PERFORMANCE SUMMARY 

788.9 KJ/HR 

848.8 KJ/HR 

563.0 KJ/HR 

1.401 

S 

(KJ/KG-C) 

.799 

.702 

.715 

.643 

.272 

.272 

.252 

.146 

.190 

.678 

.685 

.799 

(219.1 W) 

(235.8 W) 

(156.4 W) 

XL XV 

(MASS FRAC) 

.000 1.000 

.000 1.000 

.000 1.000 

.000 1.000 

1.000 .000 

1.000 .000 

1.000 .000 

1.00,0 .000 

1.000 1.000 

.000 1.000 

.000 1.000 

.000 1.000 

EVAPORATOR CAPACITY---------------

CONDENSER HEAT REJECTION RATE ----

COMPRESSOR POWER REQUIREMENT -----

COEFFICIENT OF PERFORMANCE -------

FRACTION AIR TO FRESH FOOD ------- .150 (SINGLE EVAPORATOR CYCLE) 

ESTIMATED COMPRESSION EFFICIENCY -

ESTIMATED MOTOR-PUMP EFFICIENCY -

ESTIMATED CLEARANCE VOLUME 

ESTIMATED SHELL LOSS 

ESTIMATED DISC TUBE HEAT LOSS 

1.348 

.449 

.022 

.825 

.387 

(COMPRESSOR EER MODEL) 

(COMPRESSOR EER MODEL) 

(COMPRESSOR EER MODEL) 

(COMPRESSOR EER MODEL) 

(COMPRESSOR EER MODEL) 

HEAT EXCHANGER PERFORMANCE SUMMARY 

XQ 

1.000 

1.000 

1.000 

1.000 

.000 

.000 

.000 

.000 

.206 

1.000 

1.000 

1.000 

EXCHANGER EFFECTIVENESS, % SUBCOOLED FRACTION, % SUPERHEATED FRACTION, % 

EVAPORATOR --------- 96.2 

CONDENSER ---------- 89.4 

N/A 

.0 

COMPRESSOR PERFORMANCE SUMMARY 

REFRIGERANT MASS FLOW RATE -----

VOLUMETRIC EFFICIENCY ----------

PRESSURE RATIO ----------------- SUCTION PORT TEMPERATURE -------

DISCHARGE PORT TEMPERATURE -----

DISCHARGE SUPERHEAT ------------

6.040 KG/HR 

.772 

10.05 

49.9 C 

126.2 C 

26.4 C 

Figure 7-8. Cycle Analysis Output 

7-19 

2.5 

11.0 
I 77.9

+-----------+ Condenser - ------------ 77.8

I I I I-I 1

Conpr I 563.

I I

45.2 1 32 . 4 32.4

I

I I

11

12.9 I 1 -21.6

I

788. KJ/HR I

1 -23.2 1 I 1

+--X--------I Evaporator

I I

I-----------+

Figure 7-8. Cycle Analysis Output (continued)

KJ/HR

7-20

 EE-RM-93-801 COMMENT OR2

848. KJ/HR. 

51.3 I I 77.9 

+-----------+ Condenser +-----------+ 77.8 I 1 ______________________ , __ 1 __ 

I 

I 

I 

45.2 I 32.4 

I 

_1- _ i I 

I me I 

I--,-~I 12.9 I -21.6 

I 

Compr 563. KJ/HR. 

32.4 

I I 

I '788. KJ/HR. I 

I I 

I -23.2 I I I 

+--x--------I Evaporator 1-----------+ 

,----------------------1 

Figure 7-8. Cycle Analysis Output (continued) 

7-20 
7.7 Energy Consumption Results (E .OU

Output file ERA.OUT provides a summary of the calculated loads and daily energy

consumption (Figure 7-9). It also gives information on the type of refrigerator cabinet,

thermodynamic cycle, and refrigerant. For a single evaporator, the cabinet set points

are fixed and the air baffle is adjusted (mathematically) by the model to achieve the

cabinet temperatures. For some cases, this temperat ure may not be fixed, but may be

dependent on the cabinet design and the design of the refrigeration cycle (for example,

with a Lorenz cycle using natural convection evaporators). In this instance the output

will show both the desired and actual cabinet temperatures.

A number of heat load parameters appear in the summary cabinet loads table in addi

. These include : electric defrost, penetrations, heaters-tion to the wall conduction loads

and controls, fan heat, refrigerant line heat, in-wall evaporator, in-mullion evaporator,

and in-wall condenser:

® Electric Defrost -- total heat associatd with defrost, including scheduled defrost

energy from closed door test and from frosting effects associated with door openings

® Penetrations -- defined heat leaks not directly associated with controls or heaters

® Heaters and Controls -- sum of "constant` and "cycle-dependent " controls and heaters

® Fan Heat --calculated on the basis of compressor run time and fan power

® Refrigerant Line Heat -- heat from a vapor line or a liquid line used for anti-sweat

purposes that enters the cabinet around door flanges and the mullion

® In-Wall Evaporator -- additional heat flow into the cabinet from the presence of a

cold-plate evaporator, not accounted for in the cabinet loads analysis CABINET.-

OUT file

In-Mullion Evaporator -- added cooling of the fresh food section due to the presence of an evaporator in the mullion section of the freezer. The load will be negative (cooling)

In-Wall Condenser -- added cabinet heat load due to the presence of a hot-wall condenser.

The total values shown for the cabinet section are the hourly average loads which must

be removed by the refrigeration system.

Two cooling capacities are shown: 1) evaporator load, and 2) net capacity. Normally

these two quantities are the same. If a cold-plate evaporator is used, however, the total

evaporator load will be higher than the net capacity due to the heat going directly to

the back of the evaporator through the insulation.

 EE-RM-93-801 COMMENT OR2

7.7 Energy Consumption Results (ERA.OUT) 

Output file ERA.OUT provides a summary of the calculated loads and daily energy 

consumption (Figure 7-9). It also gives infonnation on the type of refrigerator cabinet, 

thennodynamic cycle, and refrigerant. For a single evaporator, the cabinet set points 

are fixed and the air baffle is adjusted (mathematically) by the model to achieve the 

cabinet temperatures. For some cases, this temperature may not be fixed, but may be 

dependent on the cabinet design and the design of the refrigeration cycle (for example, 

with a Lorenz cycle using natural convection evaporators). In this instance the output 

will show both the desired and actual cabinet temperatures. 

A number of heat load parameters appear in the summary cabinet loads table in addition to the wall conduction loads. These include: electric defrost, penetrations, heaters 

and controls, fan heat, refrigerant line heat, in-wall evaporator, in-mullion evaporator, 

and in-wall condenser: 

• Electric Defrost -- total heat associatd with defrost, including scheduled defrost 

energy from closed door test and from frosting effects associated with door openings 

• Penetrations -- defined heat leaks not directly associated with controls or heaters 

• Heaters and Controls -- sum of "constant' and "cycle-dependent" controls and heaters 

" Fan Heat --calculated on the basis of compressor run time and fan power 

" Refrigerant Line Heat -- heat from a vapor line or a liquid line used for anti-sweat 

purposes that enters the cabinet around door flanges and the mullion 

" In-Wall Evaporator -- additional heat flow into the cabinet from the presence of a 

cold-plate evaporator, not accounted for in the cabinet loads analysis CABINET.-

OUT file 

• In-Mullion Evaporator -- added cooling of the fresh food section due to the presence of an evaporator in the mullion section of the freezer. The load will be negative (cooling) 

• In-Wall Condenser -- added cabinet heat load due to the presence of a hot-wall condenser. 

The total values shown for the cabinet section are the houdy average loads which must 

be removed by the refrigeration system. 

Two cooling capacities are shown: 1) evaporator load, and 2) net capacity. Nonnally 

these two quantities are the same. If a cold-plate evaporator is used, however, the total 

evaporator load will be higher than the net capacity due to the heat going directly to 

the back of the evaporator through the insulation. 

7-21 
RUN NUMBER : FILE N : MODEL D.E

S Y RESULTS

Multiple Pathways Baseline Protot : Model -D (Top-Mount)

TOP-XOUNT REFRIGERATOR! F EZ

STANDARD SINGLE EVAPORATOR CYCLE

DATE: 03/18/93

T : 10:51

REFRIGERANT DATA FRESH FOOD FREEZER

R12 R12

SET POINTS ( C) 3.330 -15.000

CABINET LOADS (W)

CONDUCTION

FRESH FOOD

38.470

FREEZER

33.990

TOTAL

72.460

DOOR OPENINGS . 000 .000 .000

FROSTING . 000 .000 .000

ELEC DEFROST . 000 2 . 805 2.805

PENETRATIONS .000 .000 .000

HEATERS & CONTROLS .690 1.380 2.070

FAN HEAT .526 2.989 3.515

REFRIGERANT LINE . 000 1 . 200 1.200

IN WALL EVAP .000 .000 .000

IN MULLION EVAP .000 .000 .000

IN WALL COND . 000 .000 .000

TOTAL LOADS 39.686 42 . 364 82.050

REFRIGERATION CYCLE

EVAP LOAD ( W) 219.135

NET CAPACITY ( W) 219.135

MASS FLOW ( KG/HR) 6.040

COP - STEADY STATE 1.401

COP - CYCLING 1.373

DUTY CYCLE .374

COMPRESSOR (KWH/DAY) 1.433

FANS ( /DAY) .192

ELECTRONICS (KWH/DAY) .000

HEATERS & CONTROLS ( KWH/DAY) .079

DEFROST (KWH/DAY) .067

TOTAL ENERGY USE (KWH/DAY) 1.772

Figure 7-9. Energy Consumption Results

7-22

 EE-RM-93-801 COMMENT OR2

RUN NUMBER: FILE NAME: MODEL D. ERA 

SUMMARY RESULTS 

Multiple Pathways Baseline Prototype: Model D (Top-Mount) 

TOP-MOUNT REFRIGERATOR/FREEZER 

STANDARD SINGLE EVAPORATOR CYCLE 

REFRIGERANT DATA 

SET POINTS (C) 

CABINET LOADS (W) 

CONDUCTION 

DOOR OPENINGS 

FROSTING 

ELEC DEFROST 

PENETRATIONS 

HEATERS & CONTROLS 

FAN HEAT 

REFRIGERANT LINE 

IN WALL EVAP 

IN-MULLION EVAP 

IN-WALL COND 

TOTAL LOADS 

REFRIGERATION CYCLE 

EVAP LOAD (W) 

NET CAPACITY (W) 

MASS FLOW (KG/HR) 

COP - STEADY STATE 

COP - CYCLING 

DUTY CYCLE 

COMPRESSOR (KWH/DAY) 

FANS (KWH/DAY) 

ELECTRONICS (KWH/DAY) 

HEATERS , CONTROLS (KWH/DAY) 

DEFROST (KWH/DAY) 

TOTAL ENERGY USE (KWH/DAY) 

FRESH FOOD 

R12 

3.330 

FRESH FOOD 

38.470 

.000 

.000 

.000 

.000 

.690 

.526 

.000 

.000 

.000 

.000 

39.686 

219.135 

219.135 

6.040 

1.401 

1.373 

.374 

1.433 

.192 

.000 

.079 

.067 

1.772 

FREEZER 

R12 

-15.000 

FREEZER 

33.990 

.000 

.000 

2.805 

.000 

1.380 

2.989 

1.200 

.000 

.000 

.000 

42.364 

Figure 7-9. Energy Consumption Results 

7-22 

DATE: 03/18/93 

TIME: 10:51 

TOTAL 

72.460 

.000 

.000 

2.805 

.000 

2.070 

3.515 

1.200 

.000 

.000 

.000 

82.050 
The refrigerant mass flow rate and steady state COP are taken directly from the cycle

output (Figure 7-8). Duty cycle (compressor run time fraction) is calculated by the

ratio of the hourly average cabinet load and the instantaneous evaporator capacity.

Cycling losses are established from the duty cycle (see Appendix B).

The total daily energy consumption is the sum of the following:

® Compressor energy -- compressor power times duty cycle

® Fan energy -- fan power times duty cycle

® Electronics -- variable speed drive electronics loss

® Heaters and controls -- auxiliary electrical energy

® Defrost -- total defrost energy, including frosting effects associated with open doors

For the sample problem, a 1993 prototype 18 cu-ft top-mount refrigerator/freezer, the

daily energy consumption is 1.77 kWh, yielding an annual consumption of 647 kWh.

Figure 7-9 shows the summary output for a single evaporator cycle using a pure refrigerant. Alterations to this file will appear for the other refrigeration cycles.

 EE-RM-93-801 COMMENT OR2

The refrigerant mass flow rate and steady state COP are taken directly from the cycle 

output (Figure 7-8). Duty cycle (compressor run time fraction) is calculated by the 

ratio of the hourly average cabinet load and the instantaneous evaporator capacity. 

Cycling losses are established from the duty cycle (see Appendix B). 

The total daily energy consumption is the sum of the following: 

" Compressor energy -- compressor power times duty cycle 

.. Fan energy -- fan power times duty cycle 

.. Electronics -- variable speed drive electronics loss 

• Heaters and controls -- auxiliary electrical energy 

e Defrost -- total defrost energy, including frosting effects associated with open doors 

For the sample problem, a 1993 prototype 18 cu-ft top-mount refrigerator/freezer, the 

daily energy consumption is 1.77 kWh, yielding an annual consumption of 647 kWh. 

Figure 7 -9 shows the summary output for a single evaporator cycle using a pure refrigerant. Alterations to this file will appear for the other refrigeration cycles. 

7-23 
8.0 SUGGESTIONS FOR USING

8.1 Fite Naming Conventions

The ERA menu-driven input processor is capable of generating and storing a large

number of data files in a short time. Each file name can have up to 8 characters and

must have extension ERA. Since each file has a 5-line title block, the file can be read

into ERA and edited to determine the contents of the file.

A simpler means of distinguishing between the various files is to adopt a file naming

convention. One stegy is illustrated in Appendix C, which lists files prepared for the

multiple pathways study [5]. For example, Path I is based on the Model D refrigerator/freezer design. The path contains a baseline 1991 model (MODEL_D), a baseline

1993 model using C- 134a refrigerant and an HCFC blown foam (D_1993), and 10

additional steps:

Step Change File Name

1 Cut gasket loss 25% D1_01G25

2 Cut gasket loss 50% total D1_02G50

3 Liquid line mullion anti-sweat heat Dl_03LLM

4 5.5 EER Compressor D1_04C

5 Add 3/4 inch insulation to door D 1_O5DRI

6 crocell insulation D1 06MCI

7 Add 1 inch insulation everywhere D1_071N1

8 Adaptive defrost Dl_08ADF

9 ECM evaporator fan D 1_09DCE

10 ECM condenser fan D1_10DCC

The particular naming strategy adopted here is straightforward: the first letter is the

Model (D), the next two are the path identifier, then the step in path (1-10), followed

by a two or three letter code that identifies the component change.

ERA allows the use of special characters, such as the underline, slash and numbers, to

create a meaningful name for each file. There are no fixed rules for naming conventions.

8.2 Internal Documentation of the Case

The user has access to a full screen editor in the menu program to create a 5 line new

title. Each line contains up to 68 characters. When making many runs, it will be

important to fully describe the run using the built-in editor. The run title is then reproduced on the summary output file (ERA.OUT) along with the name of the data file and

the time the run was made.

 EE-RM-93-801 COMMENT OR2

8.0 SUGGESTIONS FOR USING ERA 

8.1 File Naming Conventions 

The ERA menu-driven input processor is capable of generating and storing a large 

number of data files in a short time. Each file name can have up to S characters and 

must have extension .ERA. Since each file has a 5-line title block, the file can be read 

into ERA and edited to determine the contents of the file. 

A simpler means of distinguishing between the various files is to adopt a me naming 

convention. One strategy is illustrated in Appendix C, which lists mes prepared for the 

multiple pathways study [5]. For example, Path 1 is based on the Model D refrigerator/freezer design. The path contains a baseline 1991 model (MODEL_D), a baseline 

1993 model using HFC-134a refrigerant and an HCFC blown foam (0_1993), and 10 

additional steps: 

Step Change FileName 

1 1 Cut gasket loss 25% Dl_01G25 

~ Cut gasket loss 50% total Dl_02G50 

3 Liquid line mullion anti-sweat heat Dl_03LLM 

4 5.5 EER Compressor Dl_04CMP 

5 Add 3/4 inch insulation to door Dl_05DRI 

6 Microcell insulation Dl_06MCI 

7 Add 1 inch insulation everywhere DC07INI 

S Adaptive defrost Dl_0SADF 

9 ECM evaporator fan Dl_09DCE 

10 ECM condenser fan Dl_lODCC 

The particular naming strategy adopted here is straightforward: the ftrst letter is the 

Model (D), the next two are the path identifier, then the step in path (1-10), followed 

by a two or three letter code that identifies the component change. 

ERA allows the use of special characters, such as the underline, slash and numbers, to 

create a meaningful name for each me. There are no fixed rules for naming conventions. 

8.2 Internal Documentation of the Case 

The user has access to a full screen editor in the menu program to create a 5 line new 

title. Each line contains up to 68 characters. When making many runs, it will be 

important to fully describe the run using the built-in editor. The run title is then reproduced on the summary output file (ERA. OUT) along with the name of the data me and 

the time the run was made. 

8-1 
Note that ERA will overwrite the outputfiles with each new run. Hence, when making

multiple runs, the output data should be either saved under a new name or printed after

each analysis.

8.3 Summary Output Form

ERA contains a blank form that can be used to summarize the results. An example is

shown in Figure 8-l. Copies of this form can be made by printing out file SUMMARY.

 EE-RM-93-801 COMMENT OR2

Note that ERA will overwrite the output files with each new run. Hence, when making 

multiple runs, the output data should be either saved under a new name or printed after 

each analysis. 

8.3 Summary Output Form 

ERA contains a blank form that can be used to summarize the results. An example is 

shown in Figure 8-1. Copies of this form can be made by printing out file SUMMARY. 

8-2 
RUN SYNOPSIS

Run Number : File N :

A. CABINET

Reference Cabinet Design (Code

Exceptions to Reference Desi :

R. Refrigeration Cycle

Reference Cycle Design (Code Number):

Exceptions to Reference Design:

Date:

C. Summary Results Reference Analysis

Total Cabinet Load (w)

Compressor Energy (kWh)

Total Energy Use (kWh)

D. Findings and Conclusions:

Figure 8 -1. Summary Output Form

 EE-RM-93-801 COMMENT OR2

RUN SYNOPSIS 

Run Number: ____________ _ File Name: 

A. CABINET 

Reference Cabinet Design (Code Number) : 

Exceptions to Reference Design: 

B. Refrigeration Cycle 

Reference Cycle Design (Code Number) : 

Exceptions to Reference Design: 

C. Summary Results 

Total Cabinet Load (w) 

Compressor Energy (kWh) 

Total Energy Use (kWh) 

D. Findings and Conclusions: 

Reference 

Figure 8-1. Summary Output Form. 

8-3 

Date: __________ _ 

Analysis 
9.0 REFERENCES

1. "Engineering Computer Models for Refrigerators, Freezers, Furnaces, Water Heaters, Room and Central Air Conditioners," Report to U.S. DOE, by Arthur D. Little,

Inc., November 1982.

2. McLinden, M., "Theoretical Vapor Compression Cycle, CYCLE7," unpublished.

3. Morrison, G., and McLinden, M., "Application of a Hard Sphere Equation of State

to Refrigerants and Refrigerant Mixtures," National Bureau of Standards Technical

1 2 18,1986.

4. "NIST Standard Reference Database 23: NIST Thermodynamic Properties of

Refrigerants and Refrigerant Mixtures Database, Version 3.0," NIST, December

1991.

5. "Multiple Pathways to Super Efficient Refrigerators," U.S. EPA, Global Change

Division, Office of Atmospheric Programs, 1993.

6. Janssen, M.J.P., de Wit, J.A., and Kuijpers, L.J.M., "Cycling Losses in Domestic

Appliances: An Experimental and Theoretical Analysis," Proceedings of the 1990

USNC/IIR-Purdue Refrigeration Conference, July 17-20, 1990, Purdue University, West Lafayette, Indiana

7. Alissi, H.S., Ramadhyani, S., and Schoenhals, R.J., "Effects of Ambient Temperature, Ambient Humidity, and Door Openings on Energy Consumption of a Household Refrigerator-Freezer," ASHRAE Transactions, 1988,94 (Part 2), pp.

1713-1736.

 EE-RM-93-801 COMMENT OR2

9.0 REFERENCES 

1. "Engineering Computer Models for Refrigerators, Freezers, Furnaces, Water Heaters, Room and Central Air Conditioners," Report to U.S. DOE, by Arthur D. Little, 

Inc., November 1982. 

2. McLinden, M., "Theoretical Vapor Compression Cycle, CYCLE7," unpublished. 

3. Morrison, G., and McLinden, M., "Application of a Hard Sphere Equation of State 

to Refrigerants and Refrigerant Mixtures," National Bureau of Standards Technical 

Note 1218, 1986. 

4. "NIST Standard Reference Database 23: NIST Thermodynamic Properties of 

Refrigerants and Refrigerant Mixtures Database, Version 3.0," NIST, December 

1991. 

5. "Multiple Pathways to Super Efficient Refrigerators," U.S. EPA, Global Change 

Division, Office of Atmospheric Programs, 1993. 

6. Janssen, M.J.P., de Wit, J.A., and Kuijpers, L.J.M., "Cycling Losses in Domestic 

Appliances: An Experimental and Theoretical Analysis," Proceedin~s of the 1990 

USNCIIIR-Purdue Refrigeration Conference, July 17-20, 1990, Purdue University, West Lafayette, Indiana 

7. Alissi, H.S., Ramadhyani, S., and Schoenhals, R.J., "Effects of Ambient Temperature, Ambient Humidity, and Door Openings on Energy Consumption of a Household Refrigerator-Freezer," ASHRAE Transactions, 1988,.21 (Part 2), pp. 

1713-1736. 

9-1 
APPENDIX

OVERVIEW OF C ,®® T LOADS ANALYSIS TECHNICAL APPROACH

A.1 Wall Heat Loads A-2

A.2 Advanced Insulation Panels A-3

A.3 Door Openings A-6

A.4 Gasket Model A-8

A.5 Anti-sweat Heat A-8

A.6 References A-9

 EE-RM-93-801 COMMENT OR2

APPENDIX A 

OVERVIEW OF CABINET LOADS ANALYSIS TECHNICAL APPROACH 

A.1 Wall Heat Loads A-2 

A.2 Advanced Insulation Panels A-3 

A.3 Door Openings A-6 

AA Gasket Model A-8 

A.5 Anti-sweat Heat A-8 

A.6 References A-9 

A-I 
A.1 Wall Heat Loads

The major heat load on the cabinet results from heat conduction across the walls comprising the cabinet, with convection boundary conditions. Calculation of the conduction heat flow is based on the following assumptions:

® steady heat flow, with fixed thermal properties characterizing each wall;

® constant heat transfer coefficients;

® fixed inside and outside temperatures;

® one dimensional heat transfer (longitudinal heat flow is neglected).

Corrections to the simple 1-D heat flow analyses are made for:

® comer and edge effects (to account for different outside and inside surface areas);

® composite structures, such as foam and vacuum panel sandwich constructions.

The overall heat flow across a wall of the cabinet can be written:

Qw= (UA)w(Tr -T) (A-1)

where

U = overall heat transfer conductance

A = wall area (inside surface)

Tr = room temperature

T,, = cabinet temperature

The expression UA is composed of inside and outside film coefficients and areas,

cabinet insulation properties, and correction factors for comers and edges:

UA = 1 (A -2)

1/h0Ao + 11UwA; + 1/h;A;

where

hi, ho = film coefficients, inside and outside surfaces

Ai, A, = surface areas, inside and outside cabinet

 EE-RM-93-801 COMMENT OR2

A.1 Wall Heat Loads 

The major heat load on the cabinet results from heat conduction across the walls comprising the cabinet, with convection boundary conditions. Calculation of the conduction heat flow is based on the following assumptions: 

G steady heat flow, with fixed thermal properties characterizing each wall; 

e constant heat transfer coefficients; 

G fixed inside and outside temperatures; 

" one dimensional heat transfer (longitudinal heat flow is neglected). 

Corrections to the simple 1-D heat flow analyses are made for: 

• comer and edge effects (to account for different outside and inside surface areas); 

e composite structures, such as foam and vacuum panel sandwich constructions. 

The overall heat flow across a wall of the cabinet can be written: 

(A -1) 

where 

U = overall heat transfer conductance 

A = wall area (inside surface) 

T = room temperature r 

T = cabinet temperature c 

The expression UA is composed of inside and outside film coefficients and areas, 

cabinet insulation properties, and correction factors for comers and edges: 

(A -2) 

where 

h h = film coefficients, inside and outside surfaces I' 0 

A A = surface areas, inside and outside cabinet I' 0 

A-2 
= wall conductance w

The wall conductance is the sum of the conductance across a plane, with corrections

for the additional heat flow along the edges and at the comers [1]:

U A,= kA,/x+0.54kY,1;+0.l4nkt (A-3)

where

x = thickness of wall (ft)

k = thermal conductivity (Btu/hr-ft-F)

I = inside edge length (ft)

t = average insulation thickness (ft)

n = number of corners

Equation (A-3) gives the wall conduction in English units (Btu/hr-ft2-°F); the edge and

comer correction factors assume the same units since this is the form in which they

were first published [2].

Equations (A-1) through (A-3) are applied to all surfaces, including the mullion

between the freezer and fresh food section, and the doors. Note that some average

thermal conductivity, k, is assumed for the wall. Determination of the appropriate

average value for an advanced insulation panel is discussed later.

The values assumed for the inside and outside free convective surface heat transfer

coefficients (including radiative heat transfer effects) are [1]:

h; = 1.00 Btu/hr-ft2-°F (5.68 W/m2-C)

h,, = 1.47 Btu/hr-ft2-°F (8.35 W/m2-C)

A.2 Advanced Insulation Panels

The use of advanced insulation panels may require installation of some sort of a sandwich of foam, and vacuum insulation panel. Depending on the thickness and material

properties of the enclosing material, some "edge" effects for multidimensional heat

transfer in the wall must be taken into account.

The approach adopted by ERA is to determine approximate correction factors to the

one dimensional heat flow. These factors are intended to account for: 1) heat flow

along a conducting enclosure material, and 2) incomplete coverage of the wall by the

high-R panel. Calculation of these factors is carried out in one of the Help menus in

the input processor program.

 EE-RM-93-801 COMMENT OR2

u = wall conductance w 

The wall conductance is the sum of the conductance across a plane, with corrections 

for the additional heat flow along the edges and at the corners [1]: 

where 

x = thickness of wall (ft) 

k = thermal conductivity (Btu/hr-ft-F) 

I = inside edge length (ft) 

t = average insulation thickness (ft) 

n = number of corners 

(A -3) 

Equation (A-3) gives the wall conduction in English units (Btu/hr-fr-T); the edge and 

corner correction factors assume the same units since this is the form in which they 

were first published [2]. 

Equations (A-I) through (A-3) are applied to all surfaces, including the mullion 

between the freezer and fresh food section, and the doors. Note that some average 

thermal conductivity, k, is assumed for the wall. Determination of the appropriate 

average value for an advanced insulation panel is discussed later. 

The values assumed for the inside and outside free convective surface heat transfer 

coefficients (including radiative heat transfer effects) are [1]; 

h = 1.00 Btu!hr-fe-T (5.68 W/m2-C) I 

h = 1.47 Btu/hr-ff-T (8.35 W/m2-C) o 

A.2 Advanced Insulation Panels 

The use of advanced insulation panels may require installation of some sort of a sandwich of foam, and vacuum insulation panel. Depending on the thickness and material 

properties of the enclosing material, some "edge" effects for multidimensional heat 

transfer in the wall must be taken into account. 

The approach adopted by ERA is to determine approximate correction factors to the 

one dimensional heat flow. These factors are intended to account for: 1) heat flow 

along a conducting enclosure material, and 2) incomplete coverage of the wall by the 

high-R panel. Calculation of these factors is carried out in one of the Help menus in 

the input processor program. 

A-3 
Figure A-1 illustrates the general geometrical situation treated by the model. Parameters describing the configuration are: the overall dimensions of the wall slab, the distances from the edges of the high resistance center panel to each of the four edges of

the slab (they may be different), the distances from the two faces of the panel to the

inside and outside surfaces of the wall (one or both may be zero), the panel resistivity

in the absence of edge losses, the panel enclosure thickness, and the enclosure thermal

conductivity. Note that wall slabs may have one or more beveled edges, depending on

the cabinet element under consideration.

As noted in Figure A-1, the refrigerator wall is treated as a composite system of foam

and an interior high-resistance panel. Foam along the side of the panel contributes to

the net "heat transfer coefficient" on the side by combining with the air-side film coefficient; the inverse of the net resistance is the effective heat transfer coefficient along

the panel side. Heat transfer through the foam along the edges is considered parallel

heat transfer; that is, the wall is broken into two sections, one containing the panel, and

the other containing pure foam. Although the method ignores the possibilities of "short

circuiting" of heat through the foam around the panel, detailed finite difference calculations for practical geometries and panel properties showed this to be a very small

effect. However, as discussed in the next paragraph, short circuiting of heat along the a

high conductivity panel enclosure was taken into account.

As a first step in the calculation of the overall thermal resistance, the perimeter heat

loss from a semi-infinite slab containing the thermally conducting panel enclosure is

established. A standard fin analysis is utilized to represent the longitudinal heat flows

along the enclosure surfaces towards the edges (perimeter). The calculated perimeter

heat flow is considered as a parallel heat flow term to the normal heat flow across the

semi-infinite slab.

Calculations for perimeter heat flow are carried out independently for both directions: a

semi-infinite slab in the width direction and a semi-infinite slab in the length direction.

Because of comer effects, the two perimeter heat flows are not additive. They are

combined using a correction factor, based on the relative dimensions of the panel edges

in the width and length directions. Once the total perimeter heat flow is established the

net resistance of the wall slab is determined.

Although the approach is only approximate, it is intended to capture most of the effects

associated with multidimensional heat transfer with composites of foam and vacuum

insulation panels. This has been confirmed by comparing ERA model predictions with

the results of a high resolution finite element analysis, performed on a main frame

computer, of several test conditions.

Two generic cases were considered: 1) a composite flat square slab of 36 inch by 36

inch, 1.5 inch thick, with 0.5 inch thick vacuum panel in the center, and with 0.5 inch

foam on either side; 2) a corner of a two foot cube with 1.5 inch thick walls and with a

vacuum panel located in the center of the wall. Case 1 is typical of a the geometry of a

door element. Case 2 is typical of the back wall of a cabinet (where the outside surface

is larger than the inside surface). The inner panel consists of an evacuated r-20 powder enclosed in an 8-mil stainless steel structure. The results of these two test cases are

summarized below:

A-4

 EE-RM-93-801 COMMENT OR2

Figure A-I illustrates the general geometrical situation treated by the model. Parameters describing the configuration are: the overall dimensions of the wall slab, the distances from the edges of the high resistance center panel to each of the four edges of 

the slab (they may be different), the distances from the two faces of the panel to the 

inside and outside surfaces of the wall (one or both may be zero), the panel resistivity 

in the absence of edge losses, the panel enclosure thickness, and the enclosure thermal 

conductivity. Note that wall slabs may have one or more beveled edges, depending on 

the cabinet element under consideration. 

As noted in Figure A-I, the refrigerator wall is treated as a composite system of foam 

and an interior high-resistance panel. Foam along the side of the panel contributes to 

the net "heat transfer coefficient" on the side by combining with the air-side film coefficient; the inverse of the net resistance is the effective heat transfer coefficient along 

the panel side. Heat transfer through the foam along the edges is considered parallel 

heat transfer; that is, the wall is broken into two sections, one containing the panel, and 

the other containing pure foam. Although the method ignores the possibilities of "short 

circuiting" of heat through the foam around the panel, detailed finite difference calculations for practical geometries and panel properties showed this to be a very small 

effect. However, as discussed in the next paragraph, short circuiting of heat along the a 

high conductivity panel enclosure was taken into account. 

As a first step in the calculation of the overall thermal resistance, the perimeter heat 

loss from a semi-infinite slab containing the thermally conducting panel enclosure is 

established. A standard fin analysis is utilized to represent the longitudinal heat flows 

along the enclosure surfaces towards the edges (perimeter). The calculated perimeter 

heat flow is considered as a parallel heat flow term to the normal heat flow across the 

semi-infinite slab. 

Calculations for perimeter heat flow are carried out independently for both directions: a 

semi-infinite slab in the width direction and a semi-infinite slab in the length direction. 

Because of comer effects, the two perimeter heat flows are not additive. They are 

combined using a correction factor, based on the relative dimensions of the panel edges 

in the width and length directions. Once the total perimeter heat flow is established the 

net resistance of the wall slab is determined. 

Although the approach is only approximate, it is intended to capture most of the effects 

associated with multidimensional heat transfer with composites of foam and vacuum 

insulation panels. This has been confrrmed by comparing ERA model predictions with 

the results of a high resolution finite element analysis, performed on a main frame 

computer, of several test conditions. 

Two generic cases were considered: 1) a composite flat square slab of 36 inch by 36 

inch, 1.5 inch thick, with 0.5 inch thick vacuum panel in the center, and with 0.5 inch 

foam on either side; 2) a comer of a two foot cube with 1.5 inch thick walls and with a 

vacuum panel located in the center of the wall. Case 1 is typical of a the geometry of a 

door element. Case 2 is typical of the back wall of a cabinet (where the outside surface 

is larger than the inside surface). The inner panel consists of an evacuated r-20 powder enclosed in an 8-mil stainless steel structure. The results of these two test cases are 

summarized below: 

A-4 
w

Figure A-1. Advanned Insulation Composite System

 EE-RM-93-801 COMMENT OR2

Foam 

L 

I ... w 

Figure A .. 1 .. Foam & Advanced Insulation Composite System 
Distance of Panel

from an Edge (in)

Overall Resistance

(Finite Element)

Overall Resistance

(ERA Model)

Case 1 0 14.34 14.58

1 13.69 13.90

6 11.61 11.68

12 10.54 10.57

Case 2 +1 15.66 16.05

+0.5 15.51 15.22

0 15.16 14.50

-1 14.23 13.31

-2 12.96 12.39

all foam 9.32 9.31

The maximum difference between the very detailed (and time consuming) finite

element solution and the ERA simplified algorithm solutions for these two test cases is

about 6%, with an average difference of about 2%. Hence, for the purposes of the

types of design tradeoffs to be carried out with ERA, the model appears adequate.

A.3 Door Openings

A simplified model for the effects of open doors on the cabinet loads has been developed. A basis for the model is provided by the published work of Alissi, et. al. [3].

Door openings introduce dynamic phenomena into the net heat exchange between the

cabinet and the room air. At least four flow patterns are set up during the period the

door is open: 1) cool air will drain from the bottom of the cabinet due to density gradient driving forces, 2) warm air is sucked into the cabinet as the door is opened due to

the pressure gradient caused by the opening, 3) natural convection will occur between

the warm and cool air due to the buoyancy force differences, and 4) the cabinet air will

be disturbed due to human factors.

Modeled heat and mass transfer between the cabinet and the room air assumes two distinct phenomena: 1) an initial tumbling of the air (essentially immediate replacement of

the air occurs), 2) long term continuous convective flow and mass exchange. Modeled

convective sensible heat flow rates are dependent on the room air to cabinet wall temperature difference. The air densities and partial pressures of water vapor in the compartment and room determine the rate of mass (water vapor) exchange.

All moisture that enters the cabinet is assumed to condense, releasing a heat of condensation. In addition, moisture that enters the freezer compartment, either directly or

through air exchange with the fresh food compartment, is assumed to form frost. This

releases an additional amount of heat in the freezer compartment. If the appliance uses

A-6

 EE-RM-93-801 COMMENT OR2

Distance of Panel Overall Resistance Overall Resistance 

from an Edge (in) (Finite Element) (ERA Model) 

Case 1 0 14.34 14.58 

1 13.69 13.90 

6 11.61 11.68 

12 10.54 10.57 

Case 2 +1 15.66 16.05 

+0.5 15.51 15.22 

0 15.16 14.50 

-1 14.23 13.31 

-2 12.96 12.39 

all foam 9.32 9.31 

The maximum difference between the very detailed (and time consuming) fmite 

element solution and the ERA simplified algorithm solutions for these two test cases is 

about 6%, with an average difference of about 2%. Hence, for the purposes of the 

types of design tradeoffs to be carried out with ERA, the model appears adequate. 

A.3 Door Openings 

A simplified model for the effects of open doors on the cabinet loads has been developed. A basis for the model is provided by the published work of Alissi, et. al. [3]. 

Door openings introduce dynamic phenomena into the net heat exchange between the 

cabinet and the room air. At least four flow patterns are set up during the period the 

door is open: 1) cool air will drain from the bottom of the cabinet due to density gradient driving forces, 2) warm air is sucked into the cabinet as the door is opened due to 

the pressure gradient caused by the opening, 3) natural convection will occur between 

the warm and cool air due to the buoyancy force differences, and 4) the cabinet air will 

be disturbed due to human factors. 

Modeled heat and mass transfer between the cabinet and the room air assumes two distinct phenomena: 1) an initial tumbling of the air (essentially immediate replacement of 

the air occurs), 2) long term continuous convective flow and mass exchange. Modeled 

convective sensible heat flow rates are dependent on the room air to cabinet wall temperature difference. The air densities and partial pressures of water vapor in the compartment and room determine the rate of mass (water vapor) exchange. 

All moisture that enters the cabinet is assumed to condense, releasing a heat of condensation. In addition, moisture that enters the freezer compartment, either directly or 

through air exchange with the fresh food compartment, is assumed to form frost. This 

releases an additional amount of heat in the freezer compartment. If the appliance uses 

A-6 
automatic defrost, the heat required to melt the frost will be a further heat load on the

freezer; if manual defrost is assumed, the heat of defrost is not part of the overall heat

load.

As discussed, the net heat load due to each door opening is comprised of four terms:

® Initial Sensible Load: Q,= PC,(7',- T)(Vn) (A -4)

® Initial Latent Load Q, = (0)Q -WC)hfg(Vcn) (A-5)

® Convective Sensible Load Q h[Al(°,-T )bd (A -6)

® Convective Latent Load Q ,j = hm(hig) (Op,- P)AItd (A -7)

where

Ai = inside surface area of cabinet

h = convective heat transfer coefficient

hig = heat of sublimation

hfg = heat of condensation

hm = mass transfer coefficient (related to

convective heat transfer coefficient)

T,; = cabinet air temperature

Tr = room temperature

td = length of time the door is open each hour

Vin = volume of cabinet times number of times

door opened during the hour

 EE-RM-93-801 COMMENT OR2

automatic defrost, the heat required to melt the frost will be a further heat load on the 

freezer; if manual defrost is assumed, the heat of defrost is not part of the overall heat 

load. 

As discussed, the net heat load due to each door opening is comprised of four terms: 

• Initial Sensible Load: (A -4) 

" Initial Latent Load (A -5) 

" Convective Sensible Load (A -6) 

.. Convective Latent Load (A -7) 

where 

A. = inside surface area of cabinet I 

h = convective heat transfer coefficient 

h. = heat of sublimation Ig 

hfg = heat of condensation 

h = mass transfer coefficient (related to m 

convective heat transfer coefficient) 

Tc = cabinet air temperature 

Tr = room temperature 

td = length of time the door is open each hour 

V n = volume of cabinet times number of times c 

door opened during the hour 

A-7 
and

0 = relative humidity

p^ = density of air at cabinet temperature

Pr = density of air at room temperature

= humidity ratio of room air (r)

or cabinet air (c)

The above equations hold for all cabinet types except the chest freezer. Here, it is

assumed that there is not an initial emptying of the cabinet, and that the heat and mass

transfer coefficients are one half of those for an upright unit.

AA Gasket Model

The gasket model assumes that the rate of heat input is a linear function of the gasket

path length (door perimeter) and the room-cabinet temperature difference. In actuality,

the rate of heat leak may be influenced by fan operation, and may vary according to the

tightness of fit.

A detailed finite element analysis carried out the by University of Kentucky [4] has

shown that the major paths for heat flow are along the cabinet flange and the door

flange, with a lesser amount through the gasket itself. Because of the complexity of the

heat flows in this region, ERA relies on the user to specify realistic values for the heat

loss coefficient, rather than attempting to model the gasket region itself. Typical values for heat loss are provided in the Help menu.

A.5 Anti-sweat Heat.

Anti-sweat heat may be applied along the front surface of the cabinet and across the

front face of the mullion. It may be supplied from electrical resistance heater wires,

hot gas leaving the compressor prior to entering the condenser or heat from the refrigerant leaving the condenser.

If electric heater wires are used, standard closed door rating tests normally require that

the refrigerator performance be measured with the heaters on and then with the heaters

off. The rating is based on the average of these tests. As a short cut analytical

approach, the user may assume that the DOE test conditions are equivalent to measuring performance with half the anti-sweat heat input. Operation of the heaters is continuous, not dependent on the behavior of the refrigeration system.

 EE-RM-93-801 COMMENT OR2

and 

<1> = relative humidity 

Pc = density of air at cabinet temperature 

Pr = density of air at room temperature 

ro = humidity ratio of room air (r) 

or cabinet air (c) 

The above equations hold for all cabinet types except the chest freezer. Here, it is 

assumed that there is not an initial emptying of the cabinet, and that the heat and mass 

transfer coefficients are one half of those for an upright unit. 

A.4 Gasket Model 

The gasket model assumes that the rate of heat input is a linear function of the gasket 

path length (door perimeter) and the room-cabinet temperature difference. In actuality, 

the rate of heat leak may be influenced by fan operation, and may vary according to the 

tightness of fit. 

A detailed finite element analysis carried out the by University of Kentucky [4] has 

shown that the major paths for heat flow are along the cabinet flange and the door 

flange, with a lesser amount through the gasket itself. Because of the complexity of the 

heat flows in this region, ERA relies on the user to specify realistic values for the heat 

loss coefficient, rather than attempting to model the gasket region itself. Typical values for heat loss are provided in the Help menu. 

A.5 Anti-sweat Heat. 

Anti-sweat heat may be applied along the front surface of the cabinet and across the 

front face of the mullion. It may be supplied from electrical resistance heater wires, 

hot gas leaving the compressor prior to entering the condenser or heat from the refrigerant leaving the condenser. 

If electric heater wires are used, standard closed door rating tests normally require that 

the refrigerator performance be measured with the heaters on and then with the heaters 

off. The rating is based on the average of these tests. As a short cut analytical 

approach, the user may assume that the DOE test conditions are equivalent to measuring performance with half the anti-sweat heat input. Operation of the heaters is continuous, not dependent on the behavior of the refrigeration system. 

A-8 
If hot gas from the compressor output line, or heat from the condenser liquid line, is

used for door flange and/or mullion heating, the net heat input will be dependent upon

the compressor run time. This is modelled by specifying the value for refrigerant line

anti-sweat heat input equal to that used for switchable electric heat in the on-position.

For example, if a 6 watt electric heater (average of 3 watts in simulation of the DOE

test condition) is replaced by liquid line heat, the user should specify 6 watts of refrigerant line heat. Since refrigerant line heat is not "switchable" the total heat input will

be larger than the average heat input corresponding to the DOE test conditions.

ERA will calculate the on-cycle heat removal required from the refrigerant line heater

to supply the cycle-averaged specified heat input. For example, if a cycle-average heat

input of 6 watts is specified and the duty cycle is 45%, the on-cycle heat removal must

be 6/0.45 = 13.3 watts. If this would result in an overcooling of the refrigerant line,

ERA will issue a warning message in the summary output (ERA.OUT). Then the user

must reduce the specified refrigerant line heat and replace the amount reduced with

switchable electric heat. Hence, is some situations the mullion may receive anti-sweat

from a liquid line and from a (smaller) electric heater at the same time.

AX References

1. "Engineering Computer Models for Refrigerators, Freezers, Furnaces, water Heaters, Room and Central Air Conditioners," Report to U.S. DOE by Arthur D. Little,

Inc, November, 1982.

2. Langmuir, I., Adams, E., And Meikle, G., "Flow of Heat Through Furnace Walls:

The Shape Factor," Trans. Amer. Electrochem. Soc., 24, pp. 53-84 (1913).

3. Alissi, M.S., Ramadhyani, S., and Schoenhals, R.3., "Effects of Ambient Temperature, Ambient Humidity, and Door Openings on Energy Consumption of a Household Refrigerator-Freezer," ASHRAE Transactions, 1988,94 (Part 2), pp. 1713 -

1736.

4. "Finite Element Analysis of Heat Transfer Through the Gasket Region of Refrigerator/Freezers," EPA/430/R-92/009.

 EE-RM-93-801 COMMENT OR2

If hot gas from the compressor output line, or heat from the condenser liquid line, is 

used for door flange and/or mullion heating, the net heat input will be dependent upon 

the compressor run time. This is modelled by specifying the value for refrigerant line 

anti-sweat heat input equal to that used for switchable electric heat in the on-position. 

For example, if a 6 watt electric heater (average of 3 watts in simulation of the DOE 

test condition) is replaced by liquid line heat, the user should specify 6 watts of refrigerant line heat. Since refrigerant line heat is not "switchable" the total heat input will 

be larger than the average heat input corresponding to the DOE test conditions. 

ERA will calculate the on-cycle heat removal required from the refrigerant line heater 

to supply the cycle-averaged specified heat input. For example, if a cycle-average heat 

input of 6 watts is specified and the duty cycle is 45%, the on-cycle heat removal must 

be 6/0.45 = 13.3 watts. If this would result in an overcooling of the refrigerant line, 

ERA will issue a warning message in the summary output (ERA.OUT). Then the user 

must reduce the specified refrigerant line heat and replace the amount reduced with 

switchable electric heat. Hence, is some situations the mullion may receive anti-sweat 

from a liquid line and from a (smaller) electric heater at the same time. 

A.S References 

1. "Engineering Computer Models for Refrigerators, Freezers, Furnaces, water Heaters, Room and Central Air Conditioners," Report to U.S. DOE by Arthur D. Little, 

Inc, November, 1982. 

2. Langmuir, I., Adams, E., And Meikle, G., "Flow of Heat Through Furnace Walls: 

The Shape Factor," Trans. Amer. Electrochem. Soc., 24, pp. 53-84 (1913). 

3. Alissi, M.S., Ramadhyani, S., and Schoenhals, R.J., "Effects of Ambient Temperature, Ambient Humidity, and Door Openings on Energy Consumption of a Household Refrigerator-Freezer," ASHRAE Transactions, 1988, ~ (Part 2), pp. 1713 -

1736. 

4. "Finite Element Analysis of Heat Transfer Through the Gasket Region of Refrigerator/Freezers," EPN430/R-92/009. 

A-9 
APPENDIX

OVERVIEW OF CYCLE ANALYSIS TECHNICAL APPROACH

B.1 Cycle Model Solution Procedure B-2

B.2 Compressor Performance Models B-5

B2.1 Physically Based Compressor Model B-5

B2.2 Rating Point Compressor Model B-10

B2.3 Map Based Compressor Model B-13

B.3 Cycling Losses B-15

B3.1 Cycling Rates B-16

B.3.2 Cycling Losses Without a Valve B-16

B.3.3 Cycling Effects with a Shut-off Valve B-16

B.4 Summary of Help Menu Heat Exchanger Analyses B-17

B.4.1 Air-Side Heat Transfer Coefficients B-18

B.4.2 Refrigerant-Side Heat Transfer Coefficients and

Pressure Drops

B- 19

B.4.3 Fluid Properties B-20

B.5 Corrections for Hot-Wall Condenser or Cold-Wall Evaporator B-20

B.6 Matching Evaporator Capacities and Cabinet Loads B-22

B.6.1 Single Evaporator Cycle B-22

B.6.2 Dual Loop B-23

B.6.3 Dual Evaporator Cycle B-23

B.7 Variable Speed Operation B-23

B.8 References B-24

 EE-RM-93-801 COMMENT OR2

APPENDIX B 

OVERVIEW OF CYCLE ANALYSIS TECHNICAL APPROACH 

B.1 Cycle Model Solution Procedure B-2 

B.2 Compressor Perfonnance Models B-5 

B2.1 Physically Based Compressor Model B-5 

B2.2 Rating Point Compressor Model B-lO 

B2.3 Map Based Compressor Model B-13 

B.3 Cycling Losses B-15 

B3.1 Cycling Rates B-16 

B.3.2 Cycling Losses Without a Valve B-16 

B.3.3 Cycling Effects with a Shut-off Valve B-16 

BA Summary of Help Menu Heat Exchanger Analyses B-17 

B.4.1 Air-Side Heat Transfer Coefficients B-18 

BA.2 Refrigerant-Side Heat Transfer Coefficients and B-19 

Pressure Drops 

BA.3 Fluid Properties B-20 

B.5 Corrections for Hot-Wall Condenser or Cold-Wall Evaporator B-20 

B.6 Matching Evaporator Capacities and Cabinet Loads B-22 

B.6.1 Single Evaporator Cycle B-22 

B.6.2 Dual Loop B-23 

B.6.3 Dual Evaporator Cycle B-23 

B.7 Variable Speed Operation B-23 

B.8 References B-24 

B-1 
B.1 Cycle Model Solution Procedure

E CYC.E is an iterative solver that starts with initial guesses for the refrigerant

mass flow rate and the refrigerant temperatures at the exits of the condenser and evaporator. A converged solution is reached when a global energy balance for the entire

refrigeration system is satisfied while satisfying local energy balances and heat transfer

relationships for each system component. Schematic diagrams of a two evaporator system and single evaporator system, along with refrigerant state points are shown in Figures B-i and B-2. The refrigerant state points are defined in Table B-1.

Table B-1. Summary of Refrigerant State Point Locations

compressor inlet

compressor outlet

condenser inlet

refrigerant dew point within condenser

refrigerant bubble point within condenser

condenser exit

inlet to high temperature interchanger

outlet from high temperature interchanger

(also the inlet to the low temperature interchanges)

9* outlet from the low temperature interchanger

10 freezer evaporator inlet

11" freezer evaporator outlet

(also the inlet to the low temperature interchanger)

12" fresh food evaporator inlet

(also the outlet from the low temperature interchanger)

13 refrigerant dew point within fresh food evaporator

14 fresh food evaporator outlet

(also the inlet to the high temperature evaporator)

15 outlet from the high temperature evaporator

- This state point is set equal to state (8) when a single evaporator

cycle is specified.

"° - These state points are set equal to state ( 10) when a single evaporator cycle is specified.

For calculation purposes, the program divides the refrigeration cycle into the following

two major subsystems:

1. a high-pressure subsystem that includes the compressor, condenser, and refrigerant

lines, including state (1) up through and including state (7) on Figure B-1, and

2. a low-pressure subsystem that includes the high and low temperature interchangers,

expansion device, freezer and fresh food evaporators, and refrigerant lines starting

after state (7) up through and including state (15).

 EE-RM-93-801 COMMENT OR2

B.1 Cycle Model Solution Procedure 

ERACYC.EXE is an iterative solver that starts with initial guesses for the refrigerant 

mass flow rate and the refrigerant temperatures at the exits of the condenser and evaporator. A converged solution is reached when a global energy balance for the entire 

refrigeration system is satisfied while satisfying local energy balances and heat transfer 

relationships for each system component Schematic diagrams of a two evaporator system and single evaporator system, along with refrigerant state points are shown in Figures B-1 and B-2. The refrigerant state points are defined in Table B-l. 

Table B-1. Summary of Refrigerant State Point Locations 

compressor 

2 compressor outlet 

3 condenser inlet 

4 refrigerant dew point within condenser 

5 refrigerant bubble point within condenser 

6 condenser exit 

7 inlet to high temperature interchanger 

8 outlet from high temperature interchanger 

(also the inlet to the low temperature interchanger) 

9' outlet from the low temperature interchanger 

10 freezer evaporator inlet 

11" freezer evaporator outlet 

(also the inlet to the low temperature interchanger) 

12" fresh food evaporator inlet 

(also the outlet from the low temperature interchanger) 

13 refrigerant dew point within fresh food evaporator 

14 fresh food evaporator outlet 

(also the inlet to the high temperature evaporator) 

15 outlet from the high temperature evaporator 

" - This state point is set equal to state (8) when a single evaporator 

cycle is specified. 

** - These state points are set equal to state (10) when a single evaporator cycle is specified. 

For calculation purposes, the program divides the refrigeration cycle into the following 

two major subsystems: 

1. a high-pressure subsystem that includes the compressor, condenser, and refrigerant 

lines, including state (1) up through and including state (7) on Figure B-1, and 

2, a low-pressure subsystem that includes the high and low temperature interchangers, 

expansion device, freezer and fresh food evaporators, and refrigerant lines starting 

after state (7) up through and including state (15). 

B-2 
5

condenser

compressor

high t p

Interchan r

low temp

I nterchanger

expansion

device

0

15

12

10

re "r! :- it flow

fresh food

evaporator

13

14

freezer

evaporator

11

Figure S-1. Schematic Diagram of a Two Evaporator Cycle and Corresponding Refrigerant State Points

5 4

t- condenser --f

3

compressor

interchan er

expansion

device

7

0

0

L

15

evaporator -I

13

refrigerant flow

Figure B-2. Schematic Diagram of a Single Evaporator Cycle and Corresponding Refrigerant State Points

 EE-RM-93-801 COMMENT OR2

Figure 8-1. Schematic Diagram of a Two Evaporator Cycle and Corresponding Refrigerant State Points 

interchanger 

expansion 

device 

5 4 6 ,--------, 3 

.-----+-+--+- condenser -+-+-+--.... --. 

compressor 

7 15 

r-+-+-, refrigerant flow 

8 

L-----t-t--- evaporator -+--+-+-_.-J 

12~----------~14 

13 

Figure 8-2. Schematic Diagram of a Single Evaporator Cycle and Corresponding Refrigerant State Points 

B-3 
The low-pressure subsystem is broken further into the following two components:

a. a fresh food component that includes the high temperature interchanger and

fresh food evaporator, from (but not including) state (7) and including states

(8), (12), (13), (14), and (15).

b. a freezer evaporator component that includes the low temperature interchanger,

expansion device, freezer evaporator, from (but not including) state (8) and

including states (9), (10), and (11), and up to, but not including state (12).

An outline of the general solution algorithm is as follows:

1. The program guesses initial values for the refrigerant mass flow rate, condenser exit

temperature, fresh food evaporator exit temperature, and freezer evaporator temperature, which correspond to states (6), (14), and (11) on Figure B-1.

2. Based on the user specified values for liquid subcooling at the condenser exit and

vapor superheating at the evaporator exit, the program calculates the liquid bubble

point at state (5) and the vapor dew point at state ( 13). Based on these temperatures, the remainder of the refrigerant properties, (i.e., saturation pressures, enthalpies, specific volumes, etc.) are calculated. The program then calculates the

remainder of the refrigerant properties at states (6) and (14).

3. Holding the refrigerant mass flow rate and properties at state (7) constant, the program iterates to solve an energy balance and the heat transfer relationships for the

low pressure side of the system, as described in the following:

a. Based on the refrigerant properties at states (7) and (14), state (8) at the high

temperature is determined.

b. Using state (8) as the inlet to the low temperature interchanger, the program

iterates to solve for states (9), (10), (11), and (12) and the freezer evaporator

performance. The freezer evaporator performance is determined using the heat

exchanger relationships for the evaporator along with refrigerant-side and airside energy balances. Convergence is achieved when the difference between

the values of the refrigerant temperature at the freezer evaporator exit for two

successive iterations is less than a user defined value (see file CYCLE.TOL).

If a single evaporator system is specified , the program internally sets refrigerant

state (9) equal to state (8), and (11 ) and (12) equal to state ( 10). A single evaporator system is shown schematically in Figure B-2.

c. Using state ( 12) as the inlet state to the fresh food evaporator , the program

solves for the heat transfer in the fresh food evaporator based on heat

exchanger relationships for the evaporator along with refrigerant-side and airside energy balances.

 EE-RM-93-801 COMMENT OR2

The low-pressure subsystem is broken further into the following two components: 

a. a fresh food component that includes the high temperature interchanger and 

fresh food evaporator, from (but not including) state (7) and including states 

(8), (12), (13), (14), and (15). 

b. a freezer evaporator component that includes the low temperature interchanger, 

expansion device, freezer evaporator, from (but not including) state (8) and 

including states (9), (10), and (11), and up to, but not including state (12). 

An outline of the general solution algorithm is as follows: 

1. The program guesses initial values for the refrigerant mass flow rate, condenser exit 

temperature, fresh food evaporator exit temperature, and freezer evaporator temperature, which correspond to states (6), (14), and (11) on Figure B-l. 

2. Based on the user specified values for liquid subcooling at the condenser exit and 

vapor superheating at the evaporator exit, the program calculates the liquid bubble 

point at state (5) and the vapor dew point at state (13). Based on these temperatures, the remainder of the refrigerant properties, (Le., saturation pressures, enthalpies, specific volumes, etc.) are calculated. The program then calculates the 

remainder of the refrigerant properties at states (6) and (14). 

3. Holding the refrigerant mass flow rate and properties at state (7) constant, the program iterates to solve an energy balance and the heat transfer relationships for the 

low pressure side of the system, as described in the following: 

a. Based on the refrigerant properties at states (7) and (14), state (8) at the high 

temperature is determined. 

b. Using state (8) as the inlet to the low temperature interchanger, the program 

iterates to solve for states (9), (10), (11), and (12) and the freezer evaporator 

performance. The freezer evaporator performance is determined using the heat 

exchanger relationships for the evaporator along with refrigerant-side and airside energy balances. Convergence is achieved when the difference between 

the values of the refrigerant temperature at the freezer evaporator exit for two 

successive iterations is less than a user defined value (see file CYCLE.TOL). 

If a single evaporator system is specified, the program internally sets refrigerant 

state (9) equal to state (8), and (11) and (12) equal to state (10). A single evaporator system is shown schematically in Figure B-2. 

c. Using state (12) as the inlet state to the fresh food evaporator, the program 

solves for the heat transfer in the fresh food evaporator based on heat 

exchanger relationships for the evaporator along with refrigerant-side and airside energy balances. 

B-4 
d. The refrigerant enthalpy difference between states (14) and (12) are compared

to the heat transfer calculated in Step 3c. Depending on the difference between

these two quantities, the refrigerant exit temperature (state (14)) is adjusted to

reduce this difference.

e. Steps 3a through 3d are repeated until a converged solution is reached for the

low pressure side of the system . A converged solution on the low-pressure side

of the system is achieved when the difference in the refrigerant evaporator exit

temperatures for two successive iteration steps is less than a user defined value

(see file CYCLE.TOL).

4. Based on states (7) and (14), the high temperature interchangerperformance is

determined, along with state (15).

5. State (1) at the inlet to the compressor is determined.

6. Compressor performance is determined using a theoretically based model, an efficiency/capacity based model, or a tabulated performance based model. Outputs

from the compressor calculation include the compressor power requirement,

compressor heat loss, the refrigerant properties at state (2), and a new value for the

refrigerant mass flow rate.

7. The refrigerant properties at the condenser inlet, state (3), are calculated.

8. Next, the program solves for the heat transfer in the condenser, based on heat

exchanger relationships for the condenser along with refrigerant-side and air-side

energy balances.

9. The refrigerant enthalpy difference between states (6) and (3) are compared to the

heat transfer calculated in Step S. Depending on the difference between these two

quantities, the refrigerant exit temperature at state (6) is adjusted to reduce this difference.

10. Based on the new values for the refrigerant mass flow rate and refrigerant properties

at state (6), the program repeats Steps 2 through 9 until a converged solution for

condenser exit temperature and refrigerant mass flow rate has been obtained. A

converged solution on the high-pressure side of the system is achieved when the

differences between the refrigerant condenser exit temperatures and the refrigerant

mass flow rates for two successive iteration steps are less than user defined values

(see file CYCLE.TOL).

8.2 Compressor Performance Models

B.2.1. Physically Based Compressor Model (Efficiency Model)

This section summarizes the basic structure of the physically based compressor model

employed in the program module ERACYC. The analysis is a hybrid between a purely

theoretical model and an empirical model in that it uses empirical coefficients as inputs

 EE-RM-93-801 COMMENT OR2

d. The refrigerant enthalpy difference between states (14) and (12) are compared 

to the heat transfer calculated in Step 3c. Depending on the difference between 

these two quantities, the refrigerant exit temperature (state (14» is adjusted to 

reduce this difference. 

e. Steps 3a through 3d are repeated until a converged solution is reached for the 

low pressure side of the system. A converged solution on the low-pressure side 

of the system is achieved when the difference in the refrigerant evaporator exit 

temperatures for two successive iteration steps is less than a user defmed value 

(see file CYCLE.TOL). 

4. Based on states (7) and (14), the high temperature interchanger performance is 

determined, along with state (15). 

5. State (1) at the inlet to the compressor is determined. 

6. Compressor performance is determined using a theoretically based model, an efficiency/capacity based model, or a tabulated performance based model. Outputs 

from the compressor calculation include the compressor power requirement, 

compressor heat loss, the refrigerant properties at state (2), and a new value for the 

refrigerant mass flow rate. 

7. The refrigerant properties at the condenser inlet, state (3), are calculated. 

8. Next, the program solves for the heat transfer in the condenser, based on heat 

exchanger relationships for the condenser along with refrigerant-side and air-side 

energy balances. 

9. The refrigerant enthalpy difference between states (6) and (3) are compared to the 

heat transfer calculated in Step 8. Depending on the difference between these two 

quantities, the refrigerant exit temperature at state (6) is adjusted to reduce this difference. 

10. Based on the new values for the refrigerant mass flow rate and refrigerant properties 

at state (6), the program repeats Steps 2 through 9 until a converged solution for 

condenser exit temperature and refrigerant mass flow rate has been obtained. A 

converged solution on the high-pressure side of the system is achieved when the 

differences between the refrigerant condenser exit temperatures and the refrigerant 

mass flow rates for two successive iteration steps are less than user defined values 

(see file CYCLE.TOL). 

13.2 Compressor Performance Models 

B.2.1. Physically Based Compressor Model (Efficiency Model) 

This section summarizes the basic structure of the physically based compressor model 

employed in the program module ERACYC. The analysis is a hybrid between a purely 

theoretical model and an empirical model in that it uses empirical coefficients as inputs 

B-5 
to theoretically derived equations. A description is provided of the basic physical processes that are represented, the analysis assumptions, and the equation set developed to

characterize the performance parameters.

Physical Processes Modeled

The model is based on representing the following physical processes depicted in Figure

B-3:

® The compressor is a low side hermetic reciprocating design.

• Suction gas (state point 1 in Figure B-3) enters the shell and is in thermal communication with the discharge line and with the motor, providing its main cooling.

® The motor is entirely within the shell and is physically separated from it.

® The suction gas transfers heat to the shell which is in thermal communication with its

environment.

® The suction gas enters the pump inlet valve in a heated condition (state point 2) and

is compressed to a higher pressure.

® At the outlet of the pump (state point 3) the refrigerant gas enters a discharge line

which is in thermal communication with the refrigerant vapor contained within the

compressor shell volume.

® After losing heat to the gas within the shell, the high pressure discharge gas leaves

the compressor (state point 4).

® No pressure changes are taken into account within the shell other than across the

pump (point 2 to 3). The net pressure change includes pressure losses through the

pump suction and discharge valves.

Figure B-4 illustrates the thermodynamic state points of the gas throughout the modeled

process.

 EE-RM-93-801 COMMENT OR2

to theoretically derived equations. A description is provided of the basic physical processes that are represented, the analysis assumptions, and the equation set developed to 

characterize the performance parameters. 

Physical Processes Modeled 

The model is based on representing the following physical processes depicted in Figure 

B-3: 

.. The compressor is a low side hermetic reciprocating design. 

.. Suction gas (state point 1 in Figure B-3) enters the shell and is in thermal communication with the discharge line and with the motor, providing its main cooling. 

" The motor is entirely within the shell and is physically separated from it. 

" The suction gas transfers heat to the shell which is in thermal communication with its 

environment. 

.. The suction gas enters the pump inlet valve in a heated condition (state point 2) and 

is compressed to a higher pressure. 

.. At the outlet of the pump (state point 3) the refrigerant gas enters a discharge line 

which is in thermal communication with the refrigerant vapor contained within the 

compressor shell volume. 

.. Mter losing heat to the gas within the shell, the high pressure discharge gas leaves 

the compressor (state point 4). 

.. No pressure changes are taken into account within the shell other than across the 

pump (point 2 to 3). The net pressure change includes pressure losses through the 

pump suction and discharge valves. 

Figure B-4 illustrates the thermodynamic state points of the gas throughout the modeled 

process. 

B-6 
2

motor

w

Figure B®3. Physical Processes in Compressor

pressure, p

enthalpy,

Figure B-4. Thermodynamic State Points in Compressor

 EE-RM-93-801 COMMENT OR2

4 

., 

I - 1 2 3 

"'" "'" - - pump 

J J 

motor 

A~ 

w 

Figure B-3. Physical Processes in Compressor 

4 3 

pressure, p 

2 

enthalpy, h 

Figure B-4. Thermodynamic State Points in Compressor 

B-7 
The thermal processes represented are:

® The shell heat transfer is correlated to motor inlet power. For the purposes of simplification, it is assumed that the constant of proportionality is independent of the actual

operating conditions. Input values for the shell heat loss are based on actual

compressor performance data and are typically 70 - 80 percent of the compressor

inlet power.

® The internal heat exchange between the high pressure gas within the discharge line

and the low pressure gas within the shell can be also represented as a fraction of the

compressor input power.

® Work of compression is determined using an isentropic efficiency.

Goveming Eauations

Six equations represent the physical processes within the shell:

Overall Energy Balance

W =rh(h4-hl)+QS

where

W = compressor motor input power

QS = rate of heat loss from shell

Shell Heat Loss to the Environment

QS -JW

where

.f = correlating parameter

Suction Gas Heat Balance

rh(h2-hj) _ (1-11m)W+Q3-4 Qs

where

TIM = motor efficiency

Q3-4 = discharge line heat loss

Discharge Line Heat Loss

(B - 1)

(B -2)

(B -3)

Q3-4=aW = rh(h4-h3) (B-4)

 EE-RM-93-801 COMMENT OR2

The thermal processes represented are: 

.. The shell heat transfer is correlated to motor inlet power. For the purposes of simplification, it is assumed that the constant of proportionality is independent of the actual 

operating conditions. Input values for the shell heat loss are based on actual 

compressor performance data and are typically 70 - 80 percent of the compressor 

inlet power. 

.. The internal heat exchange between the high pressure gas within the discharge line 

and the low pressure gas within the shell can be also represented as a fraction of the 

compressor input power. 

.. Work of compression is determined using an isentropic efficiency. 

Governing Equations 

Six equations represent the physical processes within the shell: 

Overall Energy Balance 

where 

W = compressor motor input power 

Qs = rate of heat loss from shell 

Shell Heat Loss to the Environment 

where 

f = correlating parameter 

Suction Gas Heat Balance 

where 

11m = motor efficiency 

Q3-4 = discharge line heat loss 

Discharge Line Heat Loss 

B-8 

(B -1) 

(B -2) 

(B -3) 

(B -4) 
where

a = correlating parameter

Compressor Work Input

il.W -m(h3- )

Compressor Efficiency

h3 = h2 + (h3, - hz)

T1$

(B -5)

(B -6)

where

rls = isentropic efficiency

and the subscripts refers to the enthalpy that would exist if the compression

process were reversible and adiabatic and therefore, isentropic.

Eqns (B-1) through (B-6) are solved iteratively to determine the enthalpies at the pump

inlet, h2, and outlet, h3. The shell discharge condition, h4, is found from:

(h3 - hi) h4=h1+ a

1+UO'D

The refrigerant mass flow rate is then calculated from

(60rpm)'nvdisp

m=

vsuc

where

rpm = compressor speed in rpm

lisp = cylinder displacement volume

vs„c = specific volume of refrigerant vapor at the pump inlet valve

Iv = volumetric efficiency

The volumetric efficiency is determined from:

III, =0.92 1-Cv p3 n-1

Pa

(B-7)

(B -8)

(B -9)

where

 EE-RM-93-801 COMMENT OR2

where 

a. = correlating parameter 

Compressor Work Input 

(B -5) 

Compressor Efficiency 

(B -6) 

where 

'Tls = isentropic efficiency 

and the subscript s refers to the enthalpy that would exist if the compression 

process were reversible and adiabatic and therefore, isentropic. 

Eqns (B-1) through (B-6) are solved iteratively to determine the enthalpies at the pump 

inlet, hb and outlet, h3• The shell discharge condition, h4' is found from: 

(B -7) 

The refrigerant mass flow rate is then calculated from 

. (60rpm)T1vdisp 

m= (B -8) 

where 

rpm = compressor speed in rpm 

disp = cylinder displacement volume 

Valle = specific volume of refrigerant vapor at the pump inlet valve 

'Tlv = volumetric efficiency 

The volumetric efficiency is determined from: 

(B -9) 

where 

B-9 
Cv = clearance volume, expressed as a fraction of the displacement volume

and

n = polytropic exponent, defined as n = 0.97y, where y is the specific

heat capacity ratio of the suction vapor.

Model Ingul Parameters

The following data are required input to the model:

anutacturer

Speed (rpm) 3450 Manufacturer

Clearance volume (%) 2 Manufacturer

Compression (isentropic) efficiency 1.3 Model Fit

Motor-pump efficiency (-) 0.41 Estimate

Shell loss (% of power input) 75 Data

Discharge tube heat loss 35 Model Fit

isplacement (cc or cu-in ...........g..(0.

(% of power input)

Data values for most of the parameters are either known from the manufacturer's

literature or can be estimated. Model fits have to be carried out to arrive at values for

the isentropic efficiency, which has a value greater than one as a result of its definition.

Strictly speaking, the so-called isentropic efficiency uses as a reference value for the

minimum work input the amount of work required to compress the refrigerant during a

reversible and adiabatic (hence, isentropic) process. In the actual compression process,

significant heat loss from the refrigerant occurs to the cylinder walls, resulting in a

lower refrigerant enthalpy at the end of the compression process compared to the ideal

process, thereby corresponding to an efficiency greater than one. This does not imply,

however, that the work input is less than the ideal process.

B.2.2. Rating Point Compressor Model (EER and Capacity Model)

Generally, the only information that can be obtained for a particular compressor are the

rating point capacity, motor power input (or EER), displacement volume, and the type

of shell cooling that was employed (i.e., static or fan-forced). The model discussed in

the following is an empirical model that allows realistic simulation of compressor performance with a minimum of required input parameters.

The foundation of this model is comprehensive compressor performance data from

AHAM [1] that includes compressor capacity, input power, refrigerant mass flow rate,

and refrigerant temperatures at various locations within the compressor, all as a function

of evaporating and condensing temperatures and type of compressor shell cooling.

Analysis of this data yielded the following important conclusions:

 EE-RM-93-801 COMMENT OR2

and 

Cv = clearance volume, expressed as a fraction of the displacement volume 

n = polytropic exponent, defined as n = 0.97"(, where "( is the specific 

heat capacity ratio of the suction vapor. 

Modellnout Parameters 

The fo~owing data are required input to the model: 

Speed (rpm) 3450 Manufacturer 

Clearance volume (%) 2 Manufacturer 

Compression (isentropic) efficiency 1.3 Model Fit 

Motor-pump efficiency (-) 0.41 Estimate 

Shell loss (% of power input) 75 Data 

Discharge tube heat loss 35 Model Fit 

(% of power input) 

Data values for most of the parameters are either !mown from the manufacturer's 

literature or can be estimated. Model fits have to be carried out to arrive at values for 

the isentropic efficiency, which has a value greater than one as a result of its definition. 

Strictly speaking, the so-called isentropic efficiency uses as a reference value for the 

minimum work input the amount of work required to compress the refrigerant during a 

reversible and adiabatic (hence, isentropic) process. In the actual compression process, 

significant heat loss from the refrigerant occurs to the cylinder walls, resulting in a 

lower refrigerant enthalpy at the end of the compression process compared to the ideal 

process, thereby corresponding to an efficiency greater than one. This does not imply, 

however, that the work input is less than the ideal process. 

13.2.2. Rating Point Compressor Model (EER and Capacity Model) 

Generally, the only information that can be obtained for a particular compressor are the 

rating point capacity. motor power input (or EER), displacement volume, and the type 

of shell cooling that was employed (i.e., static or fan-forced). The model discussed in 

the following is an empirical model that allows realistic simulation of compressor performance with a minimum of required input parameters. 

The foundation of this model is comprehensive compressor performance data from 

AHAM [1] that includes compressor capacity, input power, refrigerant mass flow rate, 

and refrigerant temperatures at various locations within the compressor, all as a function 

of evaporating and condensing temperatures and type of compressor shell cooling. 

Analysis of this data yielded the following important conclusions: 

B-lO 
1. The compression process behaves like a polytropic process with a polytropic exponent defined as n = 0.97y, where 'y is the refrigerant suction vapor specific heat

capacity ratio.

2. The refrigerant vapor temperature at the suction port can be correlated with EER at

the rating point.

3. The ratio of compressor discharge temperature and suction port temperature (both in

absolute units) is nearly constant at 1.2.

4. The compressor discharge temperature can be correlated with the cylinder discharge

temperature, ambient temperature, and the type of compressor cooling.

Model in uls

The model requires the following information as inputs:

compressor type (reciprocating or rotary),

compressor capacity at the rating point,

EER at the rating point,

compressor displacement volume,

compressor speed (usually about 3450 - 3500 rpm), and

type of compressor cooling.

Compressor Parameters

At the beginning of the program, the model estimates values for the volumetric and

isentropic efficiencies from the compressor rating point capacity and EER using the procedures described below.

Compressor Clearance Volume

The compressor clearance volume is calculated using the following algorithm.

1. The model calculates the enthalpy of refrigerant vapor and liquid at 32°C

(90°F) and at pressures corresponding to the saturation pressures at -23°C

(-10°F) and 54°C (130°F).

2. The refrigerant mass flow rate is calculated using the rating point capacity

divided by the quantity (vapor enthalpy - liquid enthalpy).

3. The refrigerant vapor temperature at the compressor suction point is calculated

using the following correlations:

Ts^ = 479.59 - 64.815EER, reciprocating - static cooling,

Ts. = 427.84 - 57.895EER, reciprocating - fan cooling, or

TSB = 120, rotary.

where the temperatures are expressed in Fahrenheit.

 EE-RM-93-801 COMMENT OR2

1. The compression process behaves like a polytropic process with a polytropic exponent defined as n = 0.97"{, where "{ is the refrigerant suction vapor specific heat 

capacity ratio. 

2. The refrigerant vapor temperature at the suction port can be correlated with EER at 

the rating point. 

3. The ratio of compressor discharge temperature and suction port temperature (both in 

absolute units) is nearly constant at 1.2. 

4. The compressor discharge temperature can be correlated with the cylinder discharge 

temperature, ambient temperature, and the type of compressor cooling. 

Model Inputs 

The model requires the following information as inputs: 

compressor type (reciprocating or rotary), 

compressor capacity at the rating point, 

EER at the rating point, 

compressor displacement volume, 

compressor speed (usually about 3450 - 3500 rpm), and 

type of compressor cooling. 

Compressor Parameters 

At the beginning of the program, the model estimates values for the volumetric and 

isentropic efficiencies from the compressor rating point capacity and EER using the procedures described below. 

Compressor Clearance Volume 

The compressor clearance volume is calculated using the following algorithm. 

1. The model calculates the enthalpy of refrigerant vapor and liquid at 32°C 

(9OOF) and at pressures corresponding to the saturation pressures at -23°C 

(-lOOF) and 54°C (130°F). 

2. The refrigerant mass flow rate is calculated using the rating point capacity 

divided by the quantity (vapor enthalpy -liquid enthalpy). 

3. The refrigerant vapor temperature at the compressor suction point is calculated 

using the following correlations: 

Tsuc = 479.59 - 64.815EER, reciprocating - static cooling, 

Tsuc = 427.84 - 57 . 895EER , reciprocating - fan cooling, or 

Tsuc = 120, rotary. 

where the temperatures are expressed in Fahrenheit 

B-U 
4. The refrigerant density at the suction port is calculated at the suction pressure

calculated in Step 1; the suction temperature calculated in Step 3.

5. The volumetric efficiency is calculated using the following relationship:

rn

I° 60 • ps,, • rpm • lisp

where

rrc = refrigerant mass flow rate

ps„, = density of the refrigerant suction vapor

rpm compressor speed in rpm

lisp = compressor displacement volume

6. The clearance volume C, is determined from the following relationship:

rlY = coast 1 - Cv Pis

n

-1

PsU

where const=0.92 and const=l.0 for reciprocating and rotary compressors, respectively, and pdi., and ps,,, are the discharge and suction pressures, respectively. The

exponent that best fits the data has been determined to be n = 0.97y.

Isentropic Efficiency

The isentropic efficiency is determined using the following procedure:

1. Calculate the enthalpy and entropy of the refrigerant vapor at the suction port.

2. Calculate refrigerant enthalpy hdi,,s at the discharge pressure assuming an isentropic process.

3. Calculate the isentropic efficiency as

TL = (hd s,s - hsuc)m'Wr

where W,. is the compressor work at the rating point.

It is assumed that the isentropic efficiency determined in the above equation

applies for all operating conditions.

 EE-RM-93-801 COMMENT OR2

4. The refrigerant density at the suction port is calculated at the suction pressure 

calculated in Step 1; the suction temperature calculated in Step 3. 

5. The volumetric efficiency is calculated using the following relationship: 

where 

llv = 60 d' . Psuc . rpm· lSP 

m = refrigerant mass flow rate 

Psuc = density of the refrigerant suction vapor 

rpm =, compressor speed in rpm 

disp = compressor displacement volume 

6. The clearance volume Cv is determined from the following relationship: 

where const=O.92 and const=l.O for reciprocating and rotary compressors, respectively, and Pdis and Psuc are the discharge and suction pressures, respectively. The 

exponent that best fits the data has been determined to be n = 0.97"(. 

Isentropic Efficiency 

The isentropic efficiency is determined using the following procedure: 

1. Calculate the enthalpy and entropy of the refrigerant vapor at the suction port. 

2. Calculate refrigerant enthalpy hdJs,Jl at the discharge pressure assuming an isentropic process. 

3. Calculate the isentropic efficiency as 

where W, is the compressor work at the rating point. 

It is assumed that the isentropic efficiency determined in the above equation 

applies for all operating conditions. 

B-12 
Performance Analysis

The above parameters are used in the calculation of compressor performance at conditions off the rating point using the following algorithm.

1. Input the values of the suction and discharge pressures from the main program.

2. Estimate the refrigerant temperature at the suction port using

T5, = T; + 389.59 - 64.815EER , reciprocating - static cooling,

T5,6C = T, + 337.84 - 57.895EER, reciprocating - fan cooling, or

T5,6C = T; + 30, rotary.

where T; is the temperature of the refrigerant entering the compressor shell,

expressed in Fahrenheit.

3. Calculate the refrigerant density, enthalpy and entropy at suction port conditions.

4. Calculate refrigerant enthalpy hdi, ,., at the discharge pressure assuming an isentropic

process.

5. Calculate the required work input using

hdi,- hs,,,

is

6. Using the value of clearance volume determined previously, calculate the volumetric

efficiency using the following equation:

11„ = const

where const=0.92 and const=l.0 for reciprocating and rotary compressors, respectively.

7. Finally, the mass flow rate and the heat losses from the compressor shell and discharge tube are calculated.

B.2.3. Map-Based Compressor Model

The third method of calculating compressor performance is a map-based model that uses

actual compressor map data applicable to a particular compressor. The user inputs data

points for compressor capacity and motor power input as a function of evaporating and

condensing temperatures. This data must be at the standard rating condition in which

the temperature of the vapor exiting the evaporator (and entering the compressor), the

 EE-RM-93-801 COMMENT OR2

Performance Analysis 

The above parameters are used in the calculation of compressor performance at conditions off the rating point using the following algorithm. 

1. Input the values of the suction and discharge pressures from the main program. 

2. Estimate the refrigerant temperature at the suction port using 

Tsuc = Tj + 389.59 - 64.815EER, reciprocating - static cooling, 

Tsuc = Tj + 337.84 - 57 .895EER , reciprocating - fan cooling, or 

Tsuc = Tj + 30, rotary. 

where Tj is the temperature of the refrigerant entering the compressor shell, 

expressed in Fahrenheit. 

3. Calculate the refrigerant density, enthalpy and entropy at suction port conditions. 

4. Calculate refrigerant enthalpy hdis,s at the discharge pressure assuming an isentropic 

process. 

5. Calculate the required work input using 

w = hdis ,s - hsuc 

11. 

6. Using the value of clearance volume determined previously, calculate the volumetric 

efficiency using the following equation: 

where const=D.92 and const=1.0 for reciprocating and rotary compressors, respectively. 

7. Finally, the mass flow rate and the heat losses from the compressor shell and discharge tube are calculated. 

B.2.3. Map-Based Compressor Model 

The third method of calculating compressor performance is a map-based model that uses 

actual compressor map data applicable to a particular compressor. The user inputs data 

points for compressor capacity and motor power input as a function of evaporating and 

condensing temperatures. This data must be at the standard rating condition in which 

the temperature of the vapor exiting the evaporator (and entering the compressor), the 

B-13 
liquid exiting the condenser and the ambient are all at 32°C (90°F). The data for compressor capacity and motor power input is stored in a user-supplied file with extension

.TAB in the following form.

TV)

Tc(2)

Te(1)

cap(1,1)

cap(2,1)

Te(2) ® ®

cap(1,2)

cap(2,2)

1 Te(Ne)

cap(1,Ne)

cap(2,Ne)

0

and

TT(N^) cap(N,,,1) cap(Nc,N0)

TV)

Tc(2)

Te(1)

pow(1,1)

pow(2,1)

Te(2)

pow(1,2)

pow(2,2)

T0(N0)

pow(1,Ne)

pow(2,Ne)

0 e

Tc(Nc) pow(N,1) pow(Nc)a)

where Te and TT are the evaporating and condensing temperatures, respectively. The

terms cap and pow refer to the compressor capacity and motor power input, respectively. Units for the data can be input in either °F, Btu/hr, and watts, or °C, kcal/hr, and

watts. Up to 20 data points in each of the Te and TT directions can be input, resulting in

a maximum of 400 data points for the capacity and compressor power . The user must

specify whether the compressor is a reciprocating or rotary type.

The user does not specify the type of refrigerant in the compressor map file. Hence, it is

necessary that the user insures that the refrigerant with which the compressor was tested

to generate the performance data corresponds to the refrigerant specified in the ERACYC model input data.

Upon the initial call of the compressor subroutine the program reads the data file and

stores the data internally in arrays.

The input variables transferred from the main program include the suction and discharge

pressures, and suction and ambient temperatures. Subroutine output variables output to

the main program include the refrigerant mass flow rate , compressor power input and

shell heat loss.

Note that the compressor capacity is not included in the list of output variables . This is

because the capacity as listed in the performance data is determined at fixed values of

temperature of vapor exiting the evaporator and liquid exiting the condenser. These

conditions do not, in general, exist in an actual refrigerator during normal operation.

Thus, use of the capacity as listed in the performance data is incorrect, even for identical

evaporating and condensing temperatures . This subroutine answers the following question: "Given specified compressor suction and discharge pressures and a vapor tempera-

 EE-RM-93-801 COMMENT OR2

liquid exiting the condenser and the ambient are all at 32°C (90°F). The data for compressor capacity and motor power input is stored in a user-supplied file with extension 

.TAB in the following form. 

T.(l) T.(2) .. " T.(NJ 

Til) cap( 1,1) cap(l,2) .. .. cap(lN.) 

Ti2) cap(2,1) cap(2,2) 0 " cap(2N.) 

• 0 0 0 " " .. .. " .. e .. 

TiN) cap(Nc,l) " .. .. cap (NcN.) 

and 

Til) T.(2) .. " T.(NJ 

Til) pow(1,l) pow(l,2) " " pow(lNe) 

Tc(2) pow(2,1) pow(2,2) .. .. pow(2N.) 

• " " .. .. " .. " .. .. " .. 

TiN) pow(Nc,l) .. .. .. pow(NcN.) 

where T. and Tc are the evaporating and condensing temperatures, respectively. The 

terms cap and pow refer to the compressor capacity and motor power input, respectively. Units for the data can be input in either OF, Btu/hr, and watts, or ·C, kcal/hr, and 

watts. Up to 20 data points in each of the Te and Tc directions can be input, resulting in 

a maximum of 400 data points for the capacity and compressor power. The user must 

specify whether the compressor is a reciprocating or rotary type. 

The user does not specify the type of refrigerant in the compressor map fIle. Hence, it is 

necessary that the user insures that the refrigerant with which the compressor was tested 

to generate the performance data corresponds to the refrigerant specified in the ERACYC model input data. 

Upon the initial call of the compressor subroutine the program reads the data fIle and 

stores the data internally in arrays. 

The input variables transferred from the main program include the suction and discharge 

pressures, and suction and ambient temperatures. Subroutine output variables output to 

the main program include the refrigerant mass flow rate, compressor power input and 

. shell heat loss. 

Note that the compressor capacity is not included in the list of output variables. This is 

because the capacity as listed in the perfonnance data is determined at fixed values of 

temperature of vapor exiting the evaporator and liquid exiting the condenser. These 

conditions do not, in general, exist in an actual refrigerator during normal operation. 

Thus, use of the capacity as listed in the performance data is incorrect, even for identical 

evaporating and condensing temperatures. This subroutine answers the following question: "Given specified compressor suction and discharge pressures and a vapor temperaB-14 
ture at the inlet to compressor shell, what refrigerant mass flow rate can the compressor

produce?" Once the mass flow rate is determined, the value of refrigerant mass flow

rate is output to the main program, where the evaporator capacity is determined.

The algorithm which is used to determine the refrigerant mass flow rate proceeds as follows:

1. Values for the suction and discharge pressure, refrigerant vapor temperature at the

shell, and ambient temperature are input from the main subroutine.

2. The enthalpies of the refrigerant vapor and liquid at the standard rating temperatures

and at the values of suction and discharge pressures are passed from the main program.

3. Based of the values of suction and discharge pressures input from the main program,

corresponding values for evaporating and condensing temperatures are determined.

4. Using the values for evaporating and condensing temperatures determined in Step 3,

determine values for the compressor capacity and motor power input by interpolation

from the stored performance map.

5. The refrigerant mass flow rate is calculated based on the following relationship:

refrigerant mass flow rate = (capacity from map) / (vapor enthalpy - liquid enthalpy)

where the refrigerant enthalpies are those determined in Step 3.

6. The heat loss from the compressor shell to the ambient is calculated assuming it is a

fixed fraction of the compressor power input. This fraction is assumed to be 75 percent of the compressor motor power input.

7. Now that the values for the refrigerant mass flow rate, motor power input, and shell

heat loss corresponding to the standard rating condition have been determined, the

subroutine corrects for conditions which do not correspond to the standard conditions. The means for determining the amount of correction are based on the data of

Reference [2]. The corrections to the refrigerant mass flow rate, motor power input,

and shell heat loss are normally small, generally only a few percent of the values at

the standard rating condition.

13 .3 Cycling Losses

Cycling of the compressor will normally lead to a reduction in the cycle average efficiency (COP) compared to the steady state value. This will occur due to at least three

major effects:

• during the on-time the thermal load of the heat exchangers is higher than the cycle

average load, leading to increased heat exchanger irreversibilities,

 EE-RM-93-801 COMMENT OR2

ture at the inlet to compressor shell, what refrigerant mass flow rate can the compressor 

produce?" Once the mass flow rate is determined, the value of refrigerant mass flow 

rate is output to the main program, where the evaporator capacity is determined. 

The algorithm which is used to determine the refrigerant mass flow rate proceeds as follows: 

1. Values for the suction and discharge pressure, refrigerant vapor temperature at the 

shell, and ambient temperature are input from the main subroutine. 

2. The enthalpies of the refrigerant vapor and liquid at the standard rating temperatures 

and at the values of suction and discharge pressures are passed from the main program. 

3. Based of the values of suction and discharge pressures input from the main program, 

corresponding values for evaporating and condensing temperatures are determined. 

4. Using the values for evaporating and condensing temperatures determined in Step 3, 

determine values for the compressor capacity and motor power input by interpolation 

from the stored performance map. 

5. The refrigerant mass flow rate is calculated based on the following relationship: 

refrigerant mass flow rate = (capacity from map) / (vapor enthalpy - liquid enthalpy) 

where the refrigerant enthalpies are those determined in Step 3. 

6. The heat loss from the compressor shell to the ambient is calculated assuming it is a 

fixed fraction of the compressor power input. This fraction is assumed to be 75 percent of the compressor motor power input. 

7. Now that the values for the refrigerant mass flow rate, motor power input, and shell 

heat loss corresponding to the standard rating condition have been determined, the 

subroutine corrects for conditions which do not correspond to the standard conditions. The means for determining the amount of correction are based on the data of 

Reference [2]. The corrections to the refrigerant mass flow rate, motor power input, 

and shell heat loss are normally small, generally only a few percent of the values at 

the standard rating condition. 

B.3 Cycling losses 

Cycling of the compressor will normally lead to a reduction in the cycle average efficiency (COP) compared to the steady state value. This will occur due to at least three 

major effects: 

• during the on-time the thermal load of the heat exchangers is higher than the cycle 

average load, leading to increased heat exchanger irreversibilities, 

B-15 
® when the compressor stops, the pressure ratio rapidly decreases towards one, leading

to flashing of the liquid in the condenser and condensation of liquid in the evaporator,

® vapor flows from the condenser to the evaporator where it condenses during the offcycle.

To minimize the effects of such losses, the cabinet controls are usually set to ensure a

small number of cycles per hour (typically 2 - 3). An alternate approach, suitable for a

rotary compressor, is to place a shut-off valve between the condenser and the capillary

tube which is shut during the off cycle.

Detailed analysis of cycling losses is extremely complicated (and of inherently limited

accuracy due to fundamental inabilities to accurately represent all the major mass flow

and two-phase heat transfer effects throughout the cycle). As a consequence, a simple

correlative procedure, partially based on experimental data, has been adopted. Two general situations are represented: 1) normal operation without a shut-off valve, and 2) use

of a shut-off valve.

B.3.1. Cycling Rates

The degree of cycling loss is dependent on the cycling rate since the controlling phenomena are time dependent. In general, the rate is dependent on the thermal characteristics of the refrigerator cabinet and the control system.

The cycling rate is a user input, generally ranging from 1 to 3 cycles per hour.

B.3.2. Cycling Losses Without a Valve

Janssen, de Wit, and Kuijpers have found that the cycle average COP varies roughly

linearly with cycle frequency [3]. From an analysis of the experimental data given in

Reference [3], the cycle loss can be estimated as:

Loss = 1.0%/tcycle

For example, at a cycling rate of 2.5 cycles per hour, (tcyc,e = 0.4), the cycle efficiency

loss would be about 2.5%.

8.3.3. Cycling Effects with a Shut-off Valve

Short cycling with a valve present will actually increase the cycle average COP due to

the thermal mass effects of the heat exchangers. In principle, with very massive heat

exchangers and short cycling, the theoretical performance should approach that of a

variable speed drive system due to the elimination of over- or under-shoot of the heat

exchanger temperatures. This effect is illustrated in the experimental data of Philips

Research [3].

 EE-RM-93-801 COMMENT OR2

.. when the compressor stops, the pressure ratio rapidly decreases towards one, leading 

to flashing of the liquid in the condenser and condensation of liquid in the evaporator, 

.. vapor flows from the condenser to the evaporator where it condenses during the offcycle. 

To minimize the effects of such losses, the cabinet controls are usually set to ensure a 

small number of cycles per hour (typically 2 - 3). An alternate approach, suitable for a 

rotary compressor, is to place a shut-off valve between the condenser and the capillary 

tube which is shut during the off-cycle. 

Detailed analysis of cycling losses is extremely complicated (and of inherently limited 

accuracy due to fundamental inabilities to accurately represent all the major mass flow 

and two-phase heat transfer effects throughout the cycle). As a consequence, a simple 

correlative procedure, partially based on experimental data, has been adopted. Two general situations are represented: 1) normal operation without a shut-off valve, and 2) use 

of a shut-off valve. 

B.3.1. Cycling Rates 

The degree of cycling loss is dependent on the cycling rate since the controlling phenomena are time dependent. In general, the rate is dependent on the thermal characteristics of the refrigerator cabinet and the control system. 

The cycling rate is a user input, generally ranging from 1 to 3 cycles per hour. 

B.3.2. Cycling Losses Without a Valve 

Janssen, de Wit, and Kuijpers have found that the cycle average COP varies roughly 

linearly with cycle frequency [3]. From an analysis of the experimental data given in 

Reference [3], the cycle loss can be estimated as: 

Loss = 1.0%/1;;ycle 

For example, at a cycling rate of 2.5 cycles per hour, (tcycle = 0.4), the cycle efficiency 

loss would be about 2.5%. 

B.3.3. Cycling Effects with a Shut-off Valve 

Short cycling with a valve present will actually increase the cycle average COP due to 

the thermal mass effects of the heat exchangers. In principle, with very massive heat 

exchangers and short cycling, the theoretical performance should approach that of a 

variable speed drive system due to the elimination of over- or under-shoot of the heat 

exchanger temperatures. This effect is illustrated in the experimental data of Philips 

Research [3]. 

B-16 
From the experimental data given in [3], the efficiency gain over steady state from the

presence the valve can estimated as:

Gain = 1.5%/tycie

Hence, for a system with 2 cycle/hr, the overall efficiency gain from introducing a

microvalve (rotary compressor, only) is approximately (1.0 + 1.5)10.5 = 5%.

BA Summary of Help Menu Heat Exchanger Analyses

ERA contains subroutines in the help menu to assist the user in determining the heat

exchanger input data required for the refrigeration cycle performance calculations. This

feature should be used when actual heat transfer performance data for a particular heat

exchanger is unavailable, but should not be used in lieu of actual data. A summary of

the methods used for estimating the heat exchanger performance is presented in the following paragraphs. This summary is very brief, thus the reader is referred to the references at the end of the section and to heat transfer textbooks for further information.

The help menu assists the user to estimate both the air-side and refrigerant-side heat

transfer coefficients, the refrigerant-side pressure drop, and the heat exchanger surface

areas for the following heat exchanger configurations:

Summary of Help Menu Heat Exchanger Configurations

condenser forced convection - straight fin-tube, wavy fir-tube, wire=tube

natural convection - vertical plate , hot-wall, wire-tube

evaporator forced convection - straight fin-tube, wavy fin-tube

natural convection - vertical plate, cold-wall, horizontal plate

The algorithms for calculating the average heat transfer coefficients follow the general

outline presented below:

1. Air-side heat transfer coefficients are calculated first. Generally, air-side heat transfer coefficients are reasonably independent of the refrigerant-side conditions.

2. Heat transfer coefficients for single phase refrigerant flow (i.e., refrigerant vapor or

liquid) are calculated next. Heat transfer coefficients in this flow regime are essentially independent of the air-side conditions.

3. Heat transfer coefficients and pressure losses for the condensation and evaporating

flow regimes are calculated. In general these depend strongly on the air-side heat

transfer coefficient.

4. Finally, the average overall heat transfer coefficient based on air -side surface area

corresponding to the single phase vapor , single phase liquid, condensing, and evaporating regimes are calculated. The pressure drops for the condensing and evaporating heat transfer regimes are also calculated.

 EE-RM-93-801 COMMENT OR2

From the experimental data given in (3], the efficiency gain over steady state from the 

presence the valve can estimated as: 

Gain = 1.5%/t"ycle 

Hence, for a system with 2 cycle/hr, the overall efficiency gain from introducing a 

microvalve (rotary compressor, only) is approximately (1.0 + 1.5)/0.5 = 5%. 

113.4 Summary of Help Menu Heat Exchanger Analyses 

ERA contains subroutines in the help menu to assist the user in determining the heat 

exchanger input data required for the refrigeration cycle performance calculations. This 

feature should be used when actual heat transfer performance data for a particular heat 

exchanger is unavailable, but should not be used in lieu of actual data. A summary of 

the methods used for estimating the heat exchanger performance is presented in the following paragraphs. This summary is very brief, thus the reader is referred to the references at the end of the section and to heat transfer textbooks for further information. 

The help menu assists the user to estimate both the air-side and refrigerant-side heat 

transfer coefficients, the refrigerant-side pressure drop, and the heat exchanger surface 

areas for the following heat exchanger configurations: 

Summary of Help Menu Heat Exchanger Configurations 

nf.it'!~!!!~::liilj:!:f!!~!I~!!!g~!!:'!:~!::~jjj:!t:.iIR!.~'.::i!i~!~tt!!! .. : •. :.:::j::j .. : ..•. ; ••..•• ';. 

natural convection - vertical plate, hot-wall, wire-tube 

evaporator forced convection - straight fin-tube, wavy fin-tube 

natural convection - vertical plate, cold-wall, horizontal plate 

The algorithms for calculating the average heat transfer coefficients follow the general 

outline presented below: 

1. Air-side heat transfer coefficients are calculated first. Generally, air-side heat transfer coefficients are reasonably independent of the refrigerant-side conditions. 

2. Heat transfer coefficients for single phase refrigerant flow (i.e., refrigerant vapor or 

liquid) are calculated next. Heat transfer coefficients in this flow regime are essentially independent of the air-side conditions. 

3. Heat transfer coefficients and pressure losses for the condensation and evaporating 

flow regimes are calculated. In general these depend strongly on the air-side heat 

transfer coefficient. 

4. Finally, the average overall heat transfer coefficient based on air-side surface area 

corresponding to the single phase vapor, single phase liquid, condensing, and evaporating regimes are calculated. The pressure drops for the condensing and evaporating heat transfer regimes are also calculated. 

B-17 
A brief description of the analyses is presented below.

B.4.1. Air-Side Heat Transfer Coefficients

Forced Convection - Fin-Tube

Air-side performance for fin-tube heat exchangers is calculated using methods similar to

those found in Reference [4]. Depending on user defined values for heat exchanger

geometry (i.e. tube diameter, tube spacing, fin spacing, etc.) and air flow rate, the program calculates the air-side heat exchanger area (which is required for the ERACYC

model input) and the geometric and fluid dynamic parameters required for the heat

transfer calculation. The program uses empirical heat transfer correlations to calculate

the Nusselt number of the form

Nu=CRe'Prb (R-10)

The heat transfer coefficient is calculated from a relation of the form

Nukair h

h

(R-11)

d

Separate correlations are used for the straight and wavy fin types and are based on

several sets of data for each fin type presented in Reference [4]. The Reynolds number

Re is defined in terms of the hydraulic diameter dh of the heat exchanger (calculated

internally by the program) and Pr is the Prandtl number of the fluid. The fin efficiency

is calculated based on the heat transfer coefficient calculated in Eqn. (E-11), and is used

in the calculation for the average air-side U-value.

Forced Convection - Wire-Tube

It is assumed that the heat exchanger orientation is such that the wires are aligned parallel with the air flow direction and the condenser tubes are perpendicular to the air flow

direction. The user provides information regarding diameter and spacing of the

condenser tubing and wires, and the air flow rate. Heat transfer coefficients for the

wires and the condenser tubes are calculated using correlations of the same form as

(E-10) and (B-11).

Radiative Component

A radiative component of heat transfer is added to the convective components discussed

above. The radiative component is calculated by linearizing the equations for radiation

heat transfer, from which a radiative heat transfer coefficient can be defined and calculated using the following equation:

hr,^d= 4acT; ave (B - 12)

 EE-RM-93-801 COMMENT OR2

A brief description of the analyses is presented below. 

B.4.1. Air-Side Heat Transfer Coefficients 

Forced Convection - Fin-Tube 

Air-side perfonnance for fin-tube heat exchangers is calculated using methods similar to 

those found in Reference [4]. Depending on user defined values for heat exchanger 

geometry (i.e. tube diameter, tube spacing, fin spacing, etc.) and air flow rate, the program calculates the air-side heat exchanger area (which is required for the ERACYC 

model input) and the geometric and fluid dynamic parameters required for the heat 

transfer calculation. The program uses empirical heat transfer correlations to calculate 

the Nusselt number of the fonn 

(B -10) 

The heat transfer coefficient is calculated from a relation of the fonn 

(B -11) 

Separate correlations are used for the straight and wavy fin types and are based on 

several sets of data for each fin type presented in Reference [4]. The Reynolds number 

Re is defined in tenns of the hydraulic diameter dh of the heat exchanger (calculated 

internally by the program) and Pr is the Prandtl number of the fluid. The fin efficiency 

is calculated based on the heat transfer coefficient calculated in Eqn. (B-ll), and is used 

in the calculation for the average air-side U-value. 

Forced Convection - Wire-Tube 

It is assumed that the heat exchanger orientation is such that the wires are aligned parallel with the air flow direction and the condenser tubes are perpendicular to the air flow 

direction. The user provides information regarding diameter and spacing of the 

condenser tubing and wires, and the air flow rate. Heat transfer coefficients for the 

wires and the condenser tubes are calculated using correlations of the same form as 

(B-lO) and (B-11). 

Radiative Component 

A radiative component of heat transfer is added to the convective components discussed 

above. The radiative component is calculated by linearizing the equations for radiation 

heat transfer, from which a radiative heat transfer coefficient can be defmed and calculated using the following equation: 

(B -12) 

B-18 
where Tr,QVe in Eqn. (B- 12) is the refrigerant saturation temperature in absolute temperature units and r is the Stefan-Boltzman constant which has a value of 5.67 x 10-8

W/m2-K. The surface emittance, E, is assumed equal to 0.8 for the condenser surfaces

and equal to 0.2 for the evaporator surfaces.

Natural Convection

The heat transfer coefficients for natural convection heat exchangers are composed of

two components; convective and radiative. The total heat transfer coefficient is the sum

of these two components, or

h = hnc + hrad (B -13)

Correlations for air which are appropriate for the specified geometry are used to calculate the convective component, and have the form

hnc = C I Tr,ave - Ti,

10.33 (B -14)

More detailed descriptions of the correlations can be found in References [5, 6]. The

term I T,,ave - Ti,. aI is the absolute value of the difference between the average refrigerant

saturation temperature and the bulk air temperature. The air temperature corresponds to

the ambient (i.e., room) air temperature for analyzing a condenser and the cabinet temperature for analyzing an evaporator. The constant C in Eqn. (B- 14) depends on the

heat exchanger geometry. Geometries included in these analyses are a vertical plate

condenser, hot-wall condenser, vertical wire-tube condenser, vertical plate evaporator,

cold-wall evaporator, and a horizontal plate evaporator. The user provides data for each

heat exchanger type as requested by the help menu.

B.4.2. Refrigerant-Side Heat Transfer Coefficients and Pressure Drops

Single Phase Refrigerant Flow

The single phase refrigerant heat transfer coefficients are calculated assuming fullydeveloped laminar or turbulent flow. The Nusselt number correlations used in this analysis are

Nu =3.66 (B -15)

for laminar flow, and

Nu = 0.023Reo.sPro.a (B - 16)

for turbulent flow.

In most instances, the pressure drops are small compared to the pressure drop in the condensation and evaporating flow regimes and are therefore ignored.

 EE-RM-93-801 COMMENT OR2

where Tr,ave in Eqn. (B-12) is the refrigerant saturation temperature in absolute temperature units and 0' is the Stefan-Boltzman constant which has a value of 5.67 x 10-8 

W/m2-K. The surface emittance, e, is assumed equal to 0.8 for the condenser surfaces 

and equal to 0.2 for the evaporator surfaces. 

Natural Convection 

The heat transfer coefficients for natural convection heat exchangers are composed of 

two components; convective and radiative. The total heat transfer coefficient is the sum 

of these two components, or 

(B -13) 

Correlations for air which are appropriate for the specified geometry are used to calculate the convective component, and have the form 

hnc = C I Tr.

ave - T air ,0.33 (B -14) 

More detailed descriptions of the correlations can be found in References [5, 6]. The 

term I Tr•ave - Tair I is the absolute value of the difference between the average refrigerant 

saturation temperature and the bulk air temperature. The air temperature corresponds to 

the ambient (i.e., room) air temperature for analyzing a condenser and the cabinet temperature for analyzing an evaporator. The constant C in Eqn. (B-14) depends on the 

heat exchanger geometry. Geometries included in these analyses are a vertical plate 

condenser, hot-wall condenser, vertical wire-tube condenser, vertical plate evaporator, 

cold-wall evaporator, and a horizontal plate evaporator. The user provides data for each 

heat exchanger type as requested by the help menu. 

B.4.2. Refrigerant-Side Heat Transfer Coefficients and Pressure Drops 

Single Phase Refrigerant Flow 

The single phase refrigerant heat transfer coefficients are calculated assuming fullydeveloped laminar or turbulent flow. The Nusselt number correlations used in this analysis are 

Nu =3.66 (B -15) 

for laminar flow, and 

(B -16) 

for turbulent flow. 

In most instances, the pressure drops are small compared to the pressure drop in the condensation and evaporating flow regimes and are therefore ignored. 

B-19 
Condensation Heat Transfer Regime

Heat transfer coefficients and pressure drops are calculated simultaneously in the condensing flow regime. The analysis begins at saturated vapor and marches stepwise

downstream, calculating the local heat transfer coefficient and pressure gradient until

the point at which complete condensation has occurred , from which the average heat

transfer coefficient and total pressure drop can be determined. The equations and algorithms for calculating the condensation heat transfer coefficients and two-phase pressure

drop are too complex to be presented here, but can be found in References [7 - 10].

Evaporation Heat Transfer Regime

The analysis for the evaporating heat transfer regime is very similar to that of for the

condensation regime. The major difference is that much simpler equations are used to

calculate the average evaporating heat transfer coefficient, eliminating the need for a

stepwise calculation. However, the pressure drop in the evaporating heat transfer

regime is calculated by marching stepwise downstream, calculating the local pressure

gradient, and summing the local pressure drops to calculated the total pressure drop.

The equations for calculating the average evaporating heat transfer coefficient are taken

from Reference [11] while the pressure drop is calculated using the method from Reference [10].

BA3. Fluid Properties

The help menu contains refrigerant thermodynamic and transport properties for six pure

refrigerants; CFC-12, C- 134a, C- 152a, HC-290- (propane), HC-270 (cyclopropane), and HCFC-22. For both pure fluids and mixtures in which the properties are not

tabulated, the thermophysical properties are calculated based on the critical properties

(which are stored in ERA) using various molecular models. The methods of thermophysical property calculation used in ERA are outlined in Reference [12]. Use of the

help menu to calculate the heat transfer coefficients for NARMs should be done with

caution, as NARMs generally behave very differently than pure fluids. The heat transfer

coefficient correlations used in the help menu models are derived for pure fluids, and

thus generally do not apply to NARMs.

The properties of dry air are calculated in the program based on the user defined value

of air temperature, assuming atmospheric pressure.

B.5 Corrections for Hot-Wall Condenser or Cold- Wall Evaporator

Corrections are required to the cabinet loads output from CAB.EXE to account for the

presence of a cold-wall evaporator and/or hot-wall condenser. Two factors must be considered:

® The presence of the heat exchanger over a portion of the wall reduces the thickness

of the insulation over the same area. The menu program calculates the UAs of the

cabinet walls containing the heat exchangers and inputs these values to the cycle

model in file CYCLE.DAT.

 EE-RM-93-801 COMMENT OR2

Condensation Heat Transfer Regime 

Heat transfer coefficients and pressure drops are calculated simultaneously in the condensing flow regime. The analysis begins at saturated vapor and marches stepwise 

downstream, calculating the local heat transfer coefficient and pressure gradient until 

the point at which complete condensation has occurred, from which the average heat 

transfer coefficient and total pressure drop can be determined. The equations and algorithms for calculating the condensation heat transfer coefficients and two-phase pressure 

drop are too complex to be presented here, but can be found in References [7 - 10]. 

Evaporation Heat Transfer Regime 

The analysis for the evaporating heat transfer regime is very similar to that of for the 

condensation regime. The major difference is that much simpler equations are used to 

calculate the average evaporating heat transfer coefficient, eliminating the need for a 

stepwise calculation. However, the pressure drop in the evaporating heat transfer 

regime is calculated by marching stepwise downstream, calculating the local pressure 

gradient, and summing the local pressure drops to calculated the total pressure drop. 

The equations for calculating the average evaporating heat transfer coefficient are taken 

from Reference [11] while the pressure drop is calculated using the method from Reference [10]. 

B.4.3. Fluid Properties 

The help menu contains refrigerant thermodynamic and transport properties for six pure 

refrigerants; CFC-12, HFC-134a, HFC-152a, HC-29o- (propane), HC-270 (cyclopropane), and HCFC-22. For both pure fluids and mixtures in which the properties are not 

tabulated, the thermophysical properties are calculated based on the critical properties 

(which are stored in ERA) using various molecular models. The methods of thermophysical property calculation used in ERA are outlined in Reference [12]. Use of the 

help menu to calculate the heat transfer coefficients for NARMs should be done with 

caution, as NARMs generally behave very differently than pure fluids. The heat transfer 

coefficient correlations used in the help menu models are derived for pure fluids, and 

thus generally do not apply to NARMs. 

The properties of dry air are calculated in the program based on the user defmed value 

of air temperature, assuming atmospheric pressure. 

B.5 Corrections for Hot-Wall Condenser or Cold-WalilEvaporator 

Corrections are required to the cabinet loads output from CAB.EXE to account for the 

presence of a cold-wall evaporator and/or hot-wall Gondenser. Two factors must be considered: 

.. The presence of the heat exchanger over a portion of the wall reduces the thickness 

of the insulation over the same area. The menu program calculates the U As of the 

cabinet walls containing the heat exchangers and inputs these values to the cycle 

model in me CYCLE.DAT. 

B-20 
During the on-cycle period (when the compressor is operating) the environment

communicates with the heat exchanger through the insulation. This results in an

incremental refrigeration load and a change in the cabinet load during the on-cycle

period.

As an example, assume that a cold-wall evaporator is used in the fresh food section of a

dual evaporator cycle. If the thermal conductance of the area of the wall containing the

evaporator is written:

UA_FF_EVP = UA of fresh food section wall evaporator

then the additional refrigeration load on the evaporator is

AQe = UA_FF_EVP (Ta - T0)

where Ta = room temperature and Te = evaporator temperature.

During the time the compressor is operating, the evaporator effectively isolates this portion of the cabinet wall from the environment. This will result in a correction to the

duty cycle (compressor on-time):

Duty Cycle = Cabinet Load / CAP'

where

CAP` = CAP + AQe - UA_FF_EVP (Ta - Tom)

where T = fresh food cabinet temperature and CAP is the evaporator capacity in the

absence of the additional heat input to the evaporator through the insulation.

Similar equations hold for the freezer evaporator.

The presence of a hot-wall condenser will have similar effects on the cabinet loads and

refrigeration cycle behavior. During the time the compressor is running the outside wall

will be warmer than the ambient, which will result in additional heat flow into the cabinet. As a consequence, the duty cycle will be lengthened by the additional cabinet heat

load.

For example, if the condenser is in the walls of a fresh food section, the duty cycle

becomes:

Duty = Cabinet-Load/(CAP' + AQ)

where

AQ = UA_FF_CND (TT - TO

UA_FF CND = UA value of portion of wall containing condenser

TT = condenser temperature

 EE-RM-93-801 COMMENT OR2

.. During the on-cycle period (when the compressor is operating) the environment 

communicates with the heat exchanger through the insulation. This results in an 

incremental refrigeration load and a change in the cabinet load during the on-cycle 

period. 

As an example. assume that a cold-wall evaporator is used in the fresh food section of a 

dual evaporator cycle. If the thermal conductance of the area of the wall containing the 

evaporator is writt~m: 

U A_FF _EVP = U A of fresh food section wall evaporator 

then the additional refrigeration load on the evaporator is 

where Ta = room temperature and Te = evaporator temperature. 

During the time the compressor is operating, the evaporator effectively isolates this portion of the cabinet wall from the environment. This will result in a correction to the 

duty cycle (compressor on-time): 

Duty Cycle = CabinecLoad I CAp· 

where 

where T fF = fresh food cabinet temperature and CAP is the evaporator capacity in the 

absence of the additional heat input to the evaporator through the insulation. 

Similar equations hold for the freezer evaporator. 

The presence of a hot-wall condenser will have similar effects on the cabinet loads and 

refrigeration cycle behavior. During the time the compressor is running the outside wall 

will be warmer than the ambient, which will result in additional heat flow into the cabinet. As a consequence, the duty cycle will be lengthened by the additional cabinet heat 

load. 

For example, if the condenser is in the walls of a fresh food section, the duty cycle 

becomes: 

Duty = CabinecLoad/(CAP· + AQ) 

where 

U A_FF _ CND = U A value of portion of wall containing condenser 

Tc = condenser temperature 

B-21 
Matching Evaporator Capacities and Cabinet Loads

The overall analysis of daily energy use takes place in four steps:

® Step 1: Calculate cabinet loads assuming fixed cabinet temperatures

® Step 2: Calculate cycle parameters for given cabinet air temperature

® Step 3: Perform adjustments to match cabinet loads and evaporator capacity

® Step 4: Calculate compressor run time and the net energy consumption

Steps 2 and 3 are normally done iteratively since there will often be an imbalance

between the loads of the two cabinets and the corresponding cooling rates.

The method for matching the capacities and loads depends on the refrigeration cycle and

the control option. This is discussed below for the three basic cycles: 1) single evaporator - single compressor cycle; 2) dual-loop cycle; 3) dual evaporator cycle (with one

compressor). Note that the Lorenz cycle is a subset of the dual evaporator cycle.

B.6.1. Single Evaporator Cycle

The single evaporator cycle uses an air baffle arrangement to deliver cool air to both

compartments from the single evaporator, located in the back of the freezer compartment. It is assumed that the user has properly set the baffle, or that an electronically

controlled baffle is used, to deliver the necessary air to each compartment to

simultaneously meet the two cabinet loads at the assumed setpoints.

The cooling rate of each compartment is given by:

Q = rhCp f (TTF -Tout)

Qz=rhCp (1 -f) (Trz-Tau)

where

m Cp = mass flow - specific heat of air across the evaporator

f = fraction of air going to fresh food compartment

Tout = temperature of air leaving the evaporator coil

The inlet air temperature of the coil, and the net evaporator capacity, must satisfy:

Ti. = fT +(1-f)TFZ

Capacity = rhCp (Ti. - Taut)

The equations are solved simultaneously to determine the fraction of air going to the

fresh food section (typically 10 - 15%) and the inlet air temperature to the evaporator.

 EE-RM-93-801 COMMENT OR2

B.S Matching Evaporator Capacities and Cabinet Loads 

The overall analysis of daily energy use takes place in four steps: 

" Step 1: Calculate cabinet loads assuming fixed cabinet temperatures 

" Step 2: Calculate cycle parameters for given cabinet air temperature 

" Step 3: Perform adjustments to match cabinet loads and evaporator capacity 

e Step 4: Calculate compressor run time and the net energy consumption 

Steps 2 and 3 are normally done iteratively since there will often be an imbalance 

between the loads of the two cabinets and the corresponding cooling rates. 

The method for matching the capacities and loads depends on the refrigeration cycle and 

the control option. This is discussed below for the three basic cycles: 1) single evaporator - single compressor cycle; 2) dual-loop cycle; 3) dual evaporator cycle (with one 

compressor). Note that the Lorenz cycle is a subset of the dual evaporator cycle. 

B.6.1. Single Evaporator Cycle 

The single evaporator cycle uses an air baffle arrangement to deliver cool air to both 

compartments from the single evaporator, located in the back of the freezer compartment. It is assumed that the user has properly set the baffle, or that an electronically 

controlled baffle is used, to deliver the necessary air to each compartment to 

simultaneously meet the two cabinet loads at the assumed setpoints. 

The cooling rate of each compartment is given by: 

<k = me; f (TFF - TouJ 

<k = me;, (1 - 1) (TFZ - TouJ 

where 

mCp = mass flow - specific heat of air across the evaporator 

f = fraction of air going to fresh food compartment 

Tout = temperature of air leaving the evaporator coil 

The inlet air temperature of the coil, and the net evaporator capacity, must satisfy: 

Capacity = mCp (Tin - TouJ 

The equations are solved simultaneously to determine the fraction of air going to the 

fresh food section (typically 10 - 15%) and the inlet air temperature to the evaporator. 

B-22 
B.6.2. Dual Loop

The dual loop cycle employes two separate refrigeration loops and controls, one for

each compartment. They are solved separately, and the energy consumption values

combined to establish the overall consumption level.

B.6.3. Dual Evaporator Cycle

This is the most complex cycle from a controls standpoint. Although fans could be used

in both compartments and cycled on and off to effectively couple or de-couple the evaporator from the cabinet air , it is assumed that at least one of these evaporators will be a

natural convection type. Hence, there will almost always be an imbalance between the

delivered cooling rates and the needs of the individual compartments.

ERA provides 5 options for dealing with this:

® Allow imbalance -- the summary output will note an imbalance when one occurs. A

second run can then be made with an adjustment in parameters in an attempt to

reduce the imbalance below some level. For example, most current Chinese refrigerator/freezer designs use a resistance heater in the fresh food section to artificially add

a heat load when necessary to keep the compressor running to ensure that the freezer

compartment is adequately refrigerated.

® Allow the fresh food section cabinet temperature to float when the compressor is

controlled by the freezer set point. Corrections to the fresh food section cabinet heat

load and temperature are made until the cabinet loads are in balance with the relative

evaporator capacities.

® Allow the freezer temperature to float when the compressor is controlled by the fresh

food section set point. The freezer cabinet load is adjusted, along with the freezer

temperature, to achieve a balance between the cabinet loads and evaporator capacities.

® Mathematically adjust the areas of the two evaporators to achieve the balance. The

algorithm adopted maintains total evaporator area, while adjusting the fraction in

each compartment. This is, of course, not possible in a hardware configuration.

However, it yields information useful to a researcher or designer about the proportion of evaporator areas required to achieve a correct balance.

® Bypass one of the evaporators during a portion of the cycle.

B.7 Variable Speed Operation

Variable speed control is one means of achieving efficiency improvements. Motor

speed is modulated to maintain essentially constant operation of the compressor at a

reduced capacity that nearly matches the cabinet load. Both the physically based (lossefficiency) model and rating point (EER-capacity) model for the compressor allow specification of reduced speed. Because of the complex phenomena involved throughout the

refrigeration cycle, capacity is not linear with respect to speed, but varies with some

fractional power of the speed. These variations are taken into account by the compres-

 EE-RM-93-801 COMMENT OR2

B.6.2. Dual Loop 

The dual loop cycle employes two separate refrigeration loops and controls, one for 

each compartment. They are solved separately, and the energy consumption values 

combined to establish the overall consumption level. 

B.6.3. Dual Evaporator Cycle 

This is the most complex cycle from a controls standpoint. Although fans could be used 

in both compartments and cycled on and off to effectively couple or de-couple the evaporator from the cabinet air, it is assumed that at least one of these evaporators will be a 

natural convection type. Hence, there will almost always be an imbalance between the 

delivered cooling rates and the needs of the individual compartments. 

ERA provides 5 options for dealing with this: 

" Allow imbalance -- the summary output will note an imbalance when one occurs. A 

second run can then be made with an adjustment in parameters in an attempt to 

reduce the imbalance below some level. For example, most current Chinese refrigerator/freezer designs use a resistance heater in the fresh food section to artificially add 

a heat load when necessary to keep the compressor running to ensure that the freezer 

compartment is adequately refrigerated. 

" Allow the fresh food section cabinet temperature to float when the compressor is 

controlled by the freezer set point. Corrections to the fresh food section cabinet heat 

load and temperature are made until the cabinet loads are in balance with the relative 

evaporator capacities. 

.. Allow the freezer temperature to float when the compressor is controlled by the fresh 

food section set point. The freezer cabinet load is adjusted, along with the freezer 

temperature, to achieve a balance between the cabinet loads and evaporator capacities. 

.. Mathematically adjust the areas of the two evaporators to achieve the balance. The 

algorithm adopted maintains total evaporator area, while adjusting the fraction in 

each compartment. This is, of course, not possible in a hardware configuration. 

However, it yields information useful to a researcher or designer about the proportion of evaporator areas required to achieve a correct balance. 

.. Bypass one of the evaporators during a portion of the cycle. 

B.7 Variable Speed Operation 

Variable speed control is one means of achieving efficiency improvements. Motor 

speed is modulated to maintain essentially constant operation of the compressor at a 

reduced capacity that nearly matches the cabinet load. Both the physically based (lossefficiency) model and rating point (EER-:capacity) model for the compressor allow specification of reduced speed. Because of the complex phenomena involved throughout the 

refrigeration cycle, capacity is not linear with respect to speed, but varies with some 

fractional power of the speed. These variations are taken into account by the compresB-23 
sor models. Hence, the program user merely need specify a change in the speed and

ERA will determine a corresponding capacity. Because of lubrication issues as well as

motor efficiency concerns, the minimum desirable speed would be 25 - 40% of normal

operating speed.

Electric motors show efficiency changes with speed [ 13]. ERA does not automatically

adjust for motor efficiency, but assumes the program user will account for this by inputting a lower EER level or lower pump-motor efficiency parameters, depending on the

compressor model selected.

Electronics losses will partially affect gains realized by variable speed operation. These

losses occur in the speed control device which will be located outside the refrigerator

cabinet. Two means for accounting for the electronics losses are provided: 1) specify

the losses directly when using the loss-efficiency compressor model, 2) incorporate

these losses into a reduced effective EER when using the EER-capacity compressor

model. Reference [13] discusses the nature and magnitude of such losses.

In order to realize the efficiency potential of variable speed control, reduced wattage

fans must be utilized since the fans will also be operated nearly continuously. In addition, it may be advantageous to vary the fan speed to reduce the air flow over the heat

exchanger since the dominant heat transfer resistance may be on the refrigerant side at

reduced mass flow.

A simple model is employed to estimate the variation in air flow rate and fan power as a

function of speed [14]:

Air flow -speed

Fan power a (speed)3

A calculation assist menu is available to automatically scale the air flow and fan power.

If a variable speed analysis is carried out, the calculation assist menu for evaporator and

condenser heat transfer should be utilized. The effects of both reduced refrigerant mass

flow and variable speed fan induced air flow will be taken into account.

References

1. Data received from AHAM on results of round-robbin testing of two reciprocating

domestic refrigerator compressors using CFC- 12 refrigerant.

2. Meyer, W. M., and Thompson, H. D., "An experimental Investigation Into heat

Transfer to the Suction Gas in a Low-Side Hermetic Refrigeration Compressor",

Proceedings of the 1990 International Compressor Engineering Conference, Purdue

University, West Lafayette Indiana, July 17-20, 1990, pp 908-916.

3. M.J.P. Janssen, J.A. deWit, and L.J.M. Kuijpers, "Cycling Losses in Domestic

Appliances: An Experimental and Theoretical Analysis," Proceedings of the 1990

USNC/HR - Purdue Refrigeration Conference, pp. 90-98, July, 1990.

 EE-RM-93-801 COMMENT OR2

sor models. Hence, the program user merely need specify a change in the speed and 

ERA will determine a corresponding capacity. Because of lubrication issues as well as 

motor efficiency concerns, the minimum desirable speed would be 25 - 40% of normal 

operating speed. 

Electric motors show efficiency changes with speed [13]. ERA does not automatically 

adjust for motor efficiency, but assumes the program user will account for this by inputting a lower EER level or lower pump-motor efficiency parameters, depending on the 

compressor model selected. 

Electronics losses will partially affect gains realized by variable speed operation. These 

losses occur in the speed control device which will be located outside the refrigerator 

cabinet. Two means for accounting for the electronics losses are provided: 1) specify 

the losses directly when using the loss-efficiency compressor model, 2) incorporate 

these losses into a reduced effective EER when using the EER-capacity compressor 

model. Reference [13] discusses the nature and magnitude of such losses. 

In order to realize the efficiency potential of variable speed control, reduced wattage 

fans must be utilized since the fans will also be operated nearly continuously. In addition, it may be advantageous to vary the fan speed to reduce the air flow over the heat 

exchanger since the dominant heat transfer resistance may be on the refrigerant side at 

reduced mass flow. 

A simple model is employed to estimate the variation in air flow rate and fan power as a 

function of speed [14]: 

Air flow oc speed 

Fan power oc (speed)3 

A calculation assist menu is available to automatically scale the air flow and fan power. 

If a variable speed analysis is carried out, the calculation assist menu for evaporator and 

condenser heat transfer should be utilized. The effects of both reduced refrigerant mass 

flow and variable speed fan induced air flow will be taken into account. 

B.8 References 

1. Data received from AHAM on results of round-robbin testing of two reciprocating 

domestic refrigerator compressors using CFC-12 refrigerant. 

2. Meyer, W. M., and Thompson, H. D., "An experimental Investigation Into heat 

Transfer to the Suction Gas in a Low-Side Hermetic Refrigeration Compressor", 

Proceedings of the 1990 International Compressor Engineering Conference, Purdue 

University, West Lafayette Indiana, July 17-20, 1990, pp 908-916. 

3. M.J.P. Janssen, J.A. deWit, and L.J.M. Kuijpers, "Cycling Losses in Domestic 

Appliances: An Experimental and Theoretical Analysis," Proceedings of the 1990 

USNC/llR - Purdue Refrigeration Conference, pp. 90-98, July, 1990. 

B-24 
4. Kays, W. M., London, A. L., Compact Heat Exchangers, McGraw-Hill Book Company, New York, third edition, 1984.

5. ASH RAE 1989 Handbook of Fundamentals, published by the American Society of

Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, GA, 1989.

6. Krieth, F., Pringiffles of Het Transfer, third edition, Intex Press, Inc., New York,

1973.

7. Dittus, F. W., and Boelter, L. M. K., "Heat Transfer in Automobile Radiators of the

Tubular type", Publications in Engineering, University of California, Berkeley, 2,

pp. 443-461, 1930.

8. Ackers, W. W., and Rosson, H. F., "Condensation Inside a Horizontal Tube",

Chemical Engineering Progress Symposium Series, 5,L, 30, 1960.

9. Ackers, W. W., Dean, H. A., and Crosser, D. K., "Condensing Heat Transfer Within

Horizontal Tubes", Chemical Engineering Progress Symposium Series, 55, 29,

1959.

10. Lockhart, R. W., and Martinelli, R. C., "Proposed Correlation of Data for Isothermal Two-Phase, Two-Component Flow in Pipes", Chemical Engineering Progress,

4455, 1, pp. 39-48.

11. Pierre, Bo, Ivtlteknisk Tidskrint, ., May 1957, p. 129.

12. Merriam, R. L., and Mathias, S., "Evaluation of Advanced Vapor Compression

Cycles for Use With Nonazeotropic Refrigerant Mixtures", report by Arthur D.

Little, Inc. for Oak Ridge National Laboratory, January 1988.

13 Dickmann, J., and McMahon, E, "State of the Art Survey of Motor Technology

Applicable to Hermetic Compressors for Domestic Refrigerator/Freezers," Draft

Report to the U.S. EPA by Arthur D. Little, Inc., 1991.

14 ASHRAE Equipment Handbook, "Fans".

 EE-RM-93-801 COMMENT OR2

4. Kays, W. M., London, A. L., Compact Heat Exchangers, McGraw-Hill Book Company, New York, third edition, 1984. 

5. ASHRAE 1989 Handbook of Fundamentals, published by the American Society of 

Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, GA, 1989. 

6. Krieth, E, Principles of Heat Transfer, third edition, Intex Press, Inc., New York, 

1973. 

7. Dittus, E W., and Boelter, L. M. K., "Heat Transfer in Automobile Radiators of the 

Tubular type", Publications in Engineering, University of California, Berkeley,,2, 

pp. 443-461, 1930. 

8. Ackers, W. W., and Rosson, H. E, "Condensation Inside a Horizontal Tube", 

Chemical Engineering Progress Symposium Series, j,Q, 30, 1960. 

9. Ackers, W. W., Dean, H. A., and Crosser, D. K., "Condensing Heat Transfer Within 

Horizontal Tubes", Chemical Engineering Progress Symposium Series,.5..5., 29, 

1959. 

10. Lockhart, R. W., and Martinelli, R. c., "Proposed Correlation of Data for Isothermal Two-Phase, Two-Component Flow in Pipes", Chemical Engineering Progress, 

~, 1, pp. 39-48. 

11. Pierre, Bo, Kytlteknisk Tidskript,~, May 1957, p. 129. 

12. Merriam, R. L., and Mathias, S., "Evaluation of Advanced Vapor Compression 

Cycles for Use With Nonazeotropic Refrigerant Mixtures", report by Arthur D. 

Little, Inc. for Oak Ridge National Laboratory, January 1988. 

13 Dickmann, J., and McMahon, E, "State of the Art Survey of Motor Technology 

Applicable to Hermetic Compressors for Domestic RefrigeratorlFreezers," Draft 

Report to the U.S. EPA by Arthur D. Little, Inc., 1991. 

14 ASHRAE Equipment Handbook, "Pans". 

B-25 
APPENDIX C

71- 77 D,P.®:® FILES:

on®< ..%a T INPUT

C. I Introduction

C-2

C.2 SummarY of Sample Input Data

C-2

C.3 Reference

C-2

 EE-RM-93-801 COMMENT OR2

C.l Introduction 

APPENDIXC 

SAMPLE DATA FilES: 

MULTIPLE PATHWAYS DATA INPUT 

C.2 Summary of Sample Input Data 

C.3 Reference 

C-l 

C-2 

C-2 

C-2 
C.1 Introduction

The multiple pathways analyses of alternate design concepts for super efficient refrigerators utilized the ERA program to estimate daily and annual energy use. Descriptions of

the refrigerator designs, and results of the model analyses, are summarized in the

reference document [1]. To facilitate further analyses along the lines utilized in the

Multiple Pathways analysis effort, all of the data files developed and input to ERA are

provided on diskettes accompanying ERA.

As recommended in Section 8, a naming convention has been adopted to facilitate cataloging the files. The general strategy for naming the files is given below:

Model Design 1991 Baseline Design 1993 CFC-Free Design

A Top-Mount Model_A A_1993

B Top-Mount Model_B B1993

C Top-Mount Model_C C_1993

D Top-Mount Model_D D_1993

E Bottom-Mount Model_E E_1993

F Side-by-Side Model_F F_1993

Eight character names for the remaining files are built up of 4 character fields:

The first character designates the baseline model (A - F).

® The second and third characters are the path shown in the Multiple Pathways report

(1, 1A, 2, ..., 10)

® The fourth and fifth characters are the step in the path , numbered from the baseline

unit (e.g., 01, 02, ..., 12).

The remaining three characters designate the design feature studied by the particular

run (see Table C-1)

C.2 Summary of Sample Input Data

Tables C-2 to C-18 list the sample data files with a short description of the design feature of interest to the run. Note that the analyses progress along the line of sequential

changes, where each new case incorporates the features of previous steps along the path.

C.3 Reference

1. "Multiple Pathways to Super Efficient Refrigerators," U.S. EPA, Global Change

Division, Office of Atmospheric Programs, 1993.

 EE-RM-93-801 COMMENT OR2

C.1 Introduction 

The multiple pathways analyses of alternate design concepts for super efficient refrigerators utilized the ERA program to estimate daily and annual energy use. Descriptions of 

the refrigerator designs, and results of the model analyses, are summarized in the 

reference document [1]. To facilitate further analyses along the lines utilized in the 

Multiple Pathways analysis effort, all of the data files developed and input to ERA are 

provided on diskettes accompanying ERA. 

As recommended in Section 8, a naming convention has been adopted to facilitate cataloging the meso The general strategy for naming the mes is given below: 

Model Design 1991 Baseline Design 1993 CFC -Free Design 

A Top-Mount Model_A A_1993 

B Top-Mount Model_B B_1993 

C Top-Mount Model_C C_1993 

D Top-Mount Model_D D_1993 

E Bottom-Mount Model_E E_1993 

F Side-by-Side ModeCF F_1993 

Eight character names for the remaining files are built up of 4 character fields: 

G The first character designates the baseline model (A - F). 

" The second and third characters are the path shown in the Multiple Pathways report 

(1, lA, 2, ... , 10) 

" The fourth and fifth characters are the step in the path, numbered from the baseline 

unit (e.g., 01, 02, ... , 12). 

" The remaining three characters designate the design feature studied by the particular 

run (see Table C-l) 

C.2 Summary of Sample Input Data 

Tables C-2 to C-18 list the sample data files with a short description of the design feature of interest to the run. Note that the analyses progress along the line of sequential 

changes, where each new case incorporates the features of previous steps along the path. 

C.3 Reference 

1. "Multiple Pathways to Super Efficient Refrigerators," U.S. EPA, Global Change 

Division, Office of Atmospheric Programs, 1993. 

C-2 
Tattle C-1. Three Character Code Designations for Design Feature

ADF

CBI

CCP

Adaptive defrost

Carbon black insulation

Cyclopropane refrigerant

CMP Higher EER compressor

CSC Current small compressor

C50 Increase condenser area 50%

DCC DC condenser fan

ICE DC evaporator fan

DCF DC evaporator and condenser fans

DLR Use refrigerant R152a in freezer section

and refrigerant R 142b in fresh food section

DRI Add insulation to doors

E50 Increase evaporator area 50%

FSC Future small compressors

FST Change Defrost timer

G25 Cut gasket loss 25%

G50 Cut gasket loss to 50%

HEF High efficient fans (PSC type)

HRI High-R gas filled insulation

INO Add 1/2 inch insulation all around

IN1 Add 1 inch insulation all around

IN2 Add 2 inches insulation all around

INS Add insulation everywhere except to doors

LLF Liquid line cabinet flange heat

LLM Liquid line mullion heat

LRZ Lorenz cycle

MCI Microcell insulation

REF Refrigerant 152a

SHV Shut-off valve

VCC Variable capacity compressor

VCM Vacuum insulation

VLF Vapor line heat to cabinet flange

 EE-RM-93-801 COMMENT OR2

Table Cal. Three Character Code Designations for Design Feature 

ADF Adaptive defrost 

CBI Carbon black insulation 

CCP Cyclopropane refrigerant 

CMP Higher EER compressor 

CSC Current small compressor 

C50 Increase condenser area 50% 

DCC DC condenser fan 

DCE DC evaporator fan 

DCF DC evaporator and condenser fans 

DLR Use refrigerant R152a in freezer section 

and refrigerant R 142b in fresh food. section 

DRI Add insulation to doors 

E50 Increase evaporator area 50% 

FSC Future small compressors 

FST Change Defrost timer 

025 Cut gasket loss 25% 

050 Cut gasket loss to 50% 

HEF High efficient fans (PSC type) 

HRI High-R gas filled insulation 

INO Add 1/2 inch insulation all around 

INI Add 1 inch insulation all around 

IN2 Add 2 inches insulation all around 

INS Add insulation everywhere except to doors 

LLF Liquid line cabinet flange heat 

LLM Liquid line mullion heat 

LRZ Lorenz cycle 

MCI Microcell insulation 

REF Refrigerant I52a 

SHV Shut-off valve 

VCC Variable capacity compressor 

VCM Vacuum insulation 

VLF Vapor line heat to cabinet flange 

C-3 
Table C-2. Pathway 1:

1993-CFC Model_D

1993 D_1993

1 D1_01G25

2 D2_02G50

3 D 1_03LLM

4 DI-04C

5 D1_O5DRI

6 D1_06MCI

7 D1_071N1

8 DI-08 F

9 D1_09DCE

10 D1_10DCC

Table C-3. Pathway IA:

, tep l7^ait "a

1993-CFC Model_I

1993 D_1993

1 D1_01G25

2 D2_02G50

3 D 1_03LLM

4 D1_04C

5 D1_05DRI

6 D 1_06MCI

7 D1A07ADF

8 D lA08IN2

9 D 1 A09DCE

10 D1AlODCC

Single Evaporator Cycle

Current Technologies with Increased Insulation

Model D Prc^otype Rlefrigeraior/Free r

Deev!

1993 prototype design with CFCs

1993 prototype, with HT-C-134a refrigerant and

HCFC-blown insulation

Cut gasket heat leak by 25%

Cut gasket heat leak by 50% from baseline value

Replace mullion heater with liquid line heat

Use 5.5 EER compressor (was 5.3 EER)

Add 3/4 inch insulation to both doors

Employ micro-cell insulation

Add 1 inch insulation all around (including doors)

Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

Use DC evaporator fan

Use DC condenser fan

Single Evaporator Cycle

Current Technologies with Thick Wall Cablraet

Model Prototype Refrigerator/Freezer

1993 prototype design with CFCs

1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

Cut gasket heat leak by 25%

Cut gasket heat leak by 50% from baseline value

Replace mullion heater with liquid line heat

Use 5.5 EER compressor (was 5.3 EER)

Add 3/4 inch insulation to both doors

Employ micro-cell insulation

Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

Add 2 inches insulation all around

Use DC evaporator fan

Use DC condenser fan

 EE-RM-93-801 COMMENT OR2

Table C-2. Pathway 1: 

step> IJiiMFile 

1993-CFC MOd~Lb 

1993 D_1993 

1 D1_OlG25 

2 D2_02G50 

3 D1_03LLM 

4 Dl_04CMP 

5 Dl_05DRI 

6 Dl_06MCI 

7 DL07IN1 

8 Dl_08ADF 

9 Dl_09DCE 

10 DLlODCC 

Single Evaporator Cycle 

Current Technologies with Increased Insulation 

Model D Prototype Refrigerator/Freezer 

IJdci;pit(Ji;< .......••.•.... ... ..•..•.••.......••.•..••. 

1993 protot~~a~sign~ith 1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Cut gasket heat leak by 25% 

Cut gasket heat leak by 50% from baseline value 

Replace mullion heater with liquid line heat 

Use 5.5 EER compressor (was 5.3 EER) 

Add 3/4 inch insulation to both doors 

Employ micro-cell insulation 

Add 1 inch insulation all around (including doors) 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Use DC evaporator fan 

Use DC condenser fan 

Table C-3. Pathway lA: Single Evaporator Cycle 

Current Technologies with Thick Wan Cabinet 

Model D Prototype RefrigeratoriFreezer 

1993 D_1993 1993 prototype, with HFC-134a refrigerant and 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Dl_01G25 

D2_02G50 

Dl_03LLM 

D1_04CMP 

D1_05DRI 

Dl_06MCI 

D1A07ADF 

DIA08IN2 

D1A09DCE 

D1AlODCC 

HCFC-blown insulation 

Cut gasket heat leak by 25% 

Cut gasket heat leak by 50% from baseline value 

Replace mullion heater with liquid line heat 

Use 5.5 EER compressor (was 5.3 EER) 

Add 3/4 inch insulation to both doors 

Employ micro-cell insulation 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Add 2 inches insulation all around 

Use DC evaporator fan 

Use DC condenser fan 

C-4 
Table C®4. Pathway 2: Single Evaporator Cycle

Timprove Components and Auxiliaries

Mode-17 B Fnaguiype Refriger.-Cor/Freez?r

1991 Model_B 1991 prototype design

I E2_O1C Use 5.00 EER compressor (was 4. 57 EER)

2 E2_02FST Replace 2 watt defrost timer with 1/4 watt

outside cabinet

3 IB2_03IN0 Add 1/2 insulation all around

4 E2_04DRI Add 1/2 insulation to doors

1993 E_1993 1993 prototype, with C- 134a refrigerant and

HCFC-blown insulation

6 B2_06LLM Replace mullion heater with liquid line heat

7 E2_07C Use 5.3 EER rotary compressor

8 E2_08SHV Add shut-off valve (with rotary compressor)

9 B2_09C50 Increase condenser area 50%

10 E2_10ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

11 B2_11E50 Increase evaporator area 50%

12 E2_12DCF Use DC fans

Table C-5. Pathway 3: Single Evaporator Cycle

Improved Compressor and Cabinet

Model C Prototype Refrigerator/Freezer

1991 Model_C 1991 prototype design

1 C3_O1LLF Replace freezer flange heater with liquid line heat

2 C3_02C Use 5.00 EER compressor (was 4.85 EER)

3 C3_03DCE DC evaporator fan

4 C3 04DRI Add 1 inch insulation to both doors

1993 C1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

6 C3_06G25 Cut gasket heat leak by 25%

7 C3_07C Use 5.3 EER rotary compressor

8 C3_O8DRI Add 1 inch insulation to both doors

9 C3_09INS Add 1 inch insulation everywhere except doors

10 C3_10MCI Employ micro-cell insulation

11 C3_1 IADF Use adaptive defrost (reduce frequency by 74%)

 EE-RM-93-801 COMMENT OR2

Table C-4. Pathway 2: 

$itp···<· .. · 1~9i . 

1 

2 

3 

4 

1993 

6 

7 

8 

9 

10 

11 

12 

B2_03INO 

B2_04DRI 

B_1993 

B2_06LLM 

B 2_07 CMP 

B2_08SHV 

B2_09C50 

B2_lOADF 

B2_11E50 

B2_12DCF 

Table CDS. Pathway 3: 

1 

2 

3 

4 

1993 

6 

7 

8 

9 

10 

11 

C3_01 LLF 

C3_02CMP 

C3_03DCE 

C3_04DRI 

C_1993 

C3_06G25 

C3_07CMP 

C3_08DRI 

C3_09INS 

C3_lOMCI 

C3_11ADF 

Single Evaporator Cycle 

Improved Components and Auxiliaries 

Model B Prototype Refrigerator/Freezer 

Use 5.00 EER compressor (was 4.57 EER) 

Replace 2 watt defrost timer with 1/4 watt 

outside cabinet 

Add 1/2 insulation all around 

Add 1/2 insulation to doors 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Replace mullion heater with liquid line heat 

Use 5.3 EER rotary compressor 

Add shut-off valve (with rotary compressor) 

Increase condenser area 50% 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Increase evaporator area 50% 

Usc DC fans 

Single Evaporator Cycle 

Improved Compressor and Cabinet 

Model C Prototype Refrigerator/Freezer 

prototype "'''''''~l'>'' 

Replace freezer flange heater with liquid line heat 

Use 5.00 EER compressor (was 4.85 EER) 

DC evaporator fan 

Add 1 inch insulation to both doors 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Cut gasket heat leak by 25% 

Use 5.3 EER rotary compressor 

Add 1 inch insulation to both doors 

Add 1 inch insulation everywhere except doors 

Employ micro-cell insulation 

Use adaptive defrost (reduce frequency by 74%) 

C-5 
Table C-6. Pathway 3A: Single Evaporator Cycle

Improved Compressor and Cabinet

viCh Felder ReNgerantr

Model C Prototype Reffr!gerator/Freezer

Sled Ducre Fff'c ? emc pt ®u

1991 iodel_C 1991 prototype design

1 C3_O1LL.F Replace freezer flange heater with liquid line heat

2 C3_02C Use 5.00 EER compressor (was 4.85 EER)

3 C3_03DCE DC evaporator fan

4 C3_04DRI Add 1 inch insulation to both doors

1993 C_1993 1993 prototype, with C-134a refrigerant and

HCFC-blown i l nsu ation

6 C3_0 25 Cut gasket heat leak by 25%

7 C3AO7CCP Replace IBC-134a with RC-270 (cyclopropane)

8 C3AO8CMP Use 5.3 EER rotary compressor

9 C3AO9MCI Employ micro-cell insulation

10 C3AlODRI Add 1 inch insulation to both doors

11 C3A11ADF Use adaptive defrost (reduce frequency by 74%)

12 C3A12INS Add 1 inch insulation everywhere except doors

Table C-7. Pathway 4: Single Evaporator Cycle

Current Technologies with Advanced Insulation

Model A Prototype Reffrigerator/Freezer

1991 Model_b. 1991 prototype design

1 A4_O1C Use 5.3 EER compressor (was 4.55 EER)

2 A4_02DRI Add 3/4 insulation to both doors

3 A4_03VLF Replace door flange heater with vapor line heat from

compressor exit

1993 A_1993 1993 prototype, with HFC- 134a refrigerant and

HCFC-blown insulation

5 A4_05G50 Cut gasket heat leak by 50% from baseline value

6 A4_06CMP Use 5.5 EER compressor

7 A4_07DCE Use DC evaporator fan

8 A4_08DCC Use DC condenser fan

9 A4_O9IIRI 50% coverage with high-R gas filled insulation

10 A4_10HRI 80% coverage with high-R gas filled insulation

 EE-RM-93-801 COMMENT OR2

Table C-6. Pathway 3A: Single Evaporator Cycle 

SUp 

1991 

1 

2 

3 

4 

1993 

6 

7 

8 

9 

lO 

11 

12 

Improved Compressor and Cabinet 

with Better Refrigerant 

Model C Prototype RefrigeratoriFreezer 

Diz'tQPitiF l)~~criiJtion .. MOdeLc 1991 prototype design 

C3_01LLF Replace freezer flange heater with liquid line heat 

C3_02CMP Use 5.00 EER compressor (was 4.85 EER) 

C3_03DCE DC evaporator fan 

C3_04DRI Add 1 inch insulation to both doors 

C_I993 1993 prototype, with HFC-134a refrigerant and 

C3_06G25 

C3A07CCP 

C3A08CMP 

C3A09MCI 

C3AI0DRI 

C3A11ADF 

C3A12INS 

HCFC-blown insulation 

Cut gasket heat leak by 25% 

Replace HFC-134a with RC-270 (cyclopropane) 

Use 5.3 EER rotary compressor 

Employ micro-cell insulation 

Add 1 inch insulation to both doors 

Use adaptive defrost (reduce frequency by 74%) 

Add 1 inch insulation everywhere except doors 

Table C-7. Pathway 4: Single Evaporator Cycle 

1 

2 

3 

1993 

5 

6 

7 

8 

9 

lO 

A4_01CMP 

A4_02DRI 

A4_03VLF 

A4_05G50 

A4_06CMP 

A4_07DCE 

A4_08DCC 

A4_09HRI 

A4_lOHRI 

Current Technologies with Advanced Insulation 

Model A Prototype Refrigerator/Freezer 

prototype ~_~.,.., .. 

Use 5.3 EER compressor (was 4.55 EER) 

Add 3/4 insulation to both doors 

Replace door flange heater with vapor line heat from 

compressor exit 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Cut gasket heat leak by 50% from baseline value 

Use 5.5 EER compressor 

Use DC evaporator fan 

Use DC condenser fan 

50% coverage with high-R gas filled insulation 

80% coverage with high-R gas filled insulation 

C-6 
Table C-8. Pathway 4A: - Single Evaporator Cycle

Current Technologies with Improved Insulation

Model A Prototype Refrigerator/Freezer

1991 Model_A 1991 prototype design

1 A4_01C Use 5.3 EER compressor (was 4.55 EER)

2 A4_02DRI Add 3/4 insulation to both doors

3 A4_03 VLF Replace door flange heater with vapor line heat from

compressor exit

1993 A_1993 1993 prototype, with C-134a refrigerant and

HCFC-blown insulation

5 A4_05G50 Cut gasket heat leak by 50% from baseline value

6 A4_06C Use 5.5 EER compressor

7 A4AO7REF Change to refrigerant RFC-152a

8 A4AO8MCI Employ micro- cell insulation

9 A4AO9CEI Use carbon black additive to insulation

10 A4A 10 F Use high efficiency fans (PSC type)

11 A4A 11DCF Use DC fans

Table C-9. Pathway 5: Single Evaporator Cycle

Advanced Cycle and Insulation Technologies

Model D Prototype Refrigerator/Freezer

seep D a 9 a f7i JeSciipdon

1993-CFC Model_D 1993 prototype design with CFCs

1993 D_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

1 D5_01G50 Cut gasket heat leak by 50% from baseline value

2 D5_02C Use 5.5 EER compressor (was 5.3 EER)

3 D5_03ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

4 D5_04VCC Variable capacity linear compressor (6.5 EER)

5 D5_05DCF Use DC fans

6 D5_06VCM 50% coverage with 1 inch thick r-1.6 vacuum panel

foamed into wall

7 D5_07VCM 80% coverage with 1 inch thick r-1.6 vacuum panel

foamed into wall

 EE-RM-93-801 COMMENT OR2

Table C-S. Pathway 4A: . Single Evaporator Cycle 

S~p 

1991 

1 

2 

3 

1993 

5 

6 

7 

8 

9 

10 

11 

Current Technologies with Improved Insulation 

Model A Prototype RefrigeratoriFreezer 

. 1JiJtd~il~> . liestripdiiii .. ·· ...... . Mode LA 1991 prototyPe design .. 

A4_01CMP Use 5.3 EER compressor (was 4.55 EER) 

A4_02DRI Add 3/4 insulation to both doors 

A4_03VLF Replace door flange heater with vapor line heat from 

A4_05G50 

A4_06CMP 

A4A07REF 

A4A08MCI 

A4A09CBI 

A4AlOHEF 

A4AIIDCF 

compressor exit 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Cut gasket heat leak by 50% from baseline value 

Use 5.5 EER compressor 

Change to refrigerant HFC-152a 

Employ micro-cell insulation 

Use carbon black additive to insulation 

Use high efficiency fans (PSC type) 

Use DC fans 

Table C-9. Pathway 5: Single Evaporator Cycle 

.: <$~ii: <ilJiiiiiFiit:· 

1993-CFCMOrle[O··· . 

1993 D_1993 

1 D5_01G50 

2 D5_02CMP 

3 D5_03ADF 

4 D5_04VCC 

5 D5_05DCF 

6 D5_06VCM 

7 D5_07VCM 

Advanced Cycle and Insulation Technologies 

Model D Prototype Refrigerator/Freezer 

prototype UV~".I'.U 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Cut gasket heat leak by 50% from baseline value 

Use 5.5 EER compressor (was 5.3 EER) 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Variable capacity linear compressor (6.5 EER) 

Use DC fans 

50% coverage with 1 inch thick r-1.6 vacuum panel 

foamed into wall 

80% coverage with 1 inch thick r-1.6 vacuum panel 

foamed into wall 

C-7 
Table C-10. Pathway 6: Lorenz Cycle

Improved Technologies

n^ ( J l f l' 'W

Model B Prototype Refrigerator/Freezer

e ceeylo%L

1991 odei_B 1991 prototype design

1 B2_O1CMP Use 5.00 EER compressor (was 4.57 EER)

2 B2_02FST Replace 2 watt defrost timer with 1/4 watt

outside cabinet

3 B2_03IN0 Add 1/2 insulation all around

4 B2_ DRI Add 1/2 insulation to doors

1993 B_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

6 B6_06L Lorenz cycle with ternary blend

7 B6_07G25 Reduce gasket heat leak by 25%

8 B6_08C Use 5.3 EER rotary compressor

9 B6_09SHV Add shut-off valve (with rotary compressor)

10 B6 10CBI Use carbon black additive to insulation

11 B6_1 1ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

12 B6_12DCE Use DC evaporator fan

13 B6_13DCC Use DC condenser fan

Table C-11. Pathway 7: Lorenz Cycle

Improved Components and Advanced Insulation

Model C Prototype Refrigerator/Freezer

Seep D, 94 Fa' Desc apia^rre

1991 1 ode1_C 1991 prototype design

1 C3_01LLF Replace freezer flange heater with liquid line heat

2 C3_02C Use 5.00 EER compressor (Was 4.85 EER)

3 C3_03DCE DC evaporator fan

4 C3_04DRI Add 1 inch insulation to both doors

1993 C_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

6 C7_06LRZ Lorenz cycle with ternary

7 C7_07G50 Cut gasket heat leak by 50% from baseline value

8 C7_08ADF Use adaptive defrost (reduce frequency by 74%)

9 C3_09DCC DC condenser fan

10 C3_10VCM 50% coverage with 1 inch thick r-1.6 vacuum panel

foamed into wall

11 C3_11VCM 80% coverage with 1 inch thick r-1.6 vacuum panel

foamed into wall

 EE-RM-93-801 COMMENT OR2

Table C-IO. Pathway 6: 

StlP 

1991 

1 

2 

3 

4 

1993 

6 

7 

8 

9 

10 

11 

12 

13 

·PoUJFile 

. ·Mod6CB 

B2_01CMP 

B2_02FST 

B2_03INO 

B2_04DRI 

B_1993 

B6_06LRZ 

B 6_07 G25 

B6_08CMP 

B6_09SHV 

B6_1OCBI 

B6_11ADF 

B6_12DCE 

B6_13DCC 

Table C-ll. Pathway 7: 

1 

2 

3 

4 

1993 

6 

7 

8 

9 

10 

11 

C3_01LLF 

C3_02CMP 

C3_03DCE 

C3_04DRI 

C_1993 

C7_06LRZ 

C7_07G50 

C7_08ADF 

C3_09DCC 

C3_1OVCM 

Lorenz Cycle 

Improved Technologies 

Model B Prototype Refrigerator/Freezer 

Description . 1991 prototype design 

Use 5.00 EER compressor (was 4.57 EER) 

Replace 2 watt defrost timer with 1/4 watt 

outside cabinet 

Add 1/2 insulation all around 

Add 1/2 insulation to doors 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Lorenz cycle with ternary blend 

Reduce gasket heat leak by 25% 

Use 5.3 EER rotary compressor 

Add shut-off valve (with rotary compressor) 

Use carbon black additive to insulation 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Use DC evaporator fan 

Use DC condenser fan 

Lorenz Cycle 

Improved Components and Advanced Insulation 

Model C Prototype RefrigeratorlFreezer 

prototype ____ ,.., __ 

Replace freezer flange heater with liquid line heat 

Use 5.00 EER compressor (was 4.85 EER) 

DC evaporator fan 

Add 1 inch insulation to both doors 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Lorenz cycle with ternary 

Cut gasket heat leak by 50% from baseline value 

Use adaptive defrost (reduce frequency by 74%) 

DC condenser fan 

50% coverage with 1 inch thick r-1.6 vacuum panel 

foamed into wall 

80% coverage with 1 inch thick r-1.6 vacuum panel 

foamed into wall 

C-8 
Table C-12° Pathway 8: Lorenz Cycle

Best Cycle Components and Auxiliaries

Model A Prctotype Refrigera or/Fr r

1991 M el_A 1991 prototype design

1 A4_01C Use 5.3 EER compressor (was 4.55 EER)

2 A4_02DRI Add 3/4 insulation to both doors

3 A4-03VLF Replace door flange heater with vapor line heat from

compressor exit

1993 A_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

5 A8_05L Lorenz cycle with ternary

6 A8_06C Use 5.5 EER compressor

7 A8_07C Use 6.0 EER compressor (ECM Motor)

8 A8_08DCF Use DC fans

9 A8_09ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

Table C-13° Pathway 8A: Lorenz Cycle

Current Techologies with Thick Wall Cabinet

Model A Prototype Refrigerator/Freezer

1991 Model_A 1991 prototype design

1 A4_01 C Use 5.3 EER compressor (was 4.55 EER)

2 A4_02DRI Add 3/4 insulation to both doors

3 A4_03VLF Replace door flange heater with vapor line heat from

compressor exit

1993 A_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

5 A8_05LRZ Lorenz cycle with ternary

6 A8A 25 Reduce gasket heat leak by 25%

7 A8AO7CMP Use 5.5 EER compressor

8 A8AO8DCF Use DC fans

9 A8A09IN2 Add 2 inches insulation all around

10 A8AlOADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

 EE-RM-93-801 COMMENT OR2

Table C-12. Pathway 8: 

1 

2 

3 

1993 

5 

6 

7 

8 

9 

A4_01 CMP 

A4_02DRI 

A4_03VLF 

A_1993 

A8_05LRZ 

A8_06CMP 

A8_07CMP 

A8_08DCF 

A8_09ADF 

Lorenz Cycle 

Best Cycle Components and Auxiliaries 

Model A Prototype Refrigerator/Freezer 

Use 5.3 EER compressor (was 4.55 EER) 

Add 3/4 insulation to both doors 

Replace door flange heater with vapor line heat from 

compressor exit 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Lorenz cycle with ternary 

Use 5.5 EER compressor 

Use 6.0 EER compressor (ECM Motor) 

Use DC fans 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Table C-13. Pathway SA: Lorenz Cycle 

1 

2 

3 

1993 

5 

6 

7 

8 

9 

10 

A4_OlCMP 

A4_02DRI 

A4_03VLF 

A_1993 

A8_05LRZ 

A8A06G25 

A8A07CMP 

A8A08DCF 

A8A09IN2 

A8A1OADF 

Current Techologies with Thick Wall Cabinet 

Model A Prototype RefrigeratorlFreezer 

prototype U"''''~;<'U 

Use 53 EER compressor (was 4.55 EER) 

Add 3/4 insulation to both doors 

Replace door flange heater with vapor line heat from 

compressor exit 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Lorenz cycle with ternary 

Reduce gasket heat leak by 25 % 

Use 5.5 EER compressor 

Use DC fans 

Add 2 inches insulation all around 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

C-9 
Table C-14. Pathway 9: Dual Loop Cycle

Improved Components and Thick Wall Cabinet

Model D Prototype Refrigerator/Fr zer

1993-CFC Model_D 1993 prototype design with CFCs

1993 D_1993 1993 prototype, with C- 134a refrigerant and

HCFC-blown insulation

1 D9_01CSC Dual-loop with current small compressors

2 D9_02FSC Use future small compressors (4.6 and 5.1 EER)

3 D9_03DCF Use DC fans (all four fans)

4 D9_04DLR C- 152a in freezer loop and HCFC-142b in fresh food

loop

5 D9_05G50 Cut gasket heat leak by 50% from baseline value

6 D9_06MCI Employ micro-cell insulation

7 D9_07CEI Use carbon black additive to insulation

8 D9_08IN1 Add 1 inch insulation all around

9 D9_09ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

10 D9 10IN2 Add 1 inch more of insulation all around

Table C-15. Pathway 10: Dual Loop Cycle

Improved Components with Advanced Insulation

Model A Prototype Refrigerator/Freezer

sop tDzk Filc Description

1991 iViodel_A 1991 prototype design

1 A4_01C Use 5.3 EER compressor (was 4.55 EER)

2 A4_02DRI Add 3/4 insulation to both doors

3 A4_03VLF Replace door flange heater with vapor line heat from

compressor exit

1993 A_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

5 A1005FSC Dual loop with future small compressors,

HFC-152a in freezer loop

and HCFC- 142b in fresh food loop

6 A1006G50 Cut gasket heat leak by 50% from baseline value

7 A1007ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

8 A1008DCE Use DC evaporator fans (2)

9 A1009DCC Use DC condenser fans (2)

10 A1010HRI 50% coverage with high-R gas filled insulation

11 A1011HRI 80% coverage with high-R gas filled insulation

 EE-RM-93-801 COMMENT OR2

Table C-14. Pathway 9: 

s. Iii ..•.. DiltiiFili 'P . . ... i 993-CFC ModeLD 

1993 D_1993 

1 D9_OlCSC 

2 D9_02FSC 

3 D9_03DCF 

4 D9_04DLR 

5 D9_05G50 

6 D9_06MCI 

7 D9_07CBI 

8 D9_08IN1 

9 D9_09ADF 

10 D9_10IN2 

Dual Loop Cycle 

Improved Components and Thick Wall Cabinet 

Model D Prototype Refrigerator/Freezer 

Descriptutn ...... .. (> • <:i\ •.. i·:. 

1993 prototype design with C:FC~· . 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Dual-loop with current small compressors 

Use future small compressors (4.6 and 5.1 EER) 

Use DC fans (all four fans) 

HFC-152a in freezer loop and HCFC-142b in fresh food 

loop 

Cut gasket heat leak by 50% from baseline value 

Employ micro-cell insulation 

Use carbon black additive to insulation 

Add 1 inch insulation all around 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Add 1 inch more of insulation all around 

Table C-1S. Pathway 10: Dual Loop Cycle 

1 A4_OlCMP 

2 A4_02DRI 

3 A4_03VLF 

1993 A_1993 

5 Al005FSC 

6 AlOO6G50 

7 AlOO7ADF 

8 AlOO8DCE 

9 Al009DCC 

10 AI010HRI 

11 A1011HRI 

Improved Components with Advanced Insulation 

Model A Prototype Refrigerator/Freezer 

prototype 

Use 5.3 EER compressor (was 4.55 EER) 

Add 3/4 insulation to both doors 

Replace door flange heater with vapor line heat from 

compressor exit 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Dual loop with future small compressors, 

HFC-152a in freezer loop 

and HCFC-142b in fresh food loop 

Cut gasket heat leak by 50% from baseline value 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Use DC evaporator fans (2) 

Use DC condenser fans (2) 

50% coverage with high-R gas filled insulation 

80% coverage with high-R gas filled insulation 

C-1O 
Table C-16. Pathway 11: Single Evaporator Cycle

Most Cost Effective Conventional Technologies

Vad l D Protclype'eTrigerator/Fr r

1993-CFC Model_D 1993 prototype design with CFCs

1993 D_1993 1993 prototype, with C- 134a refrigerant and

HCFC-blown insulation

1 D1101G25 Reduce gasket heat leak by 25%

2 D 1102LLM Replace mullion heater with liquid line heat

3 D1103C Use 5 . 5 EER compressor (was 5.3 EER)

4 D1104MCI Employ micro-cell insulation

5 D1105CBI Use carbon black additive to insulation

6 D l 106DCE Use DC evaporator fan

7 D 1107 F Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

Table C-17. Pathway 12: Lorenz Cycle

Most Cost Effective Advanced T echnologies

Model D Prototype Refrigerator/Freezer

c A ^? D Tcripti o

1993-CFC Model_D 1993 prototype design with CFCs

1993 D_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-blown insulation

1 D1201LRZ Lorenz cycle with propane and HCFC-123

2 D12O2CMP Use 5.5 EER compressor (was 5.3 EER)

3 D 1203DCF Use DC fans with low speed evaporator fan

4 D1204ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

5 D 1205LLM Replace mullion heater with liquid line heat

6 D1206050 Cut gasket heat leak by 50% from baseline value

7 D1207VCM 80% coverage with 1 inch thick r-1.6 vacuum panel

foamed into wall

8 D1208VCC Variable capacity linear compressor (6.5 EER)

 EE-RM-93-801 COMMENT OR2

Table C-16. Pathway 11: Single Evaporator Cycle 

1993 

1 

2 

3 

4 

5 

6 

7 

D_1993 

DllOIG25 

Dl102LLM 

D1103CMP 

D1104MCI 

D1105CBI 

D1106DCE 

Dl107ADF 

Most Cost Effective Conventional Technologies 

Model D Prototype RefrigeratorlFreezer 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Reduce gasket heat leak by 25% 

Replace mullion heater with liquid line heat 

Use 5.5 EER compressor (was 5.3 EER) 

Employ micro-cell insulation 

Use carbon black additive to insulation 

Use DC evaporator fan 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Table C-17. Pathway 12: Lorenz Cycle 

1993 

1 

2 

3 

4 

5 

6 

7 

8 

D1201LRZ 

D1202CMP 

D1203DCF 

D1204ADF 

D1205LLM 

D1206G50 

D1207VCM 

D1208VCC 

Most Cost Effective Advanced Technologies 

Model D Prototype RefrigeratorlFreezer 

prototype "'''''~'41S'' 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Lorenz cycle with propane and HCFC-123 

Use 5.5 EER compressor (was 5.3 EER) 

Use DC fans with low speed evaporator fan 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Replace mullion heater with liquid line heat 

Cut gasket heat leak by 50% from baseline value 

80% coverage with 1 inch thick r-1.6 vacuum panel 

foamed into wall 

Variable capacity linear compressor (6.5 EER) 

C-ll 
Table C-1S. Pathway 13: Single Evaporator Cycle

Most Coss E tive ConvenC!®aE TecGrano.Eogies

Model E Bu'Lltlayn-A/u(DunI

'7 - 311, Z' 47 11 1^41111_^

19'90 Mel_E

1993-CFC Model_E3

1990 prototype design with CFCs

1993 prototype design with CFCs

1993 E_1993 1993 prototype, with HIFC-134a refrigerant and

HCFC-blown insulation

1 E1301G25 Reduce gasket heat leak by 25%

2 E 1302C Use 5.5 EER compressor (was 5.15 EER)

3 E 1303MCI Employ micro-cell insulation

4 E 1304CEI Use carbon black additive to insulation

5 E 1305D Use DC evaporator fan

6 E 130b F Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

Table C-19. Pathway 14: Single Evaporator Cycle

Most Cost Effective Conventional Technologies

Model F Side-by-Side Refrigerator/Freezer

ILq

1990 Model _F 1990 prototype design with CFCs

1993-CFC Model_F3 1993 prototype design with CFCs

1993 F_1993 1993 prototype, with HFC-134a refrigerant and

HCFC-bl wn insulation

1 F1401G25

o

Reduce gasket heat leak by 25%

2 F1402C Use 5.5 EER compressor (was 5.3 EER)

3 F 1403MCI Employ micro-cell insulation

4 F1404CBI Use carbon black additive to insulation

5 F 1405DCE Use DC evaporator fan

6 F 1406ADF Use adaptive defrost (reduce frequency by 74%

and use lower wattage defrost timer)

 EE-RM-93-801 COMMENT OR2

Table CoIS. Pathway 13: Single Evaporator Cycle 

1 

2 

3 

4 

5 

6 

E1301G25 

E1302CMP 

E1303MCI 

E1304CBI 

E1305DCE 

E1306ADF 

Table C-19. Pathway 14: 

1993-CFC ModeCF3 

1993 F_1993 

1 

2 

3 

4 

5 

6 

F1401G25 

F1402CMP 

F1403MCI 

F1404CBI 

F1405DCE 

F1406ADF 

Most Cost Effective Conventional Technologies 

Model E Bottom-Mount RefrigeratorlFreezer 

prototype __ u.,.., •• 

1993 prototype design with CFCs 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Reduce gasket heat leak by 25% 

Use 5.5 EER compressor (was 5.15 EER) 

Employ micro-cell insulation 

Use carbon black additive to insulation 

Use DC evaporator fan 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

Single Evaporator Cycle 

Most Cost Effective Conventional Technologies 

Model F Side-by-Side RefrigeratorlFreezer 

prototype Uo;;,"'L~U 

1993 prototype design with CFCs 

1993 prototype, with HFC-134a refrigerant and 

HCFC-blown insulation 

Reduce gasket heat leak by 25% 

Use 5.5 EER compressor (was 5.3 EER) 

Employ micro-cell insulation 

Use carbon black additive to insulation 

Use DC evaporator fan 

Use adaptive defrost (reduce frequency by 74% 

and use lower wattage defrost timer) 

C-12