NATL INST OF STAND & TECH

A11107 3T0bba PUBLICATIONS

NBSIR 84-2867

Test Procedures for Rating

Residential Heating and Cooling

Absorption Equipment

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Building Equipment Division

Washington, DC 20234

April 1984

•QC

“

100

,1155

Sponsored by:

Oak Ridge National Laboratory

U.S. Department of Energy

Oak Ridge, Tennessee 37830

84-2857

ubrakv

NBSIR 84-2867

TEST PROCEDURES FOR RATING

RESIDENTIAL HEATING AND COOLING

ABSORPTION EQUIPMENT

Brian Weber

Reinhard Radermacher

David Didion

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Building Equipment Division

Washington, DC 20234

April 1984

Sponsored by:

Oak Ridge National Laboratory

U.S. Department of Energy

Oak Ridge, Tennessee 37830

«

O*

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige. Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

ABSTRACT

Test and rating procedures are presented for gas-fired absorption devices

operating in either the heating or cooling modes. These procedures are

designed to include the effects of part-load and cyclic operation, variations

in outdoor temperature, and frost formation during the heating mode. Both

air-source and ground water source absorption heat pumps are considered, as

well as air cooled and ground water cooled air conditioners and water

chillers. A calculation procedure is presented for estimating the heating and

cooling seasonal performance and cost of operation of residential water

chillers, air conditioners, and heat pump units.

Key words: Central air conditioners; central heating equipment; heat pumps;

heating seasonal performance; cooling seasonal performance; rating

procedure; seasonal cost of operation; test method.

iii
ACKNOWLEDGEMENTS

This study was sponsored by the U.S. Department of Energy, Office of Building

Energy Research and Development through the program management service of

Mr. Robert DeVault of the Energy Division of Oak Ridge National Laboratory.

The support of R. Radermacher during this investigation by a scholarship from

the NATO Science Committee by the German Academic Exchange Service is

gratefully acknowledged.

iv
TABLE OF CONTENTS

PAGE

ABSTRACT iii

ACKNOWLEDGEMENTS iv

LIST OF TABLES vii

NOMENCLATURE . viii

SI CONVERSION FACTORS xi

1. INTRODUCTION 1

1.1 Background I 1.2 Comparison of Different Residential Size Systems 2

1.3 Classification of Absorption Systems ... 2

1.4 Objective and Scope 4

2. RECOMMENDED RATING REQUIREMENTS 6

2.1 General 6

2.1.1 Cooling Systems 6

2.1.2 Heating Systems 6

2.2 Cooling Systems 8 2.2.1 Standard Rating Test 8

2.2.2 Steady-State Tests 8

2.2.3 Cyclic Test 10

2.2.4 Summary 11

2.3 Heating Systems 12

2.3.1 Standard Rating Test 12

2.3.2 Steady-State Tests 12

2.3.3 Frost-Accumulation Test 12

2.3.4 Cyclic Test 13

2.3.5 Summary 14

2.4 Suggested Rating Sheets 14

3. RECOMMENDED TEST PROCEDURE FOR ABSORPTION COOLING SYSTEMS .... 16

3.1 Introduction 16

3.2 Steady-State Test Procedure 16

3.2.1 Applicable Test Method 16

3.2.2 Instrumentation and Required Data 17

3.2.3 Test Operating Procedure and Results 17

3.2.4 Test Tolerances 18

3.3 Cyclic Test Procedure 19

3.3.1 Applicable Test Method 19

3.3.2 Instrumentation and Required Data 19

3.3.3 Test Operating Procedure and Results 19

3.3.4 Test Tolerances 20

4. MODEL LOADS AND CLIMATE SPECIFICATIONS FOR ABSORPTION

COOLING SYSTEMS 21

4.1 Introduction 21

4.2 Building Loads . . . .

'

v
5. CALCULATION PROCEDURE FOR ABSORPTION COOLING SYSTEMS 24

5.1 Introduction 24

5.2 Calculation Procedure for Steady-State Tests 24

5.2.1 Fuel Energy Input ..... 24

5.2.2 Electrical Energy Input 24

5.2.3 Cooling Capacity 25

5.2.4 Heat Balance - Confirming Test 26

5.3 Calculation Procedure for Cyclic Test 27

5.4 Coefficient of Performance 29

5.5 Seasonal Performance Factor and Seasonal Operating Costs . . 29

5.6 Sample Calculation 32

6. RECOMMENDED TEST PROCEDURE FOR ABSORPTION HEATING SYSTEMS .... 35

6.1 Introduction 35

6.2 Steady-State Test Procedure 35

6.2.1 Applicable Test Method 35

6.2.2 Instrumentation and Required Data 36

6.2.3 Test Operating Procedure and Results 36

6.2.4 Test Tolerances 37

6.3 Cyclic Test Procedure 38

6.3.1 Applicable Test Method 38

6.3.2 Instrumentation and Required Data 38

6.3.3 Test Operating Procedure and Results 38

6.3.4 Test Tolerances 39

6.4 Frost Accumulation Test Procedure 39

6.4.1 Applicable Test Method 39

6.4.2 Instrumentation and Required Data 39

6.4.3 Test Operating Procedure and Results 39

6.4.4 Test Tolerances 40

7. MODEL LOADS AND CLIMATE SPECIFICATIONS FOR ABSORPTION

HEATING SYSTEMS 41

7.1 Introduction 41

7.2 Building Loads 42

8. CALCULATION PROCEDURE FOR ABSORPTION HEATING SYSTEMS 43

8.1 Introduction 43

8.2 Calculation Procedure for Steady-State Tests 43

8.2.1 Fuel Energy Input 43

8.2.2 Electrical Energy Input 43

8.2.3 Cooling Capacity 44

8.2.4 Heat Balance - Confirming Test 44

8.3 Calculation Procedure for Cyclic Test 46

8.4 Coefficient of Performance 47

8.5 Seasonal Performance Factor and Seasonal Operating Costs . . 48

8.6 Sample Calculation 50

9. LIMITATIONS OF THE RECOMMENDED TEST AND RATING PROCEDURE 54

REFERENCES 55

vi
LIST OF TABLES

Page

TABLE 1 SUMMARY OF TESTING REQUIREMENTS FOR DIRECT-FIRED

AIR-COOLED AND WATER-COOLED ABSORPTION COOLING

SYSTEMS 56

TABLE 2 SUMMARY OF TESTING REQUIREMENTS FOR DIRECT-FIRED

AIR-SOURCE AND WATER-SOURCE ABSORPTION HEATING

SYSTEMS 57

TABLE 3 RATING SHEET FOR DIRECT-FIRED ABSORPTION COOLING

SYSTEMS 58

TABLE 4 FRACTIONAL TEMPERATURE BIN HOURS FOR COOLING

SEASONAL CALCULATION 59

TABLE 5 DISTRIBUTION OF ACTUAL COOLING LOAD HOURS (CLH)

THROUGHOUT THE UNITED STATES 60

TABLE 6 RATING SHEET FOR DIRECT-FIRED ABSORPTION HEATING

SYSTEMS 61

TABLE 7 MAJOR CLIMATIC REGIONS IN THE CONTINENTAL USA 62

TABLE 8 HEATING LOAD HOURS (HLH) FOR THE UNITED STATES .... 63

TABLE 9 RECOMMENDED CALCULATION SHEET FOR DETERMINING SPF

AND SOC OF DIRECT-FIRED ABSORPTION SYSTEMS 64

TABLE 10 SAMPLE CALCULATIONS FOR ABSORPTION COOLING SYSTEMS . . 65

TABLE 11 SAMPLE CALCULATIONS FOR ABSORPTION HEATING SYSTEMS . . 66

vii
NOMENCLATURE

BLdj)

C

°D

C

e C

f clf

CLH

COP

CSPF

DHR

E

fe ss(T)

E(Tj

)

h

HHV

Building load at an outdoor dry-bulb temperature Tj, kW (kBtu/hr).

Cool ing.

Degradation factor for cyclic operation, defined by equation (5.13).

Cost of electricity in $/Whr.

Cost of fuel in $/Btu.

Cooling load factor, defined as the ratio of the total cyclic

cooling done in a complete cycle or specified period consisting of an 'on'-time and an 'off'-time to the steady-state cooling done over

the same time period at constant ambient conditions. See equation

(5.11)

.

Cooling load hours, defined as the number of hours in a cooling

season that a building requires cooling. See Table 4.

Coefficient of performance, defined as the net heating done over a specified period of time divided by the total electrical energy and

fuel energy input over the same time interval.

Specific heat (heat capacity) kJ/kg # C (Btu/lbm # F)

.

Specific heat at constant pressure of air-water mixture per pound of

dry air.

Cooling seasonal performance factor, defined as the ratio of the

total cooling done to the total energy usage over a cooling season.

Design Heating Requirement (steady-state heating capacity at outdoor

design temperature, T^) , kW (kBtu/hr).

Total energy consumption during entire season kWhr, (kBtu).

Steady-state total energy input at a given water temperature T, kW

(kBtu/hr)

.

Total energy consumption at an outdoor dry-bulb temperature, T,. kW

(kBtu/hr). J

Heating

.

Higher heating value of fuel on a mass basis.

viii
HLF Heating load factor, defined as the ratio of the total cyclic

heating done in a complete cycle of specified period consisting of an 'on'-time and 'off'-time to the steady-state heating done over

the time period at constant ambient conditions. See equation

( 8 . 10 )

.

HLH Heating load hours. See Table 7.

HSPF Heating seasonal performance factor, defined as the ratio of the

total heating done to the total energy usage over a heating season.

j Outdoor dry-bulb temperature bin number. See Tables 4 and 7.

i Fuel mass flow rate. See equation (5.1).

N Total number of temperature bin hours.

n. Number of temperature bin hours in a particular bin.

J n Number of non-zero temperature bins.

n—i* Fractional number of temperature bin hours. See Tables 4 and

N 7.

PLF Part-load factor, defined as the ratio of the cyclic COP to the

steady-state COP, see equation (5.14).

P

t Total amount of electrical energy being supplied averaged over the

test duration, kW (kBtu/hr)

.

£lC y C Cyclic total capacity defined as the ratio of the total cooling done over a given time period to the duration of time the burner is on in

that period, kW (kBtu/hr).

Qj Residual energy in the products of combustion (flue gas) leaving the

system, kW (kBtu/hr).

6

j

Jacket heat loss representing the convective and radiative losses

from heated metal surfaces, kV (kBtu/hr).

Air flow rate across the condenser and absorber coil*, kg/hr (lbm/hr

or CFM)

.

ix
6SS (T) Total steady-state cooling or heating capacity at a water

temperature T, kW (kBtn/hr)

.

G Rate of thermal energy supplied to the generator, kW (kBtu/hr).

©

6_ c Steady-state capacity, kW (kBtu/hr).

RB Auxiliary electric resistance heating, kV.

RH(T-) Resistance heat energy usage in temperature bin, T-, kWhr, see equation (8.15).

SOC Seasonal Operating Costs of direct-fired absorption systems.

SPF Seasonal performance factor, defined as the ratio of the total

cooling or heating done to the total energy over a cooling or heating season.

T specified outdoor change-over temperature. V Outdoor design temperature (also *

T. Representative outdoor dry-bulb temperature for temperature bin j,

J °C (°F) . See Tables 4 and 7.

t Time, hours.

V Indoor air flow rate, m^/s (CFM), at the dry-bulb temperature,

humidity ratio, and pressure existing in the region of measurement.

v

n Specific volume of air-water mixture, at the same dry-bulb

temperature, humidity ratio, and pressure used in the determination

of the indoor air flowrate, nr /kg (ft /lbm).

VQ Humidity ratio, (the 'n' means at the nozzle [i.e., point of

measurement for air-flowrate]), kg/kg (lbm/ lbm).

x
SI CONVERSION FACTORS

MULTIPLY BY TO OBTAIN

Btu/h, Btuh 0.293 W

Btu/lbm°F, [C

p

, specific heat] 4.19 tr/k g

°i

•F °C = (°F - 32) /I .8

ft 0.3048 m

ft/min, fpm 0.00508 m/s

ft 3/ lbm 0.0623 m

3 /kg

ft 3 /min, CFM 0.472 m

3 /s

gpm (US) 0.0631 L/S

inch 25.4 mm

inch of water 3.38 kPa

kBtu/h 1055 kJ

lbm/h 0.126 g/s

ton of refrigeration capacity 3516 W

xi
: - i
1. INTRODUCTION

1 .1 Background

Absorption cycle air-conditioning and refrigerating equipment have been in

standard production for decades, and have been designed for residential,

commercial, and industrial applications. Absorption cycle heat pumps are

currently being developed for introduction into the marketplace. Absorption

equiment has typically been driven by such energy sources as fossil fuels and

waste and process steam. Capacities have ranged from three kW to approximately seven MW (3 to 2000 tons). Coefficients of performance based on full

load steadj^-state operation testing, have varied from 0.4 to values near 1.0,

depending upon whether the machine is a single or double-effect design. The

efficient performance of absorption equipment is dependent on many operating

and design variables including the temperatures at which energy is supplied

and rejected, the load imposed by the conditioned space, the required chilled

fluid temperature, various solution and fluid flow rates, and the refrigerant

and absorbent fluids selected.

Because of worldwide energy concerns and the increasing scarcity of some forms

of energy, the efficient use of absorption equipment has recently come into

sharper focus. As a result, new and more energy efficient designs are being

developed by various groups and agencies in this country and abroad. Accordingly, there is an increasing need by industry, government, and the consumer

to be able to evaluate and compare these improved systems on the same technical basis. A standardized test and rating procedure which incorporates provisions specifically tailored to the nature of each type of absorption system is

required in order to effectively compare overall system performance. Such a

test and rating procedure is the subject of this report.
1 .2 Comparison of Different Residential Size Systems

In order to compare different residential size systems such as absorption or

vapor compression air-conditioners or heat pumps, the following caution should

be taken into account. The performance of a cooling or heating system is not

only dependent upon the unit itself but also of the characteristics of the

thermostat which controls the cycling rate. Differences in thermostats can

result in cycling time lengths of unequal duration leading to fluctuations in

indoor temperatures, and consequently different energy performance of the

cooling or heating device. In this test procedure the unit is operated

according to the charcteristics of the thermostat provided by the manufacturer

however, the results of this procedure do not show differences in the comfort

for inhabitants of a room due to humidity and temperature variations during a

cycle, nor does it measure the effects on equipment life as a result of the

total number of cycles required to meet the seasonal load.

1 .3 Classification of Absorption Systems

Absorption systems are identified according to the following classification:

o Type of Service

- cooling

- heating

- both heating and cooling (reversible)

o Energy Source

- direct-fired (gas or oil combustion)

- hot water (steam)

o Application

- residential

- commercial

2
industrial

o Sink/Source Medium

- air

water

A further characterization of a system includes whether the generator unit is

single-effect or double-effect, and a specification of the ref rigerant/absorbent fluid pair.

All commercially available absorption systems are currently designed for

cooling service only. There are, however, several heat-only and reversible

absorption systems currently under development. These systems are designed

for direct firing with oil or gas, or the use of waste or process steam to

provide high temperature hot water.

In this report the terminology and classification scheme used for cooling and

heating systems is as shown below:

Air cooled E refers to units rejecting heat to air

Water cooled E refers to units rejecting heat to water

Air source E refers to units absorbing heat from air

Water source E refers to units absorbing heat from water

Heating Systems

Outdoor Side

Air Source - outdoor air temperature entering evaporator

Water Source - ground water temperature entering evaporator

3
Indoor Side

Hot Air Heat - indoor return air temperature

Hot Water Heat - indoor return water temperature

Cooling Systems

Outdoor Side

Air Sink - (i.e., air cooled) outdoor air temperature entering condenser

Water Sink - (i.e., water cooled) ground water temperature or cooling

tower water temperature entering condenser

Indoor Side

Air Conditioners - indoor return air temperature

Water Chillers - indoor return water temperature

1 .4 Objective and Scope

The objective of this study is to develop generic test and rating procedures

for absorption cooling and heating systems which are likely to be employed in

residential and light commercial buildings both now and in the future. Where

feasible, the proposed procedures include the formulation of calculation

procedures to estimate the seasonal performance and seasonal cost of operation

of these systems. The intent of the proposed procedures is to provide a means

whereby the performance of prototype and production type absorption systems

having different design characteristics may be meaningfully compared on the

same technical basis, and sound decisions may be made regarding which systems

are worthy of further development or application.

4
The test, rating, and calculation procedures recommended herein apply only to

residential and light commercial cooling and heating applications of the 10.6-

52.8kW (3-15 tons) capacity range. The procedures are restricted to directfired systems, (since these are the most likely to emerge in the residential

and small commercial markets). They are sufficiently general, however, to

include both air-cooled and water-cooled systems. The procedures are intended

to be applicable to both single-effect and double-effect machines using any

ref rigerant/absorbent fluids, and essentially treat the absorption system as a

'black box' with energy inputs and outputs. Therefore, these procedures are

as independent of thermodynamic and thermal design specifics as possible.

5
2. RECOMMENDED RATING REQUIREMENTS

2 .1 General

The recommended rating requirements for the absorption systems considered in

this study are classified according to whether the systems are designed for

cooling or heating applications. For cooling applications (i.e., waterchilling and air-conditioning), those systems which reject heat to water are

further divided according to whether heat is rejected to ground water or to an

air-cooled device (cooling tower). For heating applications, the systems are

divided according to whether they deliver heat to air or water.

2.1.1 Cooling Systems

The rating requirements for these systems include a single steady-state

maximum load rating test at specified condenser unit cooling fluid inlet

temperature and chilled fluid conditions, one or two steady-state part load

performance tests (to account for frost accumulation and high temperature

operation) and a cyclic test. The rating test is a maximum load test, run at

the 'design' conditions that are established close to the most severe

operating conditions likely to be found in the field. The steady-state part

load tests cause the unit to operate at the same maximum energy input but at a

different refrigerant flow rate. The cyclic test will result in the unit

operating to meet load either by cycling or modulation depending on the unit's

control logic.

2.1.2 Heating Systems

The rating requirements for heating systems include a steady-state rating test

(low- temperature test) at conditions specified in Table 2. This test is at

maximum load at conditions that are established close to the most severe

6
ambient conditions to be found in the field. A frost accumulation test is

required only for air-source systems and is to be run at an outdoor DB/WB

temperature of 1.7°C (35°F) /-I . 1°C (30°F). A second steady-state test (hightemperature test) is to be run with both air and water source systems. In

order to account for the performance degradation due to the unit cycling on

and off, a cycling test is also specified. This test is to be run at the same

conditions as the high temperature test for both air-source systems and watersource systems.

These tests on direct-fired systems provide data necessary to construct

performance curves which provide a basis for calculating the system's

seasonal performance factor and seasonal cost of operation.

A summary of the recommended testing requirements for direct-fired systems is

presented in Tables 1 and 2. Recommended rating sheets for the various

systems are shown in Tables 3 and 6.

It should be noted that this document differs from the ARI Standard (Ref. 9)

for absorption water chillers in its specification of the evaporator water

temperature. Whereas the ARI Standard specifies the water temperature leaving

the evaporator, here the temperature of the water entering the evaporator is

specified. This alteration was necessary to specify a definite chilled water

temperature condition for the cyclic test, which is not covered in the ARI

document

.

7
2 .2 Cooling Systems

2.2.1 Standard Rating Test

A Standard Rating Test shall be conducted according to the test procedures

specified in Section 3.2, and the performance calculated according to the

procedures discussed in Section 5. In order that the performance of different

absorption systems may be compared, the results of the rating tests and the

calculated performance shall be reported. Results to be reported are

discussed in Section 2.4 and illustrated in Table 3.

2.2.2 Steady-State Tests

A total of three steady-state tests (A, B, C, see Table 1) shall be conducted

for direct-fired absorption air-conditioners. Test A is run at the standard

rating conditions listed in Table 1. Test B is conducted at different

condenser fluid inlet conditions, selected to conform with other (nonabsorption type) air-conditioner standards (Ref. 3, 5, 7, 8). The condenser

fluid inlet temperature values in these other standards were selected as

typical field application values. Test C is intended to provide data for the

calculation of the seasonal performance factor and to determine the

performance of air-conditioners under dry evaporator coil conditions.

For direct-fired absorption water chillers. Tests A and C shall be conducted.

Test B is not applicable.

For systems rejecting heat to air the dry-bulb temperature of the ambient air

shall be 35°C (95°F) for Test A, and shall be 27.8 # C (82°F) for Tests B and C.

The first ambient condition coincides with the ARI Standard rating point for

cooling equipment that rejects heat to the outside air. The 27.8°C (82°F)

8
dry-bulb temperature for Test C is chosen because it approximates the average

operating temperature of many climates within the U.S. during the cooling

season. The data of both steady-state tests are necessary to evaluate the

seasonal performance of the system.

For systems which reject heat to a separate air-cooled condenser (cooling

tower), the condenser unit inlet water temperatures shall be 35°C (95°F) for

Test A and 23.9°C (75°F) for Tests B and C. For systems which reject heat to

ground water, the condenser inlet temperatures shall be 21.1°C (70°F) for Test

A and 15.6°C (60°F) for Tests B and C respectively. The 21.1°C (70°F) condition does not coincide with the ANSI Standard rating point of 23.1) 0 C (75°F)

(Ref. 2) for water cooled equipment; however, it does agree with reference (5)

which in turn concurs with the ARI Standard (Ref. 7). The 15.6°C (60°F)

condition selected is representative of ground wafer temperatures that are

likely to occur in the field much of the time.

For air-conditioning equipment, the dry-bulb and wet-bulb temperatures of the

air entering the cooling coil shall be 26.7°C (80°F) and 19.4°C (67°F), for

Tests A and B. For Test C the dry-bulb and wet-bulb temperatures of the

entering air shall be 26.7°C (80°F) and a low enough wet-bulb temperature to

insure that the indoor cooling coil is not condensing moisture (dry coil).

For water-chillers, the temperature of chilled water entering the evaporator

coil shall be 12.8°C (55°F) for all three tests (A, C, D). The return air

dry-bulb/wet-bulb condition of 26.7°C/19.4°C (80°F/67°F) for air— conditioners

was chosen to coincide with the ANSI standard rating points for airconditioners.

9
2 .2 .3 Cyclic Test

To complete the series of tests one cyclic test, D, is recommended for an

evaluation of the performance degradation due to off-cycle refrigerant migration and heat loss. The cyclic performance test shall be performed immediately following Test C. The steady-state Test C results and the cyclic test

results are used together to find the performance degradation.

There are two possible designs for adjusting the capacity of direct-fired

absorption air-conditioners and water-chillers to the building load. The

first is modulating the fuel flow rate to the burner and the second by

operating the system only for limited periods of time at full capacity so

that the time-averaged capacity meets the building load. The last method is

the type found in current production models of the capacity range of concern,

and is therefore the only one addressed here.

In order to calculate cycling losses and incorporate its effect in an airconditioner's seasonal performance and seasonal operating costs, it is necessary to couple the results of the cyclic test with the steady-state tests

which is done by means of the part load factor:

In the case of air-conditioners the following assumption is made in order to

consider the fact that a dry or wet cooling coil might occur:

COP

PLF eye

COP

ss

COPeye PLF = COPss dry COPss wet

10
For air-conditioners and chillers the dry-bulb and wet-bulb temperatures for

Test D are the same as those of Test C. Similarly, the condenser ambient

condition is identical to Test C: for units rejecting heat to air the outdoor

dry-bulb temperature shall be 27.8°C (82°F); for units rejecting heat to

ground water the entering water temperature shall be 15.6°C (60°F) and for

units rejecting heat to cooling tower water the entering water temperature

shall be 23.9°C (75°F).

During the cyclic test the systems shall be operated by the control-devices

supplied by the manufacturer. Tests shall be conducted with the burner on 20%

of the cyc.le time and off 80% of the time. Current absorption air conditioners incorporate a thermostat set at a maximum cycling rate of 1 1/2 cycles

per hour at a 50% on-time,. Assuming a parabolic thermostatic control curve,

the resulting burner on and off-times are 12 minutes and 48 minutes

respectively. However, if comparison with vapor compression systems is

' l intended, the on-off time should be identical to the latter system.

References (3) and (4) recommend a 20% part load test to be achieved with six

minutes on-time and 24 minutes off-time for these system comparisons.

2.2.4 Summary

The test requirements for direct-fired air-conditioning and water-chilling

systems are summarized in Table 1. The results of these tests shall be used

to calculate system cooling capacity and coefficient of performance of each

system tested, and shall also be used to calculate the seasonal performance

factor and seasonal operating cost. Pertinent test data and calculated

results shall be reported according to the recommended rating sheets discussed

in Section 2.4 and illustrated in Table 3.

11
2 .3 Heating Systems

2.3.1 Standard Rating Test

The Standard Rating Test shall be conducted according to the test procedures

specified in Section 6.2 and the performance calculated according to the

procedure discussed in Section 8. In order that the performance of different

absorption systems may be effectively compared, the results of the rating

tests and the calculated performance shall be reported. Results to be

reported are discussed in Section 2.4 and illustrated in Table 4.

2.3.2 Steady-State Tests

Two steady-state tests (A and C, see Table 2), shall be conducted for directfired absorption heat pumps.

For air source systems the dry-bulb and wet-bulb temperatures of the ambient

air shall be 8.3°C (47°F) and 6.1°C (43°F), respectively, for Test A, and

shall be -8.3°C (17°F) and -9.4°C (15°F) for Test C. For water source

systems the evaporator inlet water temperature shall be 21.1°C (70°F) during

Test A and 15.6°C (60°F) for Test C. The 15.6 # C (60# F) condition is representative of ground water temperatures that frequently occur in the field.

2.3.3 Frost-Accumul ation Test

The frost accumulation Test B applies only to air-source systems. Air

temperatures entering the evaporator and surrounding the outdoor portion of

the unit shall have ambient dry-bulb and dew-point temperatures of 1.7°C

(35°F) and -1.1°C (30°F), respectively. Air entering the indoor heating coil

of an air heating system shall have a dry-bulb temperature of 21.1°C (70°F)

12
and maximum indoor wet-bulb temperature of 15.6 # C (60°F). For a hot water

heating system the entering water temperature shall be 40.6 # C (105°F).

2.3.4 Cyclic Test

The final test required is a cyclic Test D, which evaluates the performance

degradation due to off-cycle refrigerant migration and heat losses.

The cyclic performance test shall be performed immediately following the high

temperature Test A. The dry-bulb temperature and the wet-bulb temperature of

the air entering the outdoor portion of an air-source unit shall be the same

as in the high temperature test. Similarly, the dry and wet-bulb temperatures

of the air entering and surrounding the indoor portion of air-source units

shall be the same as Test A (21.1°C (70°F)) dry-bulb, (15.6°C (60°F)) maximum

wet-bulb. The entering water temperature for hot water systems shall again be

40.6°C (105°F). For water-source systems the cyclic performance test shall

3 also be run immediately following the high temperature (steady-state) test.

The entering water temperature ahd flow rate during the on-period as well as

the dry-bulb and wet-bulb temperature of the air entering and surrounding the

unit shall be the same as the high temperature test conditions. The temperature of the entering water of a hot water system shall remain the same as in

Test A within the tolerance specified in Section 6.3.4. During the cyclic

test, the water flow and the indoor fan cycle 'on' and 'off' as the generator

cycles 'on' and 'off', except that the indoor fan cycling times may be delayed

due to controls that are normally installed with the unit. The generator

cycling times shall be 12 minutes 'on' and 48 minutes 'off', unless the

thermostat supplied by the manufacturer specifies on-off times at 805> burner

on-time that are different.

13
2.3.5 Summary

The test requirements for air-source and water-source direct-fired heat pump

systems are summarized in Table 2. The results of these tests shall be used

to calculate system heating capacity and coefficient of performance as well as

the seasonal performance factor and seasonal operating cost. Pertinent test

data and calculated results shall be reported according to the recommended

rating sheets discussed in Section 2.4 and illustrated in Table 6.

2 .4 Suggested Rating Sheets

Rating sheets for the systems examined in this study are illustrated in Tables

3 and 6.

Table 3 is applicable to Direct-Fired Absorption Cooling Systems, and requires

that the system under test be rated relative to its:

o Steady-state cooling capacity and coefficient of performance at

standard (Test A) rating conditions.

o Steady-state cooling capacity and coefficient of performance at

Test B and Test C conditions.

o Chilled fluid, condenser unit, and fuel flow rates at rated conditions,

o Coefficient of performance at cyclic Test D.

o On-off times at 20% burner on time.

o Seasonal performance factor and seasonal operating cost.

Table 6 is applicable to Direct-Fired Absorption Heating Systems, and requires

that the system under test be rated relative to its:

o Steady-state heating capacity and coefficient of performance at

standard (Test A) rating conditions.

o Steady-state heating capacity and coefficient of performance at

Test B and Test C conditions.

14
o Source fluid, evaporator, and fuel flow rates at rated conditions.

o Coefficient of performance at cyclic Test D.

o On-off times at 20% burner on time.

o Seasonal performance factor and seasonal operating cost.

5

15
3. RECOMMENDED TEST PROCEDURE FOR ABSORPTION COOLING SYSTEMS

3 .1 Introduction

The purpose of this section is to describe standard test procedures and

methods for determining accurate and reliable test data on the performance of

prototype and production type direct-fired absorption cooling systems. The

• -> cooling capacity of each system shall be directly determined from the results

of a primary test, and indirectly determined from a simultaneously conducted

heat balance confirming test. The primary test shall be considered valid when

the cooling capacity from the confirming test (heat balance) agrees within six

percent of the primary test results. Tbe primary test shall be used as a

basis for rating the equipment as recommended in Section 2. Where feasible,

the test procedures have been taken or adapted from ASHRAE Standards (Ref. 10,

11, and 12), ARI Standards (Ref. 9) and ANSI Standards (Ref. 2).

3 .2 Steady-State Test Procedure

3.2.1 Applicable Test Method

The test method most appropriate for determining the steady-state cooling

capacity of absorption air-conditioners is the air-enthalpy method. In this

method, cooling capacities are determined from measurements of the air flow

rate and the wet- and dry-bulb temperatures of the air stream entering and

leaving the cooling coil. This method shall be used as the primary test

method for absorption air-conditioning equipment covered by this report. When

required as part of the confirming test, the air enthalpy method shall also be

used to determine the heat rejected by the condenser unit of systems rejecting

heat to air. A description of this method and its associated test room and

measurement requirements is presented in Section 4 of the ASHRAE Standard

(Ref. 10).

16
The primary test for determining the cooling capacity of absorption waterchillers shall be the simultaneous measurement of the water flow rate and the

temperature difference between entering and leaving chilled water. This

method shall also be used in the confirming test to determine the energy

rejected by the condenser unit circuit of systems which reject heat to water.

For direct-fired systems, the energy input to the refrigeration cycle shall be

determined from the fuel's steady-state flow rate, its higher heating value

and the electric power consumption.

3.2.2 Instrumentation and Required Data

The steady-state performance tests shall have the same instrumentation and

data requirements as those specified in Section 9 and Table 1 of ASHRAE

Standard (Ref. 10). Provision shall be made to determine the cooling capacity

of absorption water-chilling systems.

3.2.3 Test Operating Procedure and Results

The equipment under test and the test roan reconditioning apparatus shall be

operated until 'equilibrium conditions' are attained but not for less than one

hour, before any test data is recorded. Data shall then be recorded at 10

minute intervals until seven consecutive sets of readings within the

tolerances specified in Section 3.2.4 are attained.

The steady-state results of a performance test at specified conditions shall

include each of the following quantities as are applicable to the equipment

under test:

1) Total cooling capacity, kW (Btu/hr)

.

17
2) Condenser unit heat rejection, kW (Btu/hr) .

3) Energy input to the generator, kW (Btu/hr).

4) Total electric power input to all components and accessories, kWh.

5) Coefficient of performance.

6) Flow rate of medium to be cooled (water for chillers—air for airconditioners), kg/hr (lbm/hr. or CFM)

.

7) Ground water or outside air flow rate over the condenser unit, kg/hr

(lbm/hr or CFM).

8) Fuel flow rate, kg/hr (lbm/hr or CFM).

9) Flue gas C(>2» %

10) Flue gas temperature, °C (°F).

11) Surface temperatures of the jacket, # C (°F).

Sections 11.1.3, 11.1.4, and 11.2.1 of the ASHRAE Standard (Ref. 10) shall

apply for all performance tests.

3.2.4 Test Tolerances

All steady-state tests shall be conducted within the tolerances specified in

Table II of the ASHRAE Standard (Ref. 10). Test operating tolerance is

defined as the greatest permissible difference between maximum and minimum

instrument observations during the test. Test condition tolerance is defined

as the maximum permissible variation of the average of the test observations

from the desired test conditions. Variations greater than those described

shall invalidate the test.

18
3 .3 Cyclic Test Procedure

3.3.1 Applicable Test Method

As outlined in Section 3.2.1 the air-enthalpy method shall be used as a

primary test to determine the capacity of absorption air-conditioners. The

primary test for determining the capacity of absorption water-chillers shall

be the simultaneous measurement of the water flow rate and the temperature

difference between inlet and outlet chilled water.* For direct-fired systems

the energy input to the unit shall be determined from the fuel's flow rate and

its higher heating value and the electric power consumption.

3.3.2 Instrumentation and Required Data

The cyclic test set up shall have the same instrumentation that is provided

for the steady— state tests. In addition, care must be taken to ensure that

during the on-time, sufficient data are taken to evaluate capacity and COP

with the required accuracy. Usually this is done by recording the temperature

difference between inlet and outlet of the chilled fluid continuously while

the fluid flows at a constant rate.

3.3.3 Test Operating Procedure and Results

The cyclic performance test. Test D, shall be performed immediately following

Test C. The equipment under test and the test room reconditioning apparatus

shall be operated until 'equilibrium conditions' are obtained before any test

data are recorded. 'Equilibrium conditions' means in the case of cycling

tests that during subsequent cycles the same set of data within tolerances

specified in Section 3.3.4 during the on- and off-period are obtained. Once

at 'equilibrium conditions' the data of the subsequent fourth cycle shall be

19
recorded. The results of any part load test shall include all quantities

listed in Section 3.2.3 except items 2, 3, 9, 10 and 11.

3.3.4 Test Tolerances

One minute after start up of the burner the same test tolerances shall be

applied as specified in Section 3.2.4.

20
4. MODEL LOADS AND CLIMATE SPECIFICATIONS FOR ABSORPTION COOLING SYSTEMS

4 .1 Introduction

The seasonal performance and seasonal cost of operation of any direct-fired

absorption cooling system depends not only upon the instantaneous performance

of the system under specific indoor and outdoor conditions, but also upon the

type of building in which it is installed, its thermal load, and the climate

in which the building is situated. Because of the wide range of climates in

the United States, and the even wider range of building types and thermal

requirements, it becomes extremely difficult to adequately characterize the

performance of a cooling system in all regions of the country with one or two

seasonal indicators. In order to provide the manufacturer of direct-fired

equipment some latitude and flexibility in establishing the seasonal

performance of his product, two separate evaluation approaches are recommended

for seasonal calculations of such systems:

1) The generalized climate of the United States shall be adopted using

the average cooling load hours, CLH, determined for the climate.

(Table 4).

2) Assuming a more localized climate, the Fractional Temperature Bin

Hours and Cooling Load Hours for that climate shall be used.

(Generally available Air Force Manual 88-29 and Table 5.)

In both cases, the assumed Outdoor Design Cooling Temperature and Ground Water

Temperature shall be 35°C (95°F) and 15.6°C (60°F), respectively. The

temperature bin method illustrated in Section 5.6 shall be used to determine

the seasonal performance factor and the seasonal operating cost based upon the

appropriate climate.

21
4 .2 Building Loads

Cooling requirements are determined by assuming a linear relationship between

building load and outdoor dry-bulb temperature. The cooling load line

extends from zero load at a specified outdoor temperature T„, to a value

that is 10% below the steady-state cooling capacity at an outdoor design

temperature of 35°C (95°F). The building load-temperature relationship is

given by:

BL(T-) = (5j-3)

• x > T

(Temperatures in Q F (4.1)

J l.KT^-Tg) ’ ^ c check equivalent units

for # C)

where j = 1 , 2 , . . . n. Q S s^h^ is the measured steady-state cooling

capacity of the direct-fired absorption system at the assumed design

temperature, n represents the total number of non-zero temperature bins, and

1.1 represents an arbitrary oversizing factor. Tj is the representative

temperature of the jth bin and is given by:

Tj = Tc - 3 + 5j ; Tj > Tc (4.2)

The change-over temperature Tc is assumed to be 18.3°C (65°F).

The fractional building cooling load at a representative outdoor temperature,

Tj , is expressed as:

BUT,) • -J.

J N

<WTh><5i - 3)

. 1.1 (Th

- Tc

) N

(4.1a)

22
where nj/N is the ratio of bin hours of the jth temperature bins to the total

seasonal cooling hours.

23
5. CALCULATION PROCEDURE FOR ABSORPTION COOLING SYSTEMS

5 .1 Introduction

The calculation procedure in this section describes methods for calculating

cooling capacity, condenser unit heat flow, input energy to the generator,

electric power consumption, and coefficient of performance of all the

absorption cooling systems considered in this study. In addition, a procedure

is defined for calculating the seasonal performance factor and seasonal operating cost of direct-fired units rejecting heat to air and direct-fired units

which reject heat to ground water.

5 .2 Calculation Procedure for Steady-State Tests

5.2.1 Fuel Energy Input

The rate of thermal energy Qg supplied to the generator of direct-fired

systems under steady-state conditions is:

(5.1)

where m£ is the fuel mass flow rate and HHV is the higher heating value of the

fuel on a mass basis.

5.2.2 Electrical Energy Input

The total electrical power input to the unit is defined by:

(5.2)

where Pt is the total amount of electrical power being supplied averaged over

the test duration. For water chillers Pg is the power to the chilled water

pump. If this pump is not furnished with the unit, a value of 11.4 watts/kW
(40 watts/ton) shall be assumed. For aii^conditioners P

g is the power of the

indoor fan. If a fan is not furnished as part of the model, a value of 0.777

W per JVsec (1250 Btu/hr per 1000 cfm) shall be assumed. In the case of units

which reject heat to water Pc is the power to the condenser water pump. If

this pump is not furnished with the unit, a value of 20 watts/kW (70

watts/ton) shall be assumed. For units which reject heat to outdoor air Pc is

the power to the outdoor fan. P

aux is the electrical power required by the

various controls and auzil liarie s.

5.2.3 Cooling Capacity

The steady-state cooling capacity Qss of absorption air-conditioners shall be

determined according to the air-enthalpy method outlined in Section 4 of

ASHRAE Standard (Ref. 10) using the appropriate equations specified in Section

4.6 and 7.4. For air-conditioning systems which may itot have indoor-air

circulating fans furnished as part of the system, their measured cooling

3 capacity shall be adjusted by subtracting 0.777 W per £/sec (1250 Btu/hr per

1000 cfm) of indoor aii— flow from the measured value.

For water chillers, the steady-state cooling capacity shall be determined from

6ss - "ecp

(Tel - Te2> (5 - 3 >

where m e is the water mass flow rate through the cooling coils and Tel and T e 2 are the cooling coil inlet and outlet water temperatures, respectively.

It is assumed that the effect of the chilled water circulation pump on the

capacity is negligible.

25
5.2.4 Heat Balance - Confirming Test

This method is used to confirm the direct measurement of steady-state cooling

capacity by algebraically combining the measured values of generator input

• • energy Qg, condensing unit heat Qc (includes both condenser and absorber

heats), and the total electrical energy Pt input to the unit. Accordingly the

steady-state cooling capacity by the heat balance method is:

Qss = Qc "

Qg

“ 3 - 413 * P

t +

Qj + % (5.4)

where the Q's are measured in Btu/hr and P

t in watts.

• • Qg is discussed in Section 5.2.1. Qf is the residual energy in the products

of combustion (flue gas) leaving the system, and is determined from measurement of flue gas temperature and COj content. Qj is jacket heat loss and

represents the convective and radiative losses from heated metal surfaces.

Its determination is based upon appropriate surface temperature readings and

calculation methods presented in Appendix B of reference (2). The jacket

surface temperature measurement is performed in the manner described in part

2.12 of reference (7).

6C represents the amount of energy rejected from the refrigeration machine

including energy added to the cooling fluid from fans or pumps.

For units rejecting heat to air the heat rejection shall be calculated from:

6C = 1.08 Qsc (Tc 2 - Tc j) (Temperatures in °F, Qsc in (5.5)

CFM ; check equivalent units

for °C).

26
where Q_ is in Btu/hr. V

Q is the air flow rate across the condenser and absorber coils (in

s c some units it includes the combustion flue gas as well) corrected to standard

conditions, and which is calculated from equations specified in Section 7.4 of

the ASHRAE Standard (Ref. 10). Tcl and Tc2 are the inlet and outlet

temperatures of the cooling air respectively.

g For those units, where the flue gases are mixed with the condenser unit

cooling air, is already included in the measured value of Qc

. Therefore,

term &£ in equation (5.4) shall be neglected.

For units rejecting heat to water, the heat rejection shall be determined from

6C = ic C

p

(Tc2 - Tcl > (5.6)

where m

c is the mass flow rate of the cooling water and Tcl and Tc2 are the

inlet and outlet temperatures of the cooling water, respectively, and C

p

is

the specific heat (liquid) of the water.

5 .3 Calculation Procedure for Cyclic Tests

Since the cooling capacity varies with the unit on-time the cooling done over

a complete cycle for water chillers is evaluated by:

^pump off

6cyc ”

"e C

p f

AT(t)dt (5.7)

^-pump on

27
CL_- is the cooling done over a complete cycle, m. is the flow rate of the

cy c c chilled water, assumed to be constant with time, AT is the temperature difference which is a function of time (t) and tp^p on

is the on-time of the

chilled water pump over a complete cycle.

For air-conditioners the following equation should be used to determine cyclic

cooling done.

t fan off • - L. = 60 V Cpa

/ AT(t)dt (5.8) CyC

v

n

(l + »,) J

t fan on

V is the air flow rate (which is assumed to be constant), C! is the specific

pa

heat at constant pressure of the air-water mixture per pound of dry air (Cpa =

1.01 + 1.86 W

n

, kj/kg. °C, [0.24 + 0.444 W Q

, Btu/lbm °F]), and v n and W n are

the specific volume and humidity ratio of the air-water mixture at the position where the flow rate measurements are taken. AT is the temperature difference which is a function of time and t*„.. is the on-time of the indoor tan on

fan over a complete cycle.

For air-conditioning systems which may not have indoor air circulating fans

furnished as part of the system, their measured cooling capacity shall be

adjusted by subtracting 0.777 W per £/sec (1250 Btu/hr per 1000 SCFM) of

indoor air flow from the measured value.

28
5 .4 Coefficient of Performance

The coefficient of performance for direct-fired systems shall be based on the

total fuel energy input to the system plus electrical energy supplied to fans,

pumps, controls, etc. Accordingly,

COP.

Qss

s s mf

• HHV + 3.413 P t

(5.9)

where (mf • HHV) is in Btu/hr and P

t is in watts; 3.413 is conversion from

watts to Btu/hr. P t is the total amount of electrical energy consumed during

the test duration as given by equation (5.2).

The COP„„,. for Test D shall be evaluated according to equation (5.9)

cy c with the following modifications.

Qss is replaced by QCy C (eq. 5.7), mf is replaced by the total amount of fuel

consumed during one total cycle and Pf is replaced by the total amount of

electricity consumed during the entire cycle.

5 .5 Seasonal Performance Factor and Seasonal Operating Costs

This section describes a calculation procedure for determining the seasonal

performance factor (SPF) and seasonal operating costs (SOC) of direct-fired

absorption cooling systems.

The fractional energy consumption in the jth temperature bin shall be

evaluated by:

29
Edj) (5.10)

n

.

N

CLF(T^)

1 - CD

(1 - CLF(Tj)) ss n . N

• • where Es$ = (mf • HHF) + 3.413 P t and is the steady-state energy input to the

unit ; it is assumed to be independent of temperature, because fuel flow rate

and electrical power consumption do not vary significantly with outdoor

temperature. The cooling load factor CLF is obtained by the following

equation:

CLF ( T • ) = -?L(Tij. . Qss (Tj) > BLd,) (5.11)

J 6ss ( Tj )

CLF ( T

j ) = 1 ; Qss (Tj) < BL(T '

6 s$ (Tj) is evaluated by interpolation or extrapolation of the capacities of

Tests A and B according to the following equation:

Qss (Tj) = QSS (82°F) + a(Tj - 82°F) (5.12)

Q ( 95°F) - Q ( 82 0 F

)

. , , S s s s with a = —^— —

95°F - 82 °F

The degradation factor of equation (5.10) is given by:

c = 1_- PLF( 82°F)

U 1 - CLF ( 82 0 F

)

(5.13)

30
with PLF ( 82 0 F

)

(5.14)

COPcvc

(82°F)

COP ss (82°F)

The total amount of energy consumed during an entire season divided by the

total number of temperature bin hours, N, is evaluated by:

n £ = E(T-) * (5.15)

N Z—/ J N

j = 1

where n is the number of non-zero temperature bins. The SPF is then given by

SPF = 2LZN

E/N

(5.16)

where BL

N N

j = 1

An estimation of the seasonal operating cost is given by:

SOC = ^

N

sCj + (1 - x) —1

' .413J

CLH (5.17)

E is the total energy consumption per season, divided by the total number of

temperature bin hours, N, C£ and C

g are the costs for fuel in $/Btu and

elecricity in $/Whr and CLH is the number of total cooling season hours.

Factor x in eq. (5.17) is the ratio of the seasonal primary fuel energy

consumption to the total energy consumption. Since this ratio can only be

31
approximated by a few laboratory tests, it is recommended that the cyclic test

data ratio of these energies (e.g., the fuel to total) should be used.

The SPF and SOC shall be determined from eqs. (5.16) and (5.17) for the

climate discussed in Section 4.1. Table 5 is a calculation sheet that may be

used for calculating the SPF and SOC for direct-fired absorption systems.

5 .6 Sample Calculations

The following sample calculations for a chilled water-air heat rejection unit

are based on hypothetical data obtained from Tests A, C and D. Test B results

are not given as no test is required. The total number of seasonal cooling

hours is assumed to be 3825 hours.

Test No.

A: 6 ss (95»F) = 32800 Btu/hr E

SS (95»F) = 81300 Btu/hr C0PSS (95°F) = 0.403

C: <S ss (82°F) = 36900 Btu/hr fc ss (82«F) = 81300 Btu/hr COP ( 82°F)

5 S = 0.454

D: 6

cyc (82«F) = 33415 Btu/hr Ecyc (82*F) = 81300 Btu/hr C0P

cyc (82°F) = 0.411

The fractional building load for a given temperature bin is evaluated according

to equation (4.1a). For the first bin temperature at 19.4°C (67°F):

BL * — = 3 ? 8 °Q- -P.W hr ‘ [(5 • 1) ~ 3]°.F . o.214 = 425 Btu/hr.

N 1.1 (95°F - 65°F)

The results for all bin temperatures are listed in Table 10 column D. The

CLF(Tj) is obtained according to equations (5.11) and (5.12).

For example:

32
(l ss (6l°F) = 36900 Btu/hr + 32800 Btu/hr - 36900 Btu/hr

95°F - 82 °F

(65°F - 82°F) = 41631 Btu/hr

and

CLF ( 6 7

0 F

)

32800 Btu/hr - (67°F - 6S°F)

1 . 1 ( 95°F - 65 # F) — = 0.04841631 Btu/hr

Further values of CLF(T-) are listed in column E of Table 10. The energy consumption

•I E(Tj) * Uj/N is obtained by applying equations (5.10), (5.13), and (5.14):

PLF = - = 0.905

0.454

r _ 1 - 0.905

D 1 - 0.458

0.175

E(67°F) • p- =

„ . S ;??

8— * 81300 Btu/hr • 0.214 = 1002 Btu/hr

N 1 - 0.175(1 - 0.048)

The results for other temperature bins are again listed in Table 10 column F.

The SPF is then calculated by equation (5.16):

SPF = = 0.41

28502

According to equation (5.17) the seasonal operating cost, assuming

33
Cf - 0.005 ~~ 1 kBtu

$ and C„ = 0.06 -—- and z = 0.95 and CLH = 3825

© kWh kWh

SOC = 28502 95 ( .005) + .05 3825 = $613.67

here it is assumed that the cyclic test data showed that 95% (i.e., x = 0.95)

of the total energy input is fuel.

Example calculations for an air-conditioning unit would be similar to those

for the vapor compression air-conditioners as illustrated in ASHRAE Standard

(Ref. 12).

34
6. RECOMMENDED TEST PROCEDURE FOR ABSORPTION HEATING SYSTEMS

6 .1 Introduction

The purpose of this section is to describe standard test procedures and

methods for determining accurate and reliable test data on the performance of

prototype and production type direct-fired absorption heating systems. The

heating capacity of each system shall be directly determined from the results

of a primary test, and indirectly determined from a simultaneously conducted

heat balance confirming test. The primary test shall be considered valid when

the heating capacity from the confirming test (heat balance) agrees within six

percent of the primary test results. Ihe primary test shall be used as a

basis for rating the equipment as recommended in Section 2. Where feasible,

the test procedures have been taken or adapted from ASHRAE Standards (Ref. 10 and

11 ).

6 .2 Steady-State Test Procedure

6.2.1 Applicable Test Method

The test method most appropriate for determining the steady-state heating

capacity of absorption heat pumps is the air-enthalpy method—indoor side (for

forced air heating systems). In this method, heating capacities are determined from measurements of the air flow rate and the dry bulb temperatures of

the airstream entering and leaving the heating coil. This method shall be

used as the primary test method for absorption heat pump equipment covered by

this report. When required as part of the confirming test, the air enthalpy

method shall be used to determine the heat absorbed by the evaporator unit of

air-source systems. A description of this method and its associated test room

and measurements requirements is presented in Section 3 of ASHRAE Standard

(Ref. 11)

.

35
The method used as a confirmation test to determine the energy absorbed by the

evaporator unit of water-source systems shall be the simultaneous measurement

of the water flow rate and the temperature difference between entering and

leaving water of the indoor coil.

For direct-fired systems the energy input to the refrigeration cycle shall be

determined from the fuel's steady-state flow rate, its higher heating value and

the electric power consumption.

6.2.2 Instrumentation and Required Data

The steady-state performance tests shall have the same instrumentation and

data requirements as those specified in Section 10 and Table II of ASHRAE

Standard (Ref. 11). Provision shall be made to dete’rmine the heating capacity

of absorption heat pump systems.'

6.2.3 Test Operating Procedure and Results

The equipment under test and the test room reconditioning apparatus shall be

operated until equilibrium conditions are attained, but not for less than one

hour, before any test data is recorded. Data shall then be recorded at 10

minute intervals until seven consecutive sets of readings within the

tolerances specified in Section 6.2.4 are attained.

The steady-state results of a performance test at specified conditions shall

include each of the following quantities as are applicable to the equipment

under test:

1) Total heating capacity, kW (Btu/hr)

36
2 ) Evaporator unit heat absorption, kW (Btu/hr)

3) Energy input to the generator, kW (Btu/hr)

4) Total electric power input to all components and accessories, kWh.

5) Coefficient of performance

6) Flow rate of medium to be heated (hot water or indoor air), kg/hr (lbm/hr

or CFM)

.

7) Ground water or outside air flow rate over the evaporator unit, kg/hr

(lbm/hr or CFM).

8) Fuel flow rate, kg/hr (lbm/hr or CFM).

9) Flue gas COj *

**>

10) Flue gas temperature, °C (°F)

11) Surface temperatures of the jacket, °C (°F)

Sections 12.15, 12.16, and 15 of the ASHRAE Standard (Ref. 11) shall apply for

all performance tests.

6.2.4 Test Tolerances

All steady-state tests shall be conducted within the tolerances specified in

Table III of the ASHRAE Standard (Ref. 11). Test operating tolerance is

defined as the greatest permissible difference between maximum and minimum

instrument observations during the test. Test condition tolerance is defined

as the maximum permissible variation of the average of the test observations

from the desired test conditions. Variations greater than those described

shall invalidate the test.

37
6 .3 Cyclic Test Procedure

6.3.1 Applicable Test Method

As outlined in Section 6.2.1 the air enthalpy method shall be used as a

primary test to determine the capacity of absorption heat pumps. Air-source

units coil must be clean of frost both before and throughout the test

duration.

6.3.2 Instrumentation and Required Data

The cyclic test set up shall have the same instrumentation that is provided

for the steady-state tests. In addition, care must be taken to ensure that

during the on-time, sufficient data are taken to evaluate capacity and COP

with the required accuracy. Usually this is done by recording the temperature

difference between inlet and outlet water, circulating through the condensing

unit, while the fluid flows at a' constant flow rate.

6.3.3 Test Operating Procedure and Results

The cyclic performance test. Test D, shall be performed immediately following

the high temperature test. Test A. The equipment under test and the test room

reconditioning apparatus shall be operated until 'equilibrium conditions' are

obtained before any test data are recorded. 'Equilibrium conditions' means in

the case of cycling tests that during subsequent cycles the same set of data

within tolerances specified in Section 6.3.4 during the on- and off-period are

obtained. Once at 'equilibrium conditions' the data of the subsequent fourth

cycle shall be recorded. The results of any part-load test shall include all

quantities listed in Section 6.2.3 except items 2 and 3.

38
6.3.4 Test Tolerances

One minute after start up of the burner the same test tolerances shall be

applied as specified in Section 6.2.4.

6 .4 Frost Accumulation Test Procedure

6.4.1 Applicable Test Method

This test is to be conducted solely for aii^source systems using the method

described in Section 6.2.1—Indoor side—as a primary test. A capacity

determination based on the indoor air enthalpy measurements is the only

permissible test. During this test any apparatus disturbing normal outdoor

air flow on the equipment must not be connected. The indoor airflow is to be

allowed to continue with no changes in the air flow settings for test equiment

or associated test apparatus, except that if the defrost controls provide for

stopping the indoor fan, provision shall be made to shut off flow of air

through the indoor coil from the test apparatus while the indoor fan is

stopped. The same is true for the water flow in a hot water heating system.

6.4.2 Instrumentation and Required Data

The frost accumulation performance tests shall have the same instrumentation

and data requirements as specified in Section 10 and Table II of ASHRAE

Standard (Ref. 11).

6.4.3 Test Operating Procedure and Results

The equipment under test and the test rocm reconditioning apparatus shall be

operated for a test period of three hours. If the unit is in defrost at the

end of this test period, the cycle shall be completed. Data shall be recorded

at normal ten minute intervals (see Section 11.3.2 of ASHRAE Standard (Ref.

39
11), except that during the defrost cycle data shall be recorded continuously

to establish accurately the start and completion of the defrost cycle, the

time- temperature pattern of the indoor air stream (if the indoor fan is

running) and the electrical and fuel input to the equipment.

The results of this performance test at specified conditions shall include all

quantities listed in Section 6.2.3 as are applicable to the air source units.

6.4.4 Test Tolerances

All test observations shall be within the tolerances specified in Table III of'

the ASHRAE Standard (Ref. 11), as appropriate to the test methods and type of

equipment. The maximum permissible variation of any observation during the

capacity test is listed under 'Test Operating Tolerance' in the table. This

represents the greatest permissible difference between maximum and minimum

instrument observations during the test. The maximum permissible variations

of the average of the test observations from the standard or desired test

conditions are shown in the table under 'Test Condition Tolerance'.

Variations greater than those described shall invalidate the test.

40
7. MODEL LOADS AND CLIMATE SPECIFICATIONS FOR ABSORPTION HEATING SYSTEMS

7 .1 Introdnct ion

The seasonal performance and seasonal cost of operation of any direct-fired

absorption heating system depends not only upon the instantaneous performance

of the system under specific indoor and outdoor conditions, but also upon the

type of building in which it is installed, its thermal load, and the climate

in which the building is situated. Because of the wide range of climates in

the United States, and even wider range of building types and thermal

requirements, it becomes extremely difficult to adequately characterize the

performance of a heating system in all regions of the country with one or two

seasonal indicators. In order to provide the manufacturer of direct-fired

equipment some latitude and flexibility in establishing the seasonal

performance of his product, the following evaluation approach is recommended

for seasonal performance calculations of such systems:

For Heating Only Systems -

o Identify climatic region of the United States based on Tables 7 and

8, in which the direct-fired absorption heating system is to be

located.

o Use the representative outdoor heating design temperature for this

region (listed in table) to determine the building heating

requirement

.

o Size the system heating capacity at 80% of the building heating

requirement and use add-on heat (gas furnace or electric resistance

heat as appropriate to the unit) to make up the difference.

o Use the temperature bin method to determine the seasonal performance

factor and the seasonal operating cost based upon the appropriate

climate.

For Heating and Cooling Systems -

o The system shall be sized based on the cooling load (refer to

Section 4.1)

.

41
7 .2 Building Loads

Heating requirements are determined by assuming a linear relationship between

building load and outdoor dry-bulb temperature. The heating load line extends

from zero load at a specified change-over temperature, Tc

, to a value that

equals the steady-state heating capacity or design heating requirement

(whichever is smaller) at the outdoor design temperature, T^. The building

load-temperature relationship is given by:

The change-over temperature T„ is assumed to be 18.3°C (65°F). DHR is the

Design Heating Requirement or steady-state heating capacity at T^. C is an

'experience factor* which tends to improve the agreement between calculated and

measured building loads (Ref. 8). The value for C is 0.77.

The fractional building heating load at a representative outdoor dry-bulb

temperature, Tj , is expressed as:

(C) ' (DHR) (7.1)

where T- is the representative temperature of the jth bin and is given by:

J

(7.2)

(C) • (DHR) ‘ -i- (7.1a)

n-/N is the ratio of bin hours of the jth temperature bins to the total seasonal

J heating hours.

42
8. CALCULATION PROCEDURE FOR ABSORPTION HEATING SYSTEMS

8 .

1

Introdoct ion

The calculation procedure in this section describes methods for calculating

heating capacity, evaporator unit heat flow, input energy to the generator,

electric power consumption, and coefficient of performance of all the absorption heating systems considered in this study. In addition, a procedure is

defined for calculating the seasonal performance factor and seasonal operating

cost of direct-fired air-source systems, and direct-fired water-source systems

that absorb heat from ground water.

8.2

Calculation Procedures for Steady-State Tests

8.2.1 Fuel Energy Input

fi c The rate of thermal energy Qg supplied to the generator of direct-fired

systems under steady-state conditions is:

where ?t is the total amount of electric power being supplied averaged over

the test duration. Pg is the power to the supply water pump. If thi*

pump is not furnished with the unit, a value of 20 watts/kW (70 watts/ton)

( 8 . 1 )

where m^ i$ the fuel mass flow rate and HHV is the higher heating value of the

fuel on a mass basis.

8.2.2

Electrical Energy Input

The total electrical power input to the unit is defined by:

( 8 . 2 )

43
shall be assumed. Pc is the power to the evaporator water pump, for water

source units. If this pump is not furnished with the unit, a value of 11.4

watts/kW (40 watts/ton) shall be assumed. Paux * s t*ie ©Metrical power

required by the various controls and auxil liaries. For heat pump systems

which may not have indoor air circulating fans furnished as part of the

system, the total energy used shall be adjusted by adding 0.777 V peril/sec

(1250 Btu/hr per 1000 cfm) of indoor air flow.

8.2.3 Heating Capacity

The steady-state heating capacity Qgs of absorption heat pumps shall be

determined according to the air-enthalpy method outlined in Section 3 of

ASHRAE Standard (Ref. 11) using the appropriate equations specified in Section

3.8 and 7.4. For heat pump systems which may not have indoor air-circulating

fans furnished as part of the system, their measured heating capacity shall be

adjusted by adding 0.777 W per £/sec (1250 Btu/hr per SCFM) of indoor airflow

to the measured value.

8.2.4 Heat Balance - Confirming Test

This method is used to confirm the direct measurement of steady-state heating

capacity by algebraically combining the measured values of generator input

• • energy Qg, evaporating unit heat absorption Qe and the total electrical power

power P

t input to the unit. Accordingly, the steady-state heating capacity by

the heat balance method is:

Qss = Qe + %

+ 3-413 Pt - Qj - Qf (8.3)

where the 6's are measured in Btu/hr and P

t in watts.

44
6 is discussed in Section 5.2.1. is the residual energy in the

products of combustion (flue gas) leaving the system, and is determined from

measurement of flue gas temperature and C©2 content. Qj is the jacket loss

and represents the convective and radiative losses from heated metal surfaces. Its determination is based upon appropriate surface temperature

readings and calculation methods presented in Appendix B of reference (2).

The jacket surface temperature measurement is performed in the manner

described in part 2.12 of reference (7).

6. represents the amount of energy absorbed by the refrigeration machine from

either the outside air or ground water source. For air-source systems, the

heat absorption shall be calculated from:

6. = 1.08 &_ e

(T.. - T ) (Temperatures in °F, 6 (8.4)

e s 2 1 is CFM ; check equivalent

units for ®C)

where is in Btu/hr. O C

i!

6SC is the air flow rate across the evaporator coils corrected to

standard conditions, and is calculated from equations specified in Section 7.4

of the ASHRAE Standard (Ref. 11). ^e^ and ^ej are the inlet and outlet

temperatures of the air, respectively.

For water-source systems, the heat absorption shall be determined from:

6e = ®e C

p

(Te2 ~ Te 1

) (8 - 5)

45
X X

where mg is the mass flow rate of the source water and A ej and ^ej are the

inlet and outlet temperatures of the source water, respectively. C

p

is the

specific heat (liquid) of the source (ground) water.

8 .3 Calculation Procedure for Cyclic Test

Since the heating capacity varies with the unit on-time, the heating done over

a complete cycle for a hot water heat system is evaluated by:

eye = icCp /J t

pump off

AT(t)dt

pump on

( 8 . 6 )

^cyc * s heating done over a complete cycle, mc is the flow rate of the

supply water, assumed to be constant with time, AT is the temperature difference which is a function of time (t) and on

is the on-time (t) of the

supply water pump, over a complete cycle.

For heat pumps in a hot air system the following equation should be used to

determine cyclic heating done.

eye

60

7J

t fan on V Cpa f

AT( t)dt

1 + WJn J

t fan off

(8.7)

V is the air flow rate (which is assumed to be constant), Cn_ is the specific

pa

heat at constant pressure of the air-water mixture per pound of dry air, C

pfl =

1.01 + 1.86 W

n

. kj/kg, °C, (0.24 + 0.444 WN

, Btu/lbm °F) , and v

n and W n are

the specific volume and humidity ratio of the air-water mixture at the same

46
position where the flow rate measurements are taken. AT is the temperature

difference which is a function of time and tf an on

is the on-time of the

indoor fan over a complete cycle.

For heating systems which may not have indoor air circulating fans furnished

as part of the system, their measured heating capacity shall be adjusted by

adding 0.777 W per H / sec (1250 Btu/hr per SCFH) of indoor air flow from the

measured value.

8.4 Coefficient of Performance

The coefficient of performance for direct-fired systems shall be based on the

total fuel energy input to the system plus electrical energy supplied to fans,

pumps, controls, etc. Accordingly,

8

Q

C0P

ss «

ss (8.8)

mj • HHV + 3.413 Pt

where (m£ • HHV) is in Btu/hr and Pt in watts; 3.413 is conversion from watts

to Btu/hr.

P

t is the total cmount of electrical energy consumed during the test duration

as given by equation (8.2).

The C0Pcyc for Test D shall be evaluated according to equation (8.8) with the

following modifications:

47
Qss is replaced by QCy C (eq. 8.6), m£ is replaced by tbe total amount of

fuel consumed during one total cycle and Pt is replaced by the total

amount of electricity consumed during the entire cycle.

8.5 Seasonal Performance Factor and Seasonal Operating Costs

This section describes a calculation procedure for determining the seasonal

performance factor (SPF) and seasonal operating costs (SOC) of direct-fired

absorption heating systems.

The fractional energy consumption in the jth temperature bin shall be

evaluated by:

n* HLF(Tj) n

E(T • ) U * —*1 = ...... J • F * 1

J N 1 - CD

(1 - HLF(Tj)) 88 N

(8.9)

• • where E ss = (m£ • HHV) + 3.413 Pt and is the steady-state energy input to the

unit; it is assumed to be independent of temperature, because fuel flow rate

and electrical power consumption do not vary significantly with outdoor

temperature. The heating load factor, HLF, is obtained by the following

equation:

HLF(Tj)

HLF(Tj)

BL(T.)

Qss<Tj>

BL(Tj) < Qss <Tj)

BL(Tj) > Oss (Tj)

( 8 . 10)

6ss<Tj> is evaluated by interpolation or extrapolation of the capacities of

Tests A and C according to the following equation:
6 ( 8 . 11 ) ss (T

j

) = 6ss ( 47°F) + a (Tj - 47°F)

with a Q 55 (17°F) - QSS (47°F)

17°F - 47°F

The degradation factor of equation (8.9) is given by:

c = 1 ~ PLF(47°F)

D 1 - HLF(47°F)

( 8 . 12 )

with PLF(47°F)

GOPcvc (47°F)

COP

ss (47°F)

(8.13)

The total amount of energy consumed during an entire season divided by the

total number of temperature bin hours, N, is evaluated by:

E = 2 E(Ti )

• N

j =1 J N

(8.14)

where n is the number of non-zero temperature bins. The SPF is then given by

SPC = BL/N

E/N + (RH * 3.413)*

(8.15)

vhexe Bt = 2 BUT.) • N j-1 J N

*If unit is gas-fired use |jn f

* HHvj

49
and

RH = 2

J-l

n RH(Tj)

=

° (BLdj) ~ Qssdj)) nj_

N

j = 1 3.413 * N

where BL(Tj) > Qss

(Tj)

An estimation of the seasonal operating cost is given by:

J

* HLH

+

|^RH * 3 .413

j

*

* HLH (8.16)

E/N is the total energy consumption divided by the total number of

temperature bin hours, N, per season, Cf and C

e are the costs for fuel in

$/Btu and electricity in $/Wh and HLH is the number of total heating season

hours. Factor z in equation (8.16) is the ratio of the seasonal primary fuel

energy consumption to the total energy consumption. Since this ratio can only

be approximated by a few laboratory tests, it is recommended that the cyclic

test data ratio of these energies (e.g., the fuel to total) should be used.

Table 5 is a calculation sheet that may be used for calculating the SPF and

SOC for direct-fired absorption systems.

8 .6 Sample Calculations

The following sample calculations for an air-source hot-water absorption heat

pump unit are based on hypothetical data obtained from Tests A, C and D. The

frost accumulation test (Test B) is not being considered in this example.

•If unit is gas-fired use

50
We are assuming a location in Maine, which is Region V. The heating load

hours and outdoor design temperature corresponding to this region are obtained

from Table 7.

Test No.

A: <5 ss (47«F) = 52901 Btu/hr tss (47«F) = 61365 Btu/hr COP ss (47°F) = 1.16

C: 0 SS (17«F) - 46075 Btu/hr ESS (17"F> = 43771 Btu/hr COPss (17°F) = 0.95

D: 6cyc (47«F) = 35000 Btu/hr fecyc (470F) = 25550 Btu/hr COP

cyc

(47°F) = 0.73

HLH = 2750 hours T

QD = T

h

= -23 .3°C(-10°F)

The fractional building load for a given temperature bin is evaluated according

to equation (7.1a). For the first bin temperature at 16 .7°C(62°F)

.

n l BL * —

N

-

) *(o.77) * (39932 Btu/hr)

65°F - (-10°Fy \ / \ )

* 0.106 = 130.4 Btu/hr

ss where DHR = 6CC (-10°F) = 52901 Btu/hr + Bt ^/^5 gjgg. ! B tu/hr

17°F - 47°F

(~10°F - 47 °F) = 39932 Btu/hr

is determined from equation (8.11).

The results for all bin temperatures are listed in Table 11 column D. The

HLF(T-) is obtained according to equations (8.10) and (8.11). For example:

fJ

fc cc (62°F) = 52901 Btu/hr +

5 S 46075 Btu/hr - 52901 Btu/hr

17°F - 47°F

(62 # F - 47«F)

= 563 13 .5 Btu/hr

51
and

HLF(62°F) ( 6S°F ~ 62°F \

\65°F - (-10°F)

/

(0.77) • (39932 Btu/lir) 1 56313.5 Btu/hr

0.022

Further values of HLF(Tj) are listed in column E of Table 11. The energy

consumption E(Tj) * nj/N is obtained by applying equations (8.9), (8.12), and

(8.13):

PLF = SLtli = 0.63

1 • 16

Cd

1-0.63

1 - 0.14

0.43

E(62°F) • p- = --- * 61365 Btu/hr * 0.106 = 247.0 Btu/hr

N 1 - 0.43(1 - 0.022)

The results for other temperature bins are again listed in Table 11 column F.

The SPF is then calculated by equation (8.15):

Spf — 12 155.7

" 21727.1

0.56

According to equation (8.16) the seasonal operating cost, assuming C£ = 0.005

$/kBtu and C. = 0.06 $/Kwh and x = 0.96 and HLF = 2750 is:

SOC = 21.727 .96 ( .005) + .04 -P-6 - * 2750 = $328.81

3 .413

52
where it is assumed that the cyclic test data showed that 96% (i.e.,

of the total energy input is fuel.

.

'

.

•

x = .96)
9. LIMITATIONS OF THE RECOMMENDED TEST AND RATING PROCEDURES

The test requirements described in Section 2 and illustrated in Tables 1-2

assume that the behavior of the particular system can be sufficiently

determined with only four test points. As more laboratory and field experience is acquired on the latest absorption systems, the number of test points

may have to be increased to adequately describe the system. The rating

procedure may then need to be reviewed to verify that it adequately describes

field performance.

Additionally, the climate specifications outlined in Sections 4 and 7 are

sufficiently general to warrant further investigation. While these seasonal

rating approaches suffer the inevitable disadvantages associated with climate

generalization, they do provide a suitable technique for assessing both

relative Carnot effect (i.e., the. use of various temperature reservoir

differences) and cycling effect of different absorption systems that are

designed for the same market and the same general climate.

These limitations indicate a need for further investigation.

54
REFERENCES

1. American Society of Heating, Refrigerating and Air-Conditioning

Engineers, Guide and Data Book, Equipment Volume.

2. American National Standard for Gas-Fired Absorption Summer AirConditioning Appliances, ANSI Z21.40.1, April 19, 1973.

3. Method of Testing, Rating and Estimating the Seasonal Performance of

Central Air-Conditioners and Heat Pumps Operating in the Cooling Mode,

Kelly, G. E. , and Parken W. H. , NBSIR 77-1271, April 1978.

4. Method of Testing, Rating and Estimating the Heating Seasonal Performance

of Heat Pumps, Parken, V. H., Kelly, G. E., and Didion, D. A., NBSIR 80-

2002, April 1980.

5. Method of Testing, Rating and Estimating the Seasonal Performance of

Ground Water Source Heat Pumps, Mulroy, W. J., NBSIR 81-2434, August

1982 .

6. American National Standard for Gas-Fired Central Furnaces, ANSI Z21.47-

1978.

7. Aii— conditioning and Refrigeration Institute, Standard for Ground-Water

Source Heat Pumps, ARI 325-83.

8. Recommended Testing and Calculation Procedures for Determining the

Seasonal Performance of Residential Central Furnaces and Boilers, Kelly,

G. , Chi, J. , and Kuklewicz, M. , NBSIR 78-1543, October 1978.

9. Air-Conditioning and Refrigeration Institute, Standard for Absorption

Water-Chilling Packages, ARI 560-82.

10. American Society of Heating, Refrigerating and Air-Conditioning

Engineers, Methods for Testing for Rating Heat Operated Unitary AirConditioning Equipment for Cooling, ASHRAE 40-80.

11. American Society of Heating, Refrigerating and Air-Conditioning

Engineers, Methods of Testing for Rating Unitary Air-Conditioning and

Heat Pump Equipment, ASHRAE 37-78.

12. American Society of Heating, Refrigerating and Air-Conditioning

Engineers, Methods of Testing for Seasonal Efficiency of Unitary AirConditioners and Heat Pumps, ASHRAE 116-84.

13. Air—Conditioning and Refrigeration Institute, Standard for Unitary AirConditioning Equipment, ARI 210-81.

55
Edd

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56

Standard

Rating

point.

Test B

is

not

conducted

for

water

chillers.

Test D

is

conducted

with

20%

burner

on-time

and

80%

burner

off-time;

the

pumps,

fans,

etc.

should

run

in

accordance

with

their

normal

control

system

as

it

responds

to

the

burner

condition.

A

wet-bulb

temperature

sufficiently

low

so

as

to

result

ina

completely

dry

(non-condensing)

evap-
TABLE 2

SUMMARY OF TESTING REQUIREMENTS FOR DIRECT-FIRED AIR-SOURCE AND

WATER-SOURCE ABSORPTION HEATING SYSTEMS

a) Air-Source Systems

TEST

AIR

TEMPERATURE

ENTERING

EVAPORATOR

°C (°F)

HEAT PUMPS

ENTERING WATER DB/WB TEMPERATURE

TEMPERATURE OF INDOOR RETURN AIR

°C (°F) °C (°F)

A) High-Temperature

(Steady-State)

T

nR 8.3 (47)

C 6 - 1 (43> 40.6 (105) 21.1 (70) / <15 . 6 (60)

B) Frost Accumulation TnR 1.7 (35)

Tpp -1.1 OO)

40.6 (105) 21.1 ( 70) / <15 . 6 (60)

C*) Low Temperature

(Steady-State)

T -8.3 (17)

T“ '9 ' 4 (15)

40.6 (105) 21.1 (70) /<15 .6 (60)

D**) Cyclic T 8.3 (47)

TW < 43>

40.6 (105) 21.1 (70) / <15 . 6 (60)

b) Water-Source Systems

TEST

EVAPORATOR INLET

GROUND WATER

e C (*F)

HEAT PUMPS

ENTERING WATER DB/WB TEMPERATURE

TEMPERATURE OF INDOOR RETURN AIR

°C (°F) °C ( °F)

A) High Temperature

(Steady-State)

B) Frost Accumulation

21.1 (70) 40.6 (105) 21.1 ( 70) /< 15. 6 (60)

C*) Low Temperature

(Steady-State)

15.6 (60) 40.6 (105) 21.1 ( 70) /<15 . 6 (60)

D**) Cyclic 21.1 (70) 40.6 (105) 21.1 ( 70) /<15 .6 (60)

* Standard Rating Point

** Test D is conducted with 20% burner on-time and 80% burner off-tinx .

", . entire length of the cycle is determined by the thermostat charnel « ri i supplied by the manufacturer; all pumps, fans, etc. should run in .-<< < with their normal control system as it responds to the burner coiuiit ; :

57
TABLE 3

RATING SHEET FOR DIRECT-FIRED ABSORPTION COOLING SYSTEMS

FUEL : GAS OIL OTHER

FUEL HIGHER HEATING VALUE : Btu/lbm or Btu/Ft 3

FUEL COST : $/kBtu COST OF ELECTRICAL POWER : $/kWh

DESIGN : Single-Effect Q Double Effect

COOLING LOAD HOURS

THERMOSTAT ON-OFF TIME:

TYPE: Q] Water Chiller Air Conditioner

Ground Water Sink Ground Water

Cooling Tower Sink Cooling Tower (or water

sprayed on outdoor

Outdoor Air Sink « coil)

Outdoor Air

REFRIGERANT/ABSORBENT

PERFORMANCE PARAMETER

TEST

A B** C D

COOLING CAPACITY kW (kBtu/hr)

COEFFICIENT OF PERFORMANCE

FUEL FLOWRATE kg/hr (lbm/hr or CFM)*

POWER CONSUMPTION (kWh)

EVAPORATOR (Chilled Fluid) FLOWRATE kg/hr (lbm/hr or CFM)*

CONDENSER UNIT FLOWRATE kg/hr (lbm/hr or CFM)

SEASONAL PERFORMANCE FACTOR SEASONAL OPERATING COST $

*Flowrates determined at rating conditions.

**Test is not provided for water chillers.

58
TABLE 4

FRACTIONAL TEMPERATURE BIN HOURS FOR COOLING SEASON CALCULATION

Bin No. , j

1

2

3

4

5

6

7

8

Bin Temperature,

T , °F

67

72

77

82

87

92

97

102

Fraction of Total

Temperature Bin Hours

iu/N

0.214

0.231

0.216

0.161

0.104

0.052

0.018

0.004

Cooling Load Hours, CLH - 3825

Outdoor Design Cooling Temperature - 35°C (95 °F)

Ground Water Temperature - 15.6°C (60°F)

59
T*Tt*

tdtptitt

nM

np

ACTUAL

COOLING

LOAD

HOURS^JCUQjg^

60
TABLE 6

RATING SHEET FOR DIRECT-FIRED ABSORPTION HEATING SYSTEMS

FUEL : | | Gas Oil Q] Other

FUEL HIGHER HEATING VALUE : Btu/lbm or Btu/ft 3

FUEL COST : $/kBtu COST OF ELECTRICAL POWER : $/kWh

DESIGN : [ | Single Effect Double Effect

MAJOR CLIMATIC REGION (USA) : (See Table 7, 8)

THERMOSTAT ON-OFF TIME:

REFRIGERANT/ABSORBENT

TYPE: Q Hot Air Heat

Ground Water Source

Outdoor Air Source

Hot Water Heat

Ground Water Source

Outdoor Air Source

PERFORMANCE PARAMETER

TEST

A B** C D

HEATING CAPACITY kW (kBtu/hr)

COEFFICIENT OF PERFORMANCE

FUEL FLOWRATE kg/hr (lbm/hr or CFM)*

POWER CONSUMPTION (kWh)

EVAPORATOR (Source Fluid) FLOWRATE kg/hr (lbm/hr or CFM)*

CONDENSER UNIT FLOWRATE kg/hr (lbm/hr or CFM)

SEASONAL PERFORMANCE FACTOR SEASONAL OPERATING COST $

*Flowrates determined at rating conditions.

**Test B is not for water source.

61
TABLE 7

MAJOR CLIMATIC REGIONS IN THE CONTINENTAL USA

REGION I II III IV V VI

HEATING LOAD HOURS , HLH ' 750 1250 1750 2250 2750 2750*

OUTDOOR DESIGN TEMPERATURE,

Tu FOR THE REGION, °F

H

37 27 17 5 -10 30

FRACTIONAL HOURS

n

j

/N

Bin // Bin Temp .

j = 1 T^ (°F) = 62 .291 .215 .153 .132 .106 .113

2 57 .239 .189 .142 .111 .092 .206

3 52 .194 .163 .138 .103 .086 .215

4 47 .129 .143 .137 .093 .076 .204

5 42 .081 .112 .135 .100 .078 .141

6 37 .041 .088 .118 .109 .087 .076

7 32 .019 .056 .092 .126 .102 .034

8 27 .005 .024 .047 .087 .094 .008

9 22 .001 .008 .021 .055 .074 .003

10 17 0 .002 .009 .036 .055 0

11 12 0 0 .005 .026 .047 0

12 7 0 0 .002 .013 .038 0

13 2 0 0 J001 .006 .029 0

14 -3 0 0 0 .002 .018 0

15 -8 0 0 0 .001 .010 0

16 -13 0 0 0 0 .005 0

17 -18 0 0 0 0 .002 0

18 -23 0 0 0 0 .001 0

*In Pacific Coast Region

62
HEATING

LOAD

HOURS

(HLH)

FOR

THE

UNITED

STATES

63
RECOMMENDED

CALCULATION

SHEET

FOR

DETERMINING

SPF

AND

SOC

OF

DIRECT-FIRED

ABSORPTION

SYSTEMS
SAMPLE

CALCULATIONS

FOR

ABSORPTION

COOLING

SYSTEMS

35 ELECTRICITY CONSUMPTION

•n

j/N

(watts)

15 56 91 97 82 51 21 5

418

o FUEL CONSUMPTION

•

n./N

(Btu/hr)

J

952

3629 5882 6292 5328 3312 1374 309 00

r^o

CM

pc_

FUEL

ENERGY

CONSUMPTION

•

n./N

(Btu/hr)

*

J°

1002 3820 6192 6623 5608 3486 1446 325

28502

w

ft ~

hJU C

0.048 0.174 0.310 0.458 0.619 0.795 0.986 1

Q BUILDING

LOAD

•

n./N

(Btu/hr

1)

425

1607 2576 2720 2274 1395 573 147

11717

CJ Vi® .214 .231 .216 .161 .104 .052 .018 .004

05 BIN TEMPERATURE (°F) 67 72 77 82 87 92 97

102

< BIN NUMBER icMm-ain\or--ao w

lD

cn

<-1 o

coll cjO

CO

o

t-.

CMom

oo

CM

ft. ClCO

in

r-. o

inO

o

o

l

00ino

l

ii Q

CJ

inO

O'O

II

>ao

-am

<ro

HU.J

Cl,

65

CLH

-

3825

Hours

C

c

=

0.005

$/kBtu

C

=

0.006

$/kWh
TABLE 11

SAMPLE CALCULATIONS FOR ABSORPTION HEATING SYSTEMS

A B C D E F G H

BIN

NUMBER

BIN

TEMPERATURE

(°F)

n.*

_JL

N

BUILDING

LOAD

• n./N

(Btu?hr)

HLF

( V

FUEL ENERGY

CONSUMPTION

* n./N

(Btu/hr)

FUEL

CONSUMPTION

• n./N

(Btu?hr)

ELECTRICITY

CONSUMPTION

• n^/N

(watts)

1 62 .106 130.4 .022 274.9 237.1 2.9

2 57 .092 301.7 .059 559.5 537.1 616

3 52 .086 458.3 .099 852.9 818.8 10.0

4 47 .076 560.8 .140 1306.1 994.7 12.1

5 42 .078 735.5 .182 1343.8 1290.1 15.8

6 37 .087 998.7 .227 1815.3 1742.7 21.3

7 32 .102 1380.0 .273 2485.9 2386.5 29.1

8 27 .094 1464.4 .322 2621.7 2516.8 30.7

9 22 .074 1304.5 .373 2319.0 • 2226.2 27.2

10 17 .055 1082.3 .427 1912.3 1835.8 22.4

11 12 .047 1021.3 .484 1794.0 1722.2 21.0

12 7 .038 903.6 .543 1575.9 1512.9 18.5

13 2 .029 749.0 .605 1296.9 1245.0 15.2

14 -2 .018 501.9 .672 864.2 829.6 10.1

15 -7 .010 299.3 .741 511.7 491.2 6.0

16 -13 .005 159.9 1 306.8 294.5 3.6

17 -18 .002 68.1 1 122.7 117.8 1.4

18 -23 .001 36.1 1 61.4 58.9 0.7

I 12155.9 21727.1 20857.0 254.6

*Fractional Bin Hours

PLF

0.73

1.16

0.63

1 - 0.63

1 - 0.14

0.43 SPF = 21727

*

' l = 0,56 S0C = $328 * 81

C =

e 0.06 $/kWh HLH = 2750

C

f = 0.005 $/kBtu
NBS-114A IREV. 2-BO) U S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

REPORT NO.

April 1984 SHEET (See instructions) NBSIR 84-2867

4. TITLE AND SUBTITLE

lest Procedures for Rating Residential Heating and Cooling Absorption Equipment

5. AUTHOR(S)

Brian Weber, Reinhard Radermacher, David Didion

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8 . Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

U.S. Department of Energy

Oak Ridge National Laboratory

Washington, D.C. 20585

10. SUPPLEMENTARY NOTES

QJ Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a si gn i fi cant bibliography or literature survey, mention it here)

Test and rating procedures are presented for gas-fired absorption devices

operating in either the heating or cooling modes . These procedures are designed to include the effects of part-load and cyclic operation,

variations in outdoor temperature, and frost formation during the heating

mode. Both air-source and ground water source absorption heat pumps are considered, as well as air cooled and ground water cooled air-conditioners

and water chillers. A calculation procedure is presented for estimating

the heating and cooling seasonal performance and cost of operation of

residential water chillers, air-conditioners, and heat pump units.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key • • . central air-conditioners; central heating equipment; cooling season.il : r; ; heat pumps; heating seasonal performance; rating procedure; seasonal cast

operation; test method

13. AVAILABILITY

IX I Unlimited

| | For Official Distribution. Do Not Release to NTIS

I Order From Superintendent of Documents, U.S. Government Printing Office. Washington. D.C. 20402.

[j2j| Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGE

78

15. Pn