SERI/TR-252-2774

UC Category: 59a

DE86010724

Heat and Mass Transfer Analysis

of a Desiccant Dehumidifier

Matrix

A. A. Pesaran

July 1986

Prepared under Task No. 3009.10

FTP No. 467-84

Solar Energy Research Institute

A Division of Midwest Research Institute

1617 Cole Boulevard

Golden, Colorado 80401

Prepared for the

U.S. Department of Energy

Contract No . DE-AC02-83CH10093
NOTICE

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Announcements and Index (GRA and I); Scientific and Technical Abstract Reports (STAR); and publication,

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PIlEFAe!

In keeping Y1i th the nat ional energy pol icy goal of fostering an adequate

supply of energy at a reasonable cost, the United States Department of Energy

(DOE) supports a variety of programs to promote a balanced and mixed energy

resource system. The mission of the DOE Solar Buildings Research and

Development Program is to support this goal by providing for the development

of solar technology alternatives for the buildings sector. It is the goal of

the program to establish a proven technology base to allow industry to develop

solar products and designs for buildings that are economically competitive and

can contribute significantly to the nation's building energy supplies. Toward

this end, the program sponsors research activities related to increasing the

efficiency, reducing the cost, and improving the long-term durability of

passive and active solar systems for building water and space heating,

cooling, and day1ighting applications. These activities are conducted in four

major areas: Advanced Passive Solar Materials Research, Collector Technology

Research, Cooling Systems Research, and Systems Analysis and Applications

Research.

Advanced Passive Solar Materials Research - This activity area includes work

on new aperture materials for controlling solar heat gains, and for enhancing

the use of daylight for building interior lighting purposes. It also

encompasses work on low-cost thermal storage materials that have high thermal

storage capacity and can be integrated with conventional building elements,

and work on materials and methods to transport thermal energy efficiently

between any bui 1ding exterior surface and the bui 1ding interior by

nonmechanical means.

Collector Technology Research This activity area encompasses work on

advanced low- to medium-temperature (up to 180°F useful operating temperature)

flat-plate collectors for water and space heating applications, and medium- to

high-temperature (up to 400°F useful operating temperature) evacuated

tube/concentrating collectors for space heating and cooling applications. The

focus is on design innovations using new materials and fabrication techniques.

Cool ing Sys tems Research - Thi s ac t i vi ty area involves research on highperformance dehumidifiers and chillers that can operate efficiently with the

variable thermal outputs and delivery temperatures associated with solar

collectors. It also includes work on advanced passive cooling techniques.

Systems Analysis and Applications Research - This activity area encompasses

experimental testing, analysis, and evaluation of solar heating, cooling, and

daylighting systems for residential and nonresidential buildings. This

involves system integration studies, the development of design and analysis

tools, and the establishment of overall cost, performance, and durability

targets for various technology or system options.

This report is an account of research conducted in cooling system research to

improve the performance of solid desiccant dehumidifiers by investigating the

iii
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experimental and theoretical performance of innovative geometries. Characterization of dehumidifier geometries is an important step toward achieving a

high-performance dehumidifier for solar desiccant cooling systems.

This report documents the efforts of design, fabrication, and instrumentation

of the SERl Single-Blow Test Facility and also the design and fabrication of a

highly uniform silica-gel parallel-plate test dehumidifier. Transient experiments were performed, and the results were compared with available heat and

mass transfer models. This research was performed at the Solar Energy

Research Institute (SERI) in FY 1984 and the early part of FY 1985 under task

3009.10 of the Thermal Sciences Research Branch for the Solar Desiccant

Cooling Program.

The author would like to acknowledge the contribution of James Dolan, master

technician, for assisting in the design and fabrication of the test facility

and the test dehumidifier, Sung-Ho Jo, laboratory technician, for instrumentation of the facility, and Terry Penney for his guidance during the course of

this work. Review comments by Kenneth Schultz and Eric Van den Bulck,

University of Wisconsin; Ian Maclaine-cross, University of New South Wales,

Australia; and Frank Kreith, SERI, are appreciated.

ff.,4.f'~ Ahmad A. Pesaran

Approved for

SOLAR ENERGY RESEARCH INSTITUTE

Branch

L. J.

Solar

hannon, Director

eat Research Division

1'1
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SUMMARY

Objectives

The objective of this work is to design, fabricate, and test a single-blow

test facility to obtain transient experimental data on solid desiccant

dehumidifiers with different geometry/material combinations.

Discussion

The SERI single-blow test facility was designed, fabricated, and tested (mass

airflow rate = SO-120 scfm, temperature = 2So-90oC, and humidity ratio =

0.00S-0.03 kg/kg). A silica-gel parallel-plate dehumidifier with highly

uniform passages was designed and fabricated as the first test article. The

facility operates under typical conditions that are encountered in operation

of solar desiccant cooling systems (e.g., temperatures of 3So-90 0 C and

humidity ratios of 0.012-0.025 kg/kg). A limited number of single-blow

experiments were performed, and transient heat and mass transfer data, as well

as pressure drop data across the dehumidifier, were obtained. A single-blow

test was performed by passing a process airstream through a desiccant

dehumidifier to characterize the dehumidifier's transient heat and mass

transfer performance. This is part of the Solar Energy Research Institute's

(SERI) efforts to characterize the performance of promising solar-energyregenerated dehumidifiers and validate heat and mass transfer models for

design purposes. Available heat and mass transfer models originally used for

packed beds were extended to the parallel-plate geometry, and the experimental

data were compared with model predictions. Pressure drop measurements were

also compared with model predict ions of the fully developed laminar flow

theory.

Conclusions and Recommendations

The comparisons between the predictions of the "lumped-capacitance" model and

the experimental data were generally satisfactory, within 10% for adsorption

and 30% for desorption cases. The agreements were better for adsorption cases

than desorption ones as reported by other investigators. The measured

pressure drops across the parallel-plate dehumidifier were within 15% of the

predicted pressure drops, which is reasonable.

This lumped-capacitance model can be used by researchers and industry to

reasonably predict the transient performance of a desiccant dehumidifier,

which can provide design information. The single-blow test facility can

provide data on dehumidifiers with different geometry/material combinations.

These data can be used to validate and improve the models that predict

dehumidifier performance, which can later be used in designing

dehumidifiers. Industry can also use these data to compare different

dehumidifiers and select one to suit a particular need.

A "solid-side resistance" model that does not assume symmetrical diffusion in

the particles and that is more sophisticated than the "lumped-capacitance"

model was recommended for more accurately predicting dehumidifier

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performance. More comprehensive experimental data on the silica-gel parallelplate dehumidifier and other promising geometries (e.g., staggered parallel

strip) and desiccants need to be obtained, which will result in the evaluation

of their potential as advanced geometry/material combinations for desiccant

dehumidifiers. The method of moments is recommended to estimate the heat and

mass transfer coefficients from the transient heat and mass transfer data.

vi
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TABLE OF CONTENTS

Nomenclature. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • ix

1.0 Introduction •••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1

1.1

1.2

Background •••••••••••••••••••••••••••••••••••••••••••••••••••••

Purpose of this Work•••••••••••••••••••••••••••••••••••••••••••

1

4

2.0 Description of the Single-Blow Test Facility••• ..................... 5

2.1

2.2

Configuration ••••••••••••••••••••••••••••••••••••••••••••••••••

Instrumentation and Control ••••••••••••••••••••••••••••••••••••

5

9

3.0 Description of Parallel-Plate Test Article ••••••••••••••••• 14

4.0 Experimental·Procedure •••••••••••••••••••••••••••••••••••••••••••••• 19

4.1

4.2

Preparation of the Test Article ••••••••••••••••••••••••••••••••

Process (Adsorption/Desorption) •••••••••••••••••••••••••••••••• 19

19

5.0 Heat and Mass Transfer Models ••••••••••••••• ........................ 21

.........................

......................... 5.15.2

5.3

Governing Equations ••••••••••••••••••

Auxiliary Equations •••••••••••••••••••

Pressure Drop Analysis ••••••••••••••••

21

23

25

6.0 Results and Discussion •••••••••••••••••••••••••••••••••••••••••••••• 27

Conclusions and Future Work •••••••••••••••••••••••••••••••••••••••••

Appendix A Listing of Programs •••••••••

.................................................. 38

35

33

................................. References ••••••••

7.0

8.0

Selected Distribution List••••••••••••••••••••••••••••••••••••••••••••••• 50

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LIST OF FIGURES

1-1 The Ventilation Cycle Desiccant Cooling System...................... 2

2-1a System Adsorption Stream Capabilities............................... 6

2-1b System Regeneration Stream Capabilities............................. 7

2-2 Single-Blow Test Facility........................................... 8

2-3 Test Section and Measuring Instruments of the Single-Blow

Test Facility....................................................... 10

2-4 Measurement Locations of the Test Facility•••••••••••••••••••••••••• 10

2-5 A Thermocouple Junction............................................. 11

2-6 Air Sampler, Thermocouple Array, and Test Article

in the Test Section ••••••••••••••••••••••••••••••••••••••••••••••••• 12

3-1 A Silica-Gel-Coated Polyester Tape with Attached Spacers •••••••••••• 15

3-2 Parallel-Plate Test Article ••••••••••••••••••••••••••••••••••••••••• 15

3-3 Supporting Frame of the Parallel-Plate Test Article ••••••••••••••••• 16

3-4 Finished Parallel-Plate Dehumidifier Test Article ••••••••••••••••••• 16

3-5 Cross-Sectional View of the Parallel-Plate Test Article ••••••••••••• 17

6-1 Comparison of Experimental and Predicted Results for Exp. 1 •••••••••

6-2 Comparison of Experimental and Predicted Results for Exp. 3 •••••••••

6-3 Comparison of Experimental and Predicted Results for Exp. 4 •••••••••

6-4 Comparison of Experimental and Predicted Results for Exp. 5 •••••••••

6-5 Friction Factor versus Reynolds Number--Measured and Predicted ••••••

6-6 Measured vs. Predicted Pressure Drop •.•••••••••••••••••••••••.••••••

28

28

29

29

31

32

viii
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LIST OF TABLES

Page

3-1 Specification of the Parallel-Plate Test Article Dehumidifier•••••••• 18

6-1 Experimental Parameters•••••••••••••••••••••••••••••••••••••••••••••• 27

6-2 Pressure Drop Results •••••••••••••••••••••••••••••••••••••••••••••••• 32

ix
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a

A

B

c

OAR

dh

d p

f

g

h

c

Hads

k

K

Le

Leef f

ml

me

Mo

Nt u

Nu

P

P

Pr

r

R

Re

NOMENCLATURE

surface area per volume (l!m)

frontal area (m2)

width of dehumidifier (m)

specific heat (J!kg K)

specific heat of humid air (J!kg K)

effective diffusivity (m2! s )

Ot/R2 (dimensionless)

desiccant to air ratio, PbAL/mCL (dimensionless)

hydraulic diameter (m)

particle diameter em)

Fanning friction factor

equilibrium isotherm function

convective heat transfer coefficient (W/m2 K)

heat of adsorption (J!kg water)

thermal conductivity of humid air (W!m K)

pressure drop coefficient for entrance effect inside passages

(dimensionless)

gas-side mass transfer coefficient (kg!m2s)

overall mass transfer coefficient (kg!m2s)

length of the dehumidifier (m)

Lewis number, Sc/Pr (dimensionless)

effective Lewis number, hc!Kc,effcp,e (dimensionless)

water-vapor mass fraction (kg water/kg humid air)

mass flow rate of humid air (kg!s)

dry mass of desiccant per unit area of tape (kg!m2 )

number of transfer units, KCpL!mG (dimensionless)

Nusselt number, hcdh!k (dimensionless)

pressure (Pa)

perimeter (m)

Prandtl number (dimensionless)

radial coordinate in a particle (m)

r/R (dimensionless)

particle radius (m)

Reynolds number, Vdh/v (dimensionless)

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RH relative humidity ratio, Pvapor/Psat (dimensionless)

t real time (s)

t* t/~ (dimensionless)

T temperature (oC)

TDR ratio of tape mass to dry desiccant mass (dimensionless)

Sc Schmidt number (dimensionless)

St h heat transfer Stanton number, hc/cp,ePV (dimensionless)

St m overall mass transfer Stanton number, KG,eff/pV (dimensionless)

V air velocity in a channel (m/s)

Vsup superficial air velocity (m/s)

w absolute humidity ratio (kg water/kg dry air)

W desiccant water content (kg water/kg dry desiccant)

Xgap air gap (m)

Xsh sheet thickness em)

Xsp center-to-center spacing (m)

y distance perpendicular to direction of flow from the solid

surface (m)

y* y/dp

z axial distance (m)

z* zit (dimensionless)

Greek symbols

a KG/KG,eff

a ppD/KGR (dimensionless)"

Y1 cp,l/cp,e (dimensionless)

Yb cb/cp,e (dimensionless)

~p pressure drop CPa)

E bed porosity (dimensionless)

kinematic viscosity (m2/s)

P density; humid air density (kg/m3)

duration of an experiment (s)

xi
Subscripts

1 water

avg average value

b bed

B bypass value

dp dew point temperature

e external condition

eff effective value

exp measured or experimental value

in inlet value

o initial value

out outlet value

p particle

pre predicted value

s s-surface, in gas phase adjacent to desiccant particles

sat saturation

t total

xii

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1.0 INTRODUCTION

1.1 Background

Open-cycle solid desiccant cooling is one of the promising methods of solar

cooling. Solar desiccant cooling coupled with evaporative cooling has

received considerable attention in the last several years as a mechanically

simple solar-fired option to conventional vapor compression air-conditioning

systems. The desiccant cooling system involves passing process air (which is

warm and humid) through a desiccant bed for drying, and subsequent evaporative

cooling to provide conditioned air. The desiccant is regenerated with hot air

provided by solar collectors. A typical desiccant cooling system (as seen in

Figure 1-1) consists of two evaporative coolers, a regenerative heat

exchanger, a solar heater, and a desiccant dehumidifier [1]. Several studies

have indicated that desiccant cooling systems can be competitive with vapor

compression air-conditioning if thermal coefficients of performance (COPs)

greater than 1.2 can be obtained [2,3,4]. The thermal performance of the

system depends on the efficiencies of each component. Efficient and low-cost

components should be used so that these systems can be economically viable.

The state of technology in solid desiccant dehumidifiers for air conditioning

applications is relatively new compared with other components. Development of

desiccant dehumidifiers with high-performance, low-pressure drop, and low cost

is a crucial step in making the desiccant cooling systems competitive with

vapor compression systems. The efficiency of a desiccant dehumidifier, fOI'

the most part, depends on the type of desiccant used and the geometry of the

dehumidifier.

The most common solid desiccant material proposed for solar desiccant cooling

application is silica gel [4,5,6] due to its high moisture recycling capacity

compared with other industrial desiccants. Jurinak [4] characterized the

material properties that influence the performance of dehumidifiers. These

interrelating properties are maximum water capacity, isothermal shape, heat of

adsorption, hysteresis upon thermal cycling, moisture diffusivity, and thermal

capacitance. Jurinak concluded that among those commercially available,

microporous silica gel is an attractive material for dehumidifier construction

and can result in relatively good dehumidifier performance. However, to

improve the thermal performance and r e l, i ab i lity while reducing the cost of

dehumidifiers, desiccant materials with improved properties over silica gel

are needed. Polymers with the required des iccant properties can be used to

fabricate cost-effective dehumidifiers. SERI has begun to characterize and

evaluate polymers for their potential as advanced desiccants. The Gas

Research Institute is involved in identifying and eventually developing

desiccants that can improve the performance of gas-fired desiccant cooling

systems.

The configurations that researchers have used for desiccant dehumidifier

research are packed bed [1,5,6], Illinois Institute of Technology (lIT) Teflon

fiber plates [7], Institute of Gas Technology (IGT) corrugated structure [8],

and coated parallel plate [9,10,11]. Tradi t ionally, long, packed beds have

been used in commercial and industrial applications where parasitic power

losses are not a major concern. However, in air-conditioning applications

1
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2 3 4

Outside Evap. Supply

air Rotary Rotary cooler air to

desiccant heat residence

bed exchanger Solar Evap. Exhaust Return

air heater cooler

9 8 air from 7 6 5

Backup heat residence

(e.g., gas)

10

, ...-----"""""'=::::--------l~---~8

40 70

Dry bulb temperature (0 C)

0.03

0.02

"0

E

::J

I

0.01

Figure 1-1. The Ventilation Cycle Desiccant Cooling System

there is a need to have low parasitic power losses. This resulted in the use

of thin packed beds with large cross-sectional areas [6,12], which make the

dehumidifier large and undesirable.

The dynamic performance of packed beds was investigated theoretically and

experimentally [1,5,6,13,14]. The ratio of heat transfer Stanton number to

friction factor (Sth/f) for packed beds is about 0.06 (Re = 50), while the

ratio of overall mass transfer Stanton number to friction factor (St~/f) of

packed beds is even lower (about 0.02) due to large diffusional s ol.Ld-is i.de

resistance of moisture transfer in the particles [15]. The ratios of Stanton

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numbers to friction factor (Sth/f and Stm/f), or the ratios of heat or mass

transfer coeffieient to pressure drop, are measures of compactness and

performance of the dehumidifiers. For a given pumping power the geometries

with hi ghe r Sth/f and St If provide high transfer rates and thus are more

efficient. Tnerefore, ~maller dehumidifiers can be used in a cooling

system. Large values of Sth/f and Stmlf are desired for dehumidifier

geometries. IGT [8] made an effort to improve Sth/f by using a corrugated

structure on which particles of a molecular sieve were impregnated. The Sth/f

of fully developed laminar flow with constant heat flux at walls for a

corrugated structure is about 0.32. No data on Stm/f has been reported, but

it can be estimated to be 30% to 60% lower than Sth't.

Researchers at lIT [7], the University of California at Los Angeles (UCLA)

[9,16,17], and the Solar Energy Research Institute (SERI) [10] made efforts to

increase the Sth/f and the Stm/f. The dehumidifier designed in lIT basically

consists of sil1ca gel sheets that form laminar flow channels. The silica gel

sheets were made by bonding silica gel particles (average diameter 9 ~m) with

a fine Teflon web [7]. The Sthlf of the lIT concept is 0.49 under fully

developed laminar flow conditions while its Stm/f is about 0.16 [7,15] due to

diffusional resistance of moisture transfer in the Teflon web.

The UCLA dehumidifier concept [9] consists of parallel plates coated with a

layer of fine silica gel particles (120-250 ~m). Researchers at SERl [10]

combined the UCLA concept with one using a rotary heat exchanger construction

developed by CSIRO in Australia [18]. The SERI dehumidifier has parallel

channels of double-sided polyester tapes with an adhesive on which fine

particles of silica gel are bonded. The Sth./f of laminar flow channels is

0.49, which is higher than the other dehumidifier geometries except for the

lIT concept. It is estimated that the St If of the UCLA and SERl concept is

about 0.41 [10], which is higher than the rIT concept. Since larger Sth/f and

Stmlf would result in more compact and efficient dehumidifiers, the coated

parallel-plate concept appears to have a great potential to provide an

advanced, cost-effective dehumidifier.

Researchers at UCLA [16,17] performed adiabatic single-blow experiments on a

bench-scale parallel-plate test article. Fine grains of silica gel (average

diameter 120 to 250 ~m) were bonded to one side of O.16-mm-thick Lexan@ plastic sheets using a thin layer of silicon rubber adhesive to produce a sandpaper-like surface. The coated sheets were stacked and spacers were used to

form parallel-walled, laminar flow channels. The experimental results using

this test dehumidifier were compared with a lumped-capacitance heat and mass

transfer model. The agreement was generally fair and the discrepancies were

attributed to heat losses and shortcomings of the model.

SERI tested a small-scale prototype parallel-plate dehumidifier [10]. The

prototype was built by coating both sides of a double-sided polyester tape

with fine silica gel particles and then spirally winding the coated tape to

form parallel-walled, laminar flow passages. Single-blow adsorption and

desorption experiments were performed under adiabatic conditions, and the

results were compared with a pseudo steady-state model. The equations for

simple steady-state counterflow heat and mass exchangers were used in the

model for predicting the dehumidifiers' performance. Predictions were in

3
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reasonable agreement with the experimental results for adsorption cases and

were relatively poor for desorption cases. The diffusional resistance in the

silica gel particles was estimated to be 20%-30% of gas-side film resistance

and thus an overall transfer coefficient was used. This may be one of the

reasons for the discrepancies observed between the model predictions and

experimental results.

Heat and mass transfer models that properly account for moisture diffusion

into the desiccant particles of parallel-plate dehumidifiers are required.

These models should be compared with experimental data to further improve the

models. These models can later be used in system analysis and component

design.

1.2 Purpose of this Work

The objective of this work was to obtain transient experimental data on benchscale solid desiccant dehumidifiers under conditions typical of those

encountered in solar desiccant cooling applications by fabricating a singleblow test facility and desiccant dehumidifier test articles. Another

objective of the project was to extend and improve the available heat and mass

transfer model s to silica-gel parallel-plate dehumidifiers by comparing the

experimental results and model predictions. The single-blow test facility can

be used to obtain the performance of different dehumidifier geometries with

different desiccant materials and provide data bases for comparing and

selecting geometries/material combinations. This report describes a singleblow test facility and a silica-gel parallel-plate test article with limited

test results and compares their test results with model predictions. Further

experimental and theoretical efforts were scheduled in FY 1985

(task 3022.210).

4
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2.0 DESCRIPTION OF THE SINGLE-BLOW TEST FACILITY

2.1 Configuration

The single-blow test apparatus was conceived to obtain transient adsorptionl

desorption experiments of a bench-scale dehumidifier. The reason~ble area for

the dehumidifier test section was chosen to be about 0.025 m to have a

reasonably small-scale apparatus, but with small end effects on the dehumidifier. The geometry of the test section was chosen to be square (about 0.16 m

x 0.16 m) for ease of fabricating test dehumidifiers. The design of the test

air velocity in a residential dehumidifier wheel was estimated to be about

1.2 m/s. Using this design ve1ocit3

, the design air flow rate in the dehumidifier test section was then 0.03 m Is (about 0.03 kg/s or 63 scfm). A beltdriven centrifugal blower from a previous desiccant test loop [19] was available that could produce ~his flow rate. The maximum flow rate that this fan

could produce was 0.045 m Is (about 0.045 kg/s or 100 scfm). The other design

parameters at the design flow rate were

Range of inlet adsorption temperature

Range of inlet desorption temperature

Range of inlet humidity ratio

Ambient* to 400C

600 to 90°C

Ambient* to 0.03 kg/kg

*temperature 20°-25°C; humidity 0.005 to 0.012 kg/kg

These air conditions cover the range of temperature and humidity that would be

encountered in both recirculation and ventilation modes of operation for solar

desiccant cooling systems, as shown in Figure 2-1.

To minimize duct requirements, the test rig was designed to use ambient air in

the laboratory space. We found that in the winter, room air ordinarily is low

in both dry-bulb temperature and moisture content and this permitted dehumidifier testing over the range of desired conditions. However, in the summer,

the humidi ty level is high due to the evaporative cooling component of the

building HVAC system, and we may not be able to operate at the desired conditions. In such a case, sufficient ducting supplies outside air, which is

sufficiently low in humidity because of the dry Colorado climate. The exhaust

air after adsorption/desorption tests is discharged to the laboratory space at

this time.

The schematic of the single-blow test apparatus is shown in Figure 2-2. The

setup consists of a duct heater, a humidifier, a multispeed blower, an orifice

plate, the test section, and required instrumentation for measuring temperatures, pressure drops, humidities, and air flow rate. The heater and humidifier are mounted on a square duct cross-section of galvanized iron

[0.2 x 0.2 m (8 x 8 in.), 20 gauge (0.85 rnrn) thick]. A O.lS-m (6-in.)

diameter 20-gauge circular duct was chosen (because it is rigid and leakproof) for connecting the blower to the orifice plate and then to the test

section and finally to the exhaust. A smooth transition section from circular

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80 100

...

...

. ' ...

70

. :: ; ; : :..j.:: I: ,::,~i : : . . . : I :

30

'. Facilitie's capabittttes : .: : : .

... : :. II" • =,,' '. .. : .' .. . .. . .' . ':,..::.~ : : i.. ::... .. Ii·· ":,,, ; I.,:a..•::••..•:.••.:1.: I,: ::..11; ..•.lIt:· ,.., . .. : .: .. ,I .: ,I : .'

: :::..' :: : . . .. ".. . : : -; : :: . .. . ...... . .. ..

.................... .../ .L..:::.::::.::::+>:\,.:::.),::: :::/ ; :,.:: . .Columbia..: : . . .. .. I .1 .. ' , . '. . ..' .' " a-r.-""----""1 '\. MO : :.. .: : ..:.. : :. . .

.:·1.::.·..·..... j:' ...... :1," .... : .. . . .. """ . .. ..-:

.....; ::.':::;.,::;::::::,:~::::.:: ::::!"::::::::"::::'.::i::::,.,:: ::~: :.::'.,: . : •••• : .... ' ••••••••• :.' •• ,e ..

.:"

20 40 50 60

Dry bulb temperature (0C)

Figure 2-1a. Facility Adsorption Stream Capabilities

10

• Approximate average condition

o ASH RAE 2%-5% design point

• ARI outdoor design point : .. .0:11H' .II•••:: ~.;: 10

: .. " :-

. 25

30 .-----------....-.........- ......~-_:__-:__--_:__--~:__::-r_:_-:----......, :;;:

;;;

8

5

20

o

:; 15 ....

>.

.'t::

"'0

E

:::l

I 10

to square was used to connect the circular duct to the square test section.

The test section, which contains the test article, temperature sensors, air

samplers, and pressure tap, has a cross-section of 0.161 m x 173 m and is

0.6 m long. The test section can be opened from two sides for any

modification required. Two walls of the test section, which can be removed,

are made of Lexan® for flow visualization. Major components are connected

using bolted flanges and are supported on stands approximately 0.6 m above the

floor. The bolted flanges give the system the capability of easy access to

the components in case problems arise or modifications are necessary.

The finned tubular duct heater is 4.1 kW (manufactured by Wellman) and needs

208 vol t s and a 3-phase power supply and heats up the process a i r for both

adsorption (up to 400C) and regeneration (up to 900C). Humidification of

process air is accomplished by injecting steam produced by an electric boiler

through a duct humidifier. The 50-kW, 480-volt boiler (manufactured by

Electro-Steam) used for this setup is shared with the SERl Cyclic Test

Facility. The dry steam is injected into the system using a duct humidifier

(model ST-50 manufactured by Walton) at a rate of 0.2 to 3 kg/h. The capacity

6
TR-2774

..

90 100

.. ..

.. · . ·.

....; .

..

. "

· .

.., f."

.i "

.......

f ... ' ..

•• I :.

. ','

I ~.

0' "

.. 0° •

..

.

Of I.·

.:

..

;'

.:

. . : . Facilities capabilities .• : 1 : :1: II •• I ••• t... .. ..: :: II II '" "'~' ••, II.' ':'••• : 'O ~:.of "S' II •• :. I. ': 1 ,.

;.: '!'

• !

30 40 50 60 70 80

Dry bulb temperature (OC)

Facility Regeneration Stream Capabilities

.. ;,'. Required .. ..

reqeneration..conditio~.s '.. '. . . . . '" .. ,/{ / +..:: :.:.,.::;.,:::,«::<>i":::::::":::"':::::::'':::' 'j:::::,.,::: .

Of .. : .0' ,I' ,I' •••• :....... • :.... 0' I': ," .

of 0

0':

. .

..::.. ::.~ ..: :: : ~.:: : ···-!-·····..··:··.. ··..i..·..··· ···(··::..·:·:····;:,!· ..:.: :: +:.: . .. • I, • .. • • I

.. " .' . . . : ; . :'. .' :. • • I' • "

I' .: ,II> • I .. :

I '" • I

. " . . .. ~'

•••: : I : 1:: : : : : . . .. .- ". ..

• ARI indoor

design point

--- Comfort

conditions

Figure 2-1b.

oLww,U1IJ1WJllllJ.(J;

o 10 20

30 ~----------r-~-~-....-""-----------~--" "It

25

20

5

C')

.:%:.

-

.2

-

e 15

>.

:t::

1:)

E

::J

I 10

and the arrangement of the boi l.er is such that the operation of one test

facility does not interfere with the operation of the other one.

The belt-driven air blower (manufactured by NYB) has 0.3-m (12-in.) diameter

straight radial blades and is driven by an externally mounted, 2-speed (1140

and 1725 rpm), 230-V single-phase 994-W electric motor (manufactured by

General Electric). Using a stepPjd-cone pulley system and a duct damper, air

flow rates of 0.0047 to 0.047 m /s (10 to 100 scfm) can be provided. Two

butterfly valves (manufactured by Keystone) and a gate valve (GV) are used to

send air through the test section (BV1 and GV open, BV2 closed) or through the

bypass (BVl and GV closed, BV2 open). These valves are leak-proof when

closed. The gate valve is expected to produce only small disturbances to flow

after entering the test section.

The single-blow test facility is installed in the west high bay (laboratory

158) of SERI1s Field Test Laboratory Building (FTLB). Figure 2-3 is a photograph of the test section of the single-blow test facility.

7

TR-2774

2.2 Instrumentation and Control

Important quantities to measure in the single-blow experiments are inlet and

outlet temperatures and humidities, flow rate, and pressure drop across the

dehumidifier. The temperature and humidity of air going through the bypass

are also measured before introducing air to the test article. Figure 2-4

schematically shows measurement locations in the test facility.

The data acquisition system consists of a HP-9845A desk-top computer with a

HP-3497A scanner/multiplexer/digital voltmeter. Both of these units were

available at SERI. The voltmeter was recently calibrated to the manufacturer's specifications. The accuracy of the voltmeter is less than 0.03% of

the reading with a resolution of 1 ~V.

Temperature measurements are made using gauge 30 (0.25-mm-diameter) copperconstantan (type T) thermocouples. Average inlet and outlet temperatures are

obtained by an array of four thermocouples connected in series. The arrays

are located in the duct to obtain an area weighted average. The electromotive

force (emf) produced in this manner is four times the emf of a single

thermocouple and thus the error in reading voltages by the voltmeter is

reduced by a factor of four.

Each thermocouple junction is designed [10,18] with sufficient bare wire (see

Figure 2-5) to reduce conduction and radiation errors. The actual temperature

measuring point of the sensor is not at the junction but at the copper side.

For this study it is about 5 mm on the copper side. The accuracy of the

temperature measurement depends on the air velocity. The length of bare

copper wire is about three times longer than bare constantan, since its

conductivity is higher. The emmisivity of bare wires is very low when clean

(0.03). With thin wires and air flow perpendicular to the wire, high

convective heat transfer rates are obtained. The conduction error is estimated

to be less than O.Oloe, with a radiation error of less than 0.2oC at an air

velocity of 0.8 m/s. The thermocouples are connected to an isothermal box.

The emf generated because of temperature difference between junctions and the

isothermal box is measured by the voltmeter of the HP-3497A through a voltage

card. An ice bath provides a reference emf so that absolute values of temperatures can be measured. The use of an ice bath, instead of a voltagecompensated ice junction, reduces the error of reference junction to

±O.Oloe. The emf of the thermocouple junction at the measuring location relative to the ice box can be used to obtain the temperature of the junction. To

convert this emf to temperature, a third-order regression fit, based on the

voltage-temperature calibration data obtained at SERI, was used with an error

of ±0.04oe over the range of 00 to lOOoe. Assuming the above errors combine

randomly, the uncertainty in temperature measurement is expected to be less

than a.30 e .

When the process air flows through the bypass, the temperature of the air is

monitored by a single thermocouple junction (Ta) . This thermocouple is also

used for controlling the heat input by the heater and thus controlling the dry

bulb temperature. This thermocouple is connected to a temperature proportional controller (manufactured by Omega Engineering). The controller

9

TR-2774

Junction

I. 20 mm --I

.. +10 mm

°t Wire

diameter

;:; 0.254 mm

40 mm

Bare

copper --.

Bare constantan

Insulated

constantan

measures the difference between the

process air temperature and the setpoint temperature and sends a signal

to the heater to be turned on or

off. The amount of heat required is

determined by the rate of on and off

cycles. The set-point temperature

can be approached within ±0.30C with

an oscillation period of up to about

three minutes. It was found that the

temperature control is quite

acceptable for the purpose of this

work.

Double insulated

thermocouple

A Thermocouple Junction

Insulated copper /

Figure 2-5.

Humidity measurements are made using

optical condensation dew-point hygrometers (manufactured by General

Eastern, Model llOODP/llllD). The

uncertainty of the sensors in

measuring dew point temperature is

±O .40 C. Two dew-point hygrometers

were purchased for this test

facility. The average bypass and

inlet dew-point temperatures were

measured by a single dew point sensor

using a three-way switching valve.

The average outlet dew point temperature was measured using the second

hygrometer. To ensure a representative air sample from the duct, the air for

each hygrometer was drawn by a small pump from 1/4-in. air samplers with eight

holes 0.8 mm in diameter. For the bypass the air sampler had four holes. The

air samplers were arranged across the duct perpendicular to air flow so that

air was sampled from the core of the air flow. See Figure 2-6 for a close-up

of the air sampler aud the thermocouple array.

Conversion of dew point temperature to humidity ratio was accomplished by the

relation

where

w = (2-1)

w = humidity ratio

Tdp = dew point temperature

Pt = total absolute pressure

Psa t = saturation pressure.

A correlation for saturation pressure as a function of temperature suggested

by Maclaine-cross [20] was used that has an uncertainty of less than ±O.l%.

The total uncertainty in calculating humidity ratio is estimated to be less

than 3% [11].

11
TR-2774

•

Figure 2-6. Air Sampler, Thermocouple Array, and Test Article in the

Test Section. The thermocouple array is mounted on the

air sampler.

The humidity of the process air was controlled by controlling the steam flow

rate using an electronically operated value in the steam supply line. Electrical signals, based on comparing a set-point relative humidity and the output of a resistance-type relative humidity sensor in the duct, controlled the

opening of the valve. The fluctuation in dew point temperature of the process

air in some of the tests was ±20C, which is unsatisfactory. The efforts in an

FY 1985 project were successful in resolving this problem. The results from

this project will be reported in a forthcoming report [21].

Flow rates were determined by measuring the pressure differences across ASHE

standard orifice plates. Three aluminum orifice plates with diameter ratios

(orifice diameter/duct diameter> of 0.2, 0.3, and 0.4 were made to cover the

range of flow rates (0.004-0.047 kg/s>. Ten diameters of straight duct

upstream and six diameters of straight duct downstream of the orifice plate

were installed to conform to ASME standards. A one diameter and a half

diameter pressure tap (10 and 1/20) were used for pressure drop measurements

across the orifice plate. The maximum uncertainty in mass flow rate measure~

ment is about ±2% [11].

The pressure drop across the orifice plates and across the test dehumidifier

were measured using capac i tance-type pressure sensors (manufactured by MKS

Instruments, Baratron type 2210) with a range of 0 to 10 mm Hg. The

uncertainty in pressure drop measurements is expected to be less than ±2.5% of

the reading. The pressure transducers w~re calibrated with a Owyer micrometer

12
TR-2774

with an accuracy of fO.OOOS rom Hg. The ambient absolute pressure was obtained

using a capacitance-type sensor (MKS Instruments, Baratron type 220A) with an

uncertainty of less than 1.7%.

A data acquisition program called OAP, written in BASIC, monitored the experiments and also collected the data. Appendix A lists OAP. The output voltages

from the measuring instruments are stored on a cartridge at an interval that

can be changed during the experiments. These voltages can be analyzed with

another program called PLOT that plots the experimental data in meaningful

parameters, i.e., temperatures and humidities as a function of time.

Appendix A also lists PLOT.

13
TR-2774

3.0 DESCRIPTION OF THE PARALLEL-PLATE TEST ARTICLE

The test section in the Single-Blow Test Facility was designed to facilitate

mounting various dehumidifier geometries with different desiccant materials.

This design allows testing of promising geometry/material combinations. By

measuring the performance of the geometry/material combinations one can

identify their potential. In addition, small-scale test articles can be fabricated and tested in the Single-Blow Test Fa~ility for less money compared

with testing a larger dehumidifier wheel in the Cyclic Test Facility.

The first test article we investigated in the Single-Blow Test Facility for

this study had a parallel-plate geometry. This test article simulates the

silica-gel parallel-plate dehumidifier wheel that is under testing in the SERI

Cyclic Test Facility. The single-blow test results provides supplemental

information (such as nature and magnitude of solid-side resistance) for performance analysis of the rotary dehumidifier wheel. The single-blow results

also provides data for comparison with, and validation of, detailed heat and

mass transfer models. The silica-gel parallel-plate dehumidifier wheel tested

in the SERl Cyclic Test Facility [22] had a manufacturing problem--the

passages were not uniform due to sagging of the silica-gel-coated polyester

film. In the design and fabrication of the bench-scale parallel-plate test

article, we succeeded in preventing the problem of sagging and nonuniformity~

The test article consists of a supporting frame, silica-gel-coated polyester

tapes, and spacers.

The spacers of the test unit are made of O.794-mm (l/32-in.) thick preclslon

punched aluminum shims. The spacers are 25.4 mm (1 Ln , ) wide and 0.20 m

(8 i.n , ) long with three holes of 12.7 mm (1/2 in.). The rods of the supporting frame go through these holes for keeping the spacers in place.

Figure 3-1 is a photograph of the spacers along with a silica-gel-coated polyester tape. Figure 3-2 is a schematic of the parallel-plate test article. A

double-sided polyester tape with acrylic adhesive is coated on both sides with

fine particles of silica gel 177 to 297 ~m (mesh size 50 to 80) after they are

attached to two spacers on each side. Figure 3-2 schematically shows this

arrangement. The tape (film and adhesive) is 76-~m (3-mil) thick, 0.167-m

(6.S7-in.) wide, and 0.203-m (8-in.) long. However, only 0.117 m (4.57 in.)

of the width is covered with silica gel. The rest of the width is covered

with the spacers from both ends; i.e., each tape is sandwiched between two

spacers at each end.

The sheets (i.e., the silica-gel-coated polyester tapes with four spacers,

Figure 3-1) are then stacked in the supporting frame. The supporting frame,

as seen in Figure 3-3, is made of aluminum. The solid rods, which have a

diameter of 12.7 mm (1/2 in.), were designed to have sufficient strength from

bowing and bending caused by tension from the sheets. The supporting frame

can be opened from both ends by unscrewing six screws and taking off the

lids. The lids are 19 mm (3/4 in.) thick, 0.167 m (6.57 I n , ) wide, and

0.203 m (8 in.) long. The lids are cut in half and two sliding pins keep them

together. Two back-off screws on one side of a half are provided to pull the

two halves apart. This mechanism prevents the sheets from sagging.

14



TR-2774

Table 3-1. Specification of the Parallel-Plate Test Article

Dehumidifier

Desiccant type

Particle size (d p)

Particle density (pp)

Specific heat of silica gel (cgel)

Tape type

Specific heat of tape (c t ape)

Tape thickness

Adhesive thickness (each side)

Sheet thickness (Xsh)

(silica-gel-coated tape, both sides)

Center-to-center sheet spacing (Xsp)

Spacer thickness

Flow gap (Xgap)

Silica gel density on tape,

both sides, MD

Dimensions of the dehumidifier part

Dimensions of the test article

Surface area/volume (a)

Tape to desiccant ratio (TOR)

Desiccant bed density (Pb)

18

Silica gel, Davison Grade 11

177-297 ~m (mesh size 50 to 80)

Average: 237 ~m

1131 kg/m3

921 J/kg K

AR Clad 5190, Adhesive Research,

Inc. (Double-sided polyester

tape with acrylic adhesive)

1172 J/kg K

76 ~m

25 ~m

430-670 ~m

Average: 550 ~m

1664 ~m

794 ~m {aluminum}

994 to 1234 llm

Average: 1114 ~m

0.279 kg/m2

0.117 x 0.126 x 0.203 m

(width x height x length)

0.169 x 0.161 x 0.203 m

(width x height x length)

1202 11m

0.350 kg of tape/kg of dry

desiccant

176.6 kg of dry desiccant/m3 of

bed
TR-2774

4.0 EXPERIMENTAL PROCEDURE

To obtain single-blow data, first bring the desiccant in the test article up

to initial desired conditions, and then introduce process air prepared at

specified conditions to the test article. This simulates a step change in the

inlet conditions. The inlet and outlet air conditions (temperature and

humidity) are monitored and recorded with time, and the data are collected.

The test section is insulated to simulate adiabatic operation. The following

is a step-by-step procedure for performing the experiments (see Figure 2-2).

Each test consists of preparation and process steps. Depending on the desired

initial and inlet conditions, the process step of one test can be the

preparation step for the next test.

Preparation of The Test Article

Close BVI and GV. Open BV2 and switch the three-way valve to monitor

the dew point temperature of the bypass.

Turn on the blower.

Adjust D to the desired flow rate.

Set temperature at the temperature controller and turn on 4.1-kW heater

(if heating is necessary).

Turn on the boiler and set the humidity (if humidification is necessary) •

Activate the data acquisition program. When desired temperature or

humidity is reached, adjust D again.

Open BVl and GV. Close BV2 to introduce conditioned air to the test

article. Switch the three-way valve to monitor the dew point temperature of the inlet process air.

8. Monitor inlet and outlet conditions. When the conditions are the same,

the desiccant in the test article has reached equilibrium with the process air. Note the air conditions for a period of five minutes.

9. Open BV2. Close BVl and GV. Switch the three-way valve to bypass.

10. Turn off the boiler, the heater, and finally the blower.

4.1

1.

2.

3.

4.

5.

6.

7.

4.2 Process (Adsorption/Desorption)

1. Make sure that BV! and GV are closed and BV2 is open. Switch the

three-way valve to monitor the dew point temperature of the bypass.

2. Turn on the blower (the desired pully combination and motor speed are

already set.

3. Adjust D to desired flow rate.

4. Set the temperature on the controller and turn on the heater.

5. Turn on the humidifier and set the humidity.

19
TR-2774

6. Activate the data acqua si t i on program. When desired temperature and

humdity are reached, adjust D.

7. Open BV1, and simultaneously open GV and close BV2 to start the singleblow experiment. Activate the data collection. Switch the three-way

valve to monitor the dew point temperature of the inlet process air.

8. Record inlet and outlet air temperatures and humidities and pressure

drops to measure the transient response of the test dehumidifier.

Carry out the experiment until equilibrium is reached.

9. Open BV2. Close BVl and GV.

10. Turn off the boiler, the heater, and finally the blower.

20
TR-2774

5.0 HEAT AND MASS TRANSFER MODELS

5.1 Governing Equations

The purpose' of this study is to use the available heat and mass transfer

models for other geometries than parallel plate and extend them to the geometry that is under investigation here. Among the computer codes available at

SERI (DESSIM [1], MOSHMX [20], and DESICCANT [14]), DESICCANT has the

capability of simulating transient performance of a dehumidifier by both

lumped-capacitance and solid-side-resistance models in which we are

interested. DESICCANT was originally developed and validated for packed beds,

and thus needs to be modified for parallel-plate geometry. The methodology

for developing differential equations used in DESICCANT that govern the adiabatic transient response of a desiccant bed can be found in Pesaran [14J. The

assumptions made for these governing equations are: axial and radial diffusion and conduction and the storage terms in the gas phase are negligible; the

particles are isothermal at each axial location; transfer coefficients are

constant; and axial di Efusi on and conduction in the solid phase are negligible. In this section the governing equations developed for DESICCANT are

presented.

The dimensionless form of the governing equations for the lumped-capacitance

model are as follows:

(5-1)

(5-2)

(5-4)

(5-3)

mass balance in the gas phase:

amI e

az* = Ntu,eff (ml,s - m1,e) (1 - m1,e),

mass balance in the solid phase:

aWavg = _ Ntu,eff

at* DAR (mt,s - ml,e),

energy balance in the gas phase:

aTe [ az* = -Ntu,eff Leeff + Y1(m1,s - m1,e)](Te - Ts),

and energy balance in the solid phase:

aTs Nt u eff.[ at* = Yb~AR Leeff(Te - Ts) - (Hads!Cp,e)(ml,s - ml,e)].

The above equations are coupled through the equilibrium isotherm relation

(5-5)

(5-6)

For the definition of the above parameters, see the Nomenclature. Note that

in the lumped-capacitance model the solid phase at each cross section is

treated as a lump with no concentration gradient in the solid phase perpendicular to the flow. The transfer unit Nt ff depends on the effective mass

transfer coefficient KG,eff through the rel~tlon

= KG,eff pL

Ntu,eff

21
TR-2774

where p is the perimeter of the desiccant bed. The coefficient KG depends

on the magnitude of both gas-side and solid-side mass transfer co~fficients. However, since the driving potentials in the gas and solid phases have

different units, KG ~fJ cannot be easily expressed in terms of gas- and solidside transfer coeff'1.Clents. For the small particles of silica gel used for

this study the solid-side resistance can be considered a fraction of gas-side

resistance [9], and thus one can write

(5-7) KG

KG,eff = Cl

where KG is the pure gas-side mass transfer coefficient in the passages and Cl

is a number greater than unity that depends on the particle size and diffusivity of H20 into the desiccant particles. To obtain the relation between

effective Lewis number and Cl, the analogy between heat and mass transfer for

parallel-plate geometry is used

Le = (Sc/Pr) = (5-8)

and hc

Leeff = • KG,effCp,e

Dividing Eq. 5-9 by Eq. 5-8 and substituting Eq. 5-7

Leeff

Cl = --- Le

one can obtain

(5-9)

(5-10)-

For silica-gel-coated parallel-plate geometry the specific heat of the bed cb depends on the specific heat of moist silica gel and the polyester tape

through the relation

cb = WavgCl + cdesiccant + c t a pe TOR ,

where TOR is the ratio of tape mass to dry desiccant mass.

(5-11)

The model with solid-side resistance in the DESICCANT code assumes that the

particles are spherical, that there is a concentration gradient across each

particle and that water molecules diffuse into microporous silica gel particles by surface diffusion [14]. Assuming radial symmetry for spherical silica

gel particles, the dimensionless mass balance equation in the solid phase

becomes

1 a = '/r2 "l. -.tr r or

(5-12a)

with boundary conditions:

at the center

Ir'/(=Q = Q , (5-12b)

and at the surface

= (m (5-l2c) 1 - m1 ). ,s ,e - a aw* I *

3r r =1

set of equations replaces Eq. 5-2 of the lumped-capacitance model.

governing equations of the model with solid-side resistance are the

The above

The other

22
TR-2774

same as Eqs. 5-1, 5-3, and 5-4 of the lumped-capacitance model if Nt u ~ff and

Le ff are replaced with Nt and Le, respectively. The transfer u'nl.t Nt u de~ends on the true gas-sideumass transfer coefficient KG through the relation

KGPL

Nt u =

The governing equations are coupled through

surface of desiccant particles

(5-13)

the equilibrium isotherm at the

(5-14)

An average gel water content is required for energy conservation equations,

which for a spherical particle is

1

Wavg = 3 J r*2 Wdr* • (5-15)

a

Note that part of a particle is blocked by the adhesive that bonds the

particle to the wall of passages and thus the diffusion of H20 into the

particle is not symmetrical. However, as a first approximat Ion we have

assumed that the diffusion mechanism is symmetrical.

The governing equations (Eqs. 5-1, 5-2, 5-3, 5-4, 5-5 for the lumpedcapacitance model and Eqs. 5-1, 5-3, 5-4, 5-12, 5-14, 5-15 for the solid-sideresistance model) were solved for a step change in the inlet conditions using

finite difference methods [14]. The inlet and initial 'condition for solving

the equations are:

inlet conditions

T(t*, z* = 0) = Tin'

m1,e(t*, z* = 0) = m1,in'

and initial conditions

T{ t"t = 0, z"t) = To

W(t* = 0, z'l't) = Wo

The details of the numerical procedure and the associated computer program

DESICCANT can be found in Pesaran [14]. The resul t s of solving DESICCANT,

which are in terms of mass fraction ml' can be easily converted to an absolute

humidity ratio for comparison witfi experimental results using the relation

w = m/ (1 - m) ,

5.2 Auxiliary Equations

To obtain numerical predictions several parameters that specify characteristics of the desiccant, the bed, and the flow must be known. If X h is the

thickness of a sheet of silica-gel-coated tape and X is the center-1o-center

spacing of the sheets, then the air gap of each chan~gl from Figure 3-2 is

X

gap

23

(5-16)
(5-21)

TR-2774

and thus the hydraulic diameter of each channel is

dh = 2Xgap = 2(Xs p - Xsh) • (5-17)

The number of sheets per unit height of the matrix is l/xsp and the surface

area per unit volume of the dehumidifier is

2

a =--- • (5-18) Xsp

The density of desiccant 1n the matrix Pb is

NO Pb =--- , (5-19) Xs p

where NO is the dry mass of desiccant per uni t area of sheets. Then the

desiccant-to-air ratio when a mass flow rate of mc passes through the bed

during experimental time T is

PbAL

OAR =---- , (5-20) tfJcT

where A is the frontal area of the dehumidifier matrix. The porosity of the

matrix is

£ = (Xsp - Xsh)

Xsp

Using this porosity one can find the velocity in a channel from superficial

air ve1oci~y Vsup

V - Vsup - £

where

v _Ibc

sup - pA

The Reynolds number in a channel is

Re =--\I

(5-22)

(5-23)

(5-24)

Cas-side heat or mass transfer coefficients, h or KC' can be estimated from a

theoretical Husselt number of fully deve10pecf laminar flow between parallel

plates [25] for the cases of constant wall temperature or concentration

(Hu =7.54) and constant heat or mass flux (Nu =8.325). Although the sorption process does not fit either of these limits, it is closer to the constant

heat or mass flux cases [26]. The gas-side heat transfer coefficient is

_ kNu ( hc - dh' 5-25)

where k is humid air conductivity. The gas-side mass transfer coefficient,

using an analogy between heat and mass transfer for parallel plate, is

hc KG = (5-26)

cp,eLe

The overall mass transfer coefficient is lower than the gas-side transfer

coefficient because of resistance of moisture diffusion within the desiccant

particles

24
TR-2774

KG

KG,eff = a =

cp,e Leeff (5-27)

The number of transfer units can be estimated from

(5-28)

or

(5-29) KG,effaAL

Ntu,eff = _ ......._--

dlc

Grade 11, Davison, silica gel used in this study has properties similar to

Grade 40 gel. The following polynomial [14] that fi ts the manufacturer's

vapor pressure data on Grade 40 is used to represent the equilibrium isotherm

of the desiccant:

RH = 0.0078 - 0.05759 W+ 24.16554 W2 - 124.478 W3 + 204.226 W4 (5-30)

where RH is relative humidity ratio, Pvapor/Psat. Preliminary results have

shown that the adhesive can reduce the capacity of the gel only up to 10%.

The heat of adsorption is estimated from the following relations [14]:

H W<0.05 ads =-12400 W+ 3500

Hads =-1400 W+ 2950 W~0.05

. kJ/kg water. (5-31)

The dominant mechanism of moisture diffusion within microporous silica gel

particles is surface diffusion, and a correlation for this surface diffusivity

is given in Pesaran [14], which is

D = 1.6 x 10-6 exp [-0.947 x 10-3 (Hads/(T + 273.15)] • (5-32)

5.3 Pressure Drop Analysis

Assuming fully developed laminar flow in the channels, the pressure drop

across the dehumidifier matrix for constant property is [23]

2 ~P = pV [K + 4f ~] (5-33) 2 dh '

where f is the Fanning friction factor and for rectangular passages is given

by [24]

and K = 0.686.

f = 24 1

Re (1 + Xgap/B)2 (1 - 0.639249 Xgap/B) (5-34)

The measured pressure drop is slightly different than the pressure drop across

the dehumidifier matrix because the pressure taps are positioned away from the

matrix. The correction for this configuration that is used here is recommended by Maclaine-cross and Ambrose [23]. The pressure drop between the

inlet pressure tap, and the entrance of the dehumidifier matrix is [23]

pV2 ~Pin = --2-- (1 - (Ae/Ad)2) , (5-35)

25
(5-36)

(5-37)

TR-2774

where Ae is the minimum free-flow area of the dehumidifier passages and Ad is

the cross-sectional area of the test section at the inlet pressure tap.

Equation 5-35 is obtained using Bernoulli's equation and the continuity at the

entrance of the dehumidif ier. The pressure drop between the exi t of the

dehumidifier and outlet pressure tap is [23]

pV2 ~Pout (2 ) = --2-- 2(Ae/A) - 2.4 Ae/A ,

where A is the frontal area of the dehumidifier matrix. Eq. 5-36 is obtained

using conservation of momentum and continuity at the exit of the matrix

assuming a parabolic velocity profile at the exit of the dehumidifier and a

uniform velocity at the outlet pressure tap.

The predicted pressure drop between the inlet and outlet pressure taps can be

estimated using Eqs. 5-33, 5-35, and 5-36,

~Ppre = aPin + ~P + ~Pout •

Then ~p can be directly compared with the measured pressure drop aPexpo

The expfifmental friction factor f exp can be obtained from

(5-38)

and can be compared with the predicted friction factor from Eq. 5-34.

26
6.0 RESULTS AND DISCUSSION

The major focus of this project was on the design, fabrication, instrumentation, and shakedown of the test facility. Therefore only a limited number of

experiments under adiabatic conditions were performed and compared with model

predictions. Table 6-1 summarizes the conditions of the tests performed. The

specifications of the test dehumidifier were given in Table 3-1. The

experimental results were obtained after a step change was introduced in the

air inlet conditions to the dehumidifier. Desired uniform conditions were

established before the step change. The outlet air temperature and humidity

as a function of time and pressure drop across the dehumidifier were measured

during each experiment. Figures 6-1 to 6-4 show the experimental results as

well as model predictions. The experimental data were collected in voltages,

converted to engineering units, and then plotted by an HP9845A computer. The

model predictions using DESICCANT code were obtained from a mainframe computer

(Cyber 760 at NOAA), transferred to the HP9845A, and finally plotted along

with the experimental results. Inlet and outlet conditions are shown in

Table 6-1 for both measured and predicted results as a function of time.

Experiments 1 (Figure 6-1) and 4 (Figure 6-3) are adsorption cases that were

performed by the humidification of the process air using the boilerhumidifier. The variation of the inlet humidity (±0.004 kg/kg) is large,

which can be caused by a fluctuation of supply pressure in the steam boiler

and poor control of steam flow rate by the electronic controller valve. We

can observe that the outlet humidity follows the fluctuation of the inlet

humidity and that the fluctuation in the outlet air temperature is sensitive

to inlet air humidity. Since the DESICCANT code at the present time is set up

for a constant step change in the inlet conditions, average inlet conditions

are used for obtaining the predictions.

Table 6-1. Experimental Parameters

Initial Average Inlet Average Flow

Conditions Conditions Conditions

Run Process a NC

No. To W b T· V c.Pexp

tu 0 ln win me

(OC) -(kg/kg) (Oe) (kg/kg) (g/s) (m/s> (Pa)

1 AD 24.6 0.02 30.0 0.0144 20.5 2.22 95 12.67

3 DE 25.2 0.14 56.5 0.0084 18.9 2.19 90 14.74

4 AD 21. 5 0.04 25.5 0.0125 18.1 1.89 80 14.53

5 DE 24.2 0.23 38.8 0.0670 16.2 1. 79 68 16.49

aAD = Adsorption, DE = Desorption

bCalcu1ated using Eq. 5-30

cBased on a Nusselt number of 8.235

27
UI

III

'II

- <")

o

o

rs

.032

.0413

'-J

.024

OJ

.02e~

"-

en

.x

.008

.004

o

H

I- .0200:

0:::

>-

.01SI- H

Q

H

L • 012:::J

I

30 40

Experimental

------- Predicted ("lumped

capacitance" .03S

model)

--~

20

0.

-20. 3'-_-I-_.....L-_.....L-_--'-_-.L.._---L._---L._--J._---L_~. 1300

50

-10.

80.

70.

S0.

/

I

50.

I

U I

I

I

I

I

f

W 40. f

/

0::: c--'" ::J

fCC

0::: 313.

W

a,

L

W 20. Ia:::

H

CC 10.

80. .040 N

0

0

r-

__ . _~_ Experimental 0

0

713.

Predi cted (" lumped

capac i tarce" .036

model)

60. Tout .032

50.

0)

U .a28~

-,

0)

.x

W 40. '-J

0:::: .024

:::J

I- 0

a: H

0:::: 30. IW Tin

'a2aa:

n, 0::::

:L

W >-

I- 20. .13161- H

N 0:::: Q 00 H H

a: :L

113. • 012:::J

I

0. .0138

-113. .13134

-213. .13013

a 113 20 313

TIME Crn in. ) TIME (rn in. )

Figure 6-1. Comparison of Experimental and

Predicted Results for Exp. 1

Figure 6-2. Comparison of Experimental and

Predicted Results for KIp. 3
.002

.030 UI Il'>

0 III 0

r0

.029 0

-

•

I I

.12126 "-~

.024

.922~

.s:

-, .020 m

.s:

...., .919

0

.916H....

n:

.9140::

>-

.912....

H

Q

H .910L

::J

.B0SI

.006

.004

5 10 15 20 25 39 35

Experimenta1

------- Predicted ("1 umped capacitance" model)

__._._ Predicted ("solid side resistance" model)

a

-10. r!J-_--L.._---l__L..-_..J...-_...J-_~_ ___L_ ____'L___ _g. 000

40 45

TIME (min.)

Figure 6-4. COIDparison of Experimental and

Predicted Results for hp. 5

50.

45.

40.

35.

....,

U- 30 •

w 25.~~=::::""-----

:::J

I0:

20.

W

0..

L

WIS.

IIX

H 10.

a:

60. .030 v

0

0

rExperimental 0

0

.029

50. ------- Predicted ("lumoed capacitance"

mode1)

.92G

40. .024

.022~

U 30. .x

-, •029 m

Tin .x

W ....,

0:::

20. .019

0 I- .SIGH a: I- 0::: 10.

W a:

Q.. .0140:::

:L

W >-

I- 0. •0121- H N 0::: Q

'-'> H .010;:

a:-10. ---~ ::J

•90SI

-20. .906

.004

-30.

.092

-40. .909

0 10 20 30 40 50 60

TIME (min. )

Figure 6~3. COIDparison of Experimental and

Predicted Results for hp. 4
TR-2774

Experiments 3 (Figure 6-2) and 5 (Figure 6-4) are desorption cases that were

performed by heating the process air without any humidification. The

fluctuation of the inlet air temperature is small (±0.30 C) . This low initial

inlet air temperature observed in experiments 3 and 5 is a result of the

thermal mass of the metal duct between the bypass test section and the gate

valve that initially cools the air temperature. The small fluctuation in the

inlet air humidity observed in experiments 3 and 4 is caused by a variation of

the ambient air humidity.

Predicted results using the lumped-capacitance model and the model with solidside-resistance that were solved by the DESICCANT code were obtained. For the

solid-side-resistance model, predicted results were unstable unless a large

number of integration points in three coordinates (r*, z*, t*) were used; it

appeared that the conditions of these experiments (mainly small particle size)

caused this instability. A higher number of integration points required an

excessive amount of computation time and computer cost.

The predicted results for experiment 5 using both models were compared with

experimental results (Figure 6-4). The predictions of the lumped-capacitance

model agree better with experimental results than the predictions of the

solid-side-resistance model. One may have expected that the model with solidside resistance would agree better with experimental data. For example, in

the case of packed beds with larger particle sizes the predictions of t he '

solid-side-resistance model agreed better with experimental data [14]. One

possible explanation for the unexpected result could be that the assumption of

symmetrical diffusion, of H20 within the particles in the silica-gel-coated

parallel-plate dehumidifier, was in error. In this case, parts of the

particles may be blocked by adhesive. Since the predictions of this version

of the solid-side-resistance model do not appear promising for small-particle

coated silica-gel parallel-plate geometry and the computer cost is relatively

high to obtain predictions using this model, we did not use this version of

the solid-side-resistance model for further comparison. A model based on the

same principles of this solid-side-resistance model without any SYmmetrical

diffusion within the particles is proposed in Section 7.0 for future analysis.

Predictions using the lumped-capacitance model shown in Figures 6-1 to 6-4

were obtained using an a of 1.53 (Lee£f of 1.3) based on a formula suggested

by Biswas et ale [9]. The predict10ns are similar to the experimental

results. Although there are fluctuations in the inlet and thus outlet

condi t ions of the experimental results and the model does not account for

these fluctuations, we can say that the predictions for the adsorption cases

(Figures 6-1 and 6-3) agree better with experimental results than the

desorption case predictions (Figures 6-2 and 6-4). This behavior has been

observed by other investigators [1,14] and may be attributed to the presence

of a dynamic hysteresis in the adsorption/desorption characteristics of silica

gel.

From the desorpt ion cases it is obvious that the predicted outlet humi di ty

ratio is initially higher than experimental results, and later it is lower

than the experimental outlet humidi ty and also reaches the inlet humidi ty

faster. This means that initially the model predicts a higher desorption rate

30
TR-2774

and capacity, but later it predicts a lower capacity. These predictions can

result from using inappropriate choices of the equilibrium isotherm equation

and effective amount of desiccant.

The predicted outlet air temperature is always higher than the experimental

results and reaches inlet air temperature faster. This can be due to several

factors: lower heat of adsorption in the model, dependence of heat capacity

to temperature, lower equilibrium capacity assumed in the model, heat loss

from the test section, and that initially the inlet air temperature in the

model is assumed to be higher than the experimental inlet air temperature.

Parametric studies of heat of adsorption, equilibrium capacity, and overall

mass transfer coefficient need to be done to investigate their effect for

improving the predictions. Reducing the fluctuations in the inlet air

condition also improves the comparisons.

Figure 6-5 shows the variation of the friction factor versus the Reynolds

number. Measured friction factor (Eq. 5-38) is shown to be in good agreement

with the prediction (Eq. 5-34), which is based on the assumption of a fully

developed laminar flow.

The measured pressure drops across the dehumidifier are within 15% of the

predicted pressure drops, as can be seen from Figure 6-6 and Table 6-2. The

predicted values (Eq. 5-39) were obtained based on the average air gap of the

passages. Although the variation in actual air gap of the passages is small,

the pressure drop variation is larger since the pressure drop is inversely

proportional to the third power of the air gap ~P oc X-3• Also some of the

longer particles can partially deform the flow causr~~ flow separation and

0.4

• Measured

-- Predicted

0.3

-

0

-o

co

-c 0.2 0

+::

o

.~

u,

0.1

50 100 150 200

Reynolds number Re

250 300

Figure 6-5. Friction Factor Versus Reynolds Number--Measured

and Predicted

31
increase in pressure drop. Under these circumstances, the 15% difference is

reasonable.

70 90 110

70

110---------------------""2

co

a.

a.

o

'-

"0

<I>

'-

:::J

C/)

C/)

<I>

'-

a.

"0

Q)

....

:::J

C/)

mQ)

Predicted pressure drop (Pa)

Figure 6-6. Measured versus Predicted Pressure Drop

Table 6-2. Pressure Drop Results

. (g/s) 6Pexp 6P Run No. me Re pr e Difference

(Pa) (Pa) (%)

1 20.5 248.7 95 82.6 14.9

3 18.9 215.4 90 87.4 3.0

4 18.1 221.6 80 71.1 12.5

5 16.2 192.0 68 68.2 -0.2

32
7.0 CONCLUSIONS AND FUTURE WORK

A si ngl e-rbl.ov test facility for obtaining adiabatic transient response of

desiccant dehumidifiers was designed and fabricated. A silica-gel parallelplate dehumidifier with highly uniform passages was designed and fabricated as

the first article for testing in this facility. A limited number of adiabatic

single-blow experiments were performed and the transient heat and mass

transfer data were compared with the predictions of two models in the

DESICCANT program that was originally developed for analyzing packed beds.

The predictions using the lumped-capacitance model agreed better with the

experimental results than the model with solid-side resistance. This result

was attributed to poor assumption of symmetrical diffusion in partially

blocked silica gel particles. The comparisons between the predictions of the

lumped-capacitance model and experimental data are generally satisfactory,

within 10% for adsorption and 30% for desorption. They are better for

adsorption cases than desorption cases as observed by previous investigators.

Pressure drops across the parallel-plate dehumidifier were measured and were

within 15% of the predicted pressure drops.

The results obtained in this test facility can be used to design dehumidifiers

in two ways:

• by comparing the transient performance of various geometric/material

combinations and then recommending combinations that have greater

potential to provide efficient dehumidifiers, and

• by providing the data for validating the heat and mass transfer models of

dehumidifiers and then using these validated models to design more

efficient dehumidifiers.

The inlet humidity level was not uniform when the ambient air was humidified

by injecting steam from the boiler to the process air. The fluctuations were

attributed to fluctuations in the steam supply pressure in the boiler and poor

control of steam injection rate by the controller valve. These activities and

conclusions were performed in a FY 1984 project. In FY 1985, we continued our

efforts to improve the single-blow test facility. These efforts are

documented in a forthcoming report [21]. The test article needs to be

modified by changing the air gap of the passages and particle size of the

desiccant for further testing. In FY 1985 we planned to test a promising

geometry (staggered parallel strip) to evaluate its potential as an advanced

geometry for desiccant dehumidifiers.

To improve the solid-side-resistance model we can assume that the silica gel

layers on the polyester tapes act as slabs of solid with a thickness of d and

then we solve the diffusion equation in these slabs rather than solvinl the

'1"'With the efforts in FY 1985 we were successful in Obtaining a more uniform

inlet humidity ratio by solving the humidity control problem. After resolving

this problem we obtained transient response of the parallel-plate test article

by performing experiments at different air flow rates and inlet and initial

conditions.

33
diffusion equation in spherical particles. Then the only equation that needs

to be modified is Eq. 6-12 which becomes

aw

--;; = at

a (O*~) ay* ay* (7-la)

y

*

with boundary conditions:

at the wall aw* I =0 ,

ay yA=O

at the surface of the particles adjacent to the alr gap

-6 aw I = m - m ay* y*=1 l,s 1,e·

The dimensionless parameters in the above set of equations

t; , t* = ' n* = ~:2 'a = K:P~p

are

(7-1b)

(7-1c)

Other governing equations remain the same. Solutions of this model need to be

obtained numerically and compared with the experimental results so that the

model can be improved and validated.

In FY 1985, we planned to apply the method of moments [27,28] to the transient

heat and mass transfer data to directly obtain heat and mass transfer

coefficients. Transient heat transfer tests for heat exchangers have been

interpreted using the first statistical moment of temperature distribution to

estimate the matrix heat capacity and the second moment to estimate the number

of heat transfer units and thus the heat transfer coefficient [27J. The same

method can be appl ied to transient heat and mass transfer data by using

combined potentials. Each combined potential satisfies equations analogous to

those for heat transfer alone and has a characteristic wave speed. We expect

that this method will estimate the heat and mass transfer coefficients from

the transient data and eliminate some of the subjectivity used in the

traditional method of matching the experimental transient data with the

predictions.

34
8.0 REFERENCES

1. Barlow,. R. S., Analysis of the Adsorption Process of Desiccant Cooling

S stems - A Psuedo-Stead -State Model for Cou led Heat and Mass Transfer,

SERI TR-631-1330, Golden, co: Solar Energy Research Institute, 1982.

2. Booz-Allen, and Hamilton, Evaluation of Residential and Commercial

Solar/Gas Heating and Cooling Technologies, GRI-70!0105, Chicago, IL:

Gas Research Institute, 1981.

3. Active Program Research

Science Applications, Lnc , ,

4. .Juri nak , J. J., Open Cycle Desiccant Cooling: Component Models and

System Simulations, Ph.D. Thesis, Madison, WI: University of Wisconsin,

Solar Energy Laboratory, August 1982.

5. Nienberg, J. W., "Modeling of Desiccant Performance for Solar-DesiccantEvaporative Cooling Systems," M.S. Thesis, Los Angeles, CA: University

of California, 1977.

6. PIa-Barby, F. E., G. C. Vliet, and R. L. Panton, "Performance of Rotary

Bed Silica Gel Solid Desiccant Dryers," ASME 78-HT-36, 1978.

7. Gidaspow, D., Z. Lavan, M. Onischak, and S. Perkari, "Development of a

Solar Desiccant Dehumidifier," Proceedings of the 3rd Workshop on the Use

of Solar Energy for the Cooling of Buildings, pp. 83-89, 1978.

8. Wurm J., Kinart, Rush, T. S. Zawacki, R. S. Macriss,

Development Program - Annual Program Report, Chicago, IL:

Institute of Gas Technology, 1979.

Solar-MECcCOO-4495-15,

9. Biswas, P., S. Kim, and A. F. Mills, "A Compact Low-Pressure Drop

Desiccant Bed for Solar Air Conditioning Application: Analysis and

Design," Journal of Solar Energy Engineering, Vol. 106, 1984, pp , 153-

158.

10. Schlepp, D. and R. Barlow,

Dehumidifier, SERI/TR-252-1951,

Institute, September 1984.

Performance of

Golden, co:

SERI

Solar

Parallel-Passage

Energy Research

11. Schultz, K. J. and D. Schlepp, Experimental Test Plan for Cyclic Testing

of Partlel Passage Rotary Desiccant Dehumidifers, Draft Report prepared

for the U. S. Department of Energy, April 1984.

12. Lavan, Z., V. Worek, and J. Monnier, "Cooled Bed Solar-Powered Air

Conditioning," presented at the 16th IECEC, Atlanta, GA, 1981.

35
TR-2774

13. Gunderson, M. E., Development of Solar Desiccant Dehumidifiers, Report on

Contract EG-77-C-03-1591, Torrance, CA: AiResearch Manufacturing Company

of California, 1978.

14. Pesaran, A. A., "Moisture Transport in Silica Gel Particle Beds," Ph.D.

Dissertation, Los Angeles, CA: University of California, 1983.

15. Barlow, R., An Assessment of Dehumidifier Geometries for Desiccant

Cooling Systems, SERI!TR-252-1529, Golden, CO: Solar Energy Research

Institute, June 1983.

16. Kim, S., "Development of a Laminar Flow Desiccant Bed for Solar Air

Conditioning Application," Masters Thesis, Los Angeles, Ca: University

of California, 1981.

17. Biswas, P., "An Experimental Study of the

Silica Gel Desiccant Packing Suitable

Application," Masters Thesis, Los Angeles,

1981.

Performance of a Laminar Flow

for Solar Air Conditioning

CA: University of California,

18. Ambrose, C. W., I. L. Maclain-cross, and E. B. Robsen, The Use of Rotary

Heat Regenerative Heat Exchanger for the Conservation of Energy in

Buildings. Final Report Project 109. National Energy ResearchDevelopment and Government Committee. Australian Government, Canberra,

1983.

Performance of Packed-Bed

the SERI Desiccant Test

Kutscher, C. F. and R. S. Bar1ow, _D.Ly_n~a::-m_i_c__:--__:--- _

Dehumidifiers: Ex erimental Results from

19.

Laboratory, SERl TR-252-1429, Golden, CO:

Institute, August 1982.

Solar Energy Research

20. Maclaine-cross, I. L. "A Theory of Combined Heat and Mass Transfer in

Regenerators," Ph.D. Thesis, Australia: Monasch University, 1974.

21. Pesaran, A. A., I. L. Maclaine-cross, and E. Van den Bulck, Measurements

on Promising Desiccant Dehumidifier Materials and Geometries, SERI!TR252-2898, Golden, CO: Solar Energy Research Institute, forthcoming.

22. Schultz, K. J., SERI Desiccant Cooling Facility: Status Report, SERI!TR252-2718, Golden, CO: Solar Energy Research Institute, 1986.

23. Maclaine-cross, I. L. and C. W. Ambrose, uPredicted and Measured Pressure

Drop in Parallel Plate Rotary Regenerators," Journal of Fluid

Engineering, Vol. 102, March 1980, pp. 59-63.

24. Cornish, R. J., "Flow in a Pipe of Rectangular Cross-Section,"

Proceedings of the Royal Society, Vol. A120, 1928, pp. 691-700.

25. Kays, W. M. and A. L. London, Compact Heat Exchangers, New York, NY:

McGraw-Hill Book Co., 1964.

26. Maclaine-cross, I. L., Personal Communication, University of New South

Wales, Australia, Feb. 1985.

36
TR-2774

27. Jeffreson, c. P., "Dynamic Testing--a Unification," Chemical Engineering

Science, Vol. 25, 1970, pp. 1319-1329.

28. Ruthven , D. M., Principles of Adsorption and Adsorption Processes, New

York: John Wiley and Sons, Inc., pp. 242-244, 1984.

37
TR-2774

APPENDIX A

LISTING OF PROGRAMS

This appendix lists the data acqulsltlon program (DAP) and the program that

analyzes the raw data and plots them in outlet air conditions as a function

time (PLOT). Both programs are written in BASIC for the HP9845A.

38
TR-2774

1£1 ***** DAP *****

2£1 DATA ACQUISITION PROGRAM

30 FOR COLLECTION AND STORAGE

4£1 OF DATA FROM

50 THE SERI SINGLE BLOW TEST FACILITY

60 *** AP~~ I L 22, 1985 ***

70 $$$ FORTH VERSION $S$

80 *** AHMAD PESARAN *** '30

100 OPT I Ot·~ BASE

110 OVE~:LAP

12~3 I t·nEGER P

13~3 IIH'1 1

.... (9)

1 4 ~) I ~.~ PUT II Hm~ DO 'r'0 U ~'J At·n THE 0 UTPUT [ ~3 = the' r m.a. 1 p ,a.p e'to.; 16=CRT

; 7, 6=e'pson pt-·; n t e-t"') ? II, Pr'; n t $

156 IF Pr';nt.$=1116 11 THE~'~ PRIt·HER IS 16

160 IF Pt-·; nt$=110 11 THE~'~ PRIt·nER IS £1

17~Z1 IF Pr'lnt$=117,6 11 THEN PRINTE~~ IS 7,6

180 ON KEY #2 GOTO 210

190 Bp=l

206 GOTO 240

210 Bp=0

22~j D I SF' II B\'PAS:3 CALCULAT I ous I Gt'Wr;;~ED II

2:~:6 GOTO 214~3

240 ON KEY #3 GOTO 260

250 GOTO :~:20

26~) Bp=l

27(1 II I SF' II BYPAS:; CALCULAT I ONS oucoI t.H:; II

2:::\.3 DISP II T I t1 E TE: F' T DE ~,J BF' AH ~: BP HRBP PABs DP0

SPEED II

2':;t~~1 PR I NT II T I t1E TBP TDE~'JBP AHRBP HRBP PABS DPO

SPEED II

3~j(1 GOTO 2140

:310 F 1ag=0

320 ON KEY #1 GOTO 340

336 GOTO :3713

34~) Flag=l

35~~1 I t'~PUT II t'~E~,J T I t'lE ::;TEP I t·~ t'1t'1S::; II, Dt. ne'l.J

366 GOTO 2146

:37~3 Fff=0

386 R=8314.12 !m A3*pa/kmole*K UNIVERSAL GAS CONSTANT

396 Mwa;r=28.67 ! AVERAGE MOLECULAR WEIGHT OF HUMID AIR

4 (1 (1 t'1 to. = t1I,.J.a. ; to. / F.~

410 Pconv=1.\.3133E5/760 ! CONERSION FACTOR FROM TORRS TO PASCAL

426 Scn=709 ! SCANNER ADDRESS

430 ! Pap=0 ! THERMAL PAPER ADDRESS

440 ! Crt=16 CRT ADDRESS

456 ! PRIN=7,6 EPSON PRINTER ADDRESS

46(1 RESET ::;c n

4 7~~1 OUTPUT ::k n; II ::; I II

4:::(1 I NPUT II E>~PER I t'1Et·n Rut·~ #' ? II, RI.m$

39

~1RATE(N)
TR-2774

490 PR I NT II EXPER H1ENT RUt~ # II, Run$

500 It~PUT DATE OF TEST t1M/DD/YY ? II, Dat 12'$

510 PRINT DATE OF EXPERIMENT MM/DD/YY ",DatE'$

520 INPUT TIME OF DAY HHMM ? II,Time$

530 PRINT TIME OF DAY HHMM II,TimE'$

540 INPUT TIME INTERVAL IN MMSS II,Dt

550 PRINT TIME INTERVAL OF EXPERIMENT IN MMSS II,Dt

560 It~PUT TOTAL DURATION OF EXPERIt'lENT It~ SEC ?", Trlla){

570 PRINT TOTAL DURATION OF EXPERIMENT IN SEC ?11,Trllax

580 D=6*2.54/100 ! DUCT DIAMETER(m)

590 Ar~af=9.971E-3 ! FREE AREA OF DEHUMIDIFIER (rII A 2 )

6~HZt PR I NT II DUCT DIAMETER I N METERS ", D

610 INPUT "WHAT IS THE DIAMET~R RATIO OF ORIFICE PLATE ?II, E:e·t.a

620 PRINT "DIAMETER RATIO OF ORIFICE PLATE (d/D) ",BE'ta

630 B~ta4=B~taA4

640 E=(1-Beta4)A(-.5)

650 Mconst=E*(D*Beta)A2*SQR(2)*PI/4

660 Econst=(.41+.35*Beta4)/1.4

670 Reconst=4/PI/D

680 ON KEY #6 GOTO 710

690 An$=IlN II

700 GOTO 780

710 DISABLE

72~3 An$=lIy"! INPUT "WANT CALCULATIOt·~ OF It'~LET At·HI OUTLET ('r'.····t~)?", An$

730 ! PRINT liDO vou ~~At·n CALCULATION OF H~LET AND OUTLET Cot·mITIO~·~S ('"!"/t'D?", An$

7413 I FAn$ = II 'y' II THE t~ DISP II TIM E TIN TDE~~ H~ ARHI N F.~ H H~ TOUT TDE~.JO UTAHF: 0 UT

RHOUT DPTA MRATE SPEED II

750 IF An$= II'r'" THEN PR I NT II T I ME TIN TDE~J It~ ARH I N F.~H I N TOUT TDE~'JOUT AHF.~OUT

RHOUT DPTA MRATE SPEEDII

760 Et'~ABLE

770 GOTO 2140

780 ON KEY #7 GOTO 800

790 GOTO 830

800 An$=IIN Il

810 DISP IICALAULATION OF INLET AND OUTLET CONDITIONS STOPPED II

820 GOTO 2140

830 PRINT ,Beta

840 PRINT ,Beta4,E,Mconst,Econst

850 PRINT ,Reconst

860 H~PUT IlFIRST FILE t~At'lE FOR STORAGE OF DATA O~S IF NO STORAGE IS DESIF.~ED) II, F

; 1eat

870 pF.~I~n IIFIRST FILE NArlE FOR STORAGE OF DATA O~S IF t·W :3TORAGE IS DE:::;rF~ED) II, F

; 1e'a$

8::10 HIPUT II SECOND FILE ~~AME FOR STORAGE OF DATA (NS IF t·W STORAGE U:; DES I RED) II ,

F i 1e·b$

:::9[1 PR I ~n II SECO~m FILE NAME FOR STORAGE OF DATA .:: ~~s I F NO ::nOF~AGE I ::; nes I F.~ED) II,

Fileb$

900 IF FilE'a$="NSIi THEN 990

9 10 r1 ASS STORAGE I S II: T 15 II

920 DISP "FIRST FILE IS BEH~G CREATED II

930 CREATE Filea$,350

940 ASSIGN #1 TO F;lea$

95(1 IF F;leb$=INS" THEN 990

960 DI SP II SECOND FILE I S BE H~G CREATED II

970 ! CREATE F;leb$_~A

40
TR-2774

980 ASSIGN #2 TO Fileb$

990 BEEP

10ee DIS P II 1ft he s y s t em i s read y f 0 to. t est i n9 pr-e s s CON TINUE II

10110 PAUSE

1020 DISP II TIME TBP TDEWBP RHRBP HRBP PRBS DPO MRATE(N)

SPEED II

1030 ON KEY #4 GOTO 1060

1040 Stor=0

1050 GOTO 1100

1060 PRI NT II DATA ISSTOR I NG It~ II, Fi 1e a$

1070 DISP IIDATA IS STORING

1080 Stor=1

1090 GOTO 2140

1100 ON KEY #5 GO TO 1120

1110 GOTO 1160

1120 DISP IIDATA STORAGE IS STOPPED lI

1130 PRINT IIDATA STORAGE IS STOPPED II

1140 St or'=0

1150 GOTO 2140

1160 ON INT #7 GOTO 1280

1170 CONTROL MASK 7;128

1180 CARD ENABLE 7

1190 OUTPUT Sen;lITDII

1200 ENTER Sen;Td$

1210 PRINT IITIME FROM HP 3497A II,Td$

1220 PRINT LIN(3)

1230 PRINT II TIME TBP TDEWBP AHRBP HRBP PABS DPO MRATE(N

SPEED II

1240 OUTPUT Sen;ITE0"

1250 OUTPUT S.:n USING IK";IISE10 VR5 VFl VW0 VAl AFI AL9 11

1260 OUTPUT Sen USING IAA,DDD I;"TI II,Dt

1270 OUTPUT Scn;"TE2 11

1280 DISABLE

1290 OUTPUT Sen; liTE II

13100 ENTER Scn;Time

1310 STATUS Sen;P

1320 CARD ENABLE 7

13:30 IFF 1ag=1 THE N 0UTPUT Sen US I NG II AA, DDDII ; II TI II , Dt ne ...

1340 Flag=e

1350 FOR 1=1 TO 9

13610 OUTPUT Sen USING "AA,DD";"AI",I

1370 ENTER Scn;V(I)

1380 ! PRINT 111="; I, "V(I)=";V(I)

1390 ~~EXT I

1400 ! PRINT USING 762;Time,V(*)

1410 ! IMAGE DDDD,9(IX,MDD.DDE)

1420 ! PRINT #1;Time,V<*)

1430 IF Bp=0 THEN 1740

1440! CALCULATE THE MASS FLOW RATE

1450 Pab=V(9)*1000*Pconv !ABSOLUTE PRESSURE IN PASCAL

1460 Vbp=V(1)+V(2) !SUMMATION OF e.m.f. FROM BYPASS AND BOX(mV)

1470 Tbp=FNTfv(Vbp) !TEMPERATURE OF BYPASS (C)

1480 Denair=Pab*Mr/(Tbp+273.15) !DENSITY OF AIR (kg/mA3)

1490 Dpo=V(8)*Pconv !PRESSURE DROP ACROSS ORIFICE PLATE (PASCAL)

1500 Expan=l-Econst*Dpo/Pab

41
TR-2774

1510 C=.6 ! INITIAL VALUE OF DISCHARGE COEFFICIENT

1520 Mf=Mconst*Expan*SQRCABS(Dpo*Denair»

1530 Courlt er=O

15413 !

15513 Mrate=C*Mf ! AIR MASS FLOW RATE Ckg/s)

15613 Counter=Counter+l

15713 Re=Reconst*Mrate/FNVis(Tbp+273.15)

1580 ! PRINT IIRE=II;Re,IIPAB=II;Pabjll PASCALII;II DPO=II;Dpo;1I PASCAL II ! CALCULALE

NEW VALUE OF DISCHARGE COEFFICEINT.

15913 Cnew=.5959+.e312*BetaA2.1-.184*BetaA8+.e029*BetaA2.5*(lE6/Re)A.75+.039*Bet

a4*(1-Beta4)A(-1)-.e1583*BetaA3

16013 IF ABSCCnew-C)/cnew(.ee05 THEN 1650

1610 IF Counter>=3 THEN 1650

16213 C=Cnew

1630 Mrate=C*Mf

16413 GOTD 1540

16513 Speed=Mrate/Denair/Areaf

16613 ! PRINT IIC=II; C, IIRE=II j Re, IIMRATE=II j Mr-,a.te; II (kg/s) II, II COIJt.nER= II ; CClurlte'r16713 ! CALCULATE DEW POINT TEMPERATURE OF BYPASS USING V(5)

16813 Tdewbp=V(5)*10

16913 Pvbp=FNPsat(Tdewbp+273.15)

171313 Ahrbp=.622*Pvbp/(Pab-Pvbp)

17113 Rhbp=Pvbp/FNPsat(Tbp+273.15)

17213 PRINT USING 173e;Time,Tbp,Tdewbp,Ahrbp,Rhbp,Pab,Dpo,Mrate,Counter,Speed

17313 IMAGE DDDDD,2X,DD.DDD,2X,MDD.DD,2X,D.DDDDE,2X,D.DDDD,2X,D.DDDE,2X,DDD.D,2X,

D.DDDE,II(II,D,II)II,2X, D.DDD

17413 IF Arl$=IIN II THEN 20113

17513 Vtout=V(4)/4+V(2) !BOX VOLTAGE AND OUTLET TC ARRAY

17613 Tout=FNTfvCVtout)

17713 Tdewout=V(6)*le

17813 Pvout=FNPsat(Tdewout+273.15)

17913 Ahrout=.622*Pvout/(Pab-Pvout)

181313 Rhout=Pvout/FNPsatCTout+273.15)

18113 Vtin=V(3)/4+V(2)

18213 Tin=FNTfv(Vtin)

18313 Tdewin=V(S)*le

18413 Pvin=FNPsat(Tdewin+273.15)

18513 Ahrin=.622*Pvin/(Pab-Pvin)

1860 Rhin=Pvin/FNPsatCTin+273.15)

18713 Pab=V(9)*100e*pconv

18813 Denair=Pab*Mr/(Tin+273.15)

18913 Dpo=V(8)*Pconv

191313 Expan=l-Econst*Dpo/Pab

19113 Mf=Mconst*Expan*SQRCABSCDpo*Denair»

19213 t1rat e=C*Mf

19313 Speed=Mrate/Denair/Areaf

19413 Dpta=V(7)*Pconv

19513 ! PRI t'~T II TOUT= II; Tout, II TDE~WUT= II; Tde uo ut , II AHROUT= II; Aht",.:,ut, II RHOUT= II ; Rhcll.~t

19613 ! PRI t'~T II TI t~=" j Tin, II TDEW I N= II; Tdew in, II AHR I t~= II ; Aht"· in, " RH I N= II ; Rh i n

19713 ! PRINT LIN(2)

19813 ! PRINT Time,Tin,Tdewin,Ahrin

19913 PRINT USING 20e0;Time,Tin,Tdewin,Ahrin,Rhin,Tout,Tdewout,Ahrout,Rhout,Dpta,

Mr'at e, Speed

21300 IMAGE DDDDD,2(lX, DD.DD,IX,MDD.DD,lX, .DDDDDD,lX, .DDD),2X,DDD.D,lX,D.DDDE,

U-':,D.DDD

42
TR-2774

2010

2020 IF Filea$=IINS II THEN 2110

2030 IF Stor=0 THEN 2110

2040 DISP Tlme,V(3),V(4)

2050 IF Fff=PI THEN 2100

2060 IF Fff<>PI THEN PRINT 81;T;me,V(*>

2070 ON ERROR GOTO 2090

2080 GOTO 2110

2090 Fff=PI

2100 IF Fff=PI THEN PRINT 82;T;me,V(*)

2110 !

2120 IF Time>=Tmax THEN 2170

2130 ENABLE

2140 GOTO 2140

2150 DEF FNTfveV)=.0088+26.10*eV*1000)-.7931*(V*1000)A2+.0444*(V*10(0)A3

2160 DEF FNVis(T)=1.459E-6*TA1.5/(T+110.77>

2170 STOP

2180 END

2190 DEF FNPsat(T)

2200 IF T>273.15 THEN Pr=EXPC23.28199-3780.82/T-225805/T A2)

2210 IF T<=273.15 THEN Pr=EXPC28.87-6133.8/T)

2220 RETURN Pr

2230 FNEND

43
TR-2774

****

***

***

$$$

MARCH 1, 1985

SECOND VERSION

*** AHMAD PESARAN

***

$$$

**** PLOT

THIS PROGRAM PLOTS THE

EXPERIMENTAL AND THEORF.TICAL RESULTS

THE EXPERIMENTAL RESULTS ARE FROM THE

SERI SINGLE BLOW TEST FACILITY

THE THEORETICAL RESULTS ARE FOM THE

IIDESICCANT II CDDE

513

113

213

30

40

60

713

80

90

100

110

120

130 PTION BASE 1

140 OVERLAP

150 PRINTER IS 0

160 DIM V(9),A1(102),A2(le2),A3(102)

170 R=8314.12 !m A3*pa/kmole*K UNIVERSAL GAS CONSTANT

180 Mwair=28.67 ! AVERAGE MOLECULAR WEIGHT OF HUMID AIR

190 Mr=Mwair/R

200 Pconv=1.0133E5/760 ! CONERSION FACTOR FROM TORRS TO PASCAL

210 INPUT ENTER EXPERIMENT RUN # ?1I,Run

22£1 PRINT EXPERIMENT RUN" ?1I,Run

230 INPUT DATE OF TEST MM/DD/YY ?1I,Date$

24£1 PRINT DATE OF EXPERIMENT MM/DD/YY II,Date$

250 INPUT ENTER DURATION OF EXPERIMENTCPERIOD) IN MINUTES ?1I,Time_max

260 PRINT DURATION OF EXPERIMENT IN MINUTES ?",Time_max

270 I NPUT Et~TER MAX I MUM VALUE ON TI ~1E AX I S", H1

280 PRINT ENTER MAXIMUM VALUE ON TIME AXIS",Hl

290 D=6*2.54/100 ! DUCT DIAMETER(m)

3£10 PRINT IIDUCT DIAMETER IN METERS II,D

31 0 H'~PUT II WHAT I S THE DIAMETER RAT I 0 OF OR I F ICE PLATE ? ", Be·t,..:1

320 PRINT "DIAMETER RATIO OF ORIFICE PLATE Cd/D) ",Beta

330 INPUT liDO YOU WANT TO CHANGE THE SPECIFICATIONS OF THE DEHUMIDIFIER CY/N).

?1I,Spd$

340 IF Spd$=IIY" THEN Change

350 X sh=5.8E-4

360 X=sp=1.664E-3

370 L=.2

380 Area=1.18E-1*1.28E-1

390 GOTO Coo

400 Change: I NPUT II SHEET TH I CKNESS, SPAC I ~~G BETWEE~~ SHEETS, LE~~GTH, FROt~TOL AF.~EA II ,

X sh,X sp,L,Area

410 PRI t'~T II SHEET TH I CKNESS, SPAC I NG BETWEEN SHEETS, LE~~GTH, FRONTOL AREA II , ::-::_sh, ~-<_::.

p,L,Area

420 Coo:

430 Dh=2*(X sp-X sh)

440 Porosity=(X_sp-X_sh)/X_sp

450 Areaf=Area*Porosity

44
TR-2774

460 Nu=8.235 NUSSELT NUMBER

470 Sc=.61 ! SCMIDTH NUMBER

480 Spv=2 ..... X sp

490 Beta4=BeiaA4

500 E=(1-Beta4)A(-.5)

510 Mconst=E*(D*Beta)A2*SQR(2)*PI ..... 4

520 Econst=(.41+.35*Beta4)/1.4

530 Reconst=4/PI/D

540 INPUT "ENTER FILE NAME OF THEORETICAL RESULTS (T:15) '7",Ftheo$

550 PRINT "FILE NAME OF THEORETICAL RESULTS IS ",Ftheo$

560 INPUT "WHAT IS AVERAGE INLET HUMIDITY RATIO FOR THEORETICAL SIMULATIONS '7 11,

Hrin ave

570 -PRINT "AVERAGE INLET HUMIDITY RATIO FOR THEORETICAL SIMULATIONS ?",Hrin ave

580 INPUT "WHAT IS AVERAGE INLET TEMPERATUR FOR THEORETICAL SIMULATIONS ?11,fin_

ave

590 PRINT AVERAGE INLET TEMPERATUR FOR THEORETICAL SIMULATIONS ?",Tin ave

600 INPUT ENTER FILE NAME OF EXPERIMENTAL DATA C:T14)?II,Filea$ - 610 PRINT FILE NAME OF EXPERIMENTAL DATA IS II,Filea$

620 INPUT ENTER INITIAL DATA POINT TO BE IGNORED? ",Ignore

630 PRINT INITIAL DATA POINT TO BE IGNORED? ",Ignore

640 INPUT ENTER START-UP TIME IN SECONDS? ",Stime

650 PRINT STAT-UP TIME IN SECONDS? II,Stime

660 Stime=Stime/60

670 H2=H1/2

680 H3=2*Hl/3

690 H4=-H1/18.5

700 H5=-H1/7.5

710 PRINTER IS 0

720 PLOTTER IS IIGRAPHICS"

730 PLOTTER IS 7,O, "9872A II

740 LIMIT 0,260,0,200

750 LOCATE 16,116,18,83

760 DI SP II CHANGE THE PAPER A~~D PRESS CONT I NUE II

770 BEEP

780 PAUSE

790 DIS? II II

S00 Tmin=-20

810 Tmax=80

820 SCALE Tmin,Tmax,0,H1

830 AXES 10,5,Tmax,Hl,2,2,5

840 Hmin=0

850 Hmax=.04

860 SCALE Hmin,Hmax,0,Hl

870 AXES .002,5,Hmin,0,2,2,5

880 I NPUT II DO 'y'OU WAt~T TO LABEL AX I S C(' /~D ? II , Lb1 ; t"II;;1$

890 IF Lbling$=IIN" THEN GOTO Pl'Jttit"lg

90e LORG 5 .

910 LDIR 3*PI/2

920 CSIZE 2.5

930 Y1=-.0350*CTmax-Tmin)+Tmin

940 Y2=-.115*CTmax-Tmin)+Tmin

950 Y3=1.10*(Tmax-Tmin)+Tmin

45
TR-2774

96£1

970

98£1

990

1£1£10

101£1

102£1

1030

104121

105121

106121

107121

1080

11219121

11£10

111121

112121

113121

114121

115121

1160

1170

118121

119£1

121210

1210

1220

1230

124121

1250

1260

1270

1280

1290

1300

131121

132121

1330

1340

1350

136£1

137e

1380

1390

14121121

1410

1420

14:30

1440

1450

1460

147121

148e

SCALE Tmin,Tmax,e,Hl

FOR x=e TO HI STEP Ie

MOVE Yl,Hl-X

LABEL USING IIDDDII;X

NEXT X

FOR Y=Tmin TO Tmax STEP Ie

MOVE Y,HI-H4

LABEL USING IIDDD.DII;Y

NEXT Y

CSIZE 3.5

MOVE Y2,HI-H2

LABEL USING IIK II;IITIME (min.)11

MOVE Y3,HI-H3

LABEL USING IIDDD II;Run

MOVE Y3,HI-H2

LABEL USING IIK II;IIEXPERIMENT # II

LDIR e

MOVE (Tmax+Tmin)/2,HI-H5

LABEL USING IIK II;1I0UTLET AIR TEMPERATURE ,(C)II

GOT 0 Lab 1".-

Plotting:

LDIR €I

PDIR €I

MASS STORAGE IS II:TI5 11

ASSIGN #3 TO Ftheo$

1=1

Theo: !

READ #3;Al(I),A2(I),A3(I)

Al(I)=Al(I)*Time max

PRINTER IS 16 -

PRINT ,Al(I),A2(I),A3(I)

IF Al(I»=Time_max THEN GOTO Out thea

1=1+1

IF 1>1£11 THEN GOTD Out theo

GOTO Theo -

Out theo: !

SCALE Hmin,Hmax,0,Hl

FOR J=1 TO I

PRINT Al(J),A2(J)

PLOT A2(J),HI-Al(J> PLOT HUMIDITY RATIO VS. TIME

NEXT J

MOVE £1,0

PLOT Hrin ave,HI-Al(l)

PLOT Hrin:ave,HI-Al(I)

PENUP

SCALE Tmin,Tmax,0,Hl

FOR J=1 TO I

PRINT Al(J),A3(J)

PLOT A3(J),HI-Al(J) PLOT TEMPERUTURE VS. TIME

NEXT J

PENUP

PLOT Tin ave,HI-Al(l)

PLOT Tin-ave.HI-Al(I)

46
TR-2774

14910 PENUP

151.310 LORG 5

15110 CSIZE 5

'1320 MASS STORAGE I S ": T14 II

1530 ASSIGN #1 TO Filea$

1540 Count=0

1550 Timeold=0

1360 Ms=0

11570 Nt us=0

1580 Begin: I PLOT OF EXPERIMENTAL RESULTS

1590 Count=Count+l

16010 READ #l;Time,V(*)

1610 IF Count<Ignore THEN 15910

16210 Time=Time/60

1630 Timenew=Time-Stime

1640 IF Timenew>Time max THEN Out

1650 Pab=V(9)*le00*pconv IABSOLUTE PRESSURE IN PASCAL

16610 Vbp=V(1)+V(2) ISUMMATION OF e.m.f. FROM BYPASS AND BOX(mV)

16710 Tbp=FNTfv(Vbp) ITEMPERATURE OF BYPASS (C)

16810 Denair=Pab*Mr/(Tbp+273.1S) !DENSITY OF AIR (kg/mA3)

16910 Dpo=V(8)*Pconv IPRESSURE DROP ACROSS ORIFICE PLATE (PASCAL)

17010 Expan=I-Econst*Dpo/Pab

1710 C=.6 I INITIAL VALUE OF DISCHARGE COEFFICIENT

1720 Mf=Mconst*Expan*SQR(ABS(Dpo*Denair»

17310 Counter=0

1740 !

1750 Mrate=C*Mf I AIR MASS FLOW RATE (kg/s)

1760 Counter=Counter+l

1770 Re=Reconst*Mrate/FHVis(Tbp+273.13)

1780 I PR I NT II RE= "; Re, II PAB= "; Pab; II PASCAL "; II DPO= "; Dpo; II PASCAL II I CALCULALE

HEW VALUE OF DISCHARGE COEFFICEINT.

1790 Cnew=.5959+.0312*BetaA2. 1-. 184*BetaA8+.0029*BetaA2.5*( lE6/Re)A.75+.e39*Bet

a4*(I-Beta4)A(-I)-.01583*BetaA3

18010 IF ABS(Cnew-C)/Cnew(.00e3 THEN 1850

1810 IF Counter>=3 THEN 1850

18210 C=Cnew

18310 Mrate=C*Mf

1840 GOTO 1740

1850 I

18610 ! PRI NT II C=II ; C, II RE=II ; Re, II MRAT E=II ; Mr at e; II ( kg ..... s ) II , II CO UNTER=II ; Count e r

1870 ! CALCULATE DEW POINT TEMPERATURE OF B~(PASS USING V(5)

1880 Vtout=V(4)/4+V(2) IBOX VOLTAGE AND OUTLET TC ARRAY

1890 Tout=FNTfv(Vtout)

1900 Tdewout=V(6)*10

1910 Pvout=FNPsat<Tdewout+273.15)

1920 Ahrout=~622*Pvout/(Pab-Pvout)

1930 Rhout=Pvout/FNPsat(Tout+273.15)

1940 Vtin=V(3)/4+V(2)

19510 Tin=FNTfv<Vtin)

1960 Tdewin=v(5)*10

1970 Pvin=FNPsat<Tdewin+273.15)

1980 Ahrin=.622*Puin/(Pab-Pvin)

1990 Rhin=Puin/FNPsat(Tin+273.1S)

47
TR-2774

"

2000 Pab=V(9)*100e*pconv

20110 Denair=Pab*Mr/(Tin+273.15)

2020 Expan=l-Econst*Dpo/Pab

2030 Speed=Mrate/Denair/Areaf

20410 Re dh=Mrate*Dh/Areaf/FNVisCTin+273.15)

2050 St;Nu/Re dh/Sc

21060 Ntu=St*Spv*L

2070 Mflow=Mrate*(Timenew-Timeold)

2080 Ms=Mflow+Ms

2090 Ntus=Ntu+Ntus

2100 DISP Timenew,.Mrate,Ms,Ntu

2110 SCALE Tmin,Tmax,0,H1

2120 MOVE Tin,H1-Timenew

2130 LABEL USING IIK II;II.II

2140 MOVE Tout,H1-Timenew

2150 LABEL USING IIK II;II.II

2160 SCALE Hmin,Hmax,0,H1

2170 MOVE Ahrin,H1-Timenew

21810 LABEL USING IIK II;II.11

21910 MOVE Ahrout,H1-Timenew

2200 LABEL USING "K";II.11

22110 Timeold=Timenew

22210 GOTO Begin

22310 Out:!

2240 Mrate ave=Ms/Timenew

22510 Dpta=V(7)*Pconv

22610 ! PRI tiT II TOUT= II ; Tout , II TD E~J OU T=II ; Tde·I.IJol_~t , II AHROUT =II ; Aht·'C1I.~t , II F~HO UT= II ; F.: hC1IJ t

22710 ! PRI NT II TIN =II ; Ti rl, II TDE~.J I t·~ =II ; Tde l'J i n , II AHRI t~ =II ; Ah r' in, II RHI N=II ; Rh i n

22810 ! PRINT LIN(2)

22910 ! PRINT Time,Tin,Tdewin,Ahrin

23010 PRINT USING 2310;Time,Tin,Tdewin,Ahrin,Rhin,Tout,Tdewout,AhrClut,Rhout,Dpta, ~1r'at e , Speed

23110 IMAGE DDDDD,2C1X, DD.DD,lX,MDD.DD,lX, .DDDDDD,1X, .DDD),2X,DDD.D,lX,D.DDDE,

1>::,D.DDD

2320 !

23310 PRINT "AVERAGE t'1ASSFLOW RATE Ckl;l/m"'<3) ", Mr·.ate_.3".,Je

2340 Ntu ave=Ntus/(Count-Ignore)

23510 PRIN'T II AVERAGE ~~TU II, Nt u a~..le

23610 GaTO Stop1 -

2 :3 710 Lab 1e : !

23810 SCALE Hmin,Hmax,e,H1

23910 LORG 5

241010 LDIR 3*PI/2

2410 CSIZE 2.5

24210 PRINT Hmin,Hmax

24310 Y1=-.e417*CHmax-Hmin)+Hmin

24410 Y2=-.125*(Hmax-Hmin)+Hmin

24510 Y3=1.125*(Hmax-Hmin)+Hmin

24610 FOR Y=Hmin TO Hmax STEP .10104

2470 MOVE Y,H4

24810 LABEL USING IID.DDD";'y'

24910 NEXT 'y'

:;:510121 CSIZE 3.5

48
TR-2774

251121 LDIR 121

252121 MOVE CHmax+Hmin)/2,H5

253121 LABEL USING "K"; "0UTLET HUMIDIT'y' RATIO, (kg/kg) II

254121 GOTO Plotting

255121 St op 1: !

256121 DEF FNTfv(V)=.0e88+26.10*(V*1I21e0)-.7931*(V*100121)A2+.0444*<V*100e)A3

257121 DEF FNVisCT)=1.459E-6*TA1.5/(T+11121.77)

258121 STOP

259121 END

26121121 DEF FNPsatCT)

261121 IF T>273.15 THEN P~=EXPC23.28199-37SI2l.82/T-225805/TA2)

262121 IF T<=273.15 THEN P~=EXP(28.87-6133.8/T)

263121 RETURt~ p~

264121 FNEND

49
William M. Anderson

Anderson Consulting

7605 E. Windlawn Way

Parker, CO 80134

SELECTED DISTRIBUTION LIST

Phillip Fairey

Florida Solar Energy Center

300 State Road, 401

Cape Canaveral, FL 32920

TR-2774

Carl Bergt

Trane Systems Engineering Co.

6200 Troup Highway

Tyler, TX 75711

Kennard L. Bowlen

Cargocaire Engineering Corp.

79 Monroe St.

Amesbury, MA 01913

Glen Chinery

Tennessee Valley Authority

217 Power Board Bldg

Chattanooga, TN 37401

James Coellner, Director R&E

American Solar King Corp.

700 Loop 340 South

Waco, TX 76710

Barry Cohen

Thermal Products Division

ThermoElectron Corporation

45 First Avenue

Waltham, MA 02154

Kirk Collier, Ph.D.

Everscope, Inc.

4886 W. Port Au Prince

Glendale, AZ 85306

Keith Davidson

Gas Research Institute

8600 West Bryn Mawr Avenue

Chicago, IL 60631

Jim Hill, Ph.D.

National Bureau of Standards

Technology B-148

Washington, D.C. 20585

Michael Epstein

Fauske & Associates, Inc.

162070 West 83rd Street

Burr Ridge, IL 60521

50

Stephen D. Fitch

Bry-Air

P. O. Box 795

Sunbury, OH 43074

Anthony Fraioli, Ph.D.

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

John Goldsmith

U.S. Department of Energy

Route CE-311, Room 5H065

1000 Independence Ave., S.W.

Washington, DC 20585

Anthony Hines, Ph.D.

College of Engineering

Oklahoma State University

Stillwater, OK 74078

Robert Jones

Los Alamos National Laboratory

P.O. Box 1663

Mail Stop H577

Los Alamos, NM 87545

K. LaPorta

SEIA

1156 15th St., N.W., Suite 520

Washington, DC 20005

Za1man Lavan, Ph.D.

Illinois Institute of Technology

Department of Mechanical Engineering

Illinois Institute of Technology

Center

Chicago, IL 60616

Robert LeChevalier

U.S. Department of Energy

San Francisco Operations Office

1333 Broadway

Oakland, CA 94612
George O. G. Lof, Ph.D.

Colorado State University

Solar Energy Applications Laboratory

Fort Collins? CO 80523

Ian Maclaine-cross, Ph.D.

University of New South Wales

School of Mechanical and Industrial

Engineering

P.O. Box 1

Kensington, NSW 2033 Australia

John Mitchell, Ph.D.

University of Wisconsin-Madison

Engineering Research Building

1500 Johnson Drive

Madison, WI 53706

Jeff Morehouse

Department of Mechanical Engineering

University of South Carolina

Columbia, SC 29208

Frederick Morse, Ph.D.

U.S. Department of Energy

Route CE-31, Room 5H-095

1000 Independence Ave., S.W.

Washington, DC 20585

Yves O. Parent

Res. Eng.

Industrial Chemicals Research

Davison Chemical Division

W. R. Grace & Co.

Washington Research Center

7379 Route 32

Columbia, MD 21044

David Pellish

Solar Buildings Technology Division

Office of Solar Heat Technology

U.S. Department of Energy

Forrestal Building, Room 5H-041

1000 Independence Ave., S.W.

Washington, DC 20585

D. M. Ruthven, Ph.D.

University of New Brunswick

P. O. Box 4400

Fredericton, N.B.

Canada ES8 5A3

51

TR-2774

M. Wahlig, Ph.D.

Lawrence Berkeley Laboratories

University of California

1 Cyclotron

Berkeley, CA 94720

Alex Willman

ACEC Resource and Management

Foundation

1015 15th Street, N.W.

Washington, DC 20005

Byard Wood, Ph.D.

Department of Mechanical & Aerospace

Engineering

Arizona State University

Tempe, AZ 85287
Document Control 11. SERI Report No. 12. NTIS Accession No.

Page SERI/TR-252-2774

4. Title and Subtitle

Heat &Mass Transfer Analysis of a Desiccant

Dehumidifier Matrix

7. Autho~(s)

A.A. Ppr;rtran

9. Performing Organization Name and Address

Solar Energy Research Institute

A Division of Midwest Research Institute

1617 Cole Boulevard

Golden, Colorado 80401-3393

12. Sponsoring Organization Name and Address

15. Supplementary Notes

3. Recipient's Accession No.

5. Publication Date

July 1986

6.

8. Performing Organization Rept. No.

10. Project/Task/Work Unit No.

3009.10

11. Contract (C) or Grant (G) No.

tC)

(G)

13. Type of Report & Period Covered

Technical Report

14.

16. Abstract (Limit: 200 words)

This report documents the SERI Single-Blow Test Facility's design, fabrication,

and testing for characterizing desiccant dehumidifiers for solar cooling

applications. The first test article, a silica-gel parallel-plate dehumidifier

with highly uniform passages, was designed and fabricated. Transient heat and

mass transfer data and pressure drop data across the dehumidifier were obtained.

Available heat and mass transfer models were extended to the parallel-plate

geometry, and the experimental data were compared with model predictions.

Pressure drop measurements were also compared with model predictions of the fully

developed laminar flow theory. The comparisons between the lumped-capacitance

model and the experimental data were satisfactory. The pressure drop data compared satifactorily with the theory (within 15%). A solid-side resistance model

that is more detailed and does not assume symmetrical diffusion in particles

was recommended for performance. This study has increased our understanding

of the heat and mass transfer in silica gel parallel-plate dehumidifiers.

17. Document Analysis

a. Descriptors Dehumi di fi ers ; Desi ccants ; Heat Transfer ; r·1ass Transfer ;

Silica Gel; Testing

b. Identifiers/Open-E~ed Terms

c. UC Categories

59a

18. Availability Statement

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, Virginia 22161

Form No. 0069 (3-25-82)

19. No. of Pages

63

20. Price

A04