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Advances in Technology Innovation, vol. 2, no. 2, 2017, pp. 51 - 55 

51 

Simulation of Desiccant Cooling 

Kamaruddin  A.1,*, Aep S. Uyun1, Alie Bamahry2 and Rino Imanda2 

1
The Graduate School/Renewable Energy, Darma Persada UniversityJl. Indonesia  

2
Graduate student, the Graduate School/Renewable Energy, Darma Persada University, Indonesia  

Received 09 March 2016; received in revised form 30 April 2016; accepted 05 May 2016 

 

Abstract 

Desiccant cooling system has been an at-

tractive topic for study lately, due to its envi-

ronmentally friendly nature. It also consume less 

electricity and capable to be operated without 

refrigerant. A simulation s tudy was conducted 

using 1.5 m long ducting equipped with one 

desiccant wheel, one sensible heat exchanger 

wheel, one evaporative cooling chamber and  

two blowers and one electric heater. The simu-

lation study used 8.16 m/s primary air, the dry-

ing coefficient from desiccant wheel, k1=2.1 

(1/s), mass transfer coefficient in evaporative 

cooling, k2=1.2 kg vapor/s, heat transfer coeffi-

cient in desiccant wheel, h1=4.5 W/m
2 o

C, and  

heat transfer coefficient in sensible heat e x-

changer wheel h2= 4.5 W/m
2 o

C. The simulat ion 

results show that the final temperature before 

entering into the air conditioning room was 25
 

o
C and RH of 65 %, were in accordance with the 

Indonesian comfort index. 

Keywords: desiccant wheel, desiccant cooling, 

evaporative cooling, sensible heat 

exchanger wheel, silica gel 

1. Introduction 

Indonesia lies in the tropic where the average 

air temperature is around 30 
o
C and RH around 

80% all year round. Under this weather condi-

tion it  is not fit for people to work in the office or 

stay at home.  Therefore, there is an urgent need 

for air conditioning facilities in order to be able 

to live in a better condition. There is also need 

for industry to increase their productivity by 

creating better working environment. As the 

current air conditioning system requires high 

electricity consumption which requires high 

fossil fuel input, there is a need to find alterna-

tive for the conventional air conditioning system. 

The best option would be a desiccant cooling  

system which does not need refrigerant for op-

erating the system. Through the manipu lation of 

air condition using silica gel it is possible to 

create a comfort condition of a room. 

Research on this type of air conditioning  

system is new in Indonesia and very rare if any  

attempt to apply the system in  Indonesia. Re-

search by Chadi Maalouf. at al  in France (2006) 

indicated that by using solar energy they were 

capable to construct adsorption cooling system 

for application in several city in France.  Daou et 

al. (2004) and Jurinak (1982) have 

conducted research to determine the performance

 of an adsorption cooling machine using silica 

gel the Pennington cycle. Rajat Subhra Das et al. 

(1995) study the application of solar energy for 

liquid desiccant cooling system in India Two 

dimensionless parameters - enthalpy and mois-

ture effect iveness are taken as performance 

indices of the absorber. The performance of the 

overall system is presented in terms of its cool-

ing capacity, moisture removal rate and COP 

(coefficient of performance). Davangere et al. 

(1999) had applied a desiccant cooling system 

with  capacity 10 kW (2.85 ton refrigeration) 

assisted by vapor compression machine. The 

resulting room temperature 26.7 
o
C with hu-

midity  ratio  of W=0.01183 kg/kg  dry air for the 

condition Florida which have outside air of 36 
o
C. They conducted analysis using Psychromet-

ric chart  and the result of their simulation works  

were applied to four cities in the USA. Bellia, et  

al (2000) had studied several hybrids cooling 

system using various desiccant wheels and using 

DesiCalc
TM

 computer program and applied to  

four cities in Italy. They concluded that the 

maximum saving in cost was 22%, and for the 

theater the saving were greater from 23% to 38% 

with electricity saving of up to 55%. 

The purpose of the study is to obtain 

mathematical model for the purpose of simula-

tion of desiccant cooling system. 

* Corresponding author, Email: Kamaruddinabd@gmail.com 



Advances in Technology Innovation, vol. 2, no. 2, 2017, pp. 51 - 55 

52 Copyright ©  TAETI 

2. The Working Principle of A Des-

iccant Cooling System 

Fig. 1 shows the major component of a des-

iccant cooling system which  comprises of a 

desiccant wheel containing silica-gel, sensible 

heat exchanger wheel, a hot water heater sup-

plied from solar co llector, b lowers and evapo-

rative cooler (Pons and Kodama, 2014). Outside 

air is introduced through point (1) passing the 

hot desiccant wheel where the humid ity is re-

duced to point (2). The air will further passed 

through the sensible heat exchanger (point 3) 

where its temperature will be reduced while 

keeping its RH constant. From the sensible heat 

exchanger the air will be introduced into the 

evaporative cooling where its temperature will 

be reduced by its RH will be increased (point 4). 

When entering the room the temperature and RH 

will reach 26 
o
C and 55 %, respectively, a  

comfortable condition for air conditioning. The 

air condition in the desiccant cooling system can 

also be traced using the Psychometric chart in  

Fig.2.  From the room under condition of point 

(5) the air will be passed again through the 

evaporative cooling unit which will reduced its 

temperature and increase its RH. After passing 

through the sensible heat exchanger its temper-

ature will increase while its RH is kept constant 

as in point (6). After passing through the heater, 

the air temperature increase again heating the 

desiccant wheel to the condition as point (8). 

After passing the desiccant wheel the air will 

gain moisture due to evaporation from the des-

iccant wheel and it temperature will drop. 

 

Fig. 1 Main component of desiccant cooling 

system (CNRS-LIMSI and Kumamoto  

University, 2014) 

 

Fig. 2 Air condition in a Psychometric chart  

(CNRS-LIMSI and Kumamoto University, 

2014) 

3. Mathematical Modelling 

If m is the total mass of air in the duct and x 

is the humid ity ratio then the humidity ratio  

change along the z axis of the total length of 1.5 

m of the duct can be calculated using the fol-

lowing mass balance equations 

m 0.5z0  f/)(1  orVMeMk

dz

dx
　  (1) 

m 1.5z 1.1for      /)(  Vmsxxc

dz

dx
 (2) 

To calculate the change in temperature along 

the duct from the in let to the duct out let and 

energy balance will be used.  

m 0.5z0.0for 

 )1(11



 TTxAxh

dt

dz
x

dz

dT
mCp

 (3) 

m 1.1z0.5for 

 )2(22



 TTxAxh

dt

dz
x

dz

dT
mCp

 (4) 

1.5mz1.1for  

)(



 sTTevh

dt

dz
x

dz

dT
mCp

 (5) 

For the condition of the return air from the 

air condition room, the following mass balance 

equation will be used. 



Advances in Technology Innovation, vol. 2, no. 2, 2017, pp. 51 - 55 

53 Copyright ©  TAETI 

m 1.1z 1.5for      /)(  Vmsxxc

dz

dx
 (6) 

m 0.0z0.5    f

/)(1





or

VMeMk

dz

dx

 (7) 

From the energy balance the following rela-

tion can be obtained 

1.5mz1.1for 

 )(



 sTTevh

dt

dz
x

dz

dT
mCp

 (8) 

m 0.8z1.1for 

)2(22



 TTxAxh

dt

dz
x

dz

dT
mCp

 (9) 

)2(22
2

22
TTxAxh

dt

dTx

xCpxm   (10) 

mz

ThxThxAhxh

dz

dT
mCp

5.08.0for 

)(




 (11) 

m 0.0z0.5for 

 )1(11



 TTxAxh

dt

dz
x

dz

dT
mCp

 (12) 

)1(11
1

11 TxTxAh

dt

xdT

xCpxm   (13) 

The amount of heat supplied from solar 

collector can  be calculated using the fo llowing  

equations. 

)( TaTcAcLUAcradIqu   (14) 

)( hxTTcwCpwmqu    (15) 

4. System Simulation 

With the use of parameters listed in Table 1, 

a simulation study was conducted. The results 

are as shown in Fig. 4 for humidity rat io change 

along the duct and in Fig. 5 showing the tem-

perature change. Table 2 shows simulation data 

for solar collector hot water supply. 

Table 1 Simulation data 
 

Quantity Quantity Quantity 

m=0.06kg Ts=23 
o
C hev=3.7 (W) 

V= 8.16 m/s Ax1=4.5 m
2
 mx2=1.25 kg 

k1=0.5 (1/s) Ax2=1.5 m
2
 

Cpx2=0.897 

kJ/kg 
o
C 

k2= 0.5 (kg 

vapor/s) 

h1=4.5 

W/m
2
 C 

Ahx=1.5 m
2
 

Xs=0.007 
h2=4.5 

W/m
2
 C 

hhx=3.5 

W/m
2 o

C 

Me=7(%db) Tx3=68 
o
C Thx=68 

o
C 

mx1=2.3 kg 
Cpx1=0.921 

kJ/kg 
o
C 

 

Table 2 Data for Solar Collector Heating 

 

mw (kg/s) Cpw(kJ/kg
o
C) Irad (W/m

2
 C) 

15 4.19 600 

Ac (m
2
) UL (W/m

2
 C) 

1.64 4.5 

Change in absolute humid ity of incoming  

outside air is presented in Fig. 3  while the 

change in the incoming air temperature is shown 

in Fig. 5 below. 

 

Fig. 3 Change of entering air humidity ratio  

across the duct 

 

Fig. 4 Change of entering air temperature from 

duct inlet 

0

0.005

0.01

0.015

0.02

0 0.20.40.60.8 1 1.21.4

H
u

m
id

it
y 

ra
ti

o
 (

kg
 

va
p

o
r/

kg
 d

ry
 a

ir
) 

Distance from duct inlet(m) 

0

20

40

60

0 0.2 0.4 0.6 0.8 1 1.2 1.4A
ir

 t
e

m
p

e
ra

tu
re

(o
C

) 

Distance from duct inlet (m) 



Advances in Technology Innovation, vol. 2, no. 2, 2017, pp. 51 - 55 

54 Copyright ©  TAETI 

For the returning air from the room its hu-

midity ratio and temperature change are as 

shown in Fig. 6 and 7. 

 
Fig. 5 Change in returning humidity ratio along 

the duct 

 
Fig. 6 Change in air temperature leav ing the 

conditioned room 

To achieve solar collector temperature of 75 
o
C there is a need to supply 651.9 Watt of energy 

and if this heat is supplied to the heater in the 

form of heat exchanger so that heat exchanger 

temperature can reach 65 
o
C the rate of water 

flow should be kept at  15 kg/s This temperature 

will be used to heat the desiccant wheel to drive 

the moisture out from the desiccant. 

If the results of humidity ratio change and 

the air temperature change along the duct are 

plotted in the psychrometric chart the results is 

shown as in Fig. 8. 

 
Fig. 7 Change in air condition along the duct as 

plotted in the psychrometric chart (Da-

vanagere dkk, 1999) 

As shown here the air condition entering the 

room has achieved the comfort condition of 25 
o
C and RH of 65% (see point 4). 

5. Conclusions 

1) It was possible to develop mathematical 

model for desiccant cooling. 

2) Simulation results using 0.35 x 0.35 m cross 

section and length of 1.5 m, with air flow rate 

of 0.5kg/m
2
s, and with heater temperature of 

68 
o
C and using desiccant wheel, a sensible 

heat exchanger wheel and evaporative cool-

ing  it was possible to create comfort air 

condition of  25 
o
C and RH 65%. 

3) It was necessary to supply heat from solar 

collector having area of 1.64 m
2 

with average 

solar irradiation of 600 W/m
2
 and water flow 

rate 15 kg/s in order to produce the necessary 

heating temperature of 68 
o
C. 

Acknowledgement 

The authors wish to extend their g ratitude to 

the Directorate General of Higher Education for 

providing a research grant under contract 

No.104/K3/KM/2015, February 23, 2015 and to  

Darma Persada University Research Institute 

and Public Empowerment and Cooperation 

through Contract No: 022/ SP3 /  LP2MK /  

UNSADA/II/2015 February 23, 2015. 

Nomenclature 

Ac = area of solar collector (m
2
) 

Ax1 = heat transfer surface of the desiccant (m
2
) 

Ax2 = surface heat transfer of the sensible heat 

exchanger (m
2
) 

c = mass transfer coefficient in the evaporative 

cooler (kg/s.) 

Cp = specific heat of the air (kJ/kg 
o
C) 

Cpx1 = specific heat of desiccant (kJ/kg 
o
C) 

Cpx2 = specific heat of sensible heat exchanger 

(kJ/kg 
o
C) 

h1 = heat transfer coefficient of the desiccant 

wheel (W/m
2
 
o
C) 

h2 = heat transfer coefficient of the sensible heat 

exchanger (W/m
2  o

C) 

hhx = heat transfer coefficient of the heater 

(W/m
2 o

C) 

0

0.01

0.02

0.03

1.5 1.3 1.1 0.9 0.7 0.5 0.3 0.1

H
u

m
id

it
y 

ra
ti

o
(k

g 
va

p
o

r/
kg

 d
ry

 a
ir

) 

Distance from duct inlet (m) 

0

20

40

60

80

1.5 1.3 1.1 0.9 0.7 0.5 0.3 0.1

A
ir

 t
e

m
p

e
ra

tu
re

 
(o

C
) 

Distance from duct inlet(m) 



Advances in Technology Innovation, vol. 2, no. 2, 2017, pp. 51 - 55 

55 Copyright ©  TAETI 

hev = rate of heat transfer with the evaporative 

cooling (W) 

Irad = solar irradiation (W/m
2
) 

k1 = desorption  constant (1/det.) 

m = mass of air (kg) 

mx1 = mass of desiccant wheel (kg) 

mx2 = mass of sensible heat exchanger wheel 

(kg) 

M = moisture content of desiccant (%db) 

Me = equilib rium moisture content of desiccant 

(%db) 

qu = usefull energy from the sun  (Watt) 

Ta = ambient temperature (
o
C) 

Tc = collector temperature (
o
C) 

Thx = heat exchanger temperature (
o
C) 

Ts = temperature of evaporative cooling (
o
C) 

Tx1 = desiccant temperature (
o
C) 

Tx2 = temperature of sensible heat exchanger 

(
o
C) 

UL = overall loss coefficient of the collector 

(W/m
2
 C) 

V = air flow rate (m/det.) 

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