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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. Uyun
1
, Alie Bamahry

2
 and Rino Imanda

2
 

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; accept ed 05 May 2016 

 

Abstract 

Desiccant cooling system has been an at-

tractive topic for study lately, due to its env i-

ronmentally friendly nature. It also consume less 

electric ity and capable  to be operated without 

refrigerant. A simu lation s tudy was conducted 

using 1.5 m long ducting equipped with one  

desiccant wheel, one sensible heat e xchanger 

wheel, one evaporative cooling chamber and  

two blowers and one electric heater. The simu -

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

ing coefficient fro m desiccant wheel, k1=2.1 

(1/s), mass transfer coeffic ient in evaporative  

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

cient in desiccant wheel, h 1=4.5 W/ m
2 o

C, and  

heat transfer coeffic ient in sensible heat e x-

changer wheel h2= 4.5 W/ m
2 o

C. The  simulat ion 

results show that the final te mperature before  

entering into the a ir conditioning roo m was 25
 

o
C and RH o f 65 % , we re in accordance with the 

Indonesian comfort index. 

Ke ywor ds: desiccant wheel, desiccant cooling, 

evaporative cooling, sensible heat 

exchanger wheel, silica gel 

1. Introduction 

Indonesia lies in the tropic  whe re the average  

air te mperature is around 30 
o
C and RH around 

80%  a ll year round. Under this weather cond i-

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 fac ilities 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 environ ment. As the 

current air conditioning system requires high 

electric ity consumption which requires high 

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

tive for the conventional air conditioning system. 

The best option would be a desiccan t cooling  

system wh ich does not need refrigerant for o p-

erating the system. Through the manipu lation of 

air condition using silica ge l it is possible to 

create a comfort condition of a room. 

Research on this type of a ir 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 perfo rmance

 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 T wo  

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 re moval 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 te mperature 26.7 
o
C with hu-

midity  ratio  of W=0.01183 kg/kg  dry a ir for the  

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

ric chart  and the result of their simu lation works  

were applied to four c ities in the USA. Be llia , et  

al (2000) had studied several hybrids cooling 

system using various desiccant wheels and using 

DesiCa lc
TM

 co mputer progra m and applied to  

four cities in Italy. They concluded that the 

ma ximu m saving in cost was 22% , and for the  

theater the saving were greater fro m 23%  to 38%  

with electricity saving of up to 55%. 

The purpose of the study is to obtain 

mathe matica l mode l for the purpose of simula -

tion of desiccant cooling system. 

* Corresponding aut hor, 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 ma jor co mponent of a des-

iccant cooling system which  comp rises of a  

desiccant wheel containing silica-gel, sensible 

heat exchanger whee l, a hot water heater su p-

plied fro m 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 hu mid 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. Fro m the sensible heat 

e xchanger 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  

comfo rtable condition for a ir conditioning. The  

air condition in the desiccant cooling system can 

also be traced using the Psychometric ch art in  

Fig.2.  Fro m 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 e xchanger its temper-

ature will inc rease while its RH is kept constant 

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

the air temperature inc rease again heating the 

desiccant wheel to the condition as point (8). 

After passing the desiccant wheel the a ir will 

gain moisture due to evaporation from the de s-

iccant wheel and it temperature will drop. 

 

Fig. 1 Main co mponent of desiccant cooling 

system (CNRS-LIMSI and Ku ma moto  

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 a xis of the total length of 1.5 

m of the duct can be calculated using the fo l-

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 a ir fro m 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) 

Fro m 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

T
hx

T
hx

A
hx

h

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 a mount of heat supplied fro m solar 

collector can  be ca lculated using the fo llo wing  

equations. 

)( TaTcAcLUAcrad
Iqu   (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 hu midity rat io change 

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

perature change. Table 2 shows simu lation 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 inco ming  

outside air is presented in Fig. 3  while the  

change in the incoming air te mperature is shown 

in Fig. 5 below. 

 

Fig. 3 Change of entering a ir hu midity ratio  

across the duct 

 

Fig. 4 Change of entering air te mperature fro m 

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

 r
a

ti
o

 (
k

g
 

v
a

p
o

r/
k

g
 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 fro m the room its h u-

midity ratio and te mperature change are as 

shown in Fig. 6 and 7. 

 
Fig. 5 Change in returning humidity ratio along 

the duct 

 
Fig. 6 Change in air te mperature  leav ing the 

conditioned room 

To achieve solar collector te mperature  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 e xchanger so that heat exchanger 

temperature can reach 65 
o
C the rate of water 

flow should be kept at  15 kg/s This te mperature  

will be used to heat the desiccant wheel to drive  

the moisture out from the desiccant. 

If the results of humidity ratio change an d 

the air te mperature change a long the duct are  

plotted in the psychrometric  chart the results is 

shown as in Fig. 8. 

 
Fig. 7 Change in a ir condition a long 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 mathe matica l 

model for desiccant cooling. 

2) Simu lation results using 0.35 x 0.35 m c ross 

section and length of 1.5 m, with air flow rate  

of 0.5kg/ m
2
s, and with heater te mperature of 

68 
o
C and using desiccant wheel, a sensible 

heat exchanger wheel and evaporative coo l-

ing  it was possible to create comfo rt 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 flo w 

rate 15 kg/s in order to produce the necessary 

heating temperature of 68 
o
C. 

Acknowledgement 

The authors wish to e xtend th eir g ratitude to 

the Directorate Genera l of Higher Education for 

providing a research grant under contract 

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

Darma  Pe rsada 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 coeffic ient 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

 r
a

ti
o

(k
g

 
v

a
p

o
r/

k
g

 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 riu m mo isture 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) 

T x2 = te mperature of sensible heat exchanger 

(
o
C) 

UL = overall loss coeffic ient of the collector 

(W/m
2
 C) 

V = air flow rate (m/det.) 

References 

[1] L. Be llia, P. Ma zzei, F. Min ichie llo, and D.         

Palma, “Air conditioning systems with desiccant 

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[2] C. Maalouf, E. Wurtz, and F. A lla rd, 
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the SimSPA RK  env iro n ment ,” UTA P,  

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la Housse, Reims, France, chadi. maa louf@

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[3] B. S. Davangere, S. A. She rie f, and D. Y. 

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