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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 46, 2015 

A publication of 

 
The Italian Association 

of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Peiyu Ren, Yancang Li, Huiping Song 
Copyright © 2015, AIDIC Servizi S.r.l., 
ISBN 978-88-95608-37-2; ISSN 2283-9216 

Investigation on the Effect of Fin Width on the Heat Transfer 
Performance of the Condenser Used in the Automotive Air 

Conditioning System 
Yonghua Cao*, Xiaomin Cui 

School of Mechanical and Electrical Engineering, Henan Institute of Science and Technology, Henan, Xinxiang, China. 
372669924@qq.com 

The efficiency of the air conditioning system will affect the comfort and the energy consumption. Therefore, 
study on it can help to reduce the emission reduction. In the system, condenser is a quite important part, 
which mainly affect the performance of the whole device. In this paper, a new type structure of condenser of 
automotive air conditioning system has been studied, and some conclusion has been obtained: (1) Unit area 
heat exchange decreases when the fin width increases. The resistance increases with the fin width increases, 
and the heat transfer coefficient decreases with the fin width increases; (2) The resistance has a higher 
decreasing speed and both heat transfer coefficient and the total heat flux increase at a lower speed, which 
means that the overall heat transfer rate can’t be increased just by increase the width of the fin. According to 

the study of the effect of fin width on the condenser performance, the validity of the computational fluid 
dynamics (CFD) applied on the air conditioning system has been proven. 

1. Introduction 

Modern automobile design pays more and more attention on the characteristics, including body shape (Per 
Mårtensson, Dan Zenkert, Malin Åkermo (2015)), structure lightweight (Åsa Kastensson (2015)), etc. 
Especially for the shape, the study on it mainly meets the air dynamics requirements to reduce energy 
consumption (Andrea Rusich, Romeo Danielis (2015)) and achieve the aim of energy-saving and emission 
reduction. Besides, the air conditioning system of the automobile consumes more energy, and the optimization 
of the performance of the automobile air conditioner can also help reduce the energy consumption. Therefore, 
the research on the air conditioner (S.P. Datta, P.K. Das, S. Mukhopadhyay (2014); Alison Subiantoro, Kim 
Tiow Ooi (2013)) has an important effect on the automobile energy saving. 
Automotive air conditioning system study mainly concentrates on the flow structure, heat transfer and 
resistance characteristics. There are three methods for the research of automobile air conditioning system, 
including traditional experimental study, computer programming, and computational fluid dynamics (CFD) 
technology for numerical simulation (M. Abdulkadir, V. Hernandez-Perez, S. Lo, I.S. Lowndes, B.J. Azzopardi. 
(2015)). Among of all the methods, CFD technology is a powerful tool in the research of heat transfer, mass 
transfer, momentum transfer, combustion, multiphase flow and chemical reaction. Meanwhile, the optimization 
design of automobile air conditioning system is one of the important application fields of CFD. Traditional 
automotive air conditioning system design generally relies on basic theory and experimental analysis to 
determine the structure of the automotive air conditioning system, which requires a lot of experimental funds 
as well as a quite long development cycle. For automobile air conditioning system, the flow and heat transfer 
characteristics of the internal fluid are more complex (S.P. Datta, P.K. Das, S. Mukhopadhyay. (2014)), and 
performance of the new vehicle air conditioning system can’t meet the requirement just by experimental test. 

Therefore, CFD software, which can quickly, accurately and intuitively reflects the flow of fluid in automobile 
air conditioning system, has been applied to find out the problems in the design of the flow field analysis to 
improve the design efficiency. 
The application of CFD technology in the automotive air conditioning system is mainly on the design of the 
duct (Wenxian Zheng, Ying Chen, Nan Hua, et, al (2014)), evaporator (Kyung Hwan Kim, Sun Hwa Kim, 

                               
 
 

 

 
   

                                                  
DOI: 10.3303/CET1546168

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Cao Y.H., Cui X.M., 2015, Investigation on the effect of fin width on the heat transfer performance of the condenser 
used in the automotive air conditioning system, Chemical Engineering Transactions, 46, 1003-1008  DOI:10.3303/CET1546168

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Young Rim Jung, (2008)), condenser (S.P. Datta, P.K. Das, S. Mukhopadhyay. (2014)), fan, and its vortex 
shell structure design, frost and defrost analysis and the interior structure design. In the development of 
automotive air conditioning system, the role of numerical simulation model becomes more and more important 
(B. Taxis-Reischl, S. Morgenstern, F. Brotz (2001)). For some air conditioning systems, the air duct is very 
complex, and the flow situation is very difficult to get just by the experimental test. In this case, the simulation 
tool can get quite accurate results for the numerical simulation of the concrete channel (Gerald Seider, 
Fabiano Bet, Thomas Heid, et al, (2001)). The optimization and improvement of the system can be obtained 
by the numerical simulation. In the duct design of automotive air conditioning system, flow control is optimized 
for the dual air conditioning system, and the expansion temperature is used as the key index to effectively 
control the maximum cooling rate of the automobile air conditioning system (M.H. KIM, G.Y. Jang, K.W. KIM. 
(2001).). Except the thermodynamic properties, noise of air conditioning system is another standard of 
automobile quality. The structure and air duct of the turbine fan have a great effect on the noise. In order to 
decrease the noise level, the structure of the duct should be optimized to reduce the vibration and resonance.  
In air conditioning system, function of the condenser is quite obvious. Research on the structure of the 
condenser fins and some other heat sink fins has been proposed. For the condenser structure, big automobile 
factories in the world pay much attention on it, including the width of the louvered fin spacing, angle, border 
structure and its number, etc. In addition, the CFD technology applied to the research on the development of 
condenser can effectively modify the design errors, improve the efficiency. In this paper, a new type structure 
of condenser of automotive air conditioning system has been studied. According to the determination of the fin 
width, the performance of the condenser has been realized. 

2. The model and boundary conditions 

(1) The calculating model 
The three dimensional control equations with incompressible, steady state, and the constant flow can be 
described as the following: 
1) The continuous function: 

0






i

i

u

x
  

                                                                       

(1) 

2) Momentum equation: 

( ) 2

3

     
      

         


 

i j ji k

i i j i k i

u u uu u p

x x x x x x
                                                                    (2) 

3) Energy equation: 

( ) 2

3

        
                    


  

i p ji i k

i i i j j i k

u c T uu u uT

x x x x x x x
                                                                       (3) 

In the three equations above,   is air density;   is thermal conductivity of the air; p
c

 is the air specific heat; 
, ,

i j k
u u u

 are the velocity of , ,i j k  direction; 
, ,

i j k
x x x

 are the coordinates of , ,i j k  direction;   is the 

dynamic viscosity; p  is the average pressure. 
(2) Geometric model 
The structure of the condenser is shown in Figure 1. The thickness of the core part is composed of width of 
the fin and the tube. The medium flows in the middle of the flat tube, and the heat transfers from the fin and 
tube to the airflow when the air flows through them. The fin structure is shown in Fig. 2. Here, the width of the 
fin is defined as the length of the fin along the flow direction of the air. Here, the fin width is adopted as the 
single parameter to study the heat transfer performance while the other parameters remain unchanged. The 
width of each piece of the shutter used in the experiment is 0.85 mm, and the width of the fin is set as 12.8 
mm, 14.5 mm, 16.2 mm, 17.9 mm, 19.6 mm, 21.3 mm and 23 mm, respectively. 
 

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a: distance between two fins; b: fin width 

Figure 1: Schematic view of condenser 

(3) The basic assumption and the boundary conditions 
In the fin width simulation, the main assumption includes: (1) the air can be seen as the incompressible gas; (2) 
the gravity effect is neglected; (3) the temperature of the fin is kept constant in the process of heat transfer; (4) 
Airflow in the process is steady flow. The boundary conditions include: (1) the air temperature is 35 ℃; (2) the 

temperature of fin surface is 60 ℃; (3) The rotating speed of the driving fan is 720 rpm. Distance between two 
fin is 1.5 mm. Standard k-ε equation is used in the simulation and the second order accuracy is used in the 
solution process. Both the inlet and the outlet are set with pressure condition. The detailed information is 
shown in Table. 1. 

Table 1: Simulation boundary conditions of different fin width CFD 

Boundary condtion Boundary type Parameters 

Inlet Pressure 
Temperature of the airflow through inlet: 35℃; 
Airflow velocity: 3.5 m/s 

Outlet Pressure Outlet pressure: 0 Pa. 

Wall Wall 
Material: Aluminum; 
Wall temperature: 60℃. 

3. Verification 

In order to verify the validity of the CFD simulation results, the experiment is prepared. The schematic view of 
the condenser test bench is shown in Figure 2.  
In the experiment, the absolute pressure of the cold medium in entries is 1600 + 5 kPa, and degree of 
superheat of cold medium at inlet is 25 ℃ while that at outlet is 5 ℃. Oil percentage in the circulating 
refrigerant is 5% in all the conditions. The airflow resistance has been measured and compared. In the 
experiment, the requirement of resistance value is less than 45 Pa. 
 

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condenser

Air parameter test instrument  

Figure 2: The test bench for the condenser 

The experimental results of the condenser experiment are obtained by the method of multiple measurements, 
while the reliability of the experimental results is verified by multiple experiments. In the process of the 
experiment, many parameters, including temperature and pressure of air at the inlet and outlet, temperature 
and pressure of refrigerant at the inlet and outlet, airflow resistance, heat transfer, mass flow rate of the 
refrigerant, have been monitored and recorded to ensure the correctness of the experimental procedure and 
results. Some main parameters, such as airflow resistance, heat transfer, et al, have been used to evaluate 
the performance of the condenser.  
The simulation is aiming at part of the fin, therefore, the airflow resistance is adopted as the comparative 
parameters. Airflow resistance of simulation and experimental results is shown in Tab. 2. As can be seen that 
both the results are less than 45 Pa. Under the same conditions, the absolute error between the airflow 
resistance results of simulation and experiment is 2.04 Pa and the relative error is 5.3%, which indicates the 
simulation results can better reflect the real situation. 

Table 2: The simulation and experiment results 

Item Precision of the test equipment/Pa Relative error/% 

Experimental resutls 0.4% of the test range 38.28 

Simulation results / 40.32 

Relative error / 5.3% 

 
CFD simulation results of different width of the fins are shown in Table 3. It can be seen that unit area heat 
exchange decreases when the fin width increases.  

Table 3: Effect of fin width on the heat transfer performance 

Fin 
width/mm 

Heat transfer of each unit 
area/ q /W·m 2 Heat transfer area/m2 

Total heat transfer 
quantity/W 

12.8 mm 3420 3.9127 13381.43 

14.5 mm 3012 4.4467 13393.46 

16.2mm 2801 4.9807 13950.94 

17.9 mm 2598 5.5147 14327.19 

19.6 mm 2440 6.0487 14758.83 

21.3 mm 2312 6.5827 15219.2 

23 mm 2187 7.1167 15564.22 

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Variation of heat transfer coefficient h and airflow resistance △ P with different fin width is shown in Fig. 3. It 
can be seen that the resistance increases with the fin width increases, and the heat transfer coefficient 
decreases with the fin width increases. With the increasing of the fin width of 1.7 mm, the resistance value will 
increase 1.5~6 Pa, and the heat transfer coefficient h is reduced from 1.4% to 8%. With the increasing of the 
fin width, heat transfer coefficient decreases.  
 

 

Figure 3: Variation of heat transfer coefficient h and airflow resistance P with fin width 

However, heat transfer amount and resistance are increased. In order to convenient comparison, some new 
parameters have been proposed (Hou Xianjun, Yun Xiang and Liu Zhien (2013)): 

h S

P





 , 

h

P



  

Value of the two parameters of   and   is shown in Fig. 4. Both the two curves have the downward trend, 
which means the resistance has a higher decreasing speed and both heat transfer coefficient and the total 
heat flux increase at a lower speed. Then, the overall performance of the fin decreased gradually. It can be 
seen that the total heat transfer rate can’t be increased just by increasing the width of the fin. However, if the 

resistance requirements can be met, the fin width can be increased to increase the heat transfer rate at some 
extent.  
 

 

Figure 4: Effect of fin width on  and  

4. Conclusions 

Modern automobile design pays more and more attention to the comfort and energy consumption. The 
efficiency of the air conditioning system should be relatively high, and the optimization of automobile air 
conditioner is necessary. Automotive air conditioning system study mainly concentrates on the flow structure, 
heat transfer and resistance characteristics. In various methods, computational fluid dynamics (CFD) 
technology, which is a powerful tool in the research of heat transfer, mass transfer, and so on, can be applied 
to the optimization of the air conditioning system performance. In this paper, a new type structure of 
condenser of automotive air conditioning system has been studied. According to the determination of the fin 
width, some conclusion has been obtained: 
(1) Unit area heat exchange decreases when the fin width increases. The resistance increases with the fin 
width increases, and the heat transfer coefficient decreases with the fin width increases. With the increasing of 
the fin width, heat transfer coefficient decreases. However, heat transfer amount and resistance are increased.  

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(2) The resistance has a higher decreasing speed and both heat transfer coefficient and the total heat flux 
increase at a lower speed, which means that the overall heat transfer rate can’t be increased just by 

increasing the width of the fin.  
(3) The study of the effect of fin width on the condenser performance indicates that the computational fluid 
dynamics (CFD) can be used in the automotive air conditioning system to modify the structure design. 

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