Study on Factors Affecting the Radiator-cooling of EV Power Battery

Pack

Fusheng Hu

1, a

, Chengzhi Ouyang

and Fei Xiong

GAC Automotive Engineering Institute, Guangzhou Automobile Group CO.,LTD, Guang Zhou, China

Keywords: Electric Vehicle, Thermal management, Battery cooling.

Abstract: Based on the battery pack cooled by cooling package within electric vehicle, the cooling process of the power

battery was studied by simulation and tests. The influence of the pump speed and fan level on the battery

cooling was compared. The results of the simulation and tests showed that the final battery temperature of the

high fan level was lower than 1°C relative to the low fan level, while the impact of the high speed water pump

relative to the low speed water pump is within 1°C during idle cooling procedure.

1 INTRODUCTION

Since the performance and reliability of the battery

pack dependent on its temperature (Pesaran and.

Keyser, 2001), various approaches to cool the power

battery were studied (Zhang et al, 2015) (Rao and

Wang, 2011). The liquid-cooled battery pack are

chilled by a lower temperature coolant and are more

efficient than air-cooled battery pack (Wu et al, 2002)

(Chen et al, 2016). The coolant should be cooled

down first before cooling the power batteries.

Generally, coolant can be chilled by two methods

(Wu W. 2019), one is cooled by the AC system of the

vehicle with chiller, and the other is chilled by the

ambient temperature with radiator. Chiller-cooling

and radiator-cooling are combined in one architecture

as illustrated in the Fig. 1.

Figure 1: Electric vehicle thermal management system.

Many previous studies revealed the temperature

spread within the battery pack (De et al, 2017)

(Yoong,2019). But little attention was paid on the

whole cooling structure. 1D and 3D simulation

approaches were used to analyse the radiator cooling

based on the whole cooling system in this paper.

There are two main factors influence the radiator-

cooling efficiency (Deng Y. 2018), one is the fan

speed, the other is the coolant pump working status.

Different fan speeds and pump duty cycles were

compared based on simulation and tests. The vehicle

was in idle state, that is electrical loading on the

battery pack was neglected, during the cooling

process, so the self-heating of the battery was

negligible.

2 CFD SIMULATION OF THE

COOLING PACKAGE

The radiator was mounted in the front cooling

package and coolant is cooled down by outside air

flow, therefore the air flow caused by different fan

levels should be analyzed by 3D CFD at first. The

cooling package was arranged as shown in Fig.2.

Hu, F., Ouyang, C. and Xiong, F.

Study on Factors Affecting the Radiator-cooling of EV Power Battery Pack.

DOI: 10.5220/0010017900330037

In Proceedings of the International Symposium on Frontiers of Intelligent Transport System (FITS 2020), pages 33-37

ISBN: 978-989-758-465-7

Figure 2: Cooling package arrangement.

The radiator dimensions were shown in Table1.

Table 1: Dimensions of the radiators.

Fan Levle

Width

/mm

Height

/mm

Thickness

/mm

Battery

Radiator

558 141 16

Condenser 657 356 16

Motor

Radiator

716 440 16

The RPM settings of the high and low level of fan

within the cooling package were shown in Table 2

The air flow in the cooling package was supposed

as incompressible. For CFD simulation, the following

equations were used.

div 0v 

(1)

div( grad ) div( )

ieff i eff

vv v

 







(2)

(T)

div( ) div( grad )

vT T S





 



(3)

The simulated velocity contour results of battery

radiator by CFD is shown in Fig. 3

(a) Velocity contour of low fan level

(b) Velocity contour of high fan level

Figure 3: Velocity contour of battery radiator.

The 1D simulation model was built based on the

thermal system illustrated in Fig.1. The coolant is

50%-50% glycol-water mixture. The flow resistance

curve of the thermal system was simulated. The

results were shown on Fig. 5

Figure 4: 1D simulation model of the thermal system.

The analysed work point was shown in Fig. 5.

Figure 5: Pump characteristic and flow resistance curve.

Table 2: RPM of the fan on High/Low level.

Fan Level

RPM of Left Fan

/rpm

RPM of Right Fan

/rpm

Example column 1

Example

column 2

Low 1750 1450 Example text 1 Example text 2

High 2550 2250

FITS 2020 - International Symposium on Frontiers of Intelligent Transport System

Table 3: 1D simulation results of the thermal system.

Working point

Duty cycle

Pressure Drop

/kPa

Flow rate

/ L·min-1

Pump Power

1 90 84 1450 56

2 50 44.5 2250 31

According to the above simulation, the pump

power was 51W and 31W at 90% and 50% duty cycle,

respectively. The detailed thermal flow system results

were shown in Table 3.

3 SIMULATION OF BATTERY

COOLING PROCES

The influence of the fan speed and pump duty cycle

on battery cooling process were studied based on the

previous simulated results. The simulation boundary

conditions were listed in Table 4

Table 4: Simulation conditions.

Work

Conditions

Ambient

Temp.

/°C

Initial

Temp

. /°C

Fan

level

Pump

Power

1 20 40 High 90

2 20 40 High 50

3 20 40 Low 90

4 20 40 Low 50

The heat transfer of the radiator can be calculated

by NTU (Number of Transfer Units) (Theodore,

2011) method. The Heat transfer is calculated as

followings.

11 1 2 2 2

wall

Nu A G Nu A







(4)

is the total heat transfer coefficient,

is the

hydraulic diameter,

is the nussel number,



the thermal conductivity of liquid,

is the heat

transfer area,

wall

is the thermal conductivity of

solid. The subscript represents gas-side and liquid-

side fluids.

Battery loading was ignored, so there was no self-

heating. The simulated coolant inlet temperature and

average battery temperature was shown in Fig.6 and

Fig.7

Figure 6: Coolant inlet temp. of simulation.

Figure 7: Battery average temp. of simulation.

According to the results, the effect of the fan level

on the water temperature and average temperature of

the battery was greater than the effect of the pump

speed. High fan level can accelerate the water

temperature and battery temperature drop under the

same working conditions. In addition, the working

power difference of the water pump was about 25W,

while of the fan was about 317W.

4 TESTS OF BATTERY COOLING

PROCESS

Cooling tests conditions were listed as Table 5.

Study on Factors Affecting the Radiator-cooling of EV Power Battery Pack

Table 5: Test conditions.

Work

Conditions

Ambient

Temp.

/°C

Initial

Temp.

/°C

Fan

level

Pump

Power

1 25 40 High 90

2 25 40 High 50

3 25 40 Low 90

4 25 40 Low 50

The test results temperature were shown in Fig.8

and Fig.9.

Figure 8: Coolant inlet temp. of simulation.

Figure 9: Cooling performance of test results under

different fan and pump speed.

The comparison of the simulation and tests are shown

in Fig. 10.

Figure 10: Coolant inlet temp. of simulation.

According to the comparison, the inlet

temperature and the battery average temperature

behaved the same, the simulation results were

reliable.

5 CONCLUSIONS

This paper analyses the effect of water pump and fan

on coolant temperature and battery temperature

during the heat dissipation process. The results of the

simulation and tests showed that the final battery

temperature of the high fan level was lower than 1

°C

relative to the low fan level, while the impact of the

high speed water pump relative to the low speed water

pump is within 1

°C

during idle cooling procedure.

The above analysis can be used to the battery cooling

design.

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FITS 2020 - International Symposium on Frontiers of Intelligent Transport System

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Study on Factors Affecting the Radiator-cooling of EV Power Battery Pack