Study On Performance Of Heat Pipe Based Thermal Management For Battery Module Under Fast Charge And Large Rate Discharge

The crisis of energy shortage and global warming has restricted the economic and social development greatly.As a practical and feasible solution,new energy has been vigorously developed,especially the electric vehicles(EVs)have become the global trends in the field of road transport.As a core module of EVs,the power battery generates a lot of heat due to the electrochemical reaction inside the battery,Which may overheat the battery and reduce temperature uniformity.Poor temperature performance can be detrimental to the lifespan and thermal safety of the battery.And this problem has become increasingly prominent as the increasing demands for higher power,longer endurance and shorter charge time.In order to ensure the power battery operates in a suitable temperature range,the battery thermal management system(BTMS)is essential for EVs Compared with the traditional thermal management method,the heat pipe has the advantages of high thermal conductivity,flexible arrangement and high security.Therefore,the heat pipe(HP)based BTMS has broad application prospects.In this paper,a BTMS based on embedded heat pipe is proposed for the thermal problem of a 3P4 S battery module under the condition of fast charge and large rate discharge.The evaporation section of the HP is embedded in a aluminum plate to form a composite heat conduction component with high thermal efficiency and great cooling uniformity.And the condensation section of the HP is integrated with fins array in the wind channel.The heat dissipation ability of the BTMS under different ambient temperature and wind velocity was studied by standard fast charge and large rate discharge tests.The experimental results show that,compared with the adiabatic battery module,the maximum temperature of battery under fast charge and 1C discharge decreases by 8.3℃ and 5.1℃,respectively,and the temperature difference of the battery decreases by 1.5℃ and 0.5℃,respectively,after the heat pipe is used at the wind velocity of 3m/s.It is concluded that the HP based BTMS can effectively control the excessive temperature rise of the battery and improve the temperature uniformity of the battery module.Based on the principle of equivalent thermal resistance,the thermal conductivity of copper wall,porous material core,evaporation heat transfer and condensation heat transfer of the HP were calculated respectively,and the heat transfer model of the HP was established according to the series and parallel relationship of each part of the HP.In order to accurately obtain the temperature distribution and evolution law of the battery module and BTMS,the dynamic heat generation model of the power battery module was built based on the accurate dynamic heat generation model of the battery cell and the current distribution model of the battery module.Then the dynamic heat generation model of battery module and the heat transfer model of the HP were coupled the three-dimensional model of the BTMS through the UDF program.Finally,the simulation model of the BTMS was established.The simulation and experimental data showed that the absolute errors of the battery pack temperature under different working conditions were all within 1℃,and the root mean square errors were all less than 0.7℃,which proved the simulation model of the HP based BTMS is precise enough.Based on the simulation model,this paper studied the impact of thermal conductivity of cushion,inlet velocity and inlet temperature on the cooling performance of the BTMS,the results showed that,decreasing the inlet air temperature and increasing the inlet wind velocity have the most obvious effect on the cooling capacity,while increasing the thermal conductivity coefficient of the heat conduction pad has little effect on the cooling performance.The impact of structural factors on the thermal performance of the battery thermal management system was also simulated and analyzed utilizing orthogonal test method.The large rate discharge simulation results showed that the number of fins had the greatest influence on the thermal performance of the battery thermal management system,followed by the number of heat pipes and the coefficient of thermal conductivity.Besides,the structure of BTMS was optimized based on normalized optimization objective method.The results show that when the thickness of the heat conduction pad D=2mm,the number of fins M=15,and the number of heat pipe N=9,the maximum temperature and temperature difference and ΔSOC and SOH of the battery pack is 39.66℃,1.89℃ and 0.45%,99.981%,respectively,which achieved the optimal cooling performance without adding too much weight.