Multi-objective Optimization Design Of Lithium Ion Battery Liquid Cooling System Based On Surrogate Model

In order to reduce the oil consumption and environmental pollution caused by traditional fuel vehicles,electric vehicles have been paid more and more attention all over the world.However,the performance,life and safety of lithium battery in pure electric vehicle energy system are greatly affected by the working environment temperature,so it is necessary to design a reasonable battery thermal management system to keep the battery in a reasonable temperature range.This paper mainly studies the thermal problems and the design of heat dissipation structure of square lithium iron phosphate battery.The temperature change was collected by charging and discharging tests at different times of battery.Then,the threedimensional geometry model of the battery is constructed by using the experimental battery data,and the numerical simulation is carried out,and the temperature rise characteristics of the battery are obtained.Then,the basic cold plate model is processed,and the cold plate experiment and numerical simulation are carried out by using the data of battery temperature rise.After the accuracy of the numerical simulation results is verified,the liquid cooled battery heat management system is designed by the numerical simulation method,and the system is analyzed and optimized by using single objective and multi-objective methods.(1)The charge discharge tests of square lithium iron phosphate battery with different ratio are carried out,and the temperature rise characteristics of the battery are analyzed.(2)The basic liquid cooling plate was processed,and the experiment and simulation analysis of the cold plate were carried out by using the heat production in the battery experiment.By comparison,when the coolant flow rate is 2g / s,the maximum difference is 1.35 ℃,accounting for 4.63%,which proves the accuracy of the simulation results.(3)The number of inlet and outlet,the position of inlet and outlet,the number of xaxis channel,the width of x-axis channel,the width of y-axis channel and other structural parameters of the basic liquid cooling plate were optimized with a single objective.The average temperature,pressure loss and temperature standard deviation of the optimized liquid cooling plate decreased by 1.97%,26.26% and 4.71% respectively compared with the basic working conditions.(4)In order to improve the disadvantage of high temperature in the middle area of cold plate,three parameters of x-axis channel interval length,X-axis channel width and X-axis channel interval width are adjusted to effectively reduce the high temperature in the middle area.(5)Aiming at four import and export angles and five flow variables with a wide range of variation,the RSA agent model is used for multi-objective optimization,which effectively improves the heat dissipation performance of the cold plate.(6)On the basis of the above,the numerical simulation analysis of the heat dissipation of the battery pack model was carried out,and the temperature changes of the battery pack with different discharge rates under different coolant temperatures were analyzed.So that the research content of this paper is more in line with the actual situation.