Heat Dissipation Performance Analysis And Optimum Design Of Novel Liquid Cooling Plate Applied To The Thermal Management For Lithium-ion Battery

As a core component of high-efficiency energy storage in electric vehicles（EVs）,lithium-ion（Li-ion）batteries have attracted much attention due to their high energy density,long cycle life,and low self-discharge.In order to meet the high power requirements of EVs,battery cells are connected in series and parallel to form a group.For Li-ion batteries,temperature is a key factor affecting their performance and cycle life.Li-ion batteries generate a large amount of heat during charging and discharging.If the heat is not dissipated promptly,or if three-dimensional（3D）inhomogeneous thermal effect will cause uneven heating in the battery,the reliability and service life of the battery will be reduced,and in severe cases,thermal runaway can occur,leading to explosions.Effective battery thermal management system（BTMS）is crucial for the thermal safety and uniformity of Li-ion batteries caused by high temperature.A square Li-ion battery is taken as the research object in this paper.Based on the verification of the battery cell model,two novel liquid cooling plate designs（i.e.,bionic leaf vein branch channel liquid cooling plate and non-uniform fin channel liquid cooling plate）are proposed.And the numerical simulation method is used to compare and analyze the influence of the two liquid cooling plates on the heat dissipation performance of the battery module.By comparing and analyzing the coupling effect of flow parameters and structural parameters on the comprehensive heat dissipation performance of the module,the bionic leaf vein branch channel liquid cooling plate is optimized through a combination of a proxy model（least squares method）and a genetic algorithm for multi-objective optimization of the structural design parameters so as to determine the optimal heat dissipation structure.The main research contents are as follows:（1）Based on the heat generation-transfer mechanism and the experiment of internal resistance characteristics of Li-ion battery,the thermo-physical parameters and boundary conditions of the battery are accurately obtained,so as to establish the 3D thermal model of the battery.The combined simulation and experimental method is used to compare and verify the results under different discharge rates（1C and 3C）with a maximum error of less than 3%.Based on the verification of the battery cell model,two novel liquid cooling plate designs（bionic leaf vein branch channel liquid cooling plate and non-uniform fin liquid cooling plate）are designed for heat dissipation of battery module.（2）For the bionic leaf vein branch channel liquid cooling plate,the effects of single factors,such as inlet flow rate（M）,channel width（D）,channel angle（α）and channel number（N）,on the comprehensive heat dissipation performance of battery module under 3C discharge are studied.A low M can cause an increase in heat accumulation near the outlet of the cooling plate,which reduces the temperature uniformity of the battery.Meanwhile,with the increase of D and N,the battery temperature rises instead.Asαincreases,more coolant flows back to the first branch channel near the outlet in the side channel.This leads to a decrease in battery temperature.（3）For the non-uniform fin channel liquid cooling plate,the effects of inlet flow direction of liquid cooling plate,uniform fin channel diameter and non-uniform fin channel diameter on the comprehensive heat dissipation performance of battery module under 3C discharge are analyzed.The effects of four different inlet and outlet flow arrangements on the temperature rise for heat dissipation of the module are considered.In the uniform fin channel,the battery temperature decreases with the increasing of the fin diameter.For the non-uniform finned channel,the comprehensive heat transfer performance is the best by considering the large middle fin diameter and the small fin diameter for the both sides.（4）Using the numerical simulation method,the impact of two types of liquid cooling plates on the heat dissipation performance of battery module is compared and analyzed.The bionic leaf vein branch channel shows good heat dissipation performance at the same flow rate.The effects of multiple parameter coupling,such as the inlet flow rate（M）,channel width（D）,channel angle（α）,and channel quantity（N）of the bionic leaf vein branch channel liquid cooling plate on the maximum battery temperature(T_max),maximum temperature difference of the battery(ΔT_max),and average pressure drop of the cooling liquid(ΔP_avg)are studied using orthogonal experimental range analysis and Pearson correlation coefficient method.Three objective functions,T_max,ΔT_max,andΔP_avg,are constructed using the least-squares method,and the optimal heat dissipation structure parameters are determined by using the non-dominated sorting genetic algorithm（NSGA-II）to calculate the optimization solution set of T_max,ΔT_max,andΔP_avg.