Research On Design And Optimization Of Surrounding Liquid Cooling Heat Dissipation Structure Of Li-ion Battery Modules For Electric Vehicles

As the main power source of new energy vehicles,the performance and safety of lithiumion batteries(LIBs)have received widespread attention.Limited by the volume of new energy vehicles,the battery pack is usually sealed in a small battery box.If the heat generated during the high rate charging and discharging process of the module cannot be discharged in time,it is easy to cause problems such as excessive local temperature of the battery and excessive temperature difference between the single cells,which may lead to safety accidents such as explosion.Therefore,a safe and efficient battery thermal management system is essential.This paper constructs a three-dimensional electrochemical thermal coupling model for a cylindrical18650 battery.The effects of different factors on the liquid cooling performance of the module are simulated and relevant optimization analysis is implemented.The main research content is as follows:Firstly,the structure of LIBs and the working principle of charging and discharging are introduced,and the heat generation mechanism of LIBs is analyzed in detail.The internal resistance and temperature rise of the battery at different discharge rates are obtained through thermal characteristic tests.Secondly,according to the law of energy conservation,the relationship between battery heat production,heat transfer and heat dissipation is analyzed.Based on the solid-liquid mass conservation,charge conservation,energy conservation,and electrode dynamics of the LIBs charge and discharge process,the electrochemical thermal coupling model of the LIBs is established.Through the experiment and simulation curve comparison of voltage and temperature rise at different ambient temperatures,the accuracy of the built model is verified.Then,based on the battery model and heat generation characteristics,a liquid cooling heat dissipation model of the battery pack is constructed.Through the geometric meshing and the setting of the relevant boundary conditions of the model,it is verified that the model follows the law of energy conservation during the entire heat dissipation process.The influence of channel height,channel width,coolant temperature and coolant inlet velocity on the heat dissipation performance of the module is analyzed by simulation.Finally,based on the liquid cooling model of the battery pack constructed in the previous chapter,the optimization of the geometric structure and the coolant inlet velocity are carried out.By increasing the contact area between the outermost battery and the liquid cooling channel,the heat exchange efficiency of the battery at the edge of the module is effectively improved,and a multi-layer surround design is adopted to further improve the heat dissipation effect of the liquid cooling model.Adopting the cooling strategy that the coolant inlet velocity changes with the maximum temperature of the module.The inlet velocity is adjusted in real time,which effectively reduces the fluctuation of the maximum temperature of the module in the middle and late stages of the discharge,and improves the overall temperature consistency while the power loss of the water pump is obviously reduced.