Research On Thermal Management System Based On Liquid Cooled Vehicle Power Lithium-ion Battery Pack

The working performance of battery system has a great impact on the dynamics,economy and service life of electric vehicles.In the working process of electric vehicles,the power battery will heat up.If the battery temperature exceeds a certain range,the working performance of battery will decline,and even thermal runaway will occur.In this thesis,lithium-ion power battery thermal management system(BTMS)of liquid cooling for vehicles is studied.The research contents include:(1)The basic theory of thermal analysis of lithium-ion battery was studied,including the structure,electrochemical principle,heat generation mechanism and heat transfer characteristics of lithium-ion battery are analyzed,which provides theoretical support for the simulation analysis of battery temperature field.(2)The thermal mathematical model of lithium-ion battery was established,and the thermophysical parameters and heat generation power of lithium-ion battery were determined.Fluent software was used to study the thermal characteristics of lithium-ion battery,and the temperature rise characteristics of the battery was compared and analyzed.The analysis results show that the maximum error between the experimental value and the simulation value is less than 3%,which verifies the correctness of the simulation model.(3)According to the main performance parameters of a small pure electric vehicle in China,the battery system,the battery grouping mode in the battery box and the battery thermal management system were designed.The working performance of different liquid cooling plate structures was analyzed and compared by BTMS performance evaluation index.The results show that the dual-channel labyrinth liquid cooling plate(Structure Ⅳ)has better performance in terms of heat dissipation,temperature uniformity control and power consumption.(4)The working performance of the dual-channel labyrinth liquid cooling plate was optimized from four aspects: coolant flow direction,coolant flow rate,initial coolant temperature and section width of coolant flow path.On this basis,the thermal characteristics of lithium-ion battery modules under high temperature discharge condition,low temperature heating condition and typical dynamic condition were analyzed.The results show that the optimized dual-channel labyrinth BTMS has good heat dissipation effect,and the maximum temperature difference of the battery modules can be controlled within the required range.