Thermal Field Analysis And Optimization Of Power Lithium Battery Pack With Liquid And Heat Pipe Cooling

With the improvement of people’s living standard,cars enter thousands of households.In the past decade,the car ownership has been increasing,and a large number of automobile exhaust emissions have worsened the urban air quality and the greenhouse effect.The research shows that more than half of the world ’s total oil consumption is consumed by transportation,and oil,as a non renewable resource,will eventually be exhausted.New energy electric vehicles can perfectly solve the above problems,which are sought after by major vehicle enterprises and investors.At present,the market share of electric vehicles is still low.According to the survey,consumers are mainly worried about the battery life and safety of electric vehicles,and efficient battery pack thermal management system can effectively solve the safety,service life and other problems of electric vehicles.This paper presents a heat pipe-liquid cooling structure,and studies it as follows:(1)The characteristics of air cooling,liquid cooling,phase change material cooling and heat pipe cooling are described.The basic parameters of lithium battery are introduced and its heat generation model and mechanism are summarized.Based on the Fourier law and the law of conservation of energy,the differential equation of heat conduction in three-dimensional coordinate system is derived.The internal resistance of a lithium iron phosphate battery was measured experimentally,and the relationship between internal resistance and SOC and temperature was analyzed.(2)The characteristics of air cooling,liquid cooling,phase change material cooling and heat pipe cooling are described.The basic parameters of lithium battery are introduced and its heat generation model and mechanism are summarized.Based on the Fourier law and the law of conservation of energy,the differential equation of heat conduction in three-dimensional coordinate system is derived.The internal resistance of a lithium iron phosphate battery was measured experimentally,and the relationship between internal resistance and SOC and temperature was analyzed.(3)This paper analyzes the working principle of the heat pipe,proposes a heat pipe liquid cooling composite structure,and analyzes the influence of the pipe inlet and outlet mode,coolant type,coolant flow rate and coolant type on the heat dissipation of the battery module by the method of orthogonal test.At the same time,the maximum temperature and temperature difference of the battery module are analyzed.The optimal combination is a3b2c4d1.Under this condition,the maximum temperature of the battery module is controlled at 32.54 ℃,while the temperature difference is only 2.91 ℃.(4)Through the simulation of the large module,the temperature field distribution of the whole battery pack is analyzed.The temperature field of battery pack is optimized from the aspects of pipe layout,number of heat pipes,coolant temperature and coolant flow rate.When the number of heat pipes is 8,the flow rate of coolant is0.08m/s and the temperature of coolant is 21 ℃,the maximum temperature and temperature difference of battery pack under 3C discharge are 43.51 ℃ and 3.22 ℃ respectively.