Research On Lithium-ion Battery Thermal Management For Electric Vehicles Based On Liquid Cooling

At the background of the energy and environmental problems,the development of electric vehicles is facing a new upsurge,and the lithium-ion battery is the mainstream power source of the electric vehicle because of its excellent performance.While electric vehicle driving,the lithium-ion battery pack will generated a lot of heat.If the heat can’t dissipate in time,heat will accumulate inside the lithium-ion battery pack,which causes battery temperature and temperature unevenness increase.Long-term high temperature and temperature unevenness will reduce the mileage of electric vehicles,safety,service life.Therefore,lithium-ion battery heat dissipation is still the key issue of the development of electric vehicles.This paper mainly focuses on the problem of heat dissipation of lithium-ion battery.The main work contents include:(1)This paper summarizes and analyzes the research situation of battery heat generation rate model at home and abroad,and the heat generation mechanisms.The resistance and temperature of the lithium-ion battery is measured by the experiment under the different environment temperature and discharge rate.The resistance and temperature characteristics of the lithium-ion battery are obtained.The heat generation rate of lithium-ion battery under different working conditions is predicted by the theory and experiment of battery heating rate,which provides the basis for the simulation research of lithium ion battery.(2)Based on the heat generation mechanism of lithium-ion battery,the three-dimensional model of cylindrical lithium-ion battery is established.The temperature change of lithium-ion battery model at different discharge rate is simulated by STAR CCM+.Compared the simulation results with experimental results,the comparison shows that the established model can accurately reflect the temperature variation of lithium-ion battery.(3)This paper chooses a module of lithium-ion battery pack as the research object,and studies the temperature rise of lithium-ion battery pack when there is no heat dissipation system.According to the heat dissipation requirement,eight different cooling pipe structures are designed.By compared lithium-ion battery temperature rise,temperature uniformity under each cooling pipe structure,the fifth cooling pipe structure has the best cooling effect.(4)For the fifth cooling pipe structure,this paper studies the effect of different factors such as coolant flow rate,coolant temperature and cold tube width on heat dissipation.The study found:Under the same coolant flow rate,the higher the discharge rate of the lithium-ion battery pack is,the greater the internal temperature rise and the temperature difference are.At the same discharge rate,the internal temperature rise and temperature difference of the battery pack decreases with the increase of the coolant inlet flow.However,when the flow reaches a certain degree,the temperature is no longer change with the increase of flow rate.Cooling with different temperature of coolant,the lower the coolant temperature is,the faster the temperature of lithium-ion battery pack drops.Under the same discharge rate,lithium-ion battery pack temperature difference gradually converge using different temperature of coolant for cooling.When the coolant flow rate is constant,the maximum temperature of the lithium-ion battery pack decreases with the increase of the cross section of the cold pipe.In the process of discharge,the greater the width of the cross section of the cold pipe is,the greater the lithium-ion battery pack temperature difference is in the first half of the time,the lower the temperature difference is in the latter half of the time.