Study On Layered Air Cooling Thermal Management For Lithium-ion Battery Pack

As the only power source in electric vehicles,power batteries play a vital role in the performance of vehicles,such as the driving distance,economic and dynamic performance.When the battery is working at high charge-discharge rate,the heat generated by the battery is great,which will lead to an over-high temperature and big temperature difference in the battery pack.And the working temperature and the temperature difference in batteries affect the performance and life span of the power battery.In this paper,we study the heat production principle and heat transfer mechanism of the cylindrical lithium-ion phosphate battery,and then investigate the temperature rise of it under natural convection in the experiment.In order to improve the heat dissipation capability and temperature uniformity of the battery pack,a layered air-cooling system with reverse air flow in different layer is proposed,and we combine experiment verification and CFD technology to analysis the temperature rise of the lithium-ion battery under different conditions.Finally,we put forward some optimization to further improve the performance of the cooling system.The research work of this paper includes the following aspects:? we study the heat production principle and heat transfer mechanism of the cylindrical lithium-iron phosphate battery,and then establish the 3D thermal model of the cylindrical lithium-ion battery according to the heat production principle and heat transfer theory.? Analyzed the temperature rise of the lithium-ion battery by experiment under the different discharge rate,and then simulated the temperature rise of the lithium-ion battery by FLUENT,the experiment results and simulation result show a good agreement.The result verify the accuracy of the thermal model of cylindrical lithium-ion battery.? In order to improve the heat dissipation capability and temperature uniformity of the battery pack,a layered air-cooling system with reverse air flow in different layer is proposed.And we compare the cooling performance of the layered air-cooling system with the traditional air-cooling system using CFD technology.We simulate the temperature rise of the battery under 3C charging rate at 25?,and the velocity of air flow is 2m/s,the simulation result shows that the layered air-cooling system can reduce the temperature of the battery pack and effectively improve the temperature uniformity.Furthermore,some optimization are put forward to further improve the performance of the cooling system,such as adding the spoiler panel at the inlet,changing the velocity of the air flow,varying the distance between adjacent batteries and altering the arrangement of the battery pack.? Finally,we verify the advantage of the layered air-cooling system by experiment,the Layered air-cooling system shows better cooling effect than the traditional air-cooling system.