Research Of Composite Silica Gel Plate Coupled With Secondary Heat Dissipation For Battery Thermal Management

With the continuous development of the times,the concepts of green environmental protection,energy saving and emission reduction have gradually become popular among the people.Vigorously developing of electric vehicles is an effective measure to alleviate the problems of energy and environment,and the core component of new energy vehicles is the power battery.Lithium-ion power batteries are the first choice for new energy vehicles.The research and development of effective battery thermal management systems are of great significance to their advantages of high energy density,high cycle life and high safety.Studies have shown that the best operating temperature range for lithium-ion batteries is25 °C-45 °C,and the maximum temperature difference should be within 5 °C.Therefore,this dissertation proposes a battery thermal management system based on composite thermal silica gel plate coupled with water cooling.Aiming at the square lithium iron phosphate battery,this dissertation compares the current research status of battery thermal management at home and abroad,and develops a composite thermally conductive silica gel plate with high thermal conductivity,and uses its efficient thermal conductivity to conduct the heat of the battery to the copper tubes,and then the water in the tubes perform secondary heat dissipation to cool down,which can effectively solve the cooling problem of the battery under extreme temperature conditions,and has an excellent temperature uniformity function for the battery module.The main research contents of the paper are as follows:(1)A composite thermally conductive silica gel plate with insulation and high thermal conductivity was prepared.Evaluate the applicability of CSGP in the field of battery thermal management by testing viscosity test,thermal conductivity test,insulation performance and mechanical performance test.The experimental results show that the addition of expanded graphite(EG)is beneficial to improve the thermal conductivity of silica gel(SG),but the addition of EG will inevitably increase the viscosity of SG,and an appropriate addition ratio should be selected to effectively couple with copper foam(CF).(2)The heat dissipation effects of the natural cooling system,CSGP-FC and CSGP-LC are compared through experiments.The experimental results show that CSGP can reduce the battery temperature more effectively than without cooling measures,but it still needs to add secondary heat dissipation means under severe temperature conditions.The addition of forced convection can improve the thermal performance to a certain extent,but the effect is still not as good as liquid cooling.Liquid cooling,as secondary heat dissipation method,can most effectively control the battery operating temperature within a reasonable range,and can still maintain excellent temperature control performance after cycle.(3)Analyze the heat generation mechanism of lithium iron phosphate prismatic batteries,and establish battery heat generation model through Fluent.The influence of different structures of CSGP and different directions of the airflow on the heat dissipation of the battery is calculated through theoretical simulation.It is found that CSGP has a greater disturbance to the fluid when the fin structure is used,and the heat dissipation effect is better.In addition,optimize the structure of the liquid cooling system by changing the flow direction of the fluid and reducing the number of copper tubes.The simulation results show that the countercurrent flow direction has the best cooling effect.When the number of copper tubes is reduced to 6 tubes,the cooling effect can be similar to that of 12 copper tubes.But when the number of copper tubes is reduced to 4 tubes,the heat dissipation performance is greatly reduced,so 6 tubes and countercurrent flow direction are the best design solutions.