Research On Thermal Performance Of Battery Pack Based On The Coupling Of Composite Phase Change Material And Liquid Cooling

The development of science and technology has accelerated the process of world modernization.In the development process,along with energy consumption and environmental pollution,in order to achieve the strategic goal of sustainable development,my country has vigorously promoted the development of new energy vehicles in the automotive field.For new energy vehicles,hybrid and pure electric vehicles account for the main part.Among them,power batteries are their core components and attract people’s attention.Temperature is a key factor affecting the performance of lithium batteries.If the temperature exceeds the battery working range,a short circuit will occur,Thereby causing safety hazards such as thermal runaway and spontaneous combustion.Therefore,it is very important to design a battery thermal management system.Based on the current development status and trends of battery thermal management at home and abroad,and the thermal characteristics and working principles of lithiumion phosphate prismatic batteries,this paper first conducts numerical simulation and experimental research on the heat dissipation management of lithium batteries and battery packs.Through experiments,the surface temperature changes of lithium-ion batteries under different environments and different discharge rates are studied,and the heat generation formula is obtained by using the experimental data and the heat generation of the battery is calculated.The experiment researched the change trend of the basic liquidcooled plate to the battery surface temperature under different inlet mass flow rates,and verified it through simulation.The results showed that the data error between the experiment and the simulation did not exceed 6%,indicating that the simulation results are accurate and reliable.Secondly,the influence of the layout of the liquid-cooling plate channel,the number of inlets and outlets,and the mass flow rate of the coolant inlet on the heat dissipation performance of the battery are studied,and the optimal operating conditions are selected by the comprehensive performance evaluation of battery temperature(PEC).The number of channels of the first,second,and third steps,the height of the first and second steps,the width of the first,second,and third steps,the thickness of the channel,and the width of the inlet and outlet channels have been orthogonally designed experiments.The results show that compared with the initial conditions,the maximum temperature of the battery is reduced by 21.95℃(35.98%),the average temperature is reduced by 22.04℃(37.6%),and the pressure loss is reduced by 18.66Pa(81.3%).The influence of the coolant flow direction and battery discharge rate on the heat dissipation performance of liquid-cooled battery packs is discussed.The results show that all battery packs with the same coolant flow direction have the best heat dissipation performance.As the battery discharge rate increases,the battery temperature rise trend slows down.It shows that the liquid-cooled battery pack has good heat dissipation effect under high discharge rate.Finally,the influence of the ratio and thickness of the expanded graphite(EG)/paraffin(PW)composite phase change material on the heat dissipation performance of the battery pack is studied.The results show that the 12%EG/88%PW composite phase change material with a thickness of 4mm has the best heat dissipation effect.Comparing the effects of composite phase change material cooling,liquid cooling,and liquid and composite phase change material coupling cooling on the heat dissipation performance of the battery pack,the results show that the liquid cooling effect is the best in a normal temperature environment,followed by the liquid and composite phase change material coupling cooling.For liquid cooling,liquid and composite phase change material coupling cooling research,the influence of different inlet qualities and different ambient temperatures on the heat dissipation performance of the battery pack is discussed.The results show that the liquid with the smallest coolant inlet mass flow rate is coupled with the composite phase change material in a high temperature environment.The cooled battery pack has the best heat dissipation effect.