Research On Heat Dissipation Performance Of Power Battery Based On Composite Phase Change Material

In the process of scientific and technological development,there have been global energy shortage and environmental deterioration,and China has put forward the goal of’dual carbon"to solve these problems.In order to achieve this goal,China vigorously develops pure electric vehicles.Battery thermal management system of pure electric vehicles has a crucial impact on the thermal safety of electric vehicles.No additional energy consumption is required,which has become a promising way of battery thermal management.However,the development of phase change materials is limited by the poor thermal conductivity of phase change materials and the difficulty of composite between phase change materials.Therefore,it is of great significance to prepare a phase change material with good thermal properties.At present,there are some problems in the battery thermal management system,such as the battery module is too large and the heat is concentrated in the middle position.To solve these two problems,this study takes 12 18650 cylindrical lithium-ion power batteries as the research object.By combining simulation and experiment,the battery arrangement,phase change material,battery center distance and number of fins as variables,the influence of these variables on the heat dissipation performance of the battery modules is studied,and the optimal heat dissipation system is obtained.The main research contents are as follows:(1)Summarize the research progress of air cooling,liquid cooling,phase change material cooling,phase change material coupled with air cooling,phase change material coupled with liquid cooling,heat pipe cooling and other cooling methods,introduce the internal structure and classification of lithium ion power battery,and outline phase change materials.(2)The working principle,heat generation mechanism and heat transfer mode of lithium-ion power battery were analyzed,and the heat generation rate of LG 18650 cylindrical lithium-ion power battery was calculated to be 24776W/m3.Five thermal physical parameters,namely density,specific heat capacity,circumferential thermal conductivity,radial thermal conductivity and axial thermal conductivity,were needed in the calculation simulation.(3)The thermal properties of phase change composites with different composition ratios were analyzed.When PW:EG:SiC is 70wt%:25wt%:5wt%,the thermal performance of the composites is the best.The thermal conductivity of the composites is 1.827W·m-1·K-1,the latent heat is 147.2J/g,and the transformation temperature is 311.1K.(4)A heat dissipation system with small battery module and uniform distribution of battery module heat is designed.The battery is arranged in 3×4,the phase change material is C2,the center distance of the battery is 28mm,and the two batteries in the middle are equipped with fins.This heat dissipation system can reduce the maximum temperature of the battery module to 320.97K and the maximum temperature difference to 2.13K.(5)The experimental platform is built,and the optimal cooling system obtained in the simulation is tested.The results show that the temperature of each battery in the experiment is higher than that in the simulation,and the variation trend of the experimental data is generally consistent with that of the simulation data,which verifies the validity of the simulation results.