Research On Heat Transfer Of Battery Cooling Technology With Phase Change Material And Heat Pipe

Modern car is an essential mean of transport for people to travel. However withthe world’s fast-growing automotive industry, serious energy and environmental issueswill produce. In this background, the battery pack as the power source of new energyvehicles came into being. The electric cars as the representative of the new energyvehicles gradually become a new automotive products development trend in the future.Battery pack as the core components of new energy vehicles, the reasonablestructure, heat dissipation adequacy，temperature distribution, directly affect theinternal battery charge and discharge performance，service life and reliability, therebyaffecting the safety performance of electric vehicles. Taking reasonable thermalmanagement measures to battery pack can effectively improve the performance andservice life of the battery pack and improve vehicle performance of electric vehicles.Firstly, it is provided an overview of the theory of phase change heat transfer andheat storage. The mathematical model of phase change thermal storage process isdescribed, comparing the different simulation of the temperature model and theenthalpy method. Next，detailed description of the nature of the paraffin wax andmeasuring the physical parameters, and describing how to improve the thermalconductivity of the phase change material. Physical parameters of phase changematerial “Paraffin wax added graphite composite" are measured. The results show thataddition of graphite composite thermal conductivity of the phase change materialsignificantly improved the thermal conductivity coefficient of thermal conductivitycompared with pure paraffin wax up to20times, more superior thermal properties.Then use Fluent software and experiment to analysis the batteries packtemperature that using phase change material to enhance heat transfer performance ofthe passive cooling methods. Experiment use thermocouple to measure the temperature，ten measuring points were arranged. After the measurement, as thebattery heating power increased, the maximum temperature difference of the batterypack measured point is gradually increased, but the maximum temperature differencebetween the upper limit, within3℃.Comparing with the air-cooled experimentalresults of the temperature distribution, the measure point temperature of add phasechange material cooling system tend to be more consistent. The comparison result ofthe simulation results and experimental results indicate that simulation result meetcertain precision, good agreement with the experimental results. The experimentalresults and simulation results show that the use of paraffin wax phase change materialgraphite composite passive cooling mode can meet the requirements of small andmedium load, when the battery heating power more than6.9W single cells andcontinuous operation, the cooling mode will appear temperature too high, especiallythe middle portion of the battery pack does not meet the requirements of temperaturecontrol.Finally, to meet the temperature control requirement of the heat transferenhancement technology in battery pack cooling system at high battery heating power,the heat pipe transfer enhancement technology is used in the phase change materialcooling mode.To use heat pipe in battery pack cooling system, the heat pipe wasoptimally designed, the entire cooling system was designed, and then using simulationsoftware for simulation analysis to get the temperature filed distribution and thetemperature change in the cooling system, comparing with the mode without heat pipethe results indicates that the overall temperature of the battery pack when adding heatpipe is lowered, the heat pipe and complex phase change material coupled coolingsystem can largest decline temperature up to50℃, the center temperature of thetemperature field also lower than the original, the temperature distribution of theentire battery pack even more reasonable. And high heating power battery case is stillable to meet the cooling requirements of the battery in case the temperature of theheating power of13.6W battery pack is still controlled within the optimumtemperature range to ensure that working conditions meet the entire battery packtemperature control Claim. The simulation results show that the battery pack under actual operating conditions, in order to ensure that the battery at the appropriatetemperature range, to achieve thermal management of the battery pack, the use of heatpipe cooling mode and paraffin composite phase change material coupling system isfeasible.