Investigation On Battery Thermal Management Based On Phase Change Energy Storage Technology

Electric vehicles with the advantages of policy encouragement,market guidance,and pollution-free are selected as research objects.As the only power source,the power battery directly affects the performance of the vehicle,thus affecting the cruising range.The change of temperature is the key factor affecting the performance of the battery.When the battery is at high temperature,if the effective heat dissipation measures are not taken,the battery performance will be rapidly attenuated and even cause thermal runaway.Therefore,it is of great significance to study the battery cooling system.(1)A certain piece of lithium-ion battery was selected to establish a phase change material thermal management system for the lithium battery cell and the lithium battery.The phase change material is disposed in its circumferential direction for the unit cells,and the phase change materials are staggered for the battery pack to form a sandwich-like structure.Tannic acid was chosen as the phase change material.The Euler multiphase flow model is used to simulate the existence of multiple phases in the phase change process of phase change materials.The fluid volume domain model is used to simulate the distribution and movement of the solid-liquid phase transition interface.The gravity model is used to load different gravity directions and the laminar flow is applied.The model simulates the flow state of the phase change material after melting.A separate multiphase temperature model was used to simulate the heat transfer process during the phase change.Study the temperature change and temperature difference of the battery cell and group thermal management system.(2)For a single cell PCM thermal management system,effective thermal management time can be increased compared to natural convection under the same conditions.Due to the melting characteristics of the pure phase change material,the battery temperature minimum curve will produce three inflection points,and at the second inflection point,the temperature difference of the single cell reaches the maximum value.During the phase change process,the thermal core position of the battery gradually rises.As the area increases,the absolute value of the temperature gradient in the upper region of the battery cell gradually decreases.The effective thermal management time of the battery also increases linearly with the linear increase of the thickness,and the maximum and minimum temperature curves are similar.The greater the thickness of the phase change material,the greater the maximum temperature difference of the single cell during the entire physical process,and the later the maximum value appears.(3)For the PCM thermal management system of the battery pack,the thermal management system of the battery pack can multiply the effective thermal management time.The temperature rise of the battery module is more uneven than that of the battery unit.When gravity is applied to the X direction and the Y direction,the temperature difference between the battery packs is too large and lasts for a long time,and the effective heat management time is relatively small.When the gravity is loaded into the Z direction,the maximum and minimum temperature curves of the battery pack are relatively close and the maximum temperature difference is small,and the effect is most ideal.(4)The battery pack PCM thermal management system has better insulation effect under the parking conditions than the single PCM thermal management system.The direction of gravity has no effect on the temperature drop of the battery during solidification.