基于液冷的锂离子电池组热均衡性研究

为了改善车用锂电池模组在高温高倍率工况下的热均衡性，根据圆柱形锂电池的传热特性，建立了18650锂电池单体的三维热模型，并完成40 °C环境自然对流下的热特性仿真，并通过温升试验验证了生热模型的可靠性. 在此基础之上，针对某型纯电动汽车的动力电池组，提出了一种夹套式电池模组冷却系统，利用Fluent研究了40 °C环境下冷却液流量、冷却液温度和放电倍率对电池组散热均衡性的影响. 结果表明:增加冷却液流量可以有效降低电池组最高温度、最大温差及电池自身温差，改善电池间的温度均匀性；但当入口流量增至0.03 kg/s后，对电池组散热性能的改善效果十分有限；降低冷却液温度后，电池组最高温度下降，但电池组最大温差与单体电池间温差不断上升，单体电池自身最大温差略有降低；当放电倍率增大时，电池组最高温度与最大温差均不断上升，单体电池间温差以及电池自身温差显著增大，电池组热均衡性变差. 

Study on Thermal Equilibrium of Lithium-Ion Battery Pack with Liquid Cooling

In order to improve the thermal equilibrium of automotive Lithium battery module at high temperature and high rate, according to the heat transfer characteristics of the cylindrical Lithium battery, a three-dimensional thermal model of the 18650 Lithium battery cell was established, and the thermal characteristics simulation was carried out under natural convection at 40 °C. Finally, the reliability of heat generation model was verified in a temperature rise test. On this basis, a jacketed battery module cooling system was proposed for the power battery pack of a certain type of pure electric vehicle. Fluent software was used to study the influence of coolant flow, coolant temperature and discharge ratio on the heat dissipation equilibrium of battery pack at 40 ℃. The results show that increasing the coolant flow rate can effectively reduce the maximum temperature and temperature difference of the battery pack and the temperature difference of the battery itself, and improve the temperature uniformity between single cells. But when the inlet flow is increased up to 0.03 kg/s, the improvement effect is very limited. When the coolant temperature is reduced, the maximum temperature of the battery pack decreases, but the maximum temperature difference of the whole battery pack and the temperature difference between individual batteries rise continuously, and the maximum temperature difference between the single cells decreases slightly. When the discharge rate increases, the maximum temperature and the maximum temperature difference of the battery pack continue to rise, the temperature difference between the single cells and the temperature difference of the battery itself increases significantly, and the thermal balance of the battery pack becomes worse.