制冷剂相态变化对动力电池直冷系统温控性能的影响分析

Influence of Refrigerant Phase Change on Temperature Control Performance of Direct Cooling System for Power Batteries

为了分析制冷剂相态变化对动力电池直冷系统温控性能的影响,本文提出一种基于电池等效电路模型和热阻网络模型的电热耦合分析方法并建立典型电池直冷系统的离散化模型,应用AMESim对直冷系统的温度响应进行数值研究。利用实验数据进行对比验证,通过参数化研究分析动力电池的局部温控性能,获得2 C高倍率充电和循环充放电工况下直冷系统的温控性能。结果表明:直冷板内制冷剂气液两相区和过热单相区的变化对系统性能存在显著影响,相比于传统的液冷系统,两相区能使电池最高温度降低28.3%,但过热区存在严重的传热恶化,造成电池最高温度显著升高和最大温差急剧增加,对于2 C工况,当制冷剂从两相换热变为单相换热时,表面传热系数降低约73.6%,使得对应电池单元温度升高约12~14℃;制冷剂温度过低会造成电池垂直方向温差过大,制约直冷系统在实际中的应用;提高制冷剂蒸发压力和两侧布置直冷板能够有效减小电池垂直方向的温差,但难以消除过热现象对系统性能的影响。

To determine the influence of refrigerant phase change on the temperature control performance of a power battery cooling system,an electric-thermal coupling analysis method was proposed by combining a battery equivalent circuit model and a thermal resistance network model.Subsequently,a discrete system model was built based on AMESim.Numerical research on the temperature performance of the power battery was conducted,and the results were verified using experimental data.Subsequently,parametric studies were conducted to obtain the temperature control performance of the power battery cooling system,including the temperature control performance under 2 C high-rate charging and cyclic charging-discharging conditions.The results show that the liquid-vapor heat transfer and overheated heat transfer regions of the refrigerant in the cooling plate have a significant impact on the temperature control performance.Compared with the traditional liquid cooling system,the liquid-vapor region of the direct cooling system reduces the maximum temperature of the battery by 28.3%,whereas the overheated region leads to significant heat transfer deterioration and increases the maximum temperature and temperature difference.When the refrigerant changes from liquid-vapor heat transfer to overheated vapor heat transfer at the 2 C condition,the surface coefficient of heat transfer is reduced by 73.6%,which increases the temperature of the battery units by 12-14℃.In addition,a sufficiently low refrigerant temperature increases the maximum temperature difference,which restricts the practical application of the direct cooling system.Increasing the evaporating pressure and configuring the plates on both sides can decrease the temperature difference in the vertical direction.However,these two methods cannot eliminate overheating,and thus it is necessary to design a new system to solve the problem of heat deterioration caused by refrigerant overheating.