Abstract: High operating temperature and large temperature difference of power battery will cause its performance to decline rapidly. For an effective battery thermal management system (BTMS), the maximum temperature and the surface temperature difference of power battery module should be controlled in the allowable range. With the scale and modularization of power batteries, the thermal safety problem is becoming more and more prominent, and it is urgent to develop more advanced and efficient BTMS. In this work, based on the research results of heat transfer characteristics of methanol-water binary working medium thermosiphon containing graphene nanoparticles (GNs), the experimental test system of battery thermal management was constructed with methanol-water binary working medium thermosiphon with filling rate of 50% and GNs concentration of 0.02wt%. The heat dissipation of power battery pack was researched under three discharge rate conditions of 1, 1.5, and 2 C, and were compared with natural cooling and forced air cooling results. The study results showed that, for methanol-water binary working medium thermosiphon containing GNs cooling system, the maximum battery temperature corresponding to discharge rates of 1, 1.5, and 2 C were 28.89, 32.12, and 35.76℃, respectively. Meanwhile, the average temperature rise rate of power battery pack was the lowest, which was only 0.525℃/min at 2 C discharge rate. In addition, at 2 C discharge rate, the power battery temperature of methanol-water binary working medium thermosiphon containing GNs cooling system decreased by 22.48% and 49.13% compared with forced air-cooling system and natural cooling, respectively. The heat dissipation efficiency of the methanol-water binary working medium thermosiphon containing GNs cooling system was the highest under three kinds of discharge rates, and all of them were more than 70%. The research results can provide theoretical basis and data support for the application of heat pipe cooling system in power battery thermal management system.

Key words: thermosiphon, binary working medium, graphene, battery thermal management system

摘要： 动力电池工作温度过高和温差过大都会导致其性能快速衰退，有效的热管理系统应将电池最高温度和电池模块表面温差控制在允许范围内。基于石墨烯纳米颗粒的甲醇-水二元混合工质热虹吸管的传热特性研究结果，选用充液率50%、石墨烯含量0.02wt%的甲醇-水二元工质热虹吸管为换热器件，搭建电池热管理实验测试装置，研究了模拟电池在1, 1.5, 2 C三种放电倍率下的散热性能，与自然对流和强制风冷散热进行对比。结果表明，热管散热方式三种放电倍率对应的电池最高温度分别为28.89, 32.12及35.76℃；热管散热方式平均升温速率最低，在2 C放电倍率时仅为0.525℃/min；2 C放电倍率下热管散热系统相比风冷散热方式温度下降了22.48%，相比自然对流温度下降了49.13%；三种放电倍率下热管散热系统的散热效率最高，且均超过了70%。研究结果可为热管散热系统应用于电池热管理系统提供理论依据和数据支撑。

关键词: 热虹吸管, 二元工质, 石墨烯, 电池热管理系统