基于临界换热系数与干预时间的车用锂电池热设计及运行策略

Thermal design and operation strategy of automotive lithium battery based on critical heat transfer coefficient and intervention time

针对车用锂电池在高倍率放电情况下的热管理问题开展研究。基于电池生热量和散热量匹配的热管理理念,创新性地提出了确保电池热安全运行的临界换热系数h_(cr),并基于单电池的热电耦合模型发展了一种确定临界换热系数的数值分析方法。对极端工况下的18650锂电池进行临界换热系数的数值研究,发现放电倍率和换热环境温度是其主要影响因素。换热环境温度和放电倍率增加,临界换热系数会急剧增加。为了进一步提高电池的热安全运行能力,针对h<h_(cr)的工作状况,提出了基于干预时间τ_(intv)的热管理运行策略,并详细讨论了干预时间τ_(intv)的数值确定方法和影响因素。数值结果显示,在干预时间内对锂电池实现降倍率运行等措施,可以有效地将电池温度控制在安全范围内。进一步研究还发现,给定h的锂电池干预时间受放电倍率、环境温度等因素的影响较大。本文的工作对车用锂电池热管理系统的设计以及运行管理有着良好的理论指导意义。

The thermal management of automotive lithium batteries during high-rate discharge is being investigated.Based on the thermal management concept of matching the heat generation and heat dissipation of the battery,the critical heat transfer coefficient hcr is innovatively proposed to ensure the battery's safe operation,and a set of numerical solution methods for determining h_(cr) is developed.For numerical calculation,a thermoelectric coupling model of a single cell is established.The findings indicate that the critical heat transfer coefficient of a given lithium battery is related to the discharge rate and the temperature of the heat exchange environment,and is less affected by the battery's initial temperature.The critical heat transfer coefficient increases sharply once the ambient temperature exceeds 293.15 K.A thermal management operation strategy based on the intervention time τ_(intv) is proposed for the working condition of h<h_(cr) to further improve the battery's thermal safety operation capability.Furthermore,the numerical determination method,influencing factors,and intervention effect of intervention time are thoroughly examined. The results show that theintervention time of the lithium battery for a given h is greatly affected by the discharge rate,and the reduced rate operation of the lithium battery during the intervention time caneffectively control the battery temperature within a safe range This work has importanttheoretical implications for the design and operation management of the vehicle lithium batterythermal management system.