PEMFC电堆内部水结冰、融化及冷启动过程的研究

Study of water freezing and thawing process inside PEMFC stacks during cold start

为了研究质子交换膜燃料电池(PEMFC)堆在冰点(273 K)下快速、低损坏的冷启动,建立了一个包含40片单池的二维动态堆模型,用于估计电池堆内每片单池内水的结冰/融化时间,并利用获取的液相/固相分界线分析各单池的差异性。在环境温度为260 K时,仿真模拟了电堆的结冰/融化过程并得到以下结论:(1)关机后,电堆外层单池先结冰且每片单池结冰耗时相等,但外层单池开始结冰的时间间隔较内层单池间的开始结冰时间间隔长,最里层几片单池几乎同时结冰;(2)开机前,加载热源加热质子交换膜,若内部残留水结冰则电堆的升温时间比没有残留水的升温时间要长,残留水影响电堆的冷启动过程。

In order to stud,）, a quick and scatheless cold start of PEMFC stacks under subzero temperature, a 2-D dynamical model for a PEMFC stack with 40 cells was developed and applied to investigate the water freezing/thawing process inside the stack. This model can estimate the freezing and thawing time of each cell, and describe the spatial water and ice distribution as well. Two processes under the ambient temperature 260 K were simulated and analyzed, and the simulation results show as follows： （1） after the stack shut down, the outer cells begin to freeze more rapidly than the inside cells but with the same freezing duration, and the freezing interval time between the outer cells is longer than between the inner cells which almost simultaneously freeze; （2） when the membranes are heated by the heat sources before the stack starts up, the thawing process of the stack with residual water takes longer time than of the stack without residual water because of purge operation after the stack shuts down. Therefore, it is concluded that the residual water inside the stack impacts the negative influence on the stack cold start.