1D transient model for frost heave in polymer electrolyte fuel cells - II. Parametric study

A computational model based on a frost-heave mechanism has been developed to simulate the physical damage process for polymer electrolyte fuel cells (PEFCs) during shutdown to a frozen state. In previous work by the authors, an analytical model was developed and two modes of physical damage were proposed: diffusion media (DM) punch through caused by ice-lens formation under the channel at the interface of DM and catalyst layer (CL) and catalyst delamination caused by supercooled unfrozen water flow from the electrolyte to the interface of CL and electrolyte, where it is rapidly frozen. In this study, a computational parametric study was conducted to assess the controlling parameters in the physical damage process, which were found to include (i) drainage rate of DM, CL, and electrolyte, (ii) initial water content in the electrolyte, (iii) virgin material cracks or initial interfacial gaps between the DM and the CL, (iv) the irreducible water content of PEFC components, and (v) heat-transfer rate and directional gradient within the membrane electrode assembly. The ice-lens thickness at the interface of DM and CL under the channel is not severe from a single cycle but can grow over many cycles, causing damage. (c) 2007 The Electrochemical Society.