Combining CFD and Stress Models for PEM Cells: Initial Development

Abstract

The aim of this work is to determine the relationship between the operational characteristics of a Polymer Electrolyte Membrane (PEM) fuel cell, and the relevant materials issues and in particular mechanical stresses that develop. A three dimensional, non-isothernal, single phase model of a single channel PEM fuel cell is developed to investigate the impact of temperature variation on the Membrane Electrode Assembly (MEA). The model accounts for heat transfer in solids as well as in the multi-component mixture of gases, convection and diffusion of different species in the porous electrodes and the channels, electrochemical reactions and transport of water and ions through the PEM. This model has been numerically implemented in a commercial Computational Fluid Dynamic (CFD), finite volume based code. Temperature contours derived from the model were then exported to a commercial Finite Element (FE) code to analyse the relevant mechanical issues of the PEM and in particular thermomechanical stresses that develop. Initial results verify that, even considering the polymer electrolyte membrane in isolation with mechanically free boundary conditions, there is a significant temperature difference leading to tensile stresses of up to 2.1 MPa within the membrane.