Thermal-fluid transports in a five-layer membrane-electrode assembly of a PEM fuel cell

Abstract

Thermal-fluid transport phenomena in a membrane-electrode assembly (MEA) of a polymer electrolyte membrane (PEM) fuel cell attached to interdigitated gas distributors are studied numerically. The MEA consists of two porous catalyst layers, two porous gas diffusion layers, and an impermeable PEM. In the catalyst layers, the overpotential heating by the electrochemical reaction under thermal equilibrium conditions produces heat that is removed by the fluids as well as the solid matrices. In the diffusion layers, the difference in the heat conductivities between the solid matrices and the fluids causes a thermal non-equilibrium in the porous medium. A two-equation approach is used to resolve the temperature difference between the solid matrices and the fluids. The effects of the porous Reynolds number, interfacial heat transfer coefficient, and overpotential heating are examined. It is found that the local maximum temperature occurs inside the cathodic catalyst layer. In addition, the temperature difference between the solid matrices and the fluids in the diffusion layers decreases with increasing the non-dimensional interfacial heat transfer coefficient. The present results have provided comprehensive heat transfer information that is helpful in understanding of the mechanisms responsible for thermal pathways in a PEM fuel cell.