Investigation of Porous Gas Diffusions Layer Modeling in PEM Fuel Cells

Darcy’s law, the Brinkman Equation and the modified N-S equation describe the momentum transport phenomena occurring in porous gas diffusion layer. This paper proposes to compare the differences in applying aforementioned models to describe the transport phenomena in porous gas diffusion layers, and evaluate their effects on the fuel cell performance. A two dimensional isothermal single phase PEM fuel cell model is developed, in which Darcy’s law, the Brinkman equation and the modified N-S equation are applied separately in porous electrodes. These three models show no visible effects on the fuel cell performance characterized by the polarization curves. The polarization curve shows a sharp potential drop when calculated by the pure diffusion model. Three values of GDL permeability are investigated here. The order of the magnitude of each term in the modified N-S equation is numerically evaluated. The inertial term is found much smaller than other terms, and can be dropped in the Navier-Stokes equation. Considering the boundary condition setting problem of Darcy’s law and the convergence problem of the modified N-S equation, the Brinkman equation is recommended by this paper to describe the momentum transport in porous electrodes.