Modeling Fluid Flow in the Gas Diffusion Layers in PEMFC Using the Multiple Relaxation-time Lattice Boltzmann Method

The gas diffusion layers (GDLs) are key components in proton exchange membrane fuel cells and understanding fluid flow through them plays a significant role in improving fuel cell performance. In this paper we used a combination of multiple-relaxation time lattice Boltzmann method and imaging technology to simulate fluid flow through the void space in a carbon paper GDL. The micro-structures of the GDL were obtained by digitizing 3D images acquired by X-ray computed micro-tomography at a resolution of 1.76 mu m, and fluid flow through the structures was simulated by applying pressure gradient in both through-plane and in-plane directions, respectively. The simulated velocity field at micron scale was then used to estimate the anisotropic permeability of the GDL. To test the method, we simulated fluid flow in a column packed with glass beads and the estimated permeability was found to be in good agreement with experimental measurements. The simulated results for the GDL revealed that the increase of permeability with porosity was well fitted by the model of TomadakisSotirchos [48] without fitting parameters. The permeability calculated using fluids with different viscosities indicated that the multiple-relaxation time lattice Boltzmann method provides robust solutions, giving a viscosity-independent permeability. This is a significant improvement over the commonly used single-time relaxation lattice Boltzmann model which was found to give rise to a unrealistic viscosity-dependent permeability because of its inaccuracy in solving the fluidsolid boundaries.