Intern rapport

Determination of water saturation dependent gas transport properties of PEFC gas diffusion layers via the Lattice Boltzmann method

Abstract

The development of polymer electrolyte fuel cell (PEFC) technology is increasing rapidly and scientists are continuously working on optimization strategies to further improve PEFC performance. One crucial aspect of PEFC optimization is the subject of water management inside the cell. X-ray tomographic microscopy (XTM) has been proven to be an important tool to characterize in situ water behaviour. This report focuses on investigating how liquid water saturation influences gas transport properties inside the porous gas diffusion layer (GDL) during PEFC operation. First, XTM scans were quantified using a specially developed segmentation method based on thresholding. The gas transport through the structure was simulated using an in-house single phase Lattice Boltzmann model (LBM), which was modified and verified for porous media flows. Furthermore a parameter analysis was done to see the influence from the segmentation thresholds. It was seen that saturation does have a large influence on permeability and diffusivity in the GDL. However, the current implementation of the LB model was shown to give results of permeability which have a significant dependency on the chosen lattice viscosity and this parameter must be carefully chosen in order to obtain correct results.