Improved local description of the capillary pressure - saturation relation to enhance reliability of CFD results

Over the past few decades, modeling of Proton Exchange Membrane Fuel Cells has significantly improved in many aspects. Still, specifically the description of capillary water transport within porous media has lagged behind. In most current model implementations the traditional Leverett J-function approach is used. However, this method may turn out insufficient for representing state-of-the-art Gas Diffusion Layer materials. This study demonstrates how the standard Leverett description can be replaced with a more suitable polynomial function, alongside other necessary model adjustments, to achieve more accurate predictions. The performance of the newly defined material representation is subsequently compared against both the default Computational Fluid Dynamics model and experimental data from a recently introduced open-source design stack, the generic HyFaB stack. The proposed model demonstrates strong agreement with the experimental results across a wide range of operating conditions.