CFD modeling of gas distribution in an alkaline water electrolyzer with porous electrodes

Multiphysics simulations can provide detailed insight into gas transport in alkaline water electrolyzer (AWE) cells and support the design of gas management strategies; however, such simulations are typically validated only against externally measurable quantities, e. g. , polarization curves and pressure drops. The goal of the present work is twofold. First, we extend a computational fluid dynamics (CFD) model previously implemented in OpenFOAM t4ht=© to improve the prediction of gas distribution in an AWE cell with porous electrodes. To this end, the model accounts for the effect of bubbles attached to the electrode surfaces. The model is calibrated and validated against recent neutron-imaging experiments by Kragh-Schwarz, et al. J. Power Sources 662, 2023, who reported the gas volume fraction inside AWEs with nickel-foam electrodes at current densities of 200 and 300 mA/cm 2. Second, the calibrated model is used to study the effect of cell geometry, specifically the thickness of the porous electrode and the width of the flow channel, on the gas holdup and cell potential. We study values in the range 0. 5–2. 5 mm at a current density of 300 mA/cm 2 and a fixed electrolyte flow rate. The lowest cell potentials are obtained for electrode thicknesses between 1. 75 and 2 mm, where the best trade-off between electrode area and bubble-related losses is reached. Within the investigated range, the cell potential decreases with decreasing channel thickness, since a narrower channel leads to a larger flow velocity, and subsequently, less gas accumulation within the porous electrode. The sensitivity to channel width is, however, only significant near the optimal values of electrode thickness.