Three-dimensional CFD modeling of a hydraulically integrated alkaline water electrolyzer: Flow maldistribution, bubble dynamics, and pressure effects

The study presents a 3D multiphysics CFD model of an alkaline water electrolyzer that explicitly incorporates channel and manifold geometries with the electrochemical compartments to capture realistic upstream and downstream hydrodynamic development. The proposed framework reveals inlet-driven flow maldistribution arising from the coupled effects of side-channel entry and compartment geometry, which influence gas evolution, void fraction distribution, and local current density. An Euler–Euler two-fluid model integrated with an electrochemical model was implemented in COMSOL® and validated against experimental polarization data, showing strong agreement. The results demonstrate strong hydrodynamic–electrochemical coupling: flow maldistribution leads to localized gas accumulation and non-uniform current density, while bubble diameter determines slip velocity and gas holdup. Smaller bubbles increase drag-dominated coupling and polarization losses, whereas larger bubbles enhance phase decoupling and reduce cell voltage. Increasing operating pressure reduces the gas volume fraction due to compression effects but increases cell voltage due to the thermodynamic increase in reversible potential predicted by the Nernst equation. • 3D multiphysics CFD AWE model integrating manifolds, channels, and compartments. • Hydraulic architecture shown to induce flow maldistribution and current heterogeneity. • Bubble diameter strongly affects slip velocity, gas volume fraction, and polarization behavior. • Operating pressure reduces void fraction but increases reversible voltage.