A general numerical method for cross-component gas–liquid transport in proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis constitutes a key pathway for renewable energy utilization. Given the coexistence of gas and liquid in core components of electrolyzers, including catalyst layer, transport porous layer, and flow channel, revealing the cross-component gas–liquid two-phase transport process is crucial. However, existing numerical methods for gas–liquid two-phase flow struggle to balance cross-component gas–liquid interface capture, computational scale, and computational efficiency. In this study, a continuum capillary pressure model is proposed. Combined with the VOF method, the model enables phase interface capture within the representative elementary volume of porous media, significantly improving the computational efficiency of two-phase simulation in porous media. It bridges the gap for simulating the coupled gas–liquid two-phase transport processes between the pore scale (catalyst layer, porous layer) and macroscale (flow channel). Based on the proposed method, the cross-component gas–liquid two-phase interface evolution process in proton exchange membrane electrolyzers is obtained. Compared to parameters such as flow field structure, water flow rate, and two-phase flow regime, oxygen saturation in the porous transport layer provides a more direct and effective characterization of mass transfer performance. Accordingly, a Transport Performance Index integrating the opening ratio and flow uniformity has been established to quantitatively evaluate the gas–liquid transport performance of flow fields. The simulation model and evaluation index developed in this study offer a new approach for the optimization of two-phase transport in proton exchange membrane electrolyzers.