3D Numerical Study of the Liquid Water Distribution in Bipolar Membrane Fuel Cells

Bipolar membrane fuel cells (BPM-FCs) offer unique advantages due to their hybrid acidic–alkaline membrane design. They can self-humidify under operation as water is produced directly within the membrane. Furthermore, the alkaline environment at the cathode allows the use of platinum group metal-free catalysts, reducing the system cost. However, water management is critical: membrane hydration governs the ionic conductivity and performance, while excess liquid in porous layers impedes reactant transport. To study water transport in its various phases, a three-dimensional, multiphase, steady-state CFD model of a BPM-FC was developed, incorporating liquid water transport. The model was used to investigate both self-humidification and external cathode humidification. Results show that self-humidification leads to localized high saturation, whereas external humidification yields a more uniform water distribution. A comparison of parallel and serpentine flow fields revealed that parallel designs are more suitable for self-humidifying operation, while serpentine layouts perform better under external humidification.