Non-uniform liquid flow distribution in an alkaline water electrolyzer with concave-convex bipolar plate (CCBP): A numerical study

Alkaline water electrolysis (AWE) is promising for large-scale commercial production of green hydrogen, but large overpotential hinders their promotion. To reduce overpotential, the electrolyzers should be designed to improve flow uniformity, thus requiring a quantitative evaluation of flow distribution. However, the corresponding assessment criteria and method are ambiguous. This study establishes a 3D numerical model as well as quantitative parameters to investigate the liquid flow uniformity in a concave-convex bipolar plate (CCBP) electrolyzer. The simulation result is validated by a flow visualization experiment. The simulated velocity field reveals significant non-uniform flow in the CCBP electrolyzer. A uniformity parameter δ was defined to quantify the velocity discrepancy at various horizontal sections. Additionally, residence time distribution (RTD) analysis by CFD coupled particle tracing (CFD-PT) method is applied to evaluate flow behavior inside electrolyzers. The corresponding dimensionless parameter θ can be applied as a criterion for electrolyzer structure design, operation optimization, and scale-up.