Visualization experiment to understand two-phase flow characteristics inside the anode flow path of proton exchange membrane water electrolysis with 100 cm² circular active area

To optimize the anode flow path for rapid oxygen release and improve the performance of proton exchange membrane water electrolysis (PEMWE), understanding the two-phase flow inside the cell during operation is required. In this study, visualization experiments were conducted on a 100 cm² PEMWE with a circular shape similar to that of commercial stacks. Additionally, the effect of the current collector location on the local performance of the flow path was analyzed using a visualization cell. The two-phase flow inside the anode flow path was observed using a high-speed camera, and the two-phase flow pattern evolved in the following flow order: bubbly, slug, annular, and mist. Additionally, the dry-out was observed in the upper layer of the annular bubble. The bubble area fraction and bubble velocity inside the anode flow path increased with current density, and their changes were influenced by the two-phase flow pattern and bubble length, respectively. Additionally, the electrochemical reaction was more active in the flow path near the current collector, resulting in higher oxygen production and temperature. This study provides essential data on the flow path and cell structure, which can improve the performance of PEMWE.