Two-phase flow evolution and bubble transport characteristics in flow field of proton exchange membrane water electrolyzer based on volume of fluid-coupled electrochemical method

Proton exchange membrane water electrolyzer (PEMWE) holds great promise as a hydrogen production technology powered by renewable energy sources. In this study, a novel volume of fluid (VOF)-coupled electrochemical method was developed to investigate the two-phase flow evolution and bubble transport characteristics in flow field of PEMWE. The results show the bubbles in each sub-channel undergo processes of growth, coalescence, separation, and wall adhesion. Besides the liquid water flow velocity and the adhesion of the wall to the bubble, the accumulation of bubbles in the outlet manifold also affects the bubble removal rate, and cause bubble backflow. Hydrophilic anode porous transport layer (APTL) results in higher slug flow proportion in middle channels of flow field, causing lower bubble removal rates. Film and wavy flow formation in hydrophobic APTL significantly delays bubbles reaching the outlet manifold. Moreover, a larger APTL contact angle increases liquid water transport resistance and parasitic power in PEMWE. A 10(degrees)-130(degrees) APTL contact angle change results in 89.02%, 598.79%, and 37.68% increments in average dimensionless bubble diameter, bubble coverage on the bottom wall, and pressure drop of all channels, respectively. Moreover, uniform APTL contact angle arrangement better enhances mass transport capacity in PEMWE than gradient arrangement. These findings provide valuable insights into the mass transport mechanism of PEMWE.