Impact of Multiple Inlet and Outlet Structures of Bipolar Plate Channel on the Mass Transport in ALK Electrolyzers

The flow channel structure in alkaline electrolyzers critically impacts electrolyte distribution uniformity, influencing stagnant zones, gas bubble accumulation, and electrode reactions. Conventional concave–convex bipolar plates cause uneven flow and reduced current density. Therefore, a scaled-down-sized multiple inlet setup coupled with the bipolar plate channel of three typical concave–convex structures was designed to improve the uniformity of electrolyte. Three-dimensional computational fluid dynamics was employed to analyze the flow characteristics in the channels. The results indicated that in the single inlet/outlet model, the velocity near the center axis along the mainstream direction was higher than at the edge of the channels, resulting in a non-uniform flow distribution. The vorticity intensity gradually decreased along the flow direction, while the multiple inlet/outlet structure strengthened the intensity. The multiple inlet model allowed for the electrolyte flow across more areas along the channel and enhanced the velocity uniformity. According to the velocity uniformity evaluation criteria, the flow uniformity index of the three-inlet square concave–convex structure was the highest, reaching 0.80 at the middle cross-section normal to the incoming flow and 0.88 parallel to the flow. This study may help provide a useful guide for the design and optimization of efficient electrolyzer in alkaline water electrolysis.