Three-dimensional simulation of two-phase flow distribution in spherical concave-convex shaped flow field for alkaline water electrolyzer

Alkaline water electrolyzer (AWE) with KOH aqueous solution as electrolyte is one of the most mature routes for green hydrogen production, in which spherical concave-convex (SCC) shaped flow fields are widely applied. However, while the addition of SCC is known to have significant effects on complex two-phase flow, in particular on the generated hydrogen, detailed understandings of the flow distributions are still lacking. In this paper, we propose to demonstrate the three-dimensional (3D) two-phase flow distributions in SCC shaped flow field for AWE by COMSOL simulation method. First, the typical geometric model is extracted from the practical AWE, based on which the mesh model is constructed; Moreover, the basic 3D simulation results of channel without SCC are evaluated by comparing with the previous experimental studies to demonstrate the model validation; Finally, the 3D flow velocity and hydrogen fraction distributions are carefully illustrated that the SCC shaped structure averages the distribution in the channel effectively and the hydrogen concentration on the electrode surface are reduced, beneficial to the improvement of the electrolysis efficiency, at the outlet of the channel, half of the geometric height (z = 4 mm), the hydrogen fraction in the straight channel is less than 3%, while the hydrogen fraction at the outlet of the SCC channel is about 4%, or even 5% locally. We believe this work can not only provide a guideline for the 3D model establishment for two-phase flow in AWE, but give detailed hydrogen distribution understandings in varied conditions with different current densities.