A Computational Fluid Dynamics Analysis of Multiphase Flow in the Anode Side of a Proton Exchange Membrane Electrolyzer

This work describes an innovative three-dimensional model of a proton exchange membrane electrolyzer. For the first time, a multi-phase model has captured segregated channel flow together with multiphase flow in a porous medium, as well as heat transfer and phase change employing an Eulerian multiphase model. The novel electrolyzer design investigated employs a symmetrical, interdigitated flow field to facilitate even water distribution. In the current case, a hot spot is predicted with a temperature increase of 7 °C at a current density of 1.0 A/cm${}^2$. The flow field plates are horizontally oriented, and it is shown that gravity plays an important role in the electrolyzer design and orientation. A parametric study shows, for the first time, the effect of operating a PEM electrolyzer at sub-ambient anode pressure to favorably adjust the concentration ratio between water vapor and oxygen in the anode compartment. This ratio is increased by a factor of 5.6 when the pressure is decreased from one bar to 500 mbar.