Modelling of gas-liquid, two-phase flow in porous media and channels of a PEM water electrolysis cell using the Euler-Euler framework of OpenFOAM

In PEM water electrolysis, a gaseous oxygen phase inherently develops and prevails the liquid water phase from uniformly distributing throughout the catalytic porous layer of the anode. An even distribution of liquid water not only ensures good mass transport characteristics of the reactant specie, it also secures an even heat removal of the cell. In a previous research effort, the gas-liquid, two-phase flow was investigated in the commercial CFD framework of ANSYS CFX using the Euler-Euler model. Particularly, the treatment of gas-liquid flow in a porous medium domain subject to capillary pressure was shown to push the limits of the codes ca-pabilities. In order to improve simulation stability and time, a new model is developed in the open source CFD software OpenFOAM. The customizability of this code not only allows for specific relaxation strategies, it also permits the implementation of various boundary conditions at porous-porous or porous-fluid interfaces found in the membrane electrode assembly. Particularly the treatment of a discontinuous phase volume fraction at the porous-porous interface, and the merging of two pressures fields into a single dominating at the porous-fluid interface influence the convergence stability of the solver.