Numerical assessment of flow uniformity and recirculation in a water electrolysis cell with knitted mesh and foam-like electrodes

Abstract

In this work, single-phase Computational Fluid Dynamics (CFD) simulations are used to extract, based on a Residence Time Distribution (RTD) analysis, two representative parameters that allow to quantify electrolyte flow uniformity and flow recirculation in water electrolysis cells. This then allows to compare different cell geometries on the same ground. The optimum cell configuration is the one that homogenises the flow without generating recirculation of the electrolyte within the cell. In that case, we can take advantage of the whole surface area of the electrodes, without the risk of gas bubbles being trapped inside the cell. In a first step, several modifications of the injection channels are considered in a reference configuration using knitted mesh-type spacers as porous transport layer (PTL). Although this indeed results in some improvement in the flow behaviour, significantly better results are obtained by the use of foams as PTL: they increase the effective cell volume covered by the electrolyte and at the same time lower the risk of flow recirculation within the cell. Furthermore, keeping the foam’s pore size sufficiently large on the order of 3000 µm allows to limit the pressure drop across the cell.