Analysing Gas-Liquid Flow in PEM Electrolyser Micro-Channels

Abstract

PEM water electrolysis is a key component for closing the loop of the renewable energy eco-system. These high response water electrolysers are particular suitable for fluctuating power sources. Conventional PEM water electrolysers are typically operated at a current density of around 1 A/cm2 and are fairly expensive. One means of increasing the hydrogen yield to cost ratio of such systems, is to increase the operating current density. However, at high current densities, management of heat transfer and fluid flow in the anode GDL and channel becomes crucial. This entails that further understanding of the gas-liquid flow in both the porous media and the channel is necessary for insuring proper oxygen, water and heat management of the electrolysis cell. In this work, the vertical upward gas-liquid flow pattern in a 0.5×1×94 mm micro-channel is both numerically and experimentally analysed. A sheet of titanium felt is used as a permeable wall for permeation of air to the column of water similar to the phenomenon encountered in Oxygen Evolution Reaction (OER). The transparent setup is operated in situ and the gas-liquid flow regimes are identified using a high-speed camera. The picture shows how the transparent cell is made which consists of a channel for the inlet air and a channel for the water-bubble flow. The transparent material is Plexiglas that is sealed with a sheet of silicon. The conventional co-current gas-liquid two-phase flow patterns, such as bubbly flow, slug flow and annular flow, are observed in the present micro-channel. The phenomenon is also analysed numerically in 3D, unsteady, euler/euler multiphase method using the commercial software ANSYS FLUENT 17 and the results show good agreement with the experimental data. Influence of each multiphase flow regime is described in the study as well as the recommendation for improving the performance. A well management of the multiphase flow regime along the whole micro-channel length can assure a proper distribution of water inside the titanium felt. Figure 1