Numerical Investigation on Two-Phase Flow Pressure Drop in Cathode Channels of Proton Exchange Membrane Fuel Cells

Abstract

As liquid water is produced by electrochemical reactions in a proton exchange membrane (PEM) fuel cell, liquid–gas two-phase flow forms within the porous structure of the electrodes and gas channels (GCs), resulting in complex gas pressure drop within GCs. This study investigates the two-phase flow pressure drop in a GC connected with a fibrous gas diffusion layer (GDL) using volume of fluid simulations. Fibrous GDLs are stochastically reconstructed to give a rather realistic liquid water breakthrough, and the effect of GDL straight and curved carbon fibers is studied. The results show that droplet breakthrough position and breakthrough size are dependent on the carbon fiber shape, resulting in further distinct pressure drop in GCs. It is also found that the two-phase flow pressure drop has no close correlation with the water content within the GC but a strong relationship with the liquid flow types. Specifically, the cross-section liquid area variation along the gas flow direction is found to be proportional to the pressure drop variation. This study aims to provide the information required for an accurate two-phase flow pressure drop prediction model.