Characterisation of two-phase flow and its impact on the performance of a Polymer Electrolyte Membrane fuel cell stack

Water management is one of the most critical issues for high-performance Polymer Electrolyte Membrane (PEM) fuel cells. A flow network model was developed to study the possibility of two-phase flow inception along the gas flow channels in the cathode side of a PEM fuel cell stack. The conventional Darcy-Weisbach equation and homogeneous flow model are used to estimate the pressure distributions in the network. The corresponding species concentrations as well as the thermodynamic quality distributions are also calculated. The simulation results have revealed that under certain operating conditions, the quality is lower than one for parts of the stack. However, the amount of the liquified water in the stack is not significant to cause a major pressure drop or an appreciable change in the O2 concentration. Effects of current density and channel diameter on the system quality are also investigated.