Network Modeling to Investigate the Effect of Coupling the Transport Phenomena on Water Distribution in Gas Diffusion Layers

The cathode side gas diffusion layer (GDL) in polymer electrolyte membrane fuel cells discharges out the water generated as a result of the electrochemical reaction through its porous medium. This paper criticizes the generated pore network models for GDLs assuming uniform injection of liquid water from the catalyst layer into GDL. These models lead to a roughly uniform distribution of liquid water saturation in the in-plane direction making no difference between under gas channel and under-rib regions which is in contradiction with the in-situ visualizations and imaging of GDLs. It has been attempted in this paper to couple the existing two-phase flow network models to other transport phenomena in GDL and also in other layers. To achieve this, the mentioned model is coupled to network models of oxygen and electron transport at the cathode side and also to a model of electrochemical reaction at catalyst layer and a proton transport model of the membrane. As a first result of modeling, the distribution of local water generation rate and also the temporal evolution of total water generation rate at catalyst layer are presented, the latter experiencing an approximate 50% reduction from start-up to steady state. The resulting water saturation distribution in GDL is strongly non-uniform, and maximums are observed under the ribs which is a direct result of non-uniform water generation at reaction sites.