Elucidating Liquid Water Distribution and Removal in an Operating Proton Exchange Membrane Fuel Cell via Neutron Radiography

Neutron radiography was used to quantify the steady-state water content and its distribution in a $50cm2$ operating proton exchange membrane fuel cell. It was observed that the liquid water distribution near the corners of the gas-flow channels (GFCs) is influenced by the local gas-flow velocity as determined by the cathode stoichiometric flow ratio. At low velocity, the distribution of liquid water down the channel was found to be fairly uniform with only a slight reduction in liquid water content at the exit of the GFC corners. It was further observed that as the cathode gas-flow velocity is increased, a noticeable pattern develops in which liquid water is concentrated at the entrance to the GFC corners and becomes depleted in the corner and near the exit of the corner; liquid water content again increases further down the channel away from the corners. A single-phase computational fluid dynamics (CFD) model was developed and employed to help explain the observed water-distribution patterns. Flow-fields computed from our CFD model reveal recirculation regions in the GFC corners as well as in the areas of increased local gas-flow velocity, which help explain the experimentally observed liquid water distribution.