The influence of channel wettability and geometry on water plug formation and drop location in a proton exchange membrane fuel cell flow field

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The critical volume of liquid water required to form a plug in a channel having mixed wettability similar to that found in the flow field of a proton exchange membrane (PEM) fuel cell is computed for a range of gas diffusion layer (GDL) and bipolar plate wettabilities and channel bend dihedral angles. Three gas diffusion layers (GDL) with 80, 110 and 150° contact angles are considered while the bipolar plate wettabilities are varied with static contact angles ranging from 50 to 130°. The critical volume is an intrinsic property of the channel-GDL configuration and has direct implications for the liquid holdup, the water distribution in the flow fields of PEM fuel cells as well as on the pumping parasitic power loss. The plug volume correlations may be used as an optimization tool for water management in channels of mixed wettability. The effect of cross-section geometry on the critical volume is also investigated through a comparison between a square and a trapezoidal channel. Mixed wettability drop simulations reveal that water can be passively removed from the GDL surface to the bipolar plate if the latter has a lower contact angle, potentially avoiding the flooding of the porous electrodes. © 2012 Elsevier B.V.

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Journal of Power Sources