Droplet and slug formation in polymer electrolyte membrane fuel cell flow channels: The role of interfacial forces |
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Authors: | Carlos E. Colosqui May J. CheahIoannis G. Kevrekidis Jay B. Benziger |
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Affiliation: | a Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA b Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544, USA |
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Abstract: | A microfluidic device is employed to emulate water droplet emergence from a porous electrode and slug formation in the gas flow channel of a PEM fuel cell. Liquid water emerges from a 50 μm pore forming a droplet; the droplet grows to span the entire cross-section of a microchannel and transitions into a slug which detaches and is swept downstream. Droplet growth, slug formation, detachment, and motion are analyzed using high-speed video images and pressure-time traces. Slug volume is controlled primarily by channel geometry, interfacial forces, and gravity. As water slugs move downstream, they leave residual micro-droplets that act as nucleation sites for the next droplet-to-slug transition. Residual liquid in the form of micro-droplets results in a significant decrease in slug volume between the very first slug formed in an initially dry channel and the ultimate “steady-state” slug. A physics-based model is presented to predict slug volumes and pressure drops for slug detachment and motion. |
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Keywords: | PEM fuel cell Two-phase flow Slug flow Water management Pressure drop |
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