Geometric scale effect of flow channels on performance of fuel cells

Department of Mechanical and Aerospace Engineering, San Jose State University,San Jose, California 95192-0087, USAThis paper studies the effect of flow channel scaling on fuel cell performance. In particular, the impact of dimensional scale on theorder of 100 micrometers and below has been investigated. A model based on three-dimensional computational flow dynamics hasbeen developed which predicts that very small channels result in significantly higher peak power densities compared to their largercounterparts. For experimental verification, microchannel flow structures fabricated with varying sizes in SU-8 photoepoxy havebeen tested with polymer electrolyte membrane electrode assemblies. The experimental results confirm the predicted outcome atrelatively large scales. At especially small scales ~,100 mm!, the model ~which does not consider two-phase flow! disagrees withthe measured data. Liquid water flooding at the small channel scale is hypothesized as a primary cause for this discrepancy.© 2004 The Electrochemical Society. @DOI: 10.1149/1.1799471# All rights reserved.Manuscript submitted October 14, 2003; revised manuscript received April 6, 2004. Available electronically October 8, 2004.

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