Investigating Phase‐Change‐Induced Flow in Gas Diffusion Layers in Fuel Cells with X‐ray Computed Tomography

Investigating Phase‐Change‐Induced Flow in Gas Diffusion Layers in Fuel Cells with X‐ray Computed Tomography

TitleInvestigating Phase‐Change‐Induced Flow in Gas Diffusion Layers in Fuel Cells with X‐ray Computed Tomography
Publication TypeJournal Article
Year of Publication2017
AuthorsAndrew D Shum, Dilworth Y Parkinson, Xianghui Xiao, Adam Z Weber, Odne S Burheim, Iryna V Zenyuk
JournalElectrochimica Acta
Volume256
Pagination279 - 290
Date Published12/2017
ISSN00134686
Keywordsevaporation, fuel cells, phase-change-induced flow, porous media, X-ray tomography
Abstract

The performance of polymer‐electrolyte fuel cells is heavily dependent on proper management of liquid water. One particular reason is that liquid water can collect in the gas diffusion layers (GDLs) blocking the reactant flow to the catalyst layer. This results in increased mass‐transport losses. At higher temperatures, evaporation of water becomes a dominant water‐removal mechanism and specifically phase‐change‐induced (PCI) flow is present due to thermal gradients. This study used synchrotron based micro X‐ray computed tomography (CT) to visualize and quantify the water distribution within gas diffusion layers subject to a thermal gradient. Plotting saturation as a function of through‐plane distance quantitatively shows water redistribution, where water evaporates at hotter locations and condenses in colder locations. The morphology of the GDLs on the micro‐scale, as well as evaporating water clusters, are resolved, indicating that the GDL voids are slightly prolate, whereas water clusters are oblate. From the mean radii of water distributions and visual inspection, it is observed that larger water clusters evaporate faster than smaller ones.

DOI10.1016/j.electacta.2017.10.012
Short TitleElectrochimica Acta