%0 Journal Article %A Zenyuk, Iryna V. %A Lamibrac, Adrien %A Eller, Jens %A Parkinson, Dilworth Y. %A Marone, Federica %A Büchi, Felix N. %A Weber, Adam Z. %D 2016 %T Investigating Evaporation in Gas Diffusion Layers for Fuel Cells with X‑ray Computed Tomography %U https://acs.figshare.com/articles/journal_contribution/Investigating_Evaporation_in_Gas_Diffusion_Layers_for_Fuel_Cells_with_X_ray_Computed_Tomography/4312319 %R 10.1021/acs.jpcc.6b10658.s001 %2 https://acs.figshare.com/ndownloader/files/7032644 %K evaporating water-front location %K carbon gas-diffusion layers %K saturation %K X-ray CT studies %K Gas Diffusion Layers %K gas flow rate %K understanding phase change %K evaporation rate %K GDL %K liquid-water evaporation rates %K water distribution %K evaporation rates %K liquid-water evaporation fronts %X Understanding evaporation in porous media and the associated water distribution for a given saturation is critical for optimizing many different technologies including polymer–electrolyte fuel cells. In these devices, heat and mass-transport are coupled due to the two-phase transport of water and operating temperatures from subzero to 80 °C. Especially critical is understanding phase change in the mixed wettability, carbon gas-diffusion layers (GDLs). While previous works have measured evaporation rates empirically for a given saturation, there remains a need to explore the mechanisms governing evaporation, which are tied directly to the internal water distribution. In this article, liquid-water evaporation rates in GDLs are measured in situ using synchrotron X-ray computed tomography (CT). X-ray CT allows visualizing the evaporating water-front location and interfacial water/air surface area, thereby enabling true surface-area based evaporation rates. It is found that the overall specific evaporation rate is essentially constant as a function of saturation and that the water/air interfacial area scales almost linearly with saturation. To isolate transport and kinetic contributions to the overall evaporation rate, we systematically varied gas flow rate and composition. A three-dimensional mathematical model with direct meshes of liquid-water evaporation fronts from the X-ray CT studies allowed for the determination that the evaporation is transport limited. The overall results provide insight into evaporation phenomena in porous media. %I ACS Publications