%0 Journal Article
%A Iryna V Zenyuk
%A Adrien Lamibrac
%A Jens Eller
%A Dilworth Y Parkinson
%A Federica Marone
%A Felix N Büchi
%A Adam Z Weber
%B The Journal of Physical Chemistry C
%D 2016
%G eng
%N 50
%P 28701 - 28711
%R 10.1021/acs.jpcc.6b10658
%T Investigating Evaporation in Gas Diffusion Layers for Fuel Cells with X-ray Computed Tomography
%V 120
%8 10/2017
%! J. Phys. Chem. C
%X <p><span>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&nbsp;</span><em>in situ</em><span>&nbsp;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.</span></p>