Figure 1. The conceptual sketch illustrating the mechanisms controlling evaporation from porous media. (a) Detachment of the liquid meniscus from the surface and pinning to a level below during the transition from stage-1 to stage-2 evaporation. (b) Formation of a dry layer above the surface at the onset of stage-2 evaporation. During this period, the evaporation is proceeded by liquid from the wet zone to the bottom of the dry layer supplied by the capillary flow, liquid vaporization at that level and vapor diffusion through the overlying dry layer (after Shokri and Or, 2011).
Accurate description of evaporative fluxes from porous media without invoking adjusting parameters is still a grand challenge due to the complexity of the processes controlling the evaporation dynamics including but not limited to the role of heterogeneity, the coupling between the atmospheric conditions and transport processes occurring inside porous media, properties of the evaporating fluid, and the mass exchange across turbulent boundary layers formed above the surface.
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- A wide range of numerical and experimental tools are utilized to understand and characterize evaporation from porous media under different boundary conditions including but not limited to pore network modelling, lattice Boltzmann simulation, continuum-scale simulation, X-ray tomography, neutron radiography, thermal imaging and customized laboratory experiments.
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