Infrared thermography of sorptive heating of thin porous media: experiments and continuum simulations

We have studied the imbibition of water from a stationary nozzle into thin, moving porous media that are suspended in air, as well as the accompanying evaporation and condensation processes. Due to sorptive heating and the latent heat associated with the phase change processes, the temperature of the porous medium becomes non-uniform. We have measured the temperature distributions using infrared thermography as a function of substrate speed. Moreover, we developed a numerical model coupling Darcy flow and heat transfer in the thin porous medium with gas flow, heat and water vapor transport in the surrounding gas phase. The numerical simulations reproduce the measurements very well and point at an intricate buoyancy-induced gas-phase convection pattern.