LAUSR

Abstract The onset of drying of a porous particle bed immersed in saturated water and heated with a high surface heat flux is investigated. Heating of the top surface of the porous particle bed while the bottom surface is immersed in a bulk liquid induces a decrease in the local liquid saturation due to evaporation and the liquid flow toward the heated surface due to capillary action. As long as the liquid flow is sufficient to sustain wetting of the surface, the porous medium functions as a heat sink by evaporative cooling. However, at higher heat fluxes, a dried region may form in the proximity of the heated surface, which causes significant deterioration of the heat transfer from the heat source due to thermal resistance. Two-phase flow in a porous particle bed immersed in a saturated liquid and heated with a high surface heat flux is analyzed based on a one-dimensional model. The calculated liquid saturation distribution and heat flux at the emergence of drying almost agree with the measured distribution and heat flux. The estimation with the model suggests that the heat flux at the onset of drying increases proportionally to the square root of the permeability of the porous medium up to as high as 0.1–10 MW/m2.