Hovering height of a high-temperature body over a water-containing porous plate

The hovering behavior of a high-temperature metal disk brought into proximity with a water-containing porous material plate is investigated experimentally. Vapor produced from the porous plate by the heat transferred from the hot disk flows along the small clearance between two bodies in order to establish a pressure field that acts to repel the hot disk away from the porous plate. The repelling force may just balance gravity, allowing the hot body to hover over the porous plate. In the present paper, heat transfer from a high-temperature solid to the water-containing porous material plate separated by a small gap is analyzed based on a simplified model. The calculated heat fluxes in the system and the resulting vapor production rate are compared with the measured results. An expression for the hovering force is derived as a function of the evaporation mass flux and the related parameters based on the model of the vapor flow dynamics. The hovering height of a high-temperature disk is predicted using an approximate correlation for the evaporation mass fluxes, which can express the dependency of the measured results on the temperature and the magnitude of the clearance, and is compared with the measured results.