Dynamics of heat and mass transfer through a water-air interface based on measurements of thermal radio emission at a frequency of 60 GHz

Abstract

We study the dynamics of heat and mass transfer through a water-air interface on the basis of laboratory radiometric measurements of the time dependence of thermal radio emission of water at a frequency of 60 GHz, which is related to air turbulization above its surface by a fan. We recover the dynamics for the temperature profile in water and in a viscous sublayer of air as well as for the heat flux through the water-air interface. The flux components related to evaporation and heat exchange and the rate of evaporation from a unit surface are determined. An equation for determining the thickness of the viscous sublayer in the air from the heat flux value is obtained;this thickness is about 2 mm under the experimental conditions. The process dependence on the water turbulence is established and methods for determining the thermal film thickness are proposed. In the absence of turbulence in unstable stratified water we observed the development of a periodic convective process from the time the critical value of the Rayleigh number was reached. The heat exchange dependence on the presence of petroleum film on the water surface is studied. It is found that for a film thickness of 5 μm the heat exchange rate decreases by a factor of 3 because of the petroleum presence.