On the Water Cooling of Hot Surfaces: (Analysis of Fog Cooling in the Region Equivalent to Film Boiling)

A theoretical study has been conducted on air-atomized fog cooling in the region equivalent to film boiling with low mass velocity of water. In the analysis, total heat flux is expressed by the sum of three components, i.e. radiation, forced convection by air flow and evaporation of liquid droplets. The air flow is approximated by an axisymmetric laminar stagnation flow. It is assumed that spherical droplets float on the vapor film formed along the hot surface and move in the radial direction with a droplet is estimated by conduction through the vapor film. It has been derived that heat flux by evaporation increases linearly with the mass velocity of water and inversely with the square root of diameter and impinging velocity of the droplet. The prediction performance of the proposed analysis if fairly good.