Heat transfer from a hot surface to an impinging spray

The heat transfer between a liquid spray and a surface at a temperature above the liquid boiling point is relevant to various technologies. In general the heat flux rate depends on surface temperature, surface and liquid thermophysical properties, surface conditions, drops diameter and impact velocity, flow rate of spray and orientation of surface relative to the impinging flow and to the gravity field. Most of the available literature deals with relatively large drops so that very little is known for the case of very small drops. In this situation the heat transfer rate becomes rather poor since impinging droplets do not wet the surface. Toda suggests that a decrease of drop mean diameter moves the range of the transition region toward higher temperatures. In this work experiment investigation of the heat transfer from a hot surface to very small drops is reported. (author)