Heat transfer characteristic and critical heat flux in mist dispersed flow

Recently, the heat removal by spraying water on containment vessel has been proposed for safety systems of the new generation light water reactors. In this work the heat transfer in mist cooling for low droplet density, focusing on the heat transfer characteristics, the behaviors of a liquid on a heating surface and the measurements of liquid droplets by laser doppler anemometer (LDA) were investigated experimentally. Steady heat transfer experiments of a copper block were conducted for mist flow of air and water in a range of air flow rates from 40 to 120 lN/min and water flow rates were 0.3, 0.9, 1.8, 4.0 and 8.0 l/hr. Mist flow of water and air forming in a fully conical nozzle with a mixture camber was supplied on the heating surface arranged for horizontal-upward position. The critical heat flux increased with an increasing liquid flow rate. The critical heat flux decreased as the air flow rate increased. Three correlations of the mist cooling rate for non-boiling, evaporation of droplets and evaporation of the liquid film were developed with microscopic parameters of two-phase flow