EXPERIMENTS ON STEADY-STATE HIGH HEAT FLUXES USING SPRAY COOLING

Abstract

Spray cooling is a promising technique for the removal of high heat fluxes (SSHHF) under steady state in many practical applications. This article reports on experimental results which quantify the effects that mass flow rate, surface roughness, subcooling temperature, and spray angle have on high heat fluxes under steady-state conditions using the spray cooling technique. An experimental apparatus was built to conduct the experiments consisting of a copper heater with a disk-shaped surface, an atomizer system that uses commercial nozzles, and a data acquisition system. Commercial nozzles were used to generate sprays with mean droplet diameters ranging from 85 to 100 mu m and mass flow rates between 1.48 and 2.91 L/h. The sprays were atomized into a surface that was treated to change its roughness. Two qualitative surface roughnesses were considered: smooth and rough. Curves were generated showing the steady-state boiling process for each parameter considered. A quantitative assessment was conducted based on these curves and it was clear that steady-state high heat fluxes of the order of 500 W/cm2 could be obtained using spray cooling. Higher SSHHFs were obtained when the mass flow rates and the roughness of the surfaces were increased. It was also observed that for a smooth surface, SSHHF decreased with increments in subcooling degree and impact angle.