<title>Fundamental experiments of steady-state high heat fluxes using spray cooling</title>

Abstract

Fundamental experiments of steady-state high heat fluxes using spray coolingJ.E. Gonzalez and L. OrtizDepartment of Mechanical EngineeringUniversity of Puerto Rico-MayaguezMayaguez, Puerto Rico 00680ABSTRACTSpray cooling has been considered as one of the most efficient alternatives for the removal ofhigh heat fluxes and is currently used in several modern industrial and technological applications todissipate high amounts of heat from their components such as in electronics, lasers, metallurgical, andnuclear. In many of these applications steady-state high heat fluxes (SSHHF) removal is required. Inthis research, experiments were conducted to determine parameters that affect the steady-state behaviorof high heat fluxes when using spray cooling. The parameters taken in consideration included the massflow rate, the heated surface roughness, the liquid subcooling temperature, and the spray angle. Waterwas used as the working fluid in the experiments. An experimental apparatus was built to carry-out theexperiments, consisting of a copper heater with a disc shaped surface, an atomizer system that usedcommercial nozzles, and a data acquisition system to accurately measure temperatures, heat fluxes, flowrates, and room conditions. The commercial nozzles generated mean droplet diameters ranging from 85to 1 00im and flow rates between 1 .48 and 1 .9L/hr. Two surface conditions were used; one polishedwith 0.25jim liquid solution and the other polished with 600 grit silicon carbide grinding paper. TheSSHHF was determined by observing the transient response of the surface temperature and the surfaceheat flux. Steady-state heat fluxes in the order of 1 00W/cm2 were obtained in most cases. Resultsindicated that higher SSHHF can be obtained with increasing mass flow rates and it was easier toachieve them with smooth surfaces. Results also showed that subcooling may not be significant whenhigh mass flow rates. Curves indicating maximum SSHHF were generated as function of the parametersinvestigated.Keywords: spray-cooling; steady-state; high-heat-flux; experiments.1.0 INTRODUCTION