ABSTRACT
Experiments were performed to better understand both the hydrodynamic structure of pressure sprays and cooling characteristics in the nucleate boiling regime. Sprays with large volumetric fluxes (dense sprays) were found to greatly inhibit vapor production from the heated surface, producing an unusually small boiling curve slope in the nucleate boiling regime. Experimental data demonstrated critical heat flux (CHF) is a complex function of the spray’s mean volumetric flux, spray angle, nozzle-to-surface distance, Sauter mean diameter (SMD), and subcooling. By using a model for the spatial distribution of the spray’s volumetric flux across the impact area and a correlation for SMD, a new method was developed to determine CHF without having to conduct costly and laborious drop sizing measurements. This method was successful at correlating CHF data for three fluids (FC-72, FC-87, and water) and both circular and square heaters over a broad range of Weber numbers, including both light and dense sprays.
