CORRELATION OF SAUTER MEAN DIAMETER AND CRITICAL HEAT-FLUX FOR SPRAY COOLING OF SMALL SURFACES

Experiments were performed to understand better nucleate boiling heat transfer and critical heat flux (CHF) for full cone sprays. The effects of spray nozzle, volumetric flux, subcooling and working fluid were investigated. Dense sprays great?v reduced evaporation efficiency, and their boiling curves exhibited an unusually small increase in slope upon transition between the single phase and nucleate boiling regimes. Sauter mean diameter (SMD) data were successfully correlated for fluids with vastly different values of surface tension. This correlation was based upon orifice diameter and the Weber and Reynolds numbers of the orifice Bow prior to liquid breakup. Also developed was a new CHF correlation which accurately predicted data for FC-72, FC-87 and water. This correlation shows a strong dependence of CHF on volumetric flux and Sauter mean diameter. It is shown that by combining the correlations for CHF and SMD it is possible to predict accurately CHF for full cone sprays without having to conduct expensive and laborious drop sizing measurements for each individual nozzle.