Single-phase and two-phase cooling characteristics of upward-facing and downward-facing sprays

Experiments were performed to ascertain the cooling characteristics of PF-5052 sprays impacting a square heated test surface in an upward orientation. Three full-cone spray nozzles were used to span a broad range of volumetric flux. Also examined were the effects of Sauter mean diameter and subcooling. The present data were compared to prior data for downward-oriented FC-72, FC-87 and water sprays to assess the effects of spray orientation on cooling performance. The combined database facilitated the development of generalized correlations for single-phase heat transfer, nucleate boiling, and critical heat flux (CHF). The nucleate boiling data for different fluids and both upward and downward orientation were fitted using a single correlation based on density ratio, Weber number and Jacob number. A CHF correlation previously developed for downward-oriented sprays was equally successful at predicting the present upward-oriented PF-5052 spray data. Overall, orientation showed no measurable influence on any of the spray cooling regimes examined.