A General Heat Transfer Correlation for Impacting Water Sprays on High-Temperature Surfaces

A method for the general correlation of heat transfer effectiveness for sprays impacting vertically downward on a high-temperature surface has been developed. A dimensional analysis showed that the mass velocity of the spray can be substituted for the droplet velocity in the droplet Reynolds and Weber numbers, greatly improving the correlation with the heat flux data in the film boiling regime. The spray Reynolds number, defined as Re s = Gd/ w , and spray Weber number, We s = G 2 d/ 𝜌 σ , were shown to correlate data from many authors covering a wide range of spray parameters. This correlation supports the results of previous parametric experiments, and is analogous to correlations developed for the critical heat flux of sprays and circular jets. Dependence of the heat transfer performance on spray mass flux and droplet diameter represents the influence of the overall heat transfer capacity of the spray as well as the contribution of droplet interactions. The Leidenfrost temperature of the spray was also shown to be dependent on the spray Weber number.