A Generalized Critical Heat Flux Correlation for Submerged and Free Surface Jet Impingement Boiling

A critical heat flux (CHF) correlation is developed for jet impingement boiling of a single round jet on a flat circular surface. The correlation is valid for submerged jets as well as for free surface jets with Reynolds numbers (Re) between 4000 and 60,000. Data for the correlation are obtained from an extensive experimental study of submerged jet impingement boiling performed by the authors with water at subatmospheric pressures and with FC-72 at atmospheric pressure. Additional experimental data from a free surface jet study are also incorporated to include the effect of variation in surface diameter relative to a fixed nozzle diameter, additional working fluids (water and R-113 both at atmospheric pressure), and jet configuration. The range of parameters considered include Re from 0 (pool boiling) to 60,000, jet diameter to capillary length scale ratios (d_j/L_c) ranging from 0.44 to 5.50, surface diameter to capillary length scale ratios (d_s/L_c) ranging from 4.47 to 38.42, and liquid-to-vapor density ratios from 119 to 8502. The proposed correlation is built on the framework of a forced convective CHF model. Using this correlation, 95% of the experimental CHF jet impingement data can be predicted within ±22% error. The corresponding average absolute error and the maximum absolute error are 8% and 36%, respectively, over the range of parameters considered.