Single phase cooling of large surfaces with square arrays of impinging water sprays

The single phase heat transfer from an upward facing, 100 cm2 (0.01 m2) copper surface, to square arrays of impinging water sprays was experimentally investigated. Three models of commercially-available full-cone pressure nozzles, of varying flow and pulverization characteristics, were used in runs where average impinging coolant mass flux covered the 0.28–7.2 kg/m2 s range. Array geometry was varied by adjusting nozzle-to-nozzle and nozzle-to-impingement surface distances. Experimental apparatus construction allowed for good drainage of spent coolant and unrestricted air entrainment to spray cones. The area-averaged heat transfer coefficient was found to be a strong function of coolant mass flux. Droplet Sauter mean diameter and nozzles discharge velocity appear to have secondary effects on the single phase heat transfer. Only one single geometric aspect ratio was found necessary for correlating measured data. The proposed correlation agreed with the experimental data within 18.9% error bounds (mean absolute error of 6.29%).

► The single phase heat transfer characteristics of square arrays of full-cone impinging sprays were investigated experimentally. ► The area-averaged heat transfer coefficient was found to be a strong function of the mean coolant mass flux, G  . ► The array aspect ratio, ψ=[Htan(θ/2)]/Dψ=[Htan(θ/2)]/D, only exhibits a modest effect on Nu. ► Original data spanned through the 0.1 < ψ < 0.9, 50 < Re < 900 and 2.7 < Pr < 5.6 ranges.