Impingement heat transfer and recovery effect with submerged jets of large Prandtl number liquid .1. Unconfined circular jets

Experimental study was performed to characterize recovery factor and heat transfer coefficient on vertical healers impinged by submerged circular transformer oil jets issued from both pipe and orifice nozzles. Radial distributions of local recovery factor were determined at various Reynolds numbers and nozzle-to-plate spacings, and compared with numerical result. Local Nusselt number at stagnation point was found to be proportional nearly to square root of jet Reynolds number in the range of Re = 220-1500, and essentially unaffected by nozzle-to-plate spacing for Re < 600. In total, 32 radial profiles of local heat transfer were obtained with pipe and orifice nozzles. An empirical formula was developed for correlating the local heat transfer data. Unusual variations of Nusselt number with Reynolds number were observed in stagnation zone with Reynolds number around 1300 at z/d = 16 and 20. Through numerical integration average heat transfer was determined and correlated. Copyright (C) 1996 Elsevier Science Ltd.