Prandtl-number effects and generalized correlations for confined and submerged jet impingement

The influence of fluid thermophysical properties on the heat transfer from confined and submerged impinging jets is experimentally investigated. Results from previous studies at low and high Prandtl numbers (using air and Fluorinert liquid FC-77, respectively) are supplemented by new experiments for an intermediate Prandtl number (using water). Local heat transfer coefficients are obtained from a discrete heat source under axisymmetric confined and submerged jets. The parameter ranges studied include: orifice diameters of 1.59-12.7 mm, turbulent-flow Reynolds numbers of 4000-23 000, and orifice to heat-source spacings of 1-5 jet diameters. Generalized correlations for heat transfer rates are proposed based on these results, and are valid over the range of coolant Prandtl numbers from 0.7 to 25.2. (C) 2001 Elsevier Science Ltd. All rights reserved.