Numerical study of turbulent heat transfer in confined and unconfined impinging jets

An elliptic relaxation turbulence model (v(2) - f model) has been used to s imulate the flow and heat transfer in circular confined and unconfined impi nging jet configurations. The model has been validated against available ex perimental data sets. Results have been obtained for a range of jet Reynold s numbers and jet-to-target distances. The effects of confinement on the lo cal heat transfer behavior has been determined. It has been shown that conf inement leads to a decrease in the average heat transfer rates, but the loc al stagnation heat transfer coefficient is unchanged. The effect of confine ment is only significant in very low nozzle-to-plate distances (H/D < 0.25) . In contrast, the flow characteristics in the nozzle strongly affects the heat transfer rate, especially in the stagnation region. Quantitative (up t o 30% difference) and qualitative differences have been obtained when diffe rent nozzle velocity profiles were used. (C) 1999 Elsevier Science Inc. All rights reserved.