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

An elliptic relaxation turbulence model (v² - f model) has been used to simulate the flow and heat transfer in circular confined and unconfined impinging jet configurations. The model has been validated against available experimental data sets. Results have been obtained for a range of jet Reynolds numbers and jet-to-target distances. The effects of confinement on the local heat transfer behavior has been determined. It has been shown that confinement leads to a decrease in the average heat transfer rates, but the local stagnation heat transfer coefficient is unchanged. The effect of confinement 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 to 30% difference) and qualitative differences have been obtained when different nozzle velocity profiles were used.