SIMULATION OF TURBULENT HEAT TRANSFER IN JET IMPINGEMENT OF AIR FLOW ONTO A FLAT WALL

This paper deals with the numerical prediction of a turbulent jet impinging orthogonally onto a large heated flat wall. The Reynolds number based on the jet diameter and the bulk velocity is 2.3 x 10(3), and the jet discharge is two diameters above the heated plate ( H/D = 2). The main objective has been to examine the suitability of recently developed variants of a cubic nonlinear k-epsilon model for the prediction of impinging jet flows. The numerical approach used in this study is the finite-volume method together with the SIMPLE algorithm. For the modeling of turbulence, the Launder and Sharma low-Re k-epsilon model (1974) and a new version of the nonlinear low-Re two-equation model, that has also been recently shown to produce reliable thermal predictions in impinging jet flows and also flows through pipe expansions (Craft et al., 1999), have been employed. The numerical results show that the low-Re k-epsilon model returns unrealistically high levels of turbulence energy around the stagnation point and consequently over-predicts the heat transfer coefficients in this region. The introduction of a differential form of the turbulent length-scale correction term to the dissipation rate equation improves the thermal predictions of the low-Re k-epsilon model. Moreover, the nonlinear k-epsilon model produces superior flow and heat transfer predictions compared with the linear k-epsilon. model. The results of the present investigation agree with those reported in Craft et al. (1999).