Heat transfer from a single and row of three dimensional wall jets - A combined experimental and numerical study

Abstract

This paper reports the results of experimental and numerical studies to understand the heat transfer characteristics of three-dimensional wall jets exiting from a single and a row of circular jet openings over an unheated flat plate. Infrared thermography is employed to obtain the temperature distribution over the target surface, and the semi-infinite approximation methodology is used to estimate the heat transfer coefficients. Single wire constant temperature hot-wire anemometer is used to measure the flow characteristics. Additionally, computational studies have been performed to select a suitable low Reynolds number turbulence closure models among the following models, namely (i) Spalart Almaras (SA) (ii) Realizable k-ε with enhanced wall treatment (RKE-ewt) (iii) k-ω SST and (iv) Reynolds Stress Model with enhanced wall treatment (RSM-ewt) that predicts the experimentally obtained results for heat transfer characteristics accurately. Based on the investigations carried out, it is observed that RKE-ewt turbulence closure model is not only accurate but also faster in the prediction of heat transfer coefficient. Further, it is also seen that for a fixed mass flow rate, and at a given diameter of the jet opening, widely spaced jets show higher heat transfer coefficients. Furthermore, for a row of three-dimensional wall jets correlations based on the numerical results are developed for the Nusselt number for a Reynolds number range of 5000 to 15000.