Experimental and numerical investigation of geometry effects on multiple impinging air jets

The effect of jet geometry on the flow and the heat transfer characteristics was investigated experimentally and numerically for elliptic and rectangular impinging jet arrays. Detailed heat transfer measurements over a smooth surface by elliptic and rectangular impinging jet arrays were obtained using thermal infrared camera. Velocity measurements were performed with a Laser-Doppler Anemometry (LDA) system. The aspect ratios (AR) of elliptic and rectangular jets for 1.0, 2.0 and 0.5, jet Reynolds numbers ranging from 2000 to 10,000, and jet-to-target spacings ranging from 2 to 10 were considered to investigate impingement heat transfer performance. The Nusselt numbers for the elliptic jets in the impingement regions were larger than that for a circular jet. This may be caused by the large entrainment rate and large scale coherent structure of the elliptic jet. Best heat transfer performance was obtained with the elliptic jet arrangements. Correlations have been developed for the average Nusselt numbers for elliptic and rectangular jet geometries. Additionally, simulations have been performed and velocity distributions were obtained. Axial, radial velocity distributions and turbulent kinetic energy distributions have been calculated. (C) 2014 Elsevier Ltd. All rights reserved.