Effects of pin-fin shape on cooling performance of a circular jet impinging on a flat surface

Abstract

The present study aims to investigate the effects of pin-fin shape on flow and heat transfer from a single impinging jet on a heated flat surface. Four pin-fin shapes (square, rectangular, circular and elliptical) with identical wetted area were symmetrically located in a circular arrangement. The numerical simulations have been performed by the SST k–ω model for three different jet Reynolds numbers (23,000, 35,000 and 55,000). Numerical results indicate that the pin shape has significant effect on the velocity field and the extension of the recirculation zone around the pins. In addition, the experiments have been conducted on the smooth and roughened surfaces to confirm the priority of elliptical pin-fin in cooling the heated flat plate. The elliptical pin-fins provide maximum velocities and weak back flow region around the pin. The experimental data and numerical results reveal that applying the elliptical pin-fins can significantly decrease the local temperatures in both stagnation and wall jet regions. The average Nusselt number over the surface roughened by elliptical pins increased by about 47–54% in comparison with the flat surface depending on the Reynolds number.