Effect of the shape of flow confinement on turbulent slot jet impingement cooling of a heated circular cylinder

In this paper, details of experimental and numerical investigations carried out on slot jet impingement over a heated circular cylinder with and without a flow confinement have been presented. In this study, to enhance heat transfer rate in the rear side of the cylinder, circular, quadrilateral and hexagonal flow confinements with openings at the top and bottom of the confinements are used around the target cylinder. The Reynolds number, ReD, defined based on the average velocity at the nozzle exit and the cylinder diameter, is varied from 6000 to 20000. The non-dimensional distance between the nozzle exit and the heated cylinder, H/S is varied in range of 2 ≤ H/S ≤ 12. The ratio of the cylinder diameter to the slot width, D/S = 8.5 is fixed in all the cases considered in the present study. The results of present study shows that the bottom surface of the cylinder is substantially cooled when flow confinement walls are used compared to the case of unconfined flow. The overall enhancement in the average Nusselt number over the heated cylinder due the quadrilateral and the hexagonal confinements is in the range of 20-42%.