Slot air jet impingement cooling over a heated circular cylinder with and without a flow confinement

In this work, a numerical investigation has been carried on an air slot jet impingement over a circular cylinder with and without a top confinement using the v′2‾-f turbulence model. In the parametric study, the Reynolds number (ReD), defined based on the cylinder diameter, D, is varied from 4500 to 20,000. The ratio of spacing between the nozzle exit to the cylinder target, H and the width, S of the nozzle, H/S is varied from 2 to 10. The non-dimensional slot width, D/S considered in the present study are 1, 2 and 4. The local distribution and average Nusselt numbers obtained from numerical simulations are validated against the available experimental data of jet impingement over a flat and cylindrical surfaces without confinement. It is observed that the local Nusselt numbers obtained from the present numerical model compare well with the experimental data. To understand the effect of confinement, a flat plate confinement at the exit of the nozzle has been considered. The non-dimensional length of the confinement, Lconf/D was varied from 0 to10 in the parametric study. Numerical results reveal that the top confinement reduces the average Nusselt number by 25% at ReD = 4500, D/S = 4 and H/S = 2, while the influence confinement on the cooling rate is negligible for D/S = 1. Based on the numerical study, a correlation has been provided for the average Nusselt number over the heated cylinder.