Experimental investigation and large eddy simulations of turbulent slot jet impingement cooling of a circular cylinder with and without a quadrilateral confinement

摘要

In the present study, experimental and numerical investigations have been carried out on a slot jet impinging over a circular cylinder in order to understand fluid flow and heat transfer characteristics. To understand instantaneous and average flow characteristics, large eddy simulations (LES) are carried out. To enhance heat transfer at the rear portion of the cylinder, a quadrilateral shape confinement with openings at the top and the bottom was used around the cylinder. The ratio of the cylinder diameter to the slot width is fixed at D/S = 10.6 and the non-dimensional distance from the nozzle exit to the cylinder, H/S = 4 and 8 are considered. The Reynolds number, defined based on the cylinder diameter and the average velocity at the nozzle exit, Re-D = (rho VjD/mu) considered are 12000 and 20000. The present LES results show that the average velocities and the Reynolds stresses compare well with the experimental results available in the literature. Rolled vortices are observed significantly before and after the jet impingement in the case of unconfined flow. In the case of confined flow, the local heat transfer at the bottom potion of cylinder is enhanced by around 23% due to the suppression of large recirculation and the acceleration of flow in the confined passage. The time and the span wise averaged Nusselt number of the cylinder obtained from the present LES agree well with the present experimental results.