Numerical analysis of effect of orifice-plate spacing on the flow and heat transfer characteristic of impinging jets

In this study, two infinitive horizontal plates were considered. An air jet issuing through a rectangular slot on the top plate, was impinged on the bottom hot plate to analyze the flow and heat transfer characteristics of the jet a computer program based on control volume approach and SIMPLE algorithm was developed. Bottom plate was kept at a constant tempreture and the top plate was insulated. The jet Reynolds numbers of 250, 400, 500 and 650, different values of the ratio of orifice-plate spacing to slot width (H/W=0.5, 1, 1.5, 2, 3.5, 5) were considered. It was observed that maximum heat transfer rate is obtained on stagnation point and heat transfer rate decreases along the plate. The heat transfer rate increases at all points on the plate when Reynold number increases and H/W decreases. The stagnation point Nusselt number decreases with increasing H/W value. This decrease is very high until H/W=2, but H/W=2 the decrease in Nusselt number is very small. Key Words: Impinging jet, heat transfer, Nusselt number