Heat transfer characteristics of a slot jet impinging on a semi-circular convex surface

Abstract

Surface heat transfer characteristics of a heated slot jet impinging on a semi-circular convex surface have been investigated by using the transient heating liquid crystal technique. Free jet velocity, turbulence and temperature characteristics have been determined by using a combination of an X-wire and a cold wire anemometry. The parametric effects of jet Reynolds number ( Re W ) ranging from 5600 to 13,200 and the dimensionless slot nozzle-to-impingement surface distance ( Y/ W) ranges from 2 to 10 on the local circumferential heat transfer have been studied. Local circumferential Nusselt number ( Nu S ) decreases with increasing the dimensionless circumferential distance ( S/ W) from its maximum value at the stagnation point up to S/ W=3.1. The transition in the wall jet from laminar to turbulent flow was completed by about 3.3⩽ S/ W⩽4.2 which coincided with a secondary peak in heat transfer. Correlations of local and average Nusselt numbers with Re W , Y/ W and S/ W have been established for the stagnation point and the circumferential distribution. The rate of decay of average circumferential Nusselt numbers around the semi-circular convex surface is much faster than that which occurs laterally along the flat surface. As Y/ W increases, the effect of surface curvature becomes apparent and the difference between the flat surface correlation and the convex surface becomes more pronounced.