Augmentation of Heat Transfer and Investigation of Fluid Flow Characteristics of an Impinging Air Jet on to a Flat Plate

摘要

The current work deals with the study on heat transfer augmentation and investigation of fluid flow characteristics of an impinging air jet on a flat plate. Convective heat transfer of an impinging air jet is known to yield high heat transfer coefficients. Experimentation was performed to study the effects of the nozzle diameter (D), geometric center height (H), temperature measuring distance (x), Reynolds number (ReD), velocity (v), local, stagnation and average Nusselt numbers (NuL, Nus, and Nuavg respectively) on the heat transfer distribution. The local distribution of heat transfer coefficients on the impinging flat plate was calculated. Average heat transfer distributions were compared for different velocity flow fields. Simultaneously, velocity and heat flux measurements were performed at various points on the impingement surface to explore the temporal nature of the convective heat transfer. NuL and Nuavg on the impinged surface for different nozzle configurations were studied under constant wall temperature conditions, as a function of the ReD (192.61-1661.26), D (0.5-3 mm), x (0-80 mm), and v (6.4 and 9.2 m/s). It was observed that at low nozzle to impingement surface ratio, the heat transfer distribution exhibited a peak at the center, which varied with ReD, x and H. It was also witnessed that the fluctuations in the velocity normal to the impingement surface had a more significant influence on the heat transfer than fluctuations along and parallel to the impingement surface.