Single Impinging Slot Jet on a Concave Surface: Inlet/Outlet Influence

Abstract

An experimental study of fluid flow and heat transfer has been carried out for a single slot jet impinging on a concave surface. Experiments have been conducted with nozzle exit Reynolds number (Reb = 3200), dimensionless impinging height (H/b = 7) and relative curvature (Dc/b = 5) to determine the heat transfer coefficients under a constant heat flux condition by infrared thermography (≈ 500 samples). The distributions of mean velocity and velocity fluctuation on the concave surface have been measured by using classical Particle Image Velocimetry (≈ 5000 samples). The presence of an oscillatory impinging jet around three different positions has been observed. This type of behavior modifies considerably the impinging jet structure and the turbulence values which results in a modification the cooling efficiency. In order to use this type of jet for the optimization of the cooling of a concave surface, we propose to study, in this present study, the effect of Inlet/Outlet condition (riblets and obturator). The results underline the strong effect of outlet condition (e varies from 0 to 10 mm) for a single slot impingement jet on a concave surface. The flow is characterized by an oscillatory jet when the exit is totally opened (e = 10 mm) while the jet is stabilized at the opposite part for the closed exist (e = 0 mm). Therefore, the oscillatory impinging jet generated a uniform and symmetric heat transfer area while the stabilized impinging jet causes a dissymmetrical heat transfer.