An experimental study on hot round jets impinging a concave surface

Abstract

An experimental investigation of heat transfer due to a row of air jets impinging on a concave semi-cylindrical surface is presented. Heat transfer characteristics are measured using a heat thin foil technique and infrared thermography. Adiabatic wall temperatures and local heat transfer coefficients are determined by means of a linear regression method. The effect of high relative curvature ( d/ D) is investigated by changing the jet tube diameter (impinging surface diameter remaining constant). Reynolds number, injection temperature, spacing between adjacent jets and jet exit to surface spacing are also made to vary. Curvature has different effects over the adiabatic wall temperature and Nusselt number distributions. First, the curvature increase provokes a small growth of Nusselt number in the impingement region. On the other hand, curvature produces a confinement of the jet’s flow that has two consequences: stagnation of the adiabatic wall temperature and decrease of Nusselt number distribution.