Local and average transfer coefficients due to an impinging row of jets

Abstract

The local transfer coefficients which result from the impingement of a row of circular jets on a plane surface were determined by means of the naphthalene sublimation technique in conjunction with an innovative data acquisition system. Spanwise average and surface average transfer coefficients were also deduced from the local measurements. The parameters that were varied included the jet Reynolds number, the spacing between adjacent jet orifices, and the separation distance between the jet orifices and the impingement surface. The local transfer coefficient distributions enable the identification of surface locations where the impinging jets provide effective heating (or cooling). At locations that are mid-way between adjacent jets, relatively high local transfer coefficients may exist owing to the collision of the spreading flows from adjacent impinged jets. The stagnation point transfer coefficient exhibits a maximum as a function of the orifice-to-impingement separation distance. Both the spanwise average and surface average transfer coefficients take on their largest values on the impingement line and diminish with increasing downstream distance.