Effects of Crossflow Temperature on Heat Transfer Within an Array of Impinging Jets

Abstract

Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. In the experimental model the jet flow, after impingement, was constrained to exit in a single direction along the channel formed by the jet orifice plate and heat transfer surface. In addition to the crossflow that originated from the jets following impingement, an initial crossflow was present that approached the array through an upstream extension of the channel. By varying the initial crossflow temperature, the mixed-mean crossflow temperature approching each spanwise jet row n (Tm,n) was varied independently of the jet temperature (Tj). For each row, the effect of Tm,n relative to Tj on the heat flux opposite the row was determined. Results are formulated in terms of parameters defined for each individual spanwise row domain: a crossflow-to-jet temperature difference influence factor (ηr) and a Nusselt number (Nur) as functions of jet Reynolds number, crossflow-to-jet mass flux ratio, and geometric parameters. Effects of row position within the array are also considered. It was found that ηr and Nur are nominally independent of row position after the first two rows.