Comparison and Prediction of Local and Average Heat Transfer Coefficients Under an Array of Inline and Staggered Impinging Jets

Abstract

Recent work, Van Treuren et al. (1993, 1994), has shown the transient method of measuring heat transfer under an array of impinging jets allows the determination of local values of adiabatic wall temperature and heat transfer coefficient over the complete surface of the target plate. Using this technique, an inline and staggered array of impinging jets was tested over a range of average jet Reynolds numbers (10,000–40,000) for three impingement plate to target plate separations (1, 2 and 4). The array was confined on three sides and spent flow was allowed to exit in one direction. Local and average values are presented. These values for the two array configurations are then compared with each other as well as with previously published data in related geometries. A new correlation technique is presented, based on the local data, which breaks the target surface into jet and crossflow areas of interest, with excellent results. The correlation uses the local jet Reynolds number and local jet-to-crossflow mass velocity ratio. This new technique compared favourably with published correlations. Also presented is the influence of the impingement plate on the target plate heat transfer in the form of an effectiveness parameter. This influence is accounted for in the correlation.