Effect of Reynolds number, hole patterns, and hole inclination on cooling performance of an impinging jet array-part I: Convective heat transfer results and optimization

This study comprehensively illustrates the effect of Reynolds number, hole spacing, jetto- target distance, and hole inclination on the convective heat transfer performance of an impinging jet array. Spatially resolved target surface heat transfer coefficient distributions are measured using transient liquid crystal (TLC) measurement techniques, over a range of Reynolds numbers from 5000 to 25,000. Considered are effects of streamwise and spanwise jet-to-jet spacing (X/D, Y/D: 4-8) and jet-to-target plate distance (Z/D: 0.75-3). Overall, a test matrix of 36 different configurations is employed. In addition, the effect of hole inclination (h: 0-40 deg) on the heat transfer coefficient is investigated. Optimal hole spacing arrangements and impingement distance are pointed out to maximize the area-averaged Nusselt number and minimize the amount of cooling air. Also included is a new correlation, based on that of Florschuetz et al., to predict rowaveraged Nusselt number. The new correlation is capable to cover low Z/D 0.75 and presents better prediction of row-averaged Nusselt number, which proves to be an effective impingement design tool.