Effects of Jet-to-Target Surface Spacing and Pin-Fin Height on Jet Impingement Heat Transfer in a Rectangular Channel

Abstract

An experimental study was completed to quantify heat transfer enhancement, pressure loss, and crossflow effect within a channel of inline impinging jets. The jet diameter is 5.08 mm; the jet-to-jet spacings in the streamwise and spanwise directions are fixed at x/d = 11.1 and y/d = 5.9, respectively. The effect of jet-to-target surface spacing was considered with z/d = 3 and 6. For both jet-to-target surface spacings, smooth, short pin-finned, and long pin-finned target surfaces were investigated. Both roughened surfaces have a staggered array of 120 copper pin-fins. The pin-to-jet diameter ratio is fixed at D/d = 0.94. The pin height-to-jet diameter ratio for the short and long pins are H1/d = 1.5 and H2/d = 2.75, respectively. Regionally averaged heat transfer coefficient distributions were measured on the target surface, and these distributions were coupled with pressure measurements through the array. The heat transfer augmentation and pressure penalty were investigated over a range of jet Reynolds numbers (10k–70k). The results show high discharge coefficients for all the cases. The channels with the small jet-to-target surface spacing experience double the crossflow effect of the large spacing channels. The addition of surface roughness showed a negligible effect on the crossflow. The best heat transfer performance was observed in the narrow impingement channel with the long pins.