Heat transfer enhancement factor characteristics for collective cooling using inclined air jet

Abstract

The inclined jet of air is experimentally investigated with the aim of understanding thermal characteristics for cooling applications which can be used in electronics packaging applications. Entire study and evaluations are made by insertion of jet on the leading edge of a horizontal rectangular hot target plate. The jet is placed at height H from target to be cooled, and investigated for downhill side collective cooling performance approach. The experiments are performed at jet Reynolds number in the range of 2000 ≤ Re ≤ 20000 with circular jet and inclination of 15° to 75°. The heat transfer Enhancement Factor (EF) is defined and analyzed on the basis with natural convection. The equations for maximum and minimum EF are developed imperially which is the function of Reynolds number, jet inclination, target to jet height, and jet diameter. It is experimentally observed that average EF is highest for 6a of 45°. The 60° and 75°jet inclination follows nearly similar trend, but at lower side; and 30° and 15° gives the lowest average EF. At high Reynolds number up to 20000, improved cooling performance is seen. It is followed by Reynolds number of 16000. At lesser Reynolds number, jet continuously gets attached to target plate, whereas at moderate Reynolds Number up to 20000, the flow jump is observed by which, it creates waves in flow. Evidently thermal characteristic also depends on height between target surfaces to jet. The physics of inclined flow is analyzed taking samples of three major important inclinations below 90 degree. The effect of jet to target distance (H) is also investigated in the range 0.5 ≤ H/D ≤ 6.8.