A novel control of jet impingement heat transfer in cross-flow by a vortex generator pair

Abstract

Jet impingement is an effective heat transfer method while the favorable performance is usually degraded by the cross-flow. In this article, a novel control of the impinging jet in cross-flow has been proposed. A delta winglet vortex generator pair (VGP) is installed in the cross-flow channel upstream of the jet nozzle. The jet and the cross-flow Reynolds numbers are 15,000 and 40,000, respectively. The ratio of nozzle-to-surface distance to jet diameter is 4.0. Experimental measurements are conducted to study the characteristics of heat transfer with liquid crystal thermography (LCT). Results indicate that the VGP with common-flow-up (CFU) configuration promotes the jet penetration in cross-flow and augments the impingement heat transfer greatly on the target wall compared to the baseline case without the VGP. In addition, the enhancement increases monotonically with the angle of attack of the VGP varying from α=15° to 45°. The spacing between the VGP l1=1.2d is preferred with the highest heat transfer augmentation of jet impingement among l1=0.5–2.0d. The optimal value of spacing between the VGP and the jet nozzle l2 is suggested to be 4d in terms of enhancing the heat transfer, for the measurement range from l2=2d to l2=8d. The VGP with common-flow-down (CFD) configuration is also tested, but it leads to slightly lower heat transfer than without the VGP. Pressure drop of the jet in cross-flow with VGP is measured and analyzed.