Influence of flow-induced oscillating disturbance on the surface heat transfer of impingement flow

Abstract

Flow-induced oscillation is an effective way to enhance heat transfer, which requires no extra energy consumption and can prevent fouling and soot formation. To test the flow-induced oscillation effect on the heat transfer of impingement flow, an 18 mm wide and 30 µm thick membrane tape was mounted at the exit of the ejection pipe. As the ejection Reynolds number increased from 5280 to 9827, the oscillating frequency also increased. In addition, three different oscillating regimes were observed, these being quasi-still, 2D-oscillating and 3D-oscillating, with the transition Re depending on the tape length. The heating plate was 3D-printed and electrical heating wires were embedded within it so as to predetermine the local heat flux by numerical analysis, and be able to calculate the heat transfer coefficient (HTC). The results demonstrate that heat transfer enhancement is more prominent in the vertical direction to the tape than in the parallel direction. Moreover, the distinctive heat transfer enhancement effect near the plate center becomes weaker as it goes toward the outside of the plate, and even turns negative with an increasing r/D. Using a longer piece of tape or having smaller intervals between the tape tip and plate was also shown to improve the heat transfer effect. The spontaneous oscillating disturbance method shows great promise for heat transfer regulation in impingement flow.