Development and numerical study of dimensional helical tube and its performance in heat transfer enhancement

A new dimensional taper helical tube is developed, which enhance heat transfer via the combination of inside secondary flow and outside flow-induced vibration of the tube. The inside secondary flow is induced by the variety of helical curvature and sectional ellipticity. By using the CFD software, the flow fluid and vibration characteristic of the tube is simulated. In lower Reynolds number (flow speed is less than 0.2 m/s inside the tube while flow speed is less than 0.05 m/s outside the tube), the secondary flow inside the helical tube enhances heat transfer greatly; meanwhile the flow drag is not increased seriously. The flow-induced vibration of the tube is persistent and is apt to hold in a low frequency, thus the composite heat enhancement is reached.