Heat transfer enhancement of annular finned tube exchanger using vortex generators: The effect of oriented functional circumferential arrangement

Vortex generators (VGs) are widely employed to improve the heat transfer performance of tube-fin heat exchangers. In this study, a novel arrangement of VGs with ten triangular VGs deployed around the circular tubes regularly on both sides of fins is proposed. The influences of the fins on fluid flow and heat transfer characteristics are investigated numerically using the k-epsilon model. The results show that the novel configuration avoids interactive influence between VGs and also diverts the fluid to the near-wake of the tube. With the favour of VGs, the wake regions behind circular tubes are diminished and the mixing between hot and cold fluid is enhanced. The number of the vortices is increased for the arrangement with VGs compared to that without VGs, and the secondary flow is enhanced. Simultaneously, the intensity of secondary flow in the case with VGs is also increased by 27.8%–67.5%. The value of Nu increases with increasing Re, of which the case with VGs is improved by 37.7%–42.2%. The heat transfer is enhanced with aspect ratio decreasing from 3 to 1. When the AR = 1 and the b/L is 0.36, the optimal heat transfer performance can be obtained.