Numerical study of thermal and flow characteristics for a fin-and-tube heat exchanger with arc winglet type vortex generators.
Abstract Vortex generator can effectively enhance the heat transfer performance on the fin surface by introducing the secondary flow and intensifying the mixing of fluid. In this study, four new types of arc-winglet vortex generator (VG) are proposed and the three-dimensional CFD numerical simulation was employed to investigate the fluid flow and heat transfer characteristics. The results indicate that compared with the conventional rectangular-winglet VG, the two types of plane arc VGs provide a significant improvement on the size of secondary flow behind the tubes and all the wake region size of the fins with the four types of arc-winglet VGs decreased to some extent, especially for the two types of curved arc VGs. The heat transfer enhancement of the fin with curved arc VGs is mainly completed by guiding more fluid to flow into the previous wake region and then scour the downstream tubes directly. In addition, compared with the rectangular-winglet VGs, the Nusselt number averagely increases by 11.5% for the equal-perimeter arc VGs fin, 19.9% for the curved equal-area arc VGs fin, and 35.9% for the curved equal-perimeter arc VGs fin. Although the equal-perimeter arc VG and the curved equal-perimeter arc VG have the same geometry size, the Nusselt number of the fin with the former one averagely increases by 22.2% while the pressure drop only increases by 13.5%.