Heat transfer augmentation characteristics of a fin punched with curve trapezoidal vortex generators at the rear of tubes

Abstract

The thermal-hydraulic characteristics of a novel fin punched with curve trapezoidal vortex generators (CTVGs) are investigated numerically. The effects of multi-parameters including the geometry of CTVG, the location of CTVGs, and working condition on thermal performance are considered. On one hand, CTVGs can availably lessen the size of tube wake zone, decrease the mechanical energy consumption and heighten the fin heat transfer ability in this area. On the other hand, the secondary flow strength is strengthened because the longitudinal vortices generated by CTVGs, which efficiently enhances the heat transfer on the fin downstream CTVGs. Close relationship exists between the volume-averaged secondary flow strength and the mean Nusselt number. For studied cases, the optimal circumferential location angle of ? = 90? is found, while the optimal radial location Dg is about 1.8 times the tube outside diameter. The smaller is the height or base length of CTVGs, the better the thermal performance of the enhanced fin punched with CTVGs. Better thermal performance is achieved as the fin spacing is about 0.24 times the tube outside diameter.