International Journal of Heat and Mass Transfer, Vol.129, 287-298, 2019
Comparison and analysis of the arrangement of delta winglet pair vortex generators in a half coiled jacket for heat transfer enhancement
In this paper, multiple delta winglet pairs (DWP) vortex generators were periodically mounted on the heated wall of the half coiled jacket to reinforce heat transfer capability. The jacket is approximated as a helical duct with semicircular cross section. The height of DWP is half the jacket pipe and the circumferential spacing angle between the adjacent DWPs is fixed as theta(1) = 90 degrees. Numerical investigations were performed to compare fluid flow and heat transfer performance in jackets (Re = 4000-18,000) under four types of DWP arrangement. Results according to the present study show that the common-flow-up (CFU) configuration of DWP has more advantages in heat transfer enhancement than the common-flow-down (CFD) one. The DWP with CFU-V arrangement provides best overall heat transfer performance when the attack angle beta of DWP is between 25 degrees and 30 degrees. This is due to stronger vortices produced by it, slower dissipation of the coupled vortices and subsequently emerged additional vortices. Its comprehensive evaluation factors JF range is from 1.005 to 1.082. The comprehensive heat transfer enhancement effect of CFU-V DWP decreases with the reducing of the jacket curvature epsilon. (C) 2018 Elsevier Ltd. All rights reserved.
Keywords:Heat transfer enhancement;Half coiled jacket;Winglet vortex generator;Secondary flow;Flow resistance