Numerical study on flow structure and heat transfer in a circular tube integrated with novel anchor shaped inserts

Abstract

This paper reports a numerical study of the thermal performance enhancement of a circular tube embedded with novel anchor-shaped vortex generators. The three-dimensional turbulent periodic flow in the tube subject to a constant heat-flux wall boundary condition is investigated. The fluid flow and heat transfer characteristics are presented for Reynolds number (Re) ranging from 3000 to 18,000. The influences of pitch ratios (PR = P/D = 1, 1.5, 2, and 2.5) and the anchor vortex wing aspect ratios (σ = b/a = 0.4, 0.6, 0.8, 1, and 1.2) on Nusselt Number (Nu), friction factor (f), and the thermal enhancement factor (TEF) are reported. The vortex flow induced by the anchor vortex generator (AVG) inserts leads to a better fluid mixing, thereby accompanied a high heat transfer rate. The results indicate that the presence of AVG inserts elicits a considerable enhancement of Nusselt number and friction factor, which are about 2.24–4.56 and 4.01–23.23 times of those in the corresponding smooth tube, respectively. The maximum TEF of 1.72 is obtained for b/a = 0.4 and P/D = 1 at Re = 3000. These results provide evidence that the AVG insert is a promising device for turbulent convection heat transfer enhancement in a heat exchanger tube.