Thermo-hydraulic performance in heat exchanger tube with V-shaped winglet vortex generator

Abstract

This article presents the influence of V-shaped winglet vortex generators (V-WVGs) inserted into a constant heat-fluxed tube on thermal characteristics. In the present experiment, two V-WVG types: V-shaped rectangular- and delta-winglets (V-RW and V-DW) were mounted periodically on both sides of a straight tape before insertion into the tube with four relative winglet pitches (PR = P/D = 0.5, 1.0, 1.5 and 2.0) and three winglet blockage ratios (BR = b/D = 0.1, 0.15 and 0.2) at a fixed attack angle (α = 45°). Effects of geometric parameters of both V-WVGs on thermal performance enhancement were studied using air as tested fluid in a turbulence condition, Reynolds number (Re) ranging between 4130 and 25,900. The measured result has been shown that the V-RW performs higher rate of heat transfer as well as friction loss than the V-DW and the rise in BR results in higher increase of the heat transfer rate and friction loss while the increment in PR yields the reversing tendency for both V-WVG types. A new thermal-performance enhancement factor (TEF) has been introduced and it reveals that the V-DW has TEF in a range of 1.82–2.0 or around 3% above the V-RW where its peak regarded as the optimal point is at BR = 0.15 and PR = 1.0. Empirical correlations for the Nusselt number and friction factor to assess the real merits of a heat exchanger tube with V-WVGs are determined.