Air Flow, Thermal Profile, and Thermohydraulic Performance Assessment in a Square Duct Heat Exchanger With Combined Vortex Generators: CFD Analysis

Abstract

Numerical simulations of laminar air flow, heat transfer behavior (thermal structure), and thermal performance evaluation in a square duct with combined vortex generators (CVGs) are presented. The CVG configuration consists of a combination of rectangular winglets and V‐shaped baffles. The thermal performance of two types of CVGs is compared. Type I includes a set of rectangular winglets placed on the upper and lower walls, with a V‐shaped baffle in the middle. Type II features V‐shaped baffles placed on the upper and lower walls, with a rectangular winglet in the middle. The purpose of the CVGs is to induce vortex flows, impinging flows, swirling flows, and to disturb the viscous sublayer over the duct surfaces, thereby improving the convective heat transfer coefficient and thermal efficiency. Based on the finite volume method, numerical modeling is used to analyze the effects of the position and height of CVGs on fluid and thermal characteristics for Reynolds numbers ranging from 100 to 2000. Thermal assessments of the CVGs are presented in terms of the Nusselt number ratio, friction factor ratio, and thermal enhancement factor. It is found that Type II outperforms Type I, showing the best Nusselt number ratio of 19.36 when b 1 / H = b 2 / H = 0.20 in the positive x ‐direction. However, Type I exhibits the greatest thermal enhancement factor, 4.39, which is higher than Type II when the blockage ratios are b 1 = 0.15 H and b 2 = 0.05 H in the +x FFD.