Numerical investigation of fluid flow and heat transfer in sudden expansion

Abstract

newline Heat transfer is an important and inevitable process that pertains to every activity of our day-to-day life including household heating and cooling equipment, electric power generation, thermal management of electronic equipment and many more. Compound heat transfer augmentation is of particular interest currently that involves several techniques being employed simultaneously, to get an augmentation that is superior to the individual techniques working separately. The heat transfer rate could be improved if the stagnant fluid layer within the laminar sub-layer is set into motion. Transverse vortices or primary recirculation region induced by sudden expansion and longitudinal vortices, or secondary flow imparted by winglet vortex generators are the key factors employed here in this current investigation to demolish the laminar sub-layer. Rectangular winglet vortex generator has been considered along with sudden expansion channel and water being working fluid, as its ability to augment heat transfer rate is substantially large when compared to other winglet vortex generators like trapezoidal and delta winglet vortex generators. The relative locations of leading edges and trailing edges of rectangular vortex generators in the winglet form play a pivotal role in deciding the heat transfer augmentation and pressure drop in a sudden expansion channel having expansion ratio 2:1. A numerical simulation was carried out using commercial code FLUENT 16.2. Reynolds number, angle of attack and vortex generator configuration have been considered as influential parameters affecting the thermo-hydraulic performance of the sudden expansion channel due to the combined effect of primary recirculation and secondary flow. The heat transfer augmentation along with corresponding pressure drop penalty is compared for the common-flow-down and common- newline newline