Computational investigation of heat transfer and frictional loss of fin-tube heat exchanger with delta winglet and shear-thinning fluid

Abstract

The flow characteristics of a shear-thinning fluid and their significant impacts on the heat transfer and pressure drop effectiveness of a finned-tube heat exchanger (FTHE) incorporating delta winglet vortex generators (DWVG) have been analyzed numerically. This study employed a three-dimensional numerical approach taking into account only the laminar flow of incompressible and single-phase fluid and disregarding the impact of body forces, compressibility, and radiation. The ANSYS FLUENT 2021 R1 was used to simulate the computational domain. Specifically, the flow domain comprises a rectangular duct containing three rows of inherent cylinders and punched delta winglets mounted at various attack angles ($\beta$) (160°, 165°, and 170°). The simulation was conducted over a range of Reynolds numbers (Re) from 50 to 200, using a carboxymethyl cellulose (CMC) aqueous solution at a concentration of 2000 ppm as a shear-thinning fluid. The outcomes of present study in terms of the average Nusselt number ($N{u}_m$), apparent friction factor ($f_{app}$), and quality factor ($Q_f$) were compared to those of a channel with a rectangular winglet vortex generators (RWVG) and a base channel without a DWVG. The results indicated that, compared to the rectangular winglet, the implementation of the DWVG caused a 28% decrease in $N{u}_m$ and a 34% decrease in $f_{app}$, while $Q_f$ increased by 9%. In contrast, compared to the base channel, $N{u}_m$, $f_{app}$, and $Q_f$ are increased by 81%, 33%, and 36%, respectively. The results indicate that, compared to DWVGs, RWVGs enhance heat transfer, but this comes with a significant pressure drop. Using aqueous solutions of carboxymethylcellulose as a working fluid in a channel with DWVGs enhances the $N{u}_m$ and the $Q_f$ by 147% and 104% respectively and decreases the $f_{app}$ by 40% compared to water.