Laminar convective heat transfer of shear-thinning liquids in rectangular channels with longitudinal vortex generators

Abstract

Heat and fluid flow in a rectangular channel heat sink equipped with longitudinal vortex generators have been numerically investigated in the range of Reynolds numbers between 25 and 200. Aqueous solutions of carboxymethyl cellulose (CMC) with different concentrations (200-2000 ppm), which are shear-thinning non-Newtonian liquids, have been utilised as working fluid. Three-dimensional simulations have been performed on a plain channel and a channel with five pairs of vortex generators. The channels have a hydraulic diameter of 8 mm and are heated by constant wall temperature. The vortex generators have been mounted at different angles of attack and locations inside the channel. The shear-thinning liquid flow in rectangular channels with longitudinal vortex generators are described and the mechanisms of heat transfer enhancement are discussed. The results demonstrate a heat transfer enhancement of 39-188% using CMC aqueous solutions in rectangular channels with LVGs with respect to a Newtonian liquid flow (i.e. water). Additionally, it is shown that equipping rectangular Page 2 of 40 channels with LVGs results in an enhancement of 24-135% in heat transfer performance visà-vis plain channel. However, this heat transfer enhancement is associated with larger pressure losses. For the range of parameters studied in this paper, increasing the CMC concentration, the angle of attack of vortex generators and their lateral distances leads to an increase in heat transfer performance. Additionally, heat transfer performance of rectangular channels with longitudinal vortex generators enhances with increasing the Reynolds number in the laminar flow regime.

Thermal and hydraulic performance analysis of a heat sink with corrugated channels and nanofluids

“…Accordingly, a mesh containing 930476 cells is utilised for numerical calculations. Accuracy and reliability of the present model in predicting heat and fluid flow in micro-and mini-channels have been verified in the previous studies conducted by the authors for both water and nanofluids [9,10,[63][64][65]. Further verification of the model has been performed considering the experimental and numerical data reported by Sui et al [66] for deionised water flow in a micro-channel heat sink with sixty corrugated channels in the range of Reynolds number between 300 and 800.…”

Influence of Longitudinal Vortex Generator Configuration on the Hydrodynamics in a Novel Spouted Bed

“…Using the kinetic theory of granular flows , the viscous forces and the pressure of solids phase can be described as a function of the granular temperature . The stress of the solids phase due to frictional interactions between particles is represented by the Schaeffer model and the diffusion coefficient of granular energy by the Gidaspow model . The governing equations and constitutive relations for spouted beds are listed in Tab.…”

“…The popularity of this approach compared to the DEM stems from relatively smaller CPU and memory resource requirements. As a result, the TFM approach is more commonly used for modeling practical spouting flows , , , . Lan et al numerically studied the influence of the solid‐phase wall boundary conditions in terms of specularity coefficient and particle‐wall restitution coefficient on the flow behavior of spouted beds using the TFM approach.…”

“…In recent years, the longitudinal vortex technique has been applied extensively for enhancing the thermal efficiency of heat exchangers or micromixer of the microfluidic systems . Ahmed et al reviewed heat transfer augmentation using vortex generators and nanofluids.…”

“…Datta et al numerically examined the fluid flow and heat transfer behavior in microchannels using an inclined LVG. Ebrahimi et al , numerically studied conjugated heat transfer and hydraulic performance for nanofluid flow in a rectangular microchannel heat sink with LVGs. Recently, a preliminary numerical study of the longitudinal vortex effect on gas‐solid two‐phase flow characteristics in spouted beds was conducted by Wu et al .…”