Research Papers: Heat Transfer Enhancement

Impact of Delta-Winglet Pair of Vortex Generators on the Thermal and Hydraulic Performance of a Triangular Channel Using Al2O3–Water Nanofluid

[+] Author and Article Information
Hamdi E. Ahmed

Department of Mechanical Engineering,
College of Engineering,
University of Anbar,
Anbar 31001, Iraq
Centre for Advanced Computational Engineering,
College of Engineering,
Universiti Tenaga Nasional,
Kajang 43000, Selangor, Malaysia
e-mail: hamdi_engi@yahoo.com

M. Z. Yusoff

Centre for Advanced Computational Engineering,
College of Engineering,
Universiti Tenaga Nasional,
Kajang 43000, Selangor, Malaysia

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 28, 2012; final manuscript received July 12, 2013; published online November 5, 2013. Assoc. Editor: Jose L. Lage.

J. Heat Transfer 136(2), 021901 (Nov 05, 2013) (9 pages) Paper No: HT-12-1529; doi: 10.1115/1.4025434 History: Received September 28, 2012; Revised July 12, 2013

This paper presents the laminar forced convection of Al2O3–water nanofluid in a triangular channel, subjected to a constant and uniform heat flux at the slant walls, using delta-winglet pair (DWP) of vortex generator which is numerically investigated in three dimensions. The governing equations of mass, momentum, and energy are solved using the finite volume method (FVM). The nanofluid properties are estimated as constant and temperature-dependent properties. The nanoparticle concentrations and diameters are in ranges of 1–4% and 25–85 nm, respectively. Different attack angles of vortex generators are examined which are 7 deg, 15 deg, 30 deg, and 45 deg with range of Reynolds number from 100 to 2000. The results show that the heat transfer coefficient is remarkable dependent on the attack angle of vortex generators and the volume fraction of nanoparticles. The heat transfer coefficient increases as the attack angle increases from 7 deg to 30 deg and then diminishes at 45 deg. The heat transfer rate remarkably depends on the nanoparticle concentration and diameter, attack angle of vortex generator and Reynolds number. An increase in the shear stress is found when attack angle, volume fraction, and Reynolds number increase.

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Fig. 1

Longitudinal vortex generators types

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Fig. 2

(a) Schematic diagram of triangular duct and vortex generator and (b) geometrical parameters of the vortex generator

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Fig. 3

Comparison between the present average Nusselt number and the results of the literature

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Fig. 4

Local convection heat transfer coefficient of the nanofluid based on constant and variable properties of nanofluid at α = 15 deg and Re = 100 (a) ϕ = 1% and (b) ϕ = 4%

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Fig. 5

Spanwise local Nusselt number affected by the nanoparticle concentration at α = 30 deg and Re = 2000

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Fig. 6

Effect of the nanoparticle concentration on the average heat transfer coefficient at Re = 2000

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Fig. 7

Streamlines contour for different nanofluid volume fraction at Z = 3.812, α = 30 deg, and Re = 100

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Fig. 8

Effect of nanoparticles diameter for different values of Reynolds numbers

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Fig. 9

Configurations of the vortex generator at (a) α = 7 deg, (b) α = 15 deg, (c) α = 30 deg, and (d) α = 45 deg

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Fig. 10

Effect of attack angle on the average convection heat transfer coefficient (a) Re = 2000 and (b) ϕ = 4%

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Fig. 11

Effect of the attack angle of the VG on the wall shear stress for different values of volume fraction and at Re = 2000

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Fig. 12

Effect of geometry change of the vortex generator on (a) heat transfer coefficient and (b) wall shear stress, α = 30 deg and ϕ = 4%

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Fig. 13

Effect of Reynolds number on the average heat transfer coefficient at ϕ = 4%




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