Numerical study of the relationship between heat transfer enhancement and absolute vorticity flux along main flow direction in a channel formed by a flat tube bank fin with vortex generators

Chang, Li-Min; Wang, Liang-Bi; Song, KeWei; Sun, Dongliang; Fan, Ju-Fang

doi:10.1016/j.ijheatmasstransfer.2008.09.029

Cited by 81 publications

(24 citation statements)

References 34 publications

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“…The secondary flow is more intense for the disturbance having a complex shape. In order to estimate the secondary flow, the vortex intensity was calculated at the exits of the two perturbation zones (plane-4 and plane-8) as defined by [23]:…”

Section: Vortex Intensitymentioning

confidence: 99%

“…Due to the secondary flow effect, the transversal movements of the particles increases and the axial dispersion decreases, which consequently enhanced the heat transfer [23][24]. Figure 7 and 8 display the evolutions of the vortex Intensity Ω average with Reynolds number at the exits of the two perturbation areas (plane-4 and plane-8) in the considered geometries.…”

Section: Vortex Intensitymentioning

confidence: 99%

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Effects of the Geometry Scale on the Behaviour of the Local Physical Process of the Velocity Field in the Laminar Flow

Lasbet¹,

Aidaoui²,

Loubar³

2016

IJHT

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It is well known that the convective terms in the equation of fluid motion play an outstanding role on the local proprieties of flows and they affect the local behaviour of physical processes such as deformation, rotation, stretching and folding. Large values of these processes in the flow have pronounced and lasting effects on the improvement of heat transfer and fluid mixing in ducts. The modification of the geometric scale presents an easy and adequate solution to increase these parameters. For this purpose, three dimensional zigzag channels with hydraulic diameters equal to 5 mm, 10 mm and 20 mm were examined in this study. Evolutions of the deformation rate, rotation rate and the stretching/compression coefficients of the vortices were examined for different values of the Reynolds number in three dimensional laminar open flow, using a CFD code. The results illustrate that the geometry with the smallest hydraulic diameter is the more favourable to increase the considered parameters.

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Section: Vortex Intensitymentioning

confidence: 99%

Section: Vortex Intensitymentioning

confidence: 99%

Effects of the Geometry Scale on the Behaviour of the Local Physical Process of the Velocity Field in the Laminar Flow

Lasbet¹,

Aidaoui²,

Loubar³

2016

IJHT

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“…In this study we used the absolute vortex flux J n ABS reported by Chang et al [24], Lin et al [25] and Song et al [26] to specify the intensity of secondary flow. This parameter has more general consideration than other parameter such as the swirl parameter reported by Manglik and Bergles [27] in the case of the twisted tape insert.…”

Section: List Of Symbolsmentioning

confidence: 99%

The optimum fin spacing of circular tube bank fin heat exchanger with vortex generators

Wang

et al. 2013

Heat Mass Transfer

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In real application, once the pattern of fin is determined, fin spacing of tube bank fin heat exchanger can be adjusted in a small region, and air flow velocity in the front of the heat exchanger is not all the same. Therefore, the effects of fin spacing on heat transfer performance of such heat exchanger are needed. This paper numerically studied the optimal fin spacing regarding the different front flow velocities of a circular tube bank fin heat exchanger with vortex generators. To screen the optimal fin spacing, an appropriate evaluation criterion JF was used. The results show that when front velocity is 1.75 m/s, the optimal fin spacing is 2.25 mm, when front velocity is 2.5 m/s, the optimal fin spacing is 2 mm, and when front velocity is higher than 2.5 m/s, the optimal fin spacing is 1.75 mm. List of symbolsA Cross section area of flow passage (m 2 ) A front Cross section area of flow passage at front inlet (m 2 ) c p Specific heat capacity (J/kg K) D Diameter of the tube (m) d e Characteristic length of flow channel (m) F Total surface involved in heat transfer in the computational domain (m 2 ) f Friction factor, f = Dpd e /(L x qu max 2 /2) h Convective heat transfer coefficient (W/m 2 K) H Height of winglet type vortex generator (m) J n ABS Absolute vorticity flux along the normal direction of cross section (1/s) J n ABS;S Cross section average absolute vorticity flux (1/s) J n ABS;V Volume average absolute vorticity flux (1/s) L Base length of vortex generator (m) L x Stream wise length of fin (m) n Direction normal to the cross section or wall surface N 2 Number of the tubes Nu Nusselt number, Nu = hd e /k p Pressure (Pa) Re Reynolds number, Re = qu max d e /l S 1 Transversal pitch between the tubes (m) S 2 Longitudinal pitch between the tubes (m) T p Net fin spacing (m) T Temperature (K) u front Velocity of air at front inlet (m/s) u in Velocity of air at fin passage inlet (m/s) u max Maximum average velocity of air (m/s) u i , u, v, w Components of velocity vector (m/s) x, y, z CoordinatesGreek variables k Thermal conductivity (W/m K) lViscosity (kg/m s) qDensity (kg/m 3 )

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“…An increase in heat transfer coefficient was accompanied with a large pressure drop when the inclination angle is increased. Other studies have demonstrated the influence of the longitudinal and transverse vortex generators on fluid flow structure and heat transfer enhancement in compact heat exchangers [15][16][17][18]. A relationship between the intensity of the secondary flow and the strength of convective heat transfer in a flat tube bank fin heat exchanger with VG was numerically studied by Chang et al [15].…”

Section: Introductionmentioning

confidence: 99%

“…Other studies have demonstrated the influence of the longitudinal and transverse vortex generators on fluid flow structure and heat transfer enhancement in compact heat exchangers [15][16][17][18]. A relationship between the intensity of the secondary flow and the strength of convective heat transfer in a flat tube bank fin heat exchanger with VG was numerically studied by Chang et al [15]. Joardar and Jacobi [16] demonstrated that the heat transfer coefficient of full scale wind tunnel testing of a compact plain-fin and tube heat exchanger increases by 16.5%-44% for single pair VG and 30%-68.8% for three VG array arrangements.…”

Section: Introductionmentioning

confidence: 99%

Turbulent heat transfer enhancement in a triangular duct using delta‐winglet vortex generators

Althaher

Abdul-Rassol

Ahmed

et al. 2011

Heat Trans. Asian Res.

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The augmentation of convective heat transfer of a turbulent flow using deltawinglet vortex generators (VG) in a triangular duct was experimentally investigated. Two side walls of the heated test section are electrically heated with a constant heat flux while the lower wall is indirectly heated. Single, double, and triple pairs of VG are utilized. Each pair of VG was punched on one wall of the test duct. The effects of the number of VG pairs, the VG angle of attack, the VG location from the leading edge of the test duct, the VG geometry, and Reynolds number are examined in this paper. The results indicate that the Nusselt number and friction factor are relatively proportional to the size, number, and the inclination angle of the VG. The Nusselt number increases and the friction factor decreases as the Reynolds number increases. The present results were compared with the available literature and they show good agreement. Correlation equations of Nusselt number and friction factor for turbulent flow are developed, for the cases studied, as a function of Reynolds number and VG angle of attack.

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Numerical study of the relationship between heat transfer enhancement and absolute vorticity flux along main flow direction in a channel formed by a flat tube bank fin with vortex generators

Cited by 81 publications

References 34 publications

Effects of the Geometry Scale on the Behaviour of the Local Physical Process of the Velocity Field in the Laminar Flow

Effects of the Geometry Scale on the Behaviour of the Local Physical Process of the Velocity Field in the Laminar Flow

The optimum fin spacing of circular tube bank fin heat exchanger with vortex generators

Turbulent heat transfer enhancement in a triangular duct using delta‐winglet vortex generators

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