Vortices, Generators and Heat Transfer

Fiebig, M.

doi:10.1205/026387698524686

Cited by 257 publications

(88 citation statements)

References 28 publications

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“…The wings of DWTs help create longitudinal vortices that lead to better mixing at a faster rate between the fluid at the core and the surface region and result in higher temperature gradients near the tube wall [27]. The alternating direction of DWTs also generated counter-rotating vortices, which induced additional convective thermal transport [5]. At the same time, these vortices produced a streamwise velocity profile, which led to decay of the flow.…”

Section: Validation Of the Plain Tubementioning

confidence: 99%

“…Vortex generators (VGs) have received extensive attention by researchers [1][2][3][4][5] as devices for obtaining high thermal performance by enhancing the heat-transfer coefficients of a tube heat exchanger. VGs are also regarded as potential heat-transfer augmentation devices because they create vortices that lead to high heat-transfer rates [5].…”

Section: Introductionmentioning

confidence: 99%

“…VGs are also regarded as potential heat-transfer augmentation devices because they create vortices that lead to high heat-transfer rates [5]. VGs are used to induce secondary flow, which disturbs or cuts off the thermal boundary layer developed along the wall and removes heat from the wall to the core of the flow by means of large-scale turbulence [6].…”

Section: Introductionmentioning

confidence: 99%

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Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

et al. 2018

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Abstract:The impact of double-sided delta-winglet tape (DWTs) inserts on convective heat transfer and friction behaviors in a tube was experimentally investigated. Three DWTs with ratios of winglet-height (b) to inner tube diameter (d i ) called blockage ratio (R b ) of 0.28, 0.35 and 0.42 were tested and their performance was compared to that of a longitudinal strip and plain tube under similar test flow conditions. Experiments were conducted over a wide range of flow rates, 3.35 × 10 −5 -8.33 × 10 −5 m 3 /s, which correspond to 5500 ≤ Reynolds number (Re) ≤ 14,500 in the 14.3 mm i.d. tube. The results revealed that using DWTs dramatically increased the Nusselt number (Nu) by as much as 364.3% and the friction factor (f ) by 15.5 times compared with those of a plain tube. Thermal performance (η) increased with a corresponding increase in R b . The highest thermal performance (η) obtained was 1.4. Showing a notable improvement on the thermal performance of the system, DWTs are proposed as a favorable insert device.

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Section: Validation Of the Plain Tubementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

et al. 2018

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“…This demonstrates heat transfer enhancement with small additional pressure loss is of importance. For convective heat transfer intensification, three enhancement mechanisms may be distinguished according to Fiebig [2]. They are (1) developing boundary layers; (2) swirl or vortices and (3) flow destabilization or turbulence intensification.…”

Section: List Of Symbols Amentioning

confidence: 99%

Compound heat transfer enhancement for shell side of double-pipe heat exchanger by helical fins and vortex generators

Zhang

Guo

et al. 2012

Heat Mass Transfer

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To improve heat transfer performance of shell side of double-pipe heat exchanger with helical fins on its inner tube, some vortex generators (VGs) were installed along the centerline of the helical channel. Heat transfer performance and pressure drop characteristic of the enhanced heat exchangers were investigated using air as the working fluid and steam as the heating medium. The helical fins were in the annulus and span its full width at different helical pitch. Wing-type VGs (delta or rectangular wing) and winglet-type VGs (delta or rectangular winglet pair) were used to combine with helical fins. The friction factor and Nusselt number can be well correlated by power-law correlations in the Reynolds number range studied. In order to evaluate the thermal performance of the shell side enhanced over the shell side without enhancement, comparisons were made under three constraints: (1) identical mass flow rate, IMF; (2) identical pressure drop, IPD and (3) identical pumping power, IPP. The results show the shell side enhanced by the compound heat transfer enhancement has better performance than the shell side only enhanced by helical fins at shorter helical pitch under the three constraints.

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“…The ability of these vortices to increase velocity fluctuations and flow momentum redistribution leads to better heat and mass transfer and intensifies convective phenomena and turbulent mixing with no need for external mechanical forces [2,3]. It was shown that most heat-and mass-transfer enhancement is provided essentially by streamwise vorticity, while the transverse stationary vorticity slightly enhances heat transfer in the region near the vortex generator, generally in the near-wake of the vortex generator [1,4].…”

Section: Introductionmentioning

confidence: 99%

Heat-Transfer Enhancement by Artificially Generated Streamwise Vorticity

Ghanem¹,

Habchi²,

Lemenand³

et al. 2012

J. Phys.: Conf. Ser.

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Abstract. Vortex-induced heat transfer enhancement exploits longitudinal and transverse pressure-driven vortices through the deliberate artificial generation of large-scale vortical flow structures. Thermal-hydraulic performance, Nusselt number and friction factor are experimentally investigated in a HEV (high-efficiency vortex) mixer, which is a tubular heat exchanger and static mixer equipped with trapezoidal vortex generators. Pressure gradients are generated on the trapezoidal tab initiating a streamwise swirling motion in the form of two longitudinal counter-rotating vortex pairs (CVP). Due to the Kelvin-Helmholtz instability, the shear layer generated at the tab edges, which is a production site of turbulence kinetic energy (TKE), becomes unstable further downstream from the tabs and gives rise to periodic hairpin vortices. The aim of the study is to quantify the effects of hydrodynamics on the heat-and mass-transfer phenomena accompanying such flows for comparison with the results of numerical studies and validate the high efficiency of the intensification process implementing such vortex generators. The experimental results reflect the enhancement expected from the numerical studies and confirm the high status of the HEV heat exchanger and static mixer.

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Vortices, Generators and Heat Transfer

Cited by 257 publications

References 28 publications

Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

Compound heat transfer enhancement for shell side of double-pipe heat exchanger by helical fins and vortex generators

Heat-Transfer Enhancement by Artificially Generated Streamwise Vorticity

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