Enhancement of heat transfer in a square channel by roughened surfaces in rib-elements and turbulent flow manipulation

Liu, Jian; Xie, Gongnan; Sundén, Bengt; Wang, Lei; Andersson, Martin

doi:10.1108/hff-03-2016-0120

Cited by 11 publications

(6 citation statements)

References 33 publications

(37 reference statements)

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“…Their predictions indicated that this twisted implant could improve the thermal convection performance by 1.8-4.5 times. Liu et al (2017) applied a V2F turbulence model to the analysis of turbulent thermal flow and the enhancement of thermal performance in various channels equipped with ribbed inserts. Wu and Perng (2005) combined the large eddy simulation turbulence model with the semi-implicit method for pressure-linked equation (SIMPLE-C) algorithm to simulate the turbulent thermal flow field and then evaluated the heat transfer promotion of a block-heated channel.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of turbulent thermal convection in a circular tube with a slotted twisted tape

Perng¹,

Kelana

et al. 2022

HFF

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Purpose The purpose of this paper, computational fluid dynamics (CFD) work, is to promote turbulent thermal convection in a heated circular tube using a passive scheme of a slotted twisted sheet. Design/methodology/approach The inventive design uses square-cut and conjugate triangular perforations to diversify the twisted tape for better thermal convection. The current novel passive scheme methodology is accomplished by carving the same square cuts and slitting various sizes of equilateral triangle perforations (side length varies between 8 and 16 mm). The re-normalisation group turbulence model and the semi-implicit method for pressure-linked equation method examine the turbulent thermal convection aspects of all simulations at different Reynolds numbers (6,000, 10,000 and 14,000). Findings The analyses of simulations exhibit that the placement of a twisted tape with triangle perforations and equidistant square cuts can effectually promote thermal convection in a circular tube. A larger-sized triangle perforation can increase the thermal convection enhancement and thermal performance factor, but an enlarged perforation may decrease the thermal convection enhancement and thermal performance factor. As a result, compared with the smooth circular tube, the circular tube with the slotted twisted sheet slit by a 10 mm equilateral triangle brings about the maximum improvement ratio of the mean Nusselt number of about 2.8 at Re = 6,000. Under weighing the friction through the circular tube, the tube with the slotted twisted sheet slit by a 10 mm equilateral triangle gains the best thermal performance factor of about 1.36 at Re = 6,000. Research limitations/implications The working fluid is water and its physical features are assumed to be constant. In addition, the fluid is considered a steady flow in this CFD work. Practical implications These CFD predictions will benefit the development of heat exchanger tubes equipped with a slotted twisted sheet to acquire preferable thermal convection enhancement. Social implications Higher thermal performance achieved by placing a slotted twisted tape in a heated tube will benefit society in lower energy consumption, machinery maintenance costs and impact on the environment. Originality/value This study combined triangle perforations and square cuts on the twisted sheet. This combination can induce the fluid flow across the sheet to disturb the swirling flow and then promote the fluid mixing to increase thermal convection. Therefore, this modified tape can be a profitable passive device for designing a heat exchanger.

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Section: Introductionmentioning

confidence: 99%

Enhancement of turbulent thermal convection in a circular tube with a slotted twisted tape

Perng¹,

Kelana

et al. 2022

HFF

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“…They found that the wave-shaped triangular ribs generated vortices to disorder the thermal boundary layer effectively to raise heat transfer rate. Liu et al (2017) explored the heat and fluid flow in square passages with novel ribbed structures via computational analysis. Their findings indicated that rounded transition cylindrical rib had thermal performance better than the traditional rib under considering pressure loss.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer promotion in channel laminar flow employing a slab with slits and inclined ribs protruding across

Perng

2021

HFF

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Purpose The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across. Design/methodology/approach The novel design of this study is performed through making the slits in the slab (C1–C3: with slits; C4–C6: without slits) and changing the vertical location of this slab (1/4, 1/2 and 3/4 channel height). The thermal fluid characteristics of all cases are analyzed for various Reynolds numbers (500, 1,000, 1,500 and 2,000) by the SIMPLE-C algorithm. Findings The results display that the ribbed slab effectively improves the heat transfer. The slits can modify the flow field in the vortexes around the inclined ribs and remove more heat from this zone to promote the heat transfer. As compared with C0 (without a slab), C2 (the slab with slits and inclined ribs protruding across located vertically on the 3/4 channel height) raises the averaged Nusselt number up to 27.7% at Re = 2,000. As compared with C4 (without slits), C1 (with slits) gains the maximum increase in the averaged Nusselt number by 5.07% at Re = 1,000. Research limitations/implications The constant thermo-physical properties of incompressible fluid and the steady flow are considered in this study. Practical implications The numerical results will profit the design of heated passageway using a slab with slits and inclined ribs protruding across to acquire better heat transfer promotion. Originality/value This slab with slits and inclined ribs protruding across can be applied to the heat transfer promotion and thus be viewed as a useful cooling mechanism in the thermal engineering.

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“…This was due to larger strength of cross flow induced by the jet in the downstream region. Liu et al (2017) carried out a computational study of the effect on ribs in a square channel. Among all rib geometries, the round transition cylindrical ribs gave the highest heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations and optimization of impinging jet configuration

Singh

Balaji

Prasad

2020

HFF

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Purpose Numerical simulations are performed to determine the heat transfer characteristics of slot jet impingement of air on a concave surface. The purpose of this paper is to investigate the effect of protrusions on the heat transfer by placing semi-circular protrusions on the concave surface at several positions. After identifying appropriate locations where the heat transfer is a maximum, multiple protrusions are placed at desired locations on the plate. The gap ratio, curvature ratio (d/D) and the dimensions of the plate are varied so as to obtain heat transfer data. The curvature ratio is varied first, keeping the concave diameter (D) fixed followed by a fixed slot width (d). A surrogate model based on an artificial neural network is developed to determine optimum locations of the protrusions that maximize the heat transfer from the concave surface. Design/methodology/approach The scope and objectives of the present study are two-dimensional numerical simulations of the problem by considering all the geometrical parameters (H/d, dp, Re, θ) affecting heat transfer characteristics with the help of networking tool and numerical simulation. Development of a surrogate forward model with artificial neural networks (ANNs) with a view to explore the full parametric space. To quantitatively ascertain if protrusions hurt or help heat transfer for an impinging jet on a concave surface. Determination of the location of protrusions where higher heat transfer could be achieved by using exhaustive search with the surrogate model to replace the time consuming forward model. Findings A single protrusion has nearly no effect on the heat transfer. For a fixed diameter of concave surface, a smaller jet possesses high turbulence kinetic energy with greater heat transfer. ANN is a powerful tool to not only predict impingement heat transfer characteristics by considering multiple parameters but also to determine the optimum configuration from many thousands of candidate solutions. A maximum increase of 8 per cent in the heat transfer is obtained by the best configuration constituting of multiple protrusions, with respect to the baseline smooth configuration. Even this can be considered as marginal and so it can be concluded that first cut results for heat transfer for an impinging jet on a concave surface with protrusions can be obtained by geometrically modeling a much simpler plain concave surface without any significant loss of accuracy. Originality/value The heat transfer during impingement cooling depends on various geometrical parameters but, not all the pertinent parameters have been varied comprehensively in previous studies. It is known that a rough surface may improve or degrade the amount of heat transfer depending on their geometrical dimensions of the target and the rough geometry and the flow conditions. Furthermore, to the best of authors’ knowledge, scarce studies are available with inclusion of protrusions over a concave surface. The present study is devoted to development of a surrogate forward model with ANNs with a view to explore the full parametric space.

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Enhancement of heat transfer in a square channel by roughened surfaces in rib-elements and turbulent flow manipulation

Cited by 11 publications

References 33 publications

Enhancement of turbulent thermal convection in a circular tube with a slotted twisted tape

Enhancement of turbulent thermal convection in a circular tube with a slotted twisted tape

Heat transfer promotion in channel laminar flow employing a slab with slits and inclined ribs protruding across

Numerical simulations and optimization of impinging jet configuration

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