Effect of ridge shapes on turbulent heat transfer and friction in a rectangular channel

Liou, Tong‐Miin; Hwang, Joonsik

doi:10.1016/s0017-9310(05)80277-7

Cited by 166 publications

(64 citation statements)

References 13 publications

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“…Extensive studies have been conducted on the heat transfer enhancement using turbulators in simulated heat exchangers, turbine blades and so on [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The turbulator usually generates high turbulence vortical motion in uniform flows, which may change the mean velocity fields, modify the flow turbulence properties and the structures of the near wall layers in the velocity boundary layer.…”

Section: Introductionmentioning

confidence: 99%

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Flow structures and heat transfer characteristics in fan flows with and without delta-wing vortex generators

Chen

Shu

2004

Experimental Thermal and Fluid Science

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Effects of an external delta-wing vortex generator on the flow and heat transfer characteristics in fan flows and uniform flows were experimentally investigated and compared. A heated plate, installed on the bottom wall of a duct, was used as the heat transfer surface. Three-component mean and fluctuating velocity measurements were conducted using a laser Doppler velocimetry to characterize the flow structures and to obtain the near-wall flow parameters, including the axial mean velocity, axial vorticity and turbulent kinetic energy. Temperatures on the heat transfer surface were measured using thermocouples to obtain the Nusselt numbers. Results show that the external delta-wing vortex generator in fan flows has little overall effect on the near-wall averaged axial mean velocity and axial vorticity, but increases the turbulent kinetic energy, in the investigated X/D ranges. The increase in the turbulent kinetic energy by the delta-wing has little effect on heat transfer in the inherently vortical fan flows.Consequently, the delta-wing vortex generator in fan flows has little effect on the heat transfer augmentation.

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Section: Introductionmentioning

confidence: 99%

“…Hwang et al [12] and Liou et al [13] investigated the effects of ridge shapes and rib-arrays on heat transfer. Their studies showed that various ridge shapes have comparable thermal performance and the composite-ribbed performed best in their ribbed configurations.…”

Section: Introductionmentioning

confidence: 99%

Flow structures and heat transfer characteristics in fan flows with and without delta-wing vortex generators

Chen

Shu

2004

Experimental Thermal and Fluid Science

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“…The ribs were produced by machining the surfaces of the heating plates with a NC machine tool, whose cross-sectional dimension was 0.2mmx0.2mm and with rib pitches of 2 or 4mm, respectively. Square ribs were employed as they reveal the better heat transfer performance than that of the triangular or semicircular ribs since the flow does not travel smoothly over square ribs and square crosssectional blockage accentuates inertial losses (12).…”

Section: Test Apparatusmentioning

confidence: 99%

Experimental Study on Heat Transfer Augmentation for High Heat Flux Removal in Rib-Roughened Narrow Channels.

Islam

Hino²,

Haga³

et al. 1998

J. Nucl. Sci. Technol.

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Frictional pressure drop and heat transfer performance in a very narrow rectangular channel having onesided constant heat flux and repeated-ribs were studied experimentally for turbulent water flows. Their empirical correlations were derived for designing target cooling channels to remove high heat flux generated at target plates in a high-intensity proton accelerator system. The rib pitch-to-height ratios ( p / k ) were 10 and 20 while holding the rib height constant at 0.2mm1 the Reynolds number ( R e ) from 2,400 to 98,500 under different channel heights ( H ) of 1.2 mm and 3.2 mm, the rib height-to-channel equivalent diameter ratio ( k / D , ) of 0.088 and 0.036, respectively. The results show that the rib-roughened surface augments heat transfer by about 2-2.5 times compared with the smooth surface at the expense of around 2.5 times higher frictional pressure drop under a range of Re=8,000-to-30,000 at p/k=lO, and H=1.2 mm. Experimental results of channel height, H=1.2 mm show slightly higher heat transfer and friction factor performance than that of the channel height, H=3.2 mm.

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“…Roughness elements in the form of ribs of various shapes have been employed to enhance heat transfer in heat exchanger tubes, gas turbine blade cooling channels and solar air heaters (Webb et al, 1971;Liou and Hwang, 1993;Karwa et al, 2001). From the experimental studies of the effect of artificial roughness, investigators have shown that the geometry of the roughness elements (shape, rib pitch-to-height ratio, etc.)…”

Section: Introductionmentioning

confidence: 99%

“…Flow visualization techniques, heat-mass transfer analogy, and holographic interferometry (Williams and Watts, 1970;Sparrow and Tao, 1993;Hsieh and Hong, 1989;Locket and Collins, 1990;Liou and Hwang, 1993) have been used to study the flow patterns and local heat transfer for artificially roughened surfaces. Matsuzaki et al (2004) employed hydrogen bubble method for visualization of flow structures in the wake of an inclined circular cylinder.…”

Section: Introductionmentioning

confidence: 99%

Flow visualization and local mass transfer studies for turbulent flow in a wind tunnel with chamfered ribs

Karwa

Maheshwari

Karwa

2008

J Vis

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The paper presents results of flow visualization and mass transfer studies for fully developed turbulent flow of air in a square section wind tunnel with repeated chamfered rib roughness on the bottom of the tunnel (rib head chamfer angles φ of -15 o , 0 o , and 15 o ; relative roughness pitch p/e = 3, 5, 7.5, and 10). Direct video recordings of flow patterns were made using a simple technique of particles visualization. For the positively chamfered closely spaced ribs (p/e ≤ 5) vigorous vortex shedding has been seen compared to the square or negatively chamfered ribs, which is found to be a function of the Reynolds number. For the widely spaced ribs, the study shows flow separation at the ribs and reattachment in the inter-rib region. Local mass transfer studies, based on the variation in colour of cobaltous chloride solution impregnated paper due to evaporation of water, showed a significant improvement in mass transfer rate in the recirculating region in the wake of ribs with the change in the chamfer angle from -15 o to 15 o . The positively chamfered 15 o ribs are found to be better than square section ribs at p/e ≤ 7.5. The performance of negatively chamfered ribs is found to be poor compared to other ribs irrespective of the relative roughness pitch.

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Effect of ridge shapes on turbulent heat transfer and friction in a rectangular channel

Cited by 166 publications

References 13 publications

Flow structures and heat transfer characteristics in fan flows with and without delta-wing vortex generators

Flow structures and heat transfer characteristics in fan flows with and without delta-wing vortex generators

Experimental Study on Heat Transfer Augmentation for High Heat Flux Removal in Rib-Roughened Narrow Channels.

Flow visualization and local mass transfer studies for turbulent flow in a wind tunnel with chamfered ribs

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