Unsteady flow and heat transfer in a channel obstructed by a square rod. 3rd Report. Characteristics and mechanism of heat transfer.

洋, 鈴木; 健二郎, 鈴木; 義章, 井上; 良道, 萩原

doi:10.1299/kikaib.57.1403

Cited by 7 publications

(3 citation statements)

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“…The minimum grid spacing was decided so that the grid space Reynolds number is smaller than 7.0 [19]. The maximum number of 234 × 52 grid points were distributed in the channel finely close to the rib corners.…”

Section: Methodsmentioning

confidence: 99%

Combined convection heat transfer in a channel with two ribs attached to one wall

Matsubara

Nakabe

Suzuki

et al. 1999

Heat Trans. Asian Res.

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Two-dimensional calculations were performed for combined convection heat transfer in a channel with two ribs attached to one wall, following a previous study on the forced convection case without buoyancy. The flow is heated from the surfaces of both ribs and the present study dealt with the two cases of buoyancy-assisted flow and buoyancy-opposing flow. The effect of Reynolds number, Re L , and modified Richardson number, Ri * , was examined keeping the space between ribs, σ, and blockage ratio, τ, constant (σ = 3.0, τ = 0.5). Increasing the magnitude of buoyancy, unsteady flows predicted by the present calculations are stabilized in both cases. Serious deterioration of Nusselt number on the second rib suddenly occurs in a certain range of Ri * due to the flow stabilization. This is because flow unsteadiness plays an important role for heat transfer enhancement as was described in a previous study. However, in buoyancy-assisted flow, a similar deterioration of Nusselt number also appears on the second rib even if flow remains steady. This is caused by the disappearance of a strong rotating flow which exists in the cavity between both ribs and keeps the fluid in the cavity cooler. © 1999 Scripta Technica, Heat Trans Asian Res, 28(5): 379394, 1999

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Section: Methodsmentioning

confidence: 99%

Combined convection heat transfer in a channel with two ribs attached to one wall

Matsubara

Nakabe

Suzuki

et al. 1999

Heat Trans. Asian Res.

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“…In recent studies, attempts were made to achieve dissimilar heat transfer enhancement. In their experiments on the variation of heat and momentum transfer caused by installing a rectangular lib in plane channel flow, Suzuki et al found that the spanwise vortex with the same sign of vorticity as the background shear, referred to as a cyclonic vortex, is effective in dissimilar heat transfer enhancement (Suzuki et al 1991). Katoh et al numerically investigated tubular vortices in turbulent channel flow, and found that they often incline in the spanwise direction from the streamwise direction so that their spanwise vorticity may exhibit the same sign as the mean shear, i.e.…”

Section: Introductionmentioning

confidence: 99%

Dissimilar heat transfer enhancement by introduction of a vortex tube in plane Couette flow

Kubo¹,

Kawahara²,

Shimizu³

2021

Fluid Dyn. Res.

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Recent studies have suggested that a cyclonic vortex, which has the same signed vorticity as that of background shear, can lead to dissimilar heat transfer enhancement, i.e. more heat transfer than momentum transfer. However, it has not yet been known how the cyclonic vortex achieves dissimilarity, or if other types of vortices would also lead to dissimilarity. In order to tackle these problems, we introduce a straight vortex tube into laminar plane Couette flow under various conditions and numerically investigate heat and momentum transfer therein. The essential process for dissimilarity is isolated from complex ingredients of realistic flow to consider the interaction of a vortex with background shear. It is found that introduction of a strong spanwise anti-cyclonic vortex, which has the opposite signed vorticity to that of background shear, can realize more dissimilar heat transfer than the known cyclonic vortex as a consequence of the long-term interaction with the background flow, whereas the spanwise cyclonic vortex achieves larger dissimilarity in the early stage of its time evolution. The physical mechanisms of dissimilarity due to these vortices are elucidated by interpreting the distribution of the streamwise pressure gradient and the resulting difference between temperature and streamwise velocity around the vortex.

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“…Periodically changing unsteady laminar flow, although its three-dimensional irregularity is less marked than that in turbulent flow, is of practical importance, because heat transfer is enhanced compared with that in steady laminar flow. Suzuki and coworkers [1][2][3][4] conducted numerical simulations and flow visualizations of flow in a channel obstructed by a square rod, and clarified the flow characteristics and the mechanism of heat transfer. From a practical point of view, as we pointed out in our preceding article [5], more attention should be paid to cases in which a similar flow geometry is repeated at a certain spatial pitch in the flow direction.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of flow in a channel obstructed by an array of square rods (2nd report, Investigation of a criterion for judging the uniqueness and validity of numerical results)

Murata

Sawada

Suzuki

2007

Heat Trans. Asian Res.

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Two-dimensional numerical computation is performed for unsteady laminar flow. Spatially periodic boundary conditions are adopted in the streamwise direction, and in particular, a criterion for judging the uniqueness of the numerical solution is studied. The following results were obtained. When the numerical result fluctuates with the computational domain size, various low-frequency components are markedly observed in the streamwise velocity of the calculated result. Compared with the channel flow obstructed by a single rod of the same size, the intensities of velocity fluctuation in this study are relatively high, and their distribution throughout the flow field is rather uniform. The spatially averaged kinematic energy of the velocity fluctuation is adopted as a key parameter, and a discrimination map of the uniqueness of the numerical solution is presented using a timescale ratio between mean flow and velocity fluctuation, the rod pitch, and the blockage ratio. The timescale ratio is well correlated with a geometric parameter obtained from the flow configuration, and the discrimination map can be converted such that the geometric parameter and the channel Reynolds number describe it.

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Unsteady flow and heat transfer in a channel obstructed by a square rod. 3rd Report. Characteristics and mechanism of heat transfer.

Cited by 7 publications

References 0 publications

Combined convection heat transfer in a channel with two ribs attached to one wall

Combined convection heat transfer in a channel with two ribs attached to one wall

Dissimilar heat transfer enhancement by introduction of a vortex tube in plane Couette flow

Numerical investigation of flow in a channel obstructed by an array of square rods (2nd report, Investigation of a criterion for judging the uniqueness and validity of numerical results)

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