Aspect ratio dependence of heat transport by turbulent Rayleigh–Bénard convection in rectangular cells

Zhou, Quan; Liu, Bo-Fang; Li, Chunmei; Zhong, BaoChang

doi:10.1017/jfm.2012.363

Cited by 54 publications

(29 citation statements)

References 58 publications

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“…The measured values of Nu at n = 0 (no partitions) are the same as those measured in previous studies in the same parameter range (Zhou et al 2012 and are described well by a power law Nu-Ra 0.289 . As the number of partition walls increases from 0 to 6, however, Nu shows a clear monotonic increase.…”

Section: Resultssupporting

confidence: 80%

“…Our experiments were carried out in a rectangular cell (Zhou et al 2012, which measured 50 × 15 × 10 (cm 3 ) in length (L), width (W) and height (H). The upper and lower thermally conducting plates were made of pure copper and their fluid-contact surfaces were electroplated with a thin layer of nickel to prevent oxidation by water.…”

Section: Experimental Set-upmentioning

confidence: 99%

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Enhanced heat transport in partitioned thermal convection

et al. 2015

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Enhancement of heat transport across a fluid layer is of fundamental interest as well as great technological importance. For decades, Rayleigh-Bénard convection has been a paradigm for the study of convective heat transport, and how to improve its overall heat-transfer efficiency is still an open question. Here, we report an experimental and numerical study that reveals a novel mechanism that leads to much enhanced heat transport. When vertical partitions are inserted into a convection cell with thin gaps left open between the partition walls and the cooling/heating plates, it is found that the convective flow becomes self-organized and more coherent, leading to an unprecedented heat-transport enhancement. In particular, our experiments show that with six partition walls inserted, the heat flux can be increased by approximately 30 %. Numerical simulations show a remarkable heat-flux enhancement of up to 2.3 times (with 28 partition walls) that without any partitions.

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Section: Resultssupporting

confidence: 80%

Section: Experimental Set-upmentioning

confidence: 99%

Enhanced heat transport in partitioned thermal convection

et al. 2015

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“…When the cell is level, the value of Nu is calculated to be 97.8 at Ra = 4.42 × 10 9 . In a recent experiment with a rectangular cell with Γ x = 1 and Γ y = 0.3, Nu = 99.3 has been obtained at Ra = 4.6 × 10 9 and Pr = 7 (Zhou et al 2012). This is close to the present measurement.…”

Section: The Reynolds Numberssupporting

confidence: 90%

The effect of cell tilting on turbulent thermal convection in a rectangular cell

et al. 2014

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In this study the influence of cell tilting on flow dynamics and heat transport is explored experimentally within a rectangular cell (aspect ratios Γ x = 1 and Γ y = 0.25). The measurements are carried out over a wide range of tilt angles (0 β π/2 rad) at a constant Prandtl number (Pr 6.3) and Rayleigh number (Ra 4.42 × 10 9 ). The velocity measurements reveal that the large-scale circulation (LSC) is sensitive to the symmetry of the system. In the level case, the high-velocity band of the LSC concentrates at about a quarter of the cell width from the boundary. As the cell is slightly tilted (β 0.04 rad), the position of the high-velocity band quickly moves towards the boundary. With increasing β, the LSC changes gradually from oblique ellipse-like to square-like, and other more complicated patterns. Oscillations have been found in the temperature and velocity fields for almost all β, and are strongest at around β 0.48 rad. As β increases, the Reynolds number (Re) initially also increases, until it reaches its maximum at the transition angle β = 0.15 rad, after which it gradually decreases. The cell tilting causes a pronounced reduction of the Nusselt number (Nu). As β increases from 0 to 0.15, 1.05 and π/2 rad, the reduction of Nu is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of 0 β 0.15 rad, 0.15 β 1.05 rad and 1.05 β π/2 rad, the decay slopes are 8.57 × 10 −2 , 3.27 × 10 −2 and 0.24 rad −1 , respectively.

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“…In an experimental study [3] using water (i.e. 5.18 ≤ Pr ≤ 7.03) Nu is found to be independent of the aspect ratio larger than one.…”

Section: Flow Structurementioning

confidence: 93%

“…diameter/height for a cylinder. In DNS of Rayleigh-Bénard convection in cylindrical samples filled with air the influence of the aspect ratio on the mean heat flux is reported to be small [2], while experiments in rectangular containers filled with water do not show any significant influence [3] at all. From two-dimensional DNS, it is known [4,5] that the mean heat flux is significantly influenced by changes in the global flow structure occurring for small aspect ratios.…”

Section: Introductionmentioning

confidence: 92%

Influence of the Geometry on Rayleigh-Bénard Convection

Wagner

Shishkina

Wagner

2014

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Direct numerical simulations (DNS) of Rayleigh-Bénard convection in a cube and a cylinder with equal diameter and height are performed to investigate the main responses of the system, namely heat flux and motion. Differences in the latter two quantities for the two geometries suggest a transition between different flow states in the cube, which is not observed in the cylinder due to its rotational symmetry. A method is introduced to analyse the flow dynamics in the cube, which relies on the temperature distribution at the lateral walls. It reveals that above a certain Rayleigh number the global flow structure in the cube is organized in a diagonal manner and not longer parallel to the walls, which leads to differences in the heat flux and the kinetic energy in the cylindrical and the cubic sample.

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Aspect ratio dependence of heat transport by turbulent Rayleigh–Bénard convection in rectangular cells

Cited by 54 publications

References 58 publications

Enhanced heat transport in partitioned thermal convection

Enhanced heat transport in partitioned thermal convection

The effect of cell tilting on turbulent thermal convection in a rectangular cell

Influence of the Geometry on Rayleigh-Bénard Convection

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