Heat transfer enhancement in Rayleigh-Bénard convection using a single passive barrier

Liu, Shuang; Huisman, Sander G.

doi:10.1103/physrevfluids.5.123502

Cited by 11 publications

(4 citation statements)

References 67 publications

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“…The key mechanism is to restrict the free-moving spacing of thermal plumes, which results in pronounced changes in the plume morphology. In fact, the morphology of thermal plumes in RB convection cells can also be manipulated by adding physical obstacles inside the system, such as partitioned walls [ 49 ], suspended honeycombs [ 50 ], a porous media structure [ 51 ] and even a single straight barrier [ 52 ]. All these methods have achieved heat transfer enhancement accompanied by the formation of more coherent thermal plumes.…”

Section: Manipulating Coherent Structures Through Dynamical Processesmentioning

confidence: 99%

Tuning heat transport via coherent structure manipulation: recent advances in thermal turbulence

Xia

Huang

Xie

et al. 2023

National Science Review

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Tuning transport properties through the manipulation of elementary structures has received a great success in many areas, such as condensed matter physics. However, the ability to manipulate coherent structures in turbulent flows is much less explored. This article reviews a recently discovered mechanism of tuning turbulent heat transport via coherent structure manipulation. We first show how this mechanism can be realized by applying simple geometrical confinement to a classical thermally-driven turbulence, which leads to the condensation of elementary coherent structures and significant heat-transport enhancement, despite the resultant slower flow. Some potential applications of this new paradigm in passive heat management are also discussed. We then explain how the heat transport behaviors in seemingly different turbulence systems can be understood by this unified framework of coherent structure manipulation. Several future directions in this research area are also outlined.

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Section: Manipulating Coherent Structures Through Dynamical Processesmentioning

confidence: 99%

Tuning heat transport via coherent structure manipulation: recent advances in thermal turbulence

Xia

Huang

Xie

et al. 2023

National Science Review

View full text Add to dashboard Cite

show abstract

“…2014; Xie & Xia 2017), inserting plates (Bao et al. 2015; Liu & Huisman 2020), tilting the convection cell (Zwirner & Shishkina 2018; Zwirner et al. 2020) or introducing a vibration (Wang, Zhou & Sun 2020).…”

Section: Introductionmentioning

confidence: 99%

Enhanced heat transfer and reduced flow reversals in turbulent thermal convection with an obstructed centre

Li,

Chen,

2024

J. Fluid Mech.

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We report an experimental study about the effect of an obstructed centre on heat transport and flow reversal by inserting an adiabatic cylinder at the centre of a quasi-two-dimensional Rayleigh–Bénard convection cell. The experiments are carried out in a Rayleigh number ( $Ra$ ) range of $2\times 10^7 \leq Ra \leq 2\times 10^9$ and at a Prandtl number ( $Pr$ ) of $5.7$ . It is found that for low $Ra$ , the obstructed centre leads to a heat transfer enhancement of up to 21 $\%$ , while as $Ra$ increases, the magnitude of the heat transfer enhancement decreases and the heat transfer efficiency ( $Nu$ ) eventually converges to that of the unobstructed normal cell. Particle image velocimetry measurements show that the heat transfer enhancement originates from the change in flow topology due to the presence of the cylindrical obstruction. In the low- $Ra$ regime the presence of the obstruction promotes the transition of the flow topology from the four-roll state to the abnormal single-roll state then to the normal single-roll state with increasing obstruction size. While in the high- $Ra$ regime, the flow is always in the single-roll state regardless of the obstruction size, although the flow becomes more coherent with the size of the obstruction. We also found that in the presence of the cylindrical obstruction, the stability of the corner vortices is significantly reduced, leading to a large reduction in the frequency of flow reversals.

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“…2009; Stevens, Clercx & Lohse 2013; Yang et al. 2020 b ), and the addition of passive barriers (Liu & Huisman 2020).…”

Section: Introductionmentioning

confidence: 99%

Wall-sheared thermal convection: heat transfer enhancement and turbulence relaminarization

Ben-Rui

2023

J. Fluid Mech.

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We studied the flow organization and heat transfer properties in two-dimensional and three-dimensional Rayleigh–Bénard cells that are imposed with different types of wall shear. The external wall shear is added with the motivation of manipulating flow mode to control heat transfer efficiency. We imposed three types of wall shear that may facilitate the single-roll, the horizontally stacked double-roll, and the vertically stacked double-roll flow modes, respectively. Direct numerical simulations are performed for fixed Rayleigh number $Ra = 10^{8}$ and fixed Prandtl number $Pr = 5.3$ , while the wall-shear Reynolds number ( $Re_{w}$ ) is in the range $60 \leqslant Re_{w} \leqslant 6000$ . Generally, we found enhanced heat transfer efficiency and global flow strength with the increase of $Re_{w}$ . However, even with the same magnitude of global flow strength, the heat transfer efficiency varies significantly when the cells are under different types of wall shear. An interesting finding is that by increasing the wall-shear strength, the thermal turbulence is relaminarized, and more surprisingly, the heat transfer efficiency in the laminar state is higher than that in the turbulent state. We found that the enhanced heat transfer efficiency at the laminar regime is due to the formation of more stable and stronger convection channels. We propose that the origin of thermal turbulence laminarization is the reduced amount of thermal plumes. Because plumes are mainly responsible for turbulent kinetic energy production, when the detached plumes are swept away by the wall shear, the reduced number of plumes leads to weaker turbulent kinetic energy production. We also quantify the efficiency of facilitating heat transport via external shearing, and find that for larger $Re_{w}$ , the enhanced heat transfer efficiency comes at a price of a larger expenditure of mechanical energy.

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Heat transfer enhancement in Rayleigh-Bénard convection using a single passive barrier

Cited by 11 publications

References 67 publications

Tuning heat transport via coherent structure manipulation: recent advances in thermal turbulence

Tuning heat transport via coherent structure manipulation: recent advances in thermal turbulence

Enhanced heat transfer and reduced flow reversals in turbulent thermal convection with an obstructed centre

Wall-sheared thermal convection: heat transfer enhancement and turbulence relaminarization

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