Weather and anomalous heat flow occurring near absolute zero

Niemela, Joseph

doi:10.1073/pnas.1305833110

Cited by 4 publications

(4 citation statements)

References 10 publications

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“…We have revisited our cryogenic two-fluid Rayleigh-Bénard convection experiment [14], using an aspect ratio = 2 Γ experimental cell, 30 cm in diameter. For similar experimental conditions, we confirm all results described in [14,15]. When, however, the bottom fluid layer -normal He I is replaced by superfluid He II which covers also the entire cell interior by a superfluid film and acts as a heat conduction short-circuit, we observe very different behavior.…”

Section: Discussionsupporting

confidence: 84%

“…As soon as the thermal short-circuit provided by the superfluid 4 He layer (we note that very low counterflow velocity of order 0.1 mm/s is sufficient to carry heat input of 1 W across the superfluid layer at temperatures around 2 K) and superfluid film is removed due to the superfluid to normal phase transition, we recover the more complex and highly interesting non-equilibrium situation (including detection of the rain of small helium droplets after switching off the bottom plate heater) described in detail in Ref. 14 and, from somewhat wider perspective, in the follow-up article by Niemela [15].…”

Section: Discussionsupporting

confidence: 64%

“…More recently, we modified the same apparatus in order to study two-fluid convection in a Rayleigh-Bénard cell, across two horizontal layers: liquid He I and cryogenic 4 He gas. Our experiments led to interesting results [14,15]. One of them, directly relevant to this work, can be briefly described as follows.…”

Section: Two-fluid Convectionmentioning

confidence: 87%

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Convective heat transport in two-phase superfluid/vapor 4He system

Urban

Hanzelka

Vlček

et al. 2018

Low Temperature Physics

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We have recently shown that under certain cryogenic conditions heat can flow from a colder but constantly heated body to a hotter but constantly cooled body. Specifically, we have provided experimental evidence that heat flows through normal liquid and gaseous phases of 4 He from the constantly heated, but cooler, bottom plate of a Rayleigh-Bénard convection cell to its hotter, but constantly cooled, top plate. Here we report results of a modified experiment, where the bottom normal liquid helium layer is replaced by superfluid 4 He, providing, together with a superfluid film covering the entire cell interior, an effective thermal short-circuit. Applied heat input of order 1 W to the bottom plate results in simultaneous heating of the entire cell: this physical process can be viewed, at least approximately, as a series of subsequent equilibrium states, until upon reaching the superfluid transition the non-equilibrium processes described in our previous study [Proc. Nat. Acad. Sci. USA 110, 8036 (2013)] are fully recovered.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionsupporting

confidence: 64%

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Convective heat transport in two-phase superfluid/vapor 4He system

Urban

Hanzelka

Vlček

et al. 2018

Low Temperature Physics

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“…With the additional improvements described, the apparatus has been found capable of performing experimental research on various aspects of the RBC flow, in particular for studies of open problems at very high Ra. It has also been successfully used to study two-fluid convection; these results and their impact on general thermodynamics have been published elsewhere [58,59].…”

Section: The Experimental Apparatus and Protocolmentioning

confidence: 99%

Heat transfer in cryogenic helium gas by turbulent Rayleigh–Bénard convection in a cylindrical cell of aspect ratio 1

et al. 2014

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We present experimental results on the heat transfer efficiency of cryogenic turbulent Rayleigh-Bénard convection (RBC) in a cylindrical cell 0.3 m in both diameter and height which has improvements with respect to various corrections connected with finite thermal conductivity of sidewalls and plates. The heat transfer efficiency described by the Nusselt number Here H is the total convective heat flux density, g stands for the acceleration due to gravity, and ΔT is the temperature difference between the parallel top and the bottom plates separated by the vertical distance L. The properties of the working fluid are characterized by the thermal conductivity, λ, and by the combination α νκ ( ) , where α is the isobaric thermal expansion, ν is the kinematic viscosity, and κ denotes the thermal diffusivity. New J. Phys. 16 (2014) 053042 P Urban et al New J. Phys. 16 (2014) 053042 P Urban et al New J. Phys. 16 (2014) 053042 P Urban et al 4 New J. Phys. 16 (2014) 053042 P Urban et al 5 3 Note that our Brno cryogenic data recently published in two Letters [43, 44] are erroneously treated by the authors as aspect ratio Γ = 1 2 data, while they have all been obtained for the Γ = 1 cell. New J. Phys. 16 (2014) 053042 P Urban et al 6 Figure 1. Schematic drawing of the helium cryostat [55] containing the cylindrical aspect ratio Γ = 1 RBC cell. New J. Phys. 16 (2014) 053042 P Urban et al 7 W K 1 25 38 50 New J. Phys. 16 (2014) 053042 P Urban et al 9 Pr Pr Ra c c c (white filled red circles). The black line illustrates the slope ∝ Pr Ra 0.5 . New J. Phys. 16 (2014) 053042 P Urban et al New J. Phys. 16 (2014) 053042 P Urban et al 13 New J. Phys. 16 (2014) 053042 P Urban et alWe thank many colleagues for help and stimulating discussions, especially S Babuin, X He, M Jackson, R du Puits, P-E Roche, J Salort, and D Schmoranzer. This work was supported by the GAČR 203/12/P897, and the work of MLM and LS by GAČR P203/11/0442. Appendix. Tabulated experimental dataIn tables A1 and A2, values of Ra corr and Nu corr represent the corrected data, with corrections applied as discussed in the text. All remaining values of Rayleigh, Prandtl and Nusselt numbers are not corrected in any way.New J. Phys. 16 (2014) 053042 P Urban et al

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