Comments on heat transfer efficiency in cryogenic helium turbulent Rayleigh-Bénard convection

Urban, P.; Musilová, Věra; Králı́k, Tomáš; Skrbek, L.

doi:10.1088/1742-6596/318/8/082012

Cited by 2 publications

(3 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…means a negligible 'plates effect' in RBC experiments with cryogenic helium up to about ≈ Ra 10 12 . We have discussed this criterion in our previous publication [57], where we plotted the Ra dependence of the parameter Cr evaluated for our cell as well as for the Oregon/Trieste and the Grenoble cryogenic cells of aspect ratio Γ ≃ 1; for the same Ra the values of Cr are similar in magnitude to but slightly lower than ours. This strongly suggests that the observed differences between the cryogenic RBC experiments at high > Ra 10 11 cannot be interpreted as the 'effect of plates'.…”

Section: Remarks On Corrections For the Finite Heat Conductivity And supporting

confidence: 53%

“…Our test measurements, at a deliberately substantially higher mean temperature of the RBC cell T m , revealed a spurious increase in Nu due to convection inside these venting tubes between the cell inlet (at ≈T m ) and the thermal anchor at the liquid helium vessel 140 mm above. We therefore improved the design of the cell [57] and eliminated this 'chimney effect', by mounting electrical resistance heaters and thermometers onto both venting tubes at the level of their thermal anchor to the liquid helium vessel that allow adjusting and controlling the local temperature to ⩾ T T m during measurements.…”

Section: The Experimental Apparatus and Protocolmentioning

confidence: 99%

“…When testing the newly built apparatus, we encountered problems with the thermal acoustic oscillations in these venting tubes, as mentioned in [55]. This problem was solved by using additional volumes connected to the tubes at room temperature, resulting in suppression of the observed pressure oscillations by at least two orders of magnitude [57].…”

Section: The Experimental Apparatus and Protocolmentioning

confidence: 99%

See 2 more Smart Citations

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

et al. 2014

View full text Add to dashboard Cite

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

show abstract

Section: Remarks On Corrections For the Finite Heat Conductivity And supporting

confidence: 53%

Section: The Experimental Apparatus and Protocolmentioning

confidence: 99%

Section: The Experimental Apparatus and Protocolmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2014

View full text Add to dashboard Cite

show abstract

Effect of Boundary Layers Asymmetry on Heat Transfer Efficiency in Turbulent Rayleigh-Bénard Convection at Very High Rayleigh Numbers

et al. 2012

View full text Add to dashboard Cite

The heat transfer efficiency in turbulent Rayleigh-Bénard convection is investigated experimentally, in a cylindrical cell of height 0.3 m, diameter 0.3 m. We show that for Rayleigh numbers 10(12) < or approximately equal to Ra < or approximately equal to 10(15) the Nusselt number closely follows Nu is proportional to Ra(1/3 if the mean temperature of the working fluid-cryogenic helium gas-is measured by small sensors directly inside the cell at about half of its height. In contrast, if the mean temperature is determined in a conventional way, as an arithmetic mean of the bottom and top plate temperatures, the Nu(Ra) is proportional to Ra(γ) displays spurious crossover to higher γ that might be misinterpreted as a transition to the ultimate Kraichnan regime.

show abstract

Comments on heat transfer efficiency in cryogenic helium turbulent Rayleigh-Bénard convection

Cited by 2 publications

References 11 publications

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

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

Effect of Boundary Layers Asymmetry on Heat Transfer Efficiency in Turbulent Rayleigh-Bénard Convection at Very High Rayleigh Numbers

Contact Info

Product

Resources

About