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| Description
| - We present experimental results on the heat transfer efficiency of cryogenic turbulent Rayleigh-Benard 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 Nu = Nu(Ra, Pr) is investigated for the range of Rayleigh number 10(6) < Ra < 10(15), with the Prandtl number varying such that 0.7 <= Pr < 15, using cryogenic He-4 gas with well-known and in situ tunable properties as a working fluid. For 7.2 x 10(6) < Ra < 10(11) our data (both corrected and uncorrected) agree with suitably corrected data from similar cryogenic experiments and are consistent with Nu proportional to Ra-2/7. Up to Ra similar or equal to 10(12), our data could be treated as Oberbeck-Boussinesq data. For Ra > 10(12), the heat transfer efficiency becomes affected by non-Oberbeck-Boussinesq (NOB) effects, causing asymmetry of the top and bottom boundary layers. For 10(12) <= Ra <= 10(15), the Nusselt number closely follows Nu proportional to Ra-1/3 if Nu and Ra are evaluated on the basis of the working fluid properties at the directly measured bulk temperature, T-c, and suitable corrections are taken into account. In contrast, if the mean temperature is determined as an arithmetic mean of the bottom and top plate temperatures, Nu(Ra) proportional to Ra-gamma displays spurious crossover to higher. that might be misinterpreted as a transition to the ultimate Kraichnan regime. The second step of our analysis, reported here for the first time, is to ignore the NOB effects affecting the top half of the RBC cell. We replace it by the inverted nearly OB bottom half in order to eliminate the boundary layer asymmetry. This leads to the effective temperature difference Delta T-eff = 2(T-b - T-c) where T-b denotes the bottom plate temperature, and to effective Nu(eff) and Ra-eff values.
- We present experimental results on the heat transfer efficiency of cryogenic turbulent Rayleigh-Benard 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 Nu = Nu(Ra, Pr) is investigated for the range of Rayleigh number 10(6) < Ra < 10(15), with the Prandtl number varying such that 0.7 <= Pr < 15, using cryogenic He-4 gas with well-known and in situ tunable properties as a working fluid. For 7.2 x 10(6) < Ra < 10(11) our data (both corrected and uncorrected) agree with suitably corrected data from similar cryogenic experiments and are consistent with Nu proportional to Ra-2/7. Up to Ra similar or equal to 10(12), our data could be treated as Oberbeck-Boussinesq data. For Ra > 10(12), the heat transfer efficiency becomes affected by non-Oberbeck-Boussinesq (NOB) effects, causing asymmetry of the top and bottom boundary layers. For 10(12) <= Ra <= 10(15), the Nusselt number closely follows Nu proportional to Ra-1/3 if Nu and Ra are evaluated on the basis of the working fluid properties at the directly measured bulk temperature, T-c, and suitable corrections are taken into account. In contrast, if the mean temperature is determined as an arithmetic mean of the bottom and top plate temperatures, Nu(Ra) proportional to Ra-gamma displays spurious crossover to higher. that might be misinterpreted as a transition to the ultimate Kraichnan regime. The second step of our analysis, reported here for the first time, is to ignore the NOB effects affecting the top half of the RBC cell. We replace it by the inverted nearly OB bottom half in order to eliminate the boundary layer asymmetry. This leads to the effective temperature difference Delta T-eff = 2(T-b - T-c) where T-b denotes the bottom plate temperature, and to effective Nu(eff) and Ra-eff values. (en)
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| Title
| - 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 (en)
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| skos:prefLabel
| - 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 (en)
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| skos:notation
| - RIV/68081731:_____/14:00430597!RIV15-GA0-68081731
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| http://linked.open...avai/riv/aktivita
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| http://linked.open...avai/riv/aktivity
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| http://linked.open...iv/cisloPeriodika
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| http://linked.open...vai/riv/dodaniDat
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| http://linked.open...aciTvurceVysledku
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| http://linked.open.../riv/druhVysledku
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| http://linked.open...iv/duvernostUdaju
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| http://linked.open...titaPredkladatele
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| http://linked.open...dnocenehoVysledku
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| http://linked.open...ai/riv/idVysledku
| - RIV/68081731:_____/14:00430597
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| http://linked.open...riv/jazykVysledku
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| http://linked.open.../riv/klicovaSlova
| - Rayleigh-Bénard convection; heat transfer efficiency; cryogenic helium (en)
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| http://linked.open.../riv/klicoveSlovo
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| http://linked.open...odStatuVydavatele
| - DE - Spolková republika Německo
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| http://linked.open...ontrolniKodProRIV
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| http://linked.open...i/riv/nazevZdroje
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| http://linked.open...in/vavai/riv/obor
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| http://linked.open...ichTvurcuVysledku
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| http://linked.open...cetTvurcuVysledku
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| http://linked.open...vavai/riv/projekt
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| http://linked.open...UplatneniVysledku
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| http://linked.open...v/svazekPeriodika
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| http://linked.open...iv/tvurceVysledku
| - Hanzelka, Pavel
- Králík, Tomáš
- Musilová, Věra
- Skrbek, L.
- Srnka, Aleš
- Urban, Pavel
- La Mantia, M.
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| http://linked.open...ain/vavai/riv/wos
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| issn
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| number of pages
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| http://bibframe.org/vocab/doi
| - 10.1088/1367-2630/16/5/053042
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