0383815 - ÚPT 2013 RIV US eng J - Journal Article
Urban, Pavel - Hanzelka, Pavel - Králík, Tomáš - Musilová, Věra - Srnka, Aleš - Skrbek, L.
Effect of Boundary Layers Asymmetry on Heat Transfer Efficiency in Turbulent Rayleigh-Bernard Convection at Very High Rayleigh Numbers.
Physical Review Letters. Roč. 109, č. 15 (2012), 154301:1-4. ISSN 0031-9007. E-ISSN 1079-7114
R&D Projects: GA ČR GPP203/12/P897; GA MŠMT ED0017/01/01
Institutional support: RVO:68081731
Keywords : thermal-convection
Subject RIV: BK - Fluid Dynamics
Impact factor: 7.943, year: 2012

The heat transfer efficiency in turbulent Rayleigh-Benard 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) less than or similar to Ra less than or similar to 10(15) the Nusselt number closely follows Nu 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) proportional to Ra-gamma displays spurious crossover to higher gamma that might be misinterpreted as a transition to the ultimate Kraichnan regime.
Permanent Link: http://hdl.handle.net/11104/0213647