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Heat transport in turbulent Rayleigh-Bnard convection: Effect of finite top-and bottom-plate conductivities
 

Summary: Heat transport in turbulent Rayleigh-Bénard convection:
Effect of finite top- and bottom-plate conductivities
Eric Brown, Alexei Nikolaenko, Denis Funfschilling, and Guenter Ahlers
Department of Physics and Institute for Quantum Engineering, Science, and Technology (iQUEST),
University of California, Santa Barbara, California 93106
Received 25 January 2005; accepted 11 May 2005; published online 6 July 2005
We describe three apparatus, known as the large, medium, and small apparatus, used for
high-precision measurements of the Nusselt number N as a function of the Rayleigh number R for
cylindrical samples of fluid and present results illustrating the influence of the finite conductivity of
the top and bottom plates on the heat transport in the fluid. We used water samples at a mean
temperature of 40 °C Prandtl number =4.4 . The samples in the large apparatus had a diameter
D of 49.69 cm and heights L 116.33, 74.42, 50.61, and 16.52 cm. For the medium apparatus we
had D=24.81 cm, and L=90.20 and 24.76 cm. The small apparatus contained a sample with D
=9.21 cm and L=9.52 cm. For each aspect ratio D/L the data covered a range of a little over
a decade of R. The maximum R 1 1012
with Nusselt number N 600 was reached for
=0.43. Measurements were made with both aluminum conductivity p=161 W/m K and copper
p=391 W/m K top and bottom plates of nominally identical size and shape. For the large and
medium apparatus the results with aluminum plates fall below those obtained with copper plates,
thus confirming qualitatively the prediction by Verzicco, "Effects of nonperfect thermal sources in

  

Source: Ahlers, Guenter - Department of Physics, University of California at Santa Barbara

 

Collections: Physics