Thermal Radiation in Rayleigh-B\'{e}nard Convection Experiments

• Main Authors: Urban, P, Králík, T, Hanzelka, P, Musilová, V, Věžník, T, Schmoranzer, D, Skrbek, L
• Format: Journal Article
• Language: English
• Published: 15-01-2020
• Subjects: Physics - Fluid Dynamics; Physics - Optics
• DOI: 10.48550/arxiv.2001.05181

Phys. Rev. E 101, 043106 (2020) An important question in turbulent Rayleigh-B\'{e}nard convection (RBC) is
the effectiveness of convective heat transport, which is conveniently described
via the scaling of the Nusselt number (${\rm{Nu}}$) with the Rayleigh
(${\rm{Ra}}$) and Prandtl (${\rm{Pr}}$) numbers. In RBC experiments, the heat
supplied to the bottom plate is also partly transferred by thermal radiation.
This heat transport channel, acting in parallel with the convective and
conductive heat transport channels, is usually considered insignificant and
thus neglected. Here we present a detailed analysis of conventional far-field
as well as strongly enhanced near-field radiative heat transport occurring in
various RBC experiments, and show that the radiative heat transfer partly
explains differences in ${\rm{Nu}}$ measured in different experiments. A
careful inclusion of the radiative transport appreciably changes the
${\rm{Nu}}={\rm{Nu}}({\rm{Ra}})$ scaling inferred in turbulent RBC experiments
near ambient temperature utilizing gaseous nitrogen and sulphur hexafluoride as
working fluids. On the other hand, neither the conventional far-field radiation
nor the strongly enhanced near-field radiative heat transport appreciably
affects the heat transport law deduced in cryogenic helium RBC experiments.