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Published on: June 1, 2016
Thermal radiation in Rayleigh-Bénard convection experiments
P Urban1, T Králík1, P Hanzelka1
1The Czech Academy of Sciences, Institute of Scientific Instruments, Královopolská 147, Brno, Czech Republic.
Radiative heat transport significantly impacts turbulent Rayleigh-Bénard convection (RBC) scaling near ambient temperatures, altering Nusselt number (Nu) predictions. However, this effect is negligible in cryogenic helium RBC experiments.
Area of Science:
- Thermodynamics
- Fluid Dynamics
- Heat Transfer
Background:
- Turbulent Rayleigh-Bénard convection (RBC) is crucial for understanding heat transport.
- The Nusselt number (Nu) quantifies heat transport efficiency, scaling with Rayleigh (Ra) and Prandtl (Pr) numbers.
- Thermal radiation is often neglected in RBC studies.
Purpose of the Study:
- To analyze the impact of radiative heat transport on turbulent RBC.
- To investigate both near-field and far-field radiation effects.
- To re-evaluate heat transport scaling laws in RBC.
Main Methods:
- Detailed analysis of radiative heat transport in various RBC experiments.
- Inclusion of conventional far-field and enhanced near-field radiation.
- Comparison of scaling laws with and without radiative transport considerations.
Main Results:
- Radiative transport significantly alters the Nusselt number (Nu) versus Rayleigh number (Ra) scaling near ambient temperatures for gases like nitrogen and sulfur hexafluoride.
- The influence of radiative heat transport is negligible in cryogenic helium RBC experiments.
- Near-field radiative heat transport effects were also assessed.
Conclusions:
- Accurate scaling laws for turbulent RBC near ambient conditions require accounting for radiative heat transfer.
- Cryogenic conditions minimize the impact of radiation on RBC heat transport.
- The study highlights the importance of considering all heat transfer mechanisms for precise RBC analysis.
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