scholarly journals Simplified Shape Factors for a Thermal Diffusion Column

1965 ◽  
Vol 20 (4) ◽  
pp. 521-526 ◽  
Author(s):  
C. J. G. Slieker
Keyword(s):  
Thermal Diffusion ◽  
Transport Coefficients ◽  
Experimental Results ◽  
Separation Processes ◽  
Shape Factors ◽  
Mean Temperature ◽  
Diffusion Column ◽  
The Mean

Starting from COHEN’S theory of square cascades and countercurrent separation processes, column constants for the three types of thermal diffusion columns are calculated. It is assumed that the transport coefficients may be regarded as constants, whereas their values are taken at the mean temperature in the column. By comparison with other theories and experimental results our simplified theory appears to be as good as the more refined ones.

Analysis of Turbulent Thermal Convection Between Horizontal Plates

1983 ◽  
Vol 105 (4) ◽  
pp. 789-794 ◽  
Author(s):  
M. Kaviany ◽  
R. Seban
Keyword(s):  
Temperature Distribution ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Thermal Convection ◽  
Equation Model ◽  
Experimental Results ◽  
Mixing Length ◽  
Mean Temperature ◽  
The Mean ◽  
The One

The one-equation model of turbulence is applied to the turbulent thermal convection between horizontal plates maintained at constant temperatures. A pseudo-three-layer model is used consisting of a conduction sublayer adjacent to the plates, a turbulent region within which the mixing length increases linearly, and a turbulent core within which the mixing length is a constant. It is assumed that the Nusselt number varies with the Rayleigh number to the one-third power. As a result, the steady-state distributions of the turbulent kinetic energy and the mean temperature are obtrained and presented in closed forms. These results include the effects of Prandtl number. The predictions are compared with the available experimental results for different Prandtl and Rayleigh numbers. Also included are the predictions of Kraichnan, which are based on a less exact analysis. The results of the one-equation model are in fair agreement with the experimental results for the distribution of the turbulent kinetic energy and the mean temperature distribution. The predictions of Kraichnan are in better agreement with the experimental results for the mean temperature distribution.

Turbulent Thermal Diffusion Over a Locally-Heated Two-Dimensional Hill

2010 ◽  
Author(s):  
T. Houra ◽  
Y. Nagano ◽  
M. Tagawa
Keyword(s):  
Thermal Diffusion ◽  
Passive Scalar ◽  
Heated Wall ◽  
Windward Side ◽  
Two Dimensional ◽  
Hill Model ◽  
Mean Temperature ◽  
The Mean ◽  
The Hill ◽  
Heated Case

We measure flow and thermal fields over a locally heated two-dimensional hill. The heated sections on the wall are divided into upstream and downstream portions of the hill model. These sections are heated independently, yielding various thermal boundary conditions in contrast to the uniformly heated case. In the separated region formed behind the hill, it is found that the mean temperature profiles in the uniformly heated case are well decomposed into the separately heated cases. This is because the velocity fluctuation produced by the shear layer formed behind the hill is large, so the superposition of a passive scalar in the thermal field can be successfully realized. The rapid increase in the mean temperature near the uniformly heated wall should be due to the heat transfer near the leeward slope of the hill. On the other hand, the mean temperature distributions away from the wall are strongly affected by the turbulent thermal diffusion on the windward side of the hill.

Thermal Diffusion in Mixtures of Alcohols and Aromatic Hydrocarbons

1971 ◽  
Vol 26 (1) ◽  
pp. 48-51 ◽  
Author(s):  
P. S. Belton ◽  
H. J. V. Tyrrell
Keyword(s):  
Temperature Gradient ◽  
Thermal Diffusion ◽  
Aromatic Hydrocarbons ◽  
Thermal Gradient ◽  
Average Degree ◽  
Quantitative Interpretation ◽  
Mean Temperature ◽  
The Mean ◽  
Degree Of Association

Abstract The thermal diffusion factors observed for these systems vary considerably with concentration, and frequently show a change in sign at some concentration. New data on ethanol-toluene mixtures show that the sign and magnitude of the separation of the components in a thermal gradient are also strongly dependent on the mean temperature of the system. These observations, together with earlier ones on similar systems, can be given a semi-quantitative interpretation in terms of a shift in the average degree of association of the alcohol along the temperature gradient.

Experimental Study of Turbulent Transport in Non-Isothermal Oscillating Grids Turbulence Using Particle Image Velocimetry

2003 ◽  
Author(s):  
Alexander Eidelman ◽  
Tov Elperin ◽  
Nathan Kleeorin ◽  
Alexander Krein ◽  
Igor Rogachevskii ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Spatial Distribution ◽  
Temperature Gradient ◽  
Thermal Diffusion ◽  
Particle Image ◽  
Turbulent Transport ◽  
Mean Temperature ◽  
Image Velocimetry ◽  
Oscillating Grids ◽  
The Mean

An oscillating grids turbulence generator was constructed for studies of a new effect associated with turbulent transport of inertial particles — turbulent thermal diffusion. This phenomenon was predicted theoretically in Phys. Rev. Lett. 76, 224 (1996) and has been detected experimentally in oscillating grids turbulence with an imposed mean temperature gradient in air flow. This effect implies an additional mean flux of particles in the direction opposite to the mean temperature gradient and results in formation of large-scale inhomogeneities in the spatial distribution of particles. We used Particle Image Velocimetry to determine the turbulent velocity field and an Image Processing Technique to determine the spatial distribution of particles. Velocity distributions were measured in the flow generated with one and two grids in the Oscillating Grids Turbulence Generators at RWTH (Aachen) and BGU (Beer-Sheva). Analysis of the intensity of laser light Mie scattering by particles showed that they are accumulated in the vicinity of the minimum of the mean temperature of the surrounding fluid. The latter finding confirms the existence of the effect of turbulent thermal diffusion predicted theoretically.

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