Thermal concentration gradients and the thermal diffusion ratio in3He-4He mixtures near the tricritical point

1977 ◽  
Vol 28 (3-4) ◽  
pp. 349-358 ◽  
Author(s):  
D. Roe ◽  
H. Meyer
Keyword(s):  
Thermal Diffusion ◽  
Tricritical Point ◽  
Concentration Gradients ◽  
Thermal Diffusion Ratio

The stability of a layer of binary gas mixture heated below

1973 ◽  
Vol 57 (1) ◽  
pp. 103-110 ◽  
Author(s):  
M. L. Lawson ◽  
Wen-Jei Yang
Keyword(s):  
Thermal Diffusion ◽  
Soret Effect ◽  
Weight Ratio ◽  
Gas Mixture ◽  
Vertical Temperature ◽  
Dilute Gas ◽  
Binary Gas Mixture ◽  
Transfer Equations ◽  
The Stability ◽  
Thermal Diffusion Ratio

This paper investigates the Bénard problem in a binary mixture of dilute gases in which an imposed vertical temperature gradient induces a concentration gradient owing to the thermal diffusion effect. The transfer equations are derived by first-order perturbation theory which leads to instability criteria. Numerical results indicate that instability will set in only as stationary convection. This is distinctly different from the cases of liquids and concentrated gases, in which the thermal diffusion (or Soret) effect gives rise to oscillatory instability. It is disclosed in the study that the destabilization of the dilute gas-mixture layer is enhanced by an increase in the thermal diffusion ratio and/or the molecular weight ratio of the species.

scholarly journals An elementary theory of thermal diffusion

1942 ◽  
Vol 179 (979) ◽  
pp. 461-469 ◽  
Keyword(s):  
Thermal Diffusion ◽  
Approximate Formula ◽  
Physical Mechanism ◽  
Elementary Theory ◽  
Rigorous Theory ◽  
Thermal Diffusion Ratio

Although a rigorous theory of thermal diffusion has been developed by Chapman and Enskog, it is desirable to have an approximate but elementary theory which reveals the physical mechanism of the phenomenon. This is given in the present paper by the application of a method similar to that used by Meyer for the treatment of ordinary diffusion in gases. It leads to an approximate formula for the thermal diffusion ratio, a discussion of which shows that it accounts for many of the characteristic properties of thermal diffusion.

scholarly journals Thermal diffusion in hydrogen-deuterium mixtures

1941 ◽  
Vol 178 (974) ◽  
pp. 390-399 ◽  
Keyword(s):  
Experimental Evidence ◽  
Thermal Diffusion ◽  
General Expression ◽  
Lorentz Gas ◽  
Repulsive Force ◽  
Hydrogen Deuterium ◽  
Thermal Diffusion Ratio ◽  
Made In

The separation produced by thermal diffusion in hydrogen-deuterium mixtures has been measured at temperatures between — 183 and 425° C, and the thermal diffusion ratio R T found. Theoretical values of R T for the same mixture have been calculated for various values of the force index v from Chapman’s general expression appropriate to molecules behaving as point centres of repulsive force F = κr-v . The evaluation of R T in this way is possible only for isotopic mixtures, in which the interactions between like and between unlike molecules are the same. Comparison of the experimental value of with these theoretical values indicates that the fields of the hydrogen and deuterium molecules have an index v = 12.6. This agrees with the value v = 12.5 deduced from viscosity results. It is higher than the value v = 8.5, which is found if the theoretical values of R T for a Lorentz gas are assumed to apply—an assumption necessarily made in the case of the non-isotopic mixtures examined so far. This result suggests that the discrepancies between values of v hitherto deduced from thermal diffusion measurements and those expected from viscosity values are attributable to this assumption. The calculation shows that R T depends slightly on the concentration of the mixture, a point on which the experimental evidence is inconclusive.

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