Enskog theory for multicomponent mixtures. IV. Thermal diffusion

Journal Article · Thu Jan 15 04:00:00 EST 1987 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.452243· OSTI ID:6680331

Kincaid, J M; Cohen, E G.D.; Lopez de Haro, M

Using the revised Enskog theory we derive equations for the thermal diffusion ratios k/sub T//sub i/ and thermal diffusion factors ..cap alpha../sub i//sub j/ of multicomponent hard-sphere mixtures for systems in mechanical equilibrium. The first ten Enskog approximations to the thermal diffusion factor ..cap alpha../sub i//sub j/(N) (N = 1,2,...,10) are evaluated numerically for a variety of system parameter choices appropriate to binary and ternary mixtures. We find that the first Enskog approximation does not vanish; the sequence of Enskog approximations converges most rapidly when the mass of the spheres are nearly equal. The seventh Enskog approximation was estimated to lie within about 1% of the exact value for all choices of system parameters. A comprehensive numerical study of the properties of the thermal diffusion factor for binary mixtures is given, including special mixtures such as the dusty gas, the Lorentz, quasi-Lorentz and Rayleigh gases, and isotopic mixtures. Particular emphasis is placed on showing how the properties of ..cap alpha../sub 12/ change as the density is increased. The most striking difference between the low-density (Boltzmann) and high-density values for ..cap alpha../sub 12/ is that the region of the mass ratio: diameter ratio plane for which ..cap alpha../sub 12/ is either strictly positive or negative, as a function of composition, is much smaller at high densities. Also, at higher densities ..cap alpha../sub 12/ is not a monotonic function of the mole fraction. For ternary mixtures in which two of the components are isotopes we show how the properties of the third component affect the separation of the two isotopes.

• Research Organization: Thermophysics Division, National Bureau of Standards, Gaithersburg, Maryland 20899
• OSTI ID: 6680331
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 86:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640410 -- Fluid Physics-- General Fluid Dynamics
657000* -- Theoretical & Mathematical Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHAPMAN-ENSKOG THEORY
DIFFUSION
DISPERSIONS
FLUIDS
HARD-SPHERE MODEL
MIXTURES
THERMAL DIFFUSION
TRANSPORT THEORY