Conference paper · Journal article
Theoretical and experimental comparison of the Soret coefficient for water-methanol and water-ethanol binary mixtures
Toronto Metropolitan University1
Department of Chemical and Biochemical Engineering, Technical University of Denmark2
Center for Phase Equilibria and Separation Processes, Department of Chemical and Biochemical Engineering, Technical University of Denmark3
University of Toronto4
Center for Energy Resources Engineering, Centers, Technical University of Denmark5
In multicomponent. mixtures, a much richer variety of phenomena can occur than in Simple (single-component) fluids. Natural convection in single-component. fluids is due to buoyancy forces caused by temperature gradients. In multicomponent mixtures, buoyancy forces may also be caused by concentration gradients.
Because natural convection, molecular diffusion, and thermal conduction have different relaxation time scales, a wide variety of resulting convective motions and heat, and mass distributions might occur. In some fluid mixtures such as water-ethanol system, for instance, ethanol diffuses much more slowly than heat, and because of this difference in time scales oscillatory convection might occur.
In a multocomponent mixture, the total molar flux consists of two parts: the convective molar flux and the diffusive molar flux (resulting from the difference between the component, velocity and the bulk velocity). The diffussion molar flux of a component depends, not only, on its own mole fraction gradient (Fickian diffusion). but also on the gradient of all the components present in the mixture (cross-molecular diffusion).
The diffusion flux depends also on the pressure gradient (pressure diffusion; the so-called -gravitational effect) and temperature gradient (thermal diffusion; the so-called Soret effect). Firoozabadi's thermal diffusion model was applied to calculate the Soret coefficient, as well as the thermal diffusion coefficient and molecular diffusion coefficient for methanol-water and ethanol-water mixtures at 310.6.5 K temperature and 1 bar pressure with 10% water mass fraction.
The results were compared with experimental data (J.K. Platten. in Proceedings of the 5th, International Meeting on Thermodiffusion, (IMT5); Lyngby Aug. 2002 Philos. Mag. 83. Nos. 17-18 (2003)), as well as theoretical predictions with other models. A better agreement with the experimental data using the Firoozabadi model was achieved.
Language: | English |
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Publisher: | Società Italiana di Fisica |
Year: | 2004 |
Pages: | 241-247 |
Proceedings: | International Meeting on Thermal Forces |
ISSN: | 1292895x and 12928941 |
Types: | Conference paper and Journal article |
DOI: | 10.1140/epje/i2004-10063-7 |
ORCIDs: | Stenby, Erling Halfdan |
05.60.-k Transport process 05.70.-a Thermodynamics 65.20.+w Thermal properties of liquids: heat capacity, thermal expansion, etc. Biophysics/Biomedical Physics Biotechnology Nonlinear Dynamics, Complex Systems, Chaos, Neural Networks Physical Chemistry Physics Polymer Sciences Soft Matter, Complex Fluids Surfaces and Interfaces, Thin Films