Determination of thermal diffusion and molecular diffusion coefficients in n-alkane binary mixtures


D. Alonso de Mezquia1, M. Bou-Ali1, J. Madariaga2, C. Santamaría2 and P. Urteaga1

1Mondragon Goi Eskola Politeknikoa, Spain
2University of Basque Country, Spain

Keywords: thermodiffusion, difusion, Soret
property: thermodiffusion coefficient, difusion coefficient, Soret coefficient
material: liquid mixtures, alkanes

A concentration gradient within a liquid mixture causes a transport of matter known as molecular diffusion. If this transport of matter is caused by a temperature gradient, this phenomenon is known as thermal diffusion. These phenomena have great importance in many fields like the power generation [1,2], petroleum industry [3] or life science [4].

In this work measurements of the transport and thermophysical properties in n-Alkane binary mixtures at 50% mass and molar concentration and 25 ºC have been carried out. The measurement of the thermal diffusion coefficient (DT) has been done using the thermogravitational technique [5], whilst the molecular diffusion coefficient (D) has been determined by the "Sliding Symmetric Tubes" technique [6]. The obtained results have also allowed the indirect determination of the Soret coefficient (ST=DT/D) of the studied mixtures.

Additionally, the results obtained in the measurements of the thermal diffusion coefficient carried out have been compared with the ones obtained with the expression developed by Madariaga et al. [7] for the prediction of these coefficients in normal Alkane mixtures.

The obtained results show that there exists great agreement between the obtained experimental data and the values predicted by the phenomenological law of Madariaga et al [7].

References
  1. E. Turrini, Camino del sol, Cubasolar (ed), (1990)

  2. D. Olander. Chapter 11: Fuel Chemistry, Fundamental aspects of nuclear reactor fuel elements, US Dept. of Energy, 145-171, (1976)

  3. F. Montel Importance de la Thermodiffusion en Exploration et Production Pétrolières, Entropie, 184-185, (1994).

  4. S. Duhr and D. Braun. PNAS, 103(52), (2006)

  5. P. Blanco, M.M. Bou-Ali, J.K. Platten, J.A. Madariaga, P. Urteaga and C. Santamaría. J. Non-Equilib. Thermodyn., 32, (2007)

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