Precise determination of the Soret, thermodiffusion and isothermal diffusion coefficients of binary mixtures of dodecane, isobutylbenzene and 1,2,3,4-tetrahydronaphthalene (contribution of the University of Mons to the benchmark test)

Within the framework of an international benchmark test, the Soret coefficient S-T, the thermodiffusion coefficient D-T, and the isothermal mass diffusion coefficient D of the three binary systems formed with dodecane, isobutylbenzene and 1,2,3,4-tetrahydronaphthalene (with a mass fraction of 0.5 in each component at a temperature of 25degreesC) have been measured. Convective coupling in thermogravitational columns has been used to determine DT based on the Furry-Jones-Onsager theory and the so-called open-ended capillary technique for D. The ratio of DT to D, obtained in these two independent experiments, provides the Soret coefficient. In one case, we were able to use laser Doppler velocimetry to measure the modifications of the velocity amplitude due to thermodiffusion, which is also a way to obtain the Soret coefficient. Our results for these three coefficients are in good agreement with those obtained by other benchmark tests.