Temperature dependence of Soret and diffusion coefficients for toluene-cyclohexane mixture measured in convection-free environment

We report on the measurement of diffusion (D), Soret (S-T), and thermodiffusion (D-T) coefficients in toluene-cyclohexane mixture with mass fraction of toluene 0.40 onboard of the International Space Station. The coefficients were measured in the range of the mean temperatures between 20 degrees C and 34 degrees C. The Soret coefficient is negative within the investigated temperature range and its absolute value vertical bar S-T vertical bar decreases with increasing temperature. The diffusion coefficient for this system increases with temperature rising. For comparison, the temperature dependence of diffusion coefficient was measured in ground laboratory using counter-flow cell technique and revealed a good agreement with microgravity results. A non-direct comparison of the measured onboard Soret coefficients with different systems indicated a similar trend for the temperature dependent behavior. Unexpected experimental finding is that for this system the thermodiffusion coefficient D-T does not depend on temperature. (C) 2015 AIP Publishing LLC.