Measurement of diffusion and thermal diffusion in ternary fluid mixtures using a two-color optical beam deflection technique

摘要

We have developed a highly sensitive two-color beam deflection setup to measure diffusion andnthermal diffusion in ternary fluid mixtures following a suggestion of Haugen and Firoozabadi u0003J.nPhys. Chem. B 110, 17678 u00012006u0002u0004. Simultaneous detection of two laser beams with differentnwavelengths makes it possible to determine the time dependent concentration profiles of all threencomponents. By comparing the measured beam deflection signals to a numerical solution of thencoupled heat and mass transport equations, the diffusion matrix, the thermal diffusion, and the Soretncoefficients are obtained by a numerical model combined with a nonlinear least-squares fittingnroutine. The results can be improved by additional thermal diffusion forced Rayleigh scatteringnexperiments, which yield a contrast-weighted average thermal diffusion coefficient. The three Soretncoefficients can be obtained independently from the stationary beam deflection amplitudes.nMeasurements have been performed on the symmetric u0001equal weight fractionsu0002 ternary mixturesndodecane/isobutylbenzene/1,2,3,4-tetrahydronaphthalene and 1-methylnaphthalene/octane/decane.nThere is only partial agreement between our results and literature data.