Soret effect in ternary fluids

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Heat and mass transport in multicomponent fluids are coupled due to the Soret effect (thermodiffusion). Based on recent experimental developments, with important contribution stemming from the group of the submitter, the investigation of ternary systems has now become feasible. Ternary systems are a first step towards realistic multi component systems. At the same time they are not yet too complex for a theoretical treatment. During the first period of the project a very well performing multicolor OBD instrument (OBD = optical beam deflection) has been developed and successfully been employed for measurements of the so-called benchmark system dodecane-isobutylbenzene-tetrahydronaphtalene (DCMIX1). In the new project period the investigation of this system shall be completed and new model systems shall be investigated. In the focus of interest are the so-called DCMIX-systems methanol-toluene-cyclohexane (DCMIX2) and triethylenglykol-ethanol-water (DCMIX3). A few selected compositions of these systems are presently investigated under microgravity conditions within the framework of an international ESA project with participation of the submitter. An essential aim of the here proposed project is the determination of the diffusion, thermodiffusion and Soret coefficients of these systems within the entire ternary parameter space. The accuracy of the concentration measurement in optical multicolor techniques, like the here employed OBD, decisively depends on the quality of the contrast factor matrix, which needs to be inverted. With the additional knowledge of the density, a theoretically motivated and consistent parameterization of the contrast factors can be achieved. This allows also in a moderately ill-conditioned case for an inversion of the contrast matrix with sufficient accuracy. In collaboration with theoretical groups the concepts developed for binary mixtures will be transfered to ternary systems.