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Development of the shadowgraph method for the accurate determination of diffusivities of fluid mixtures under high pressures and high temperatures

Subject Area Technical Thermodynamics
Term from 2017 to 2024
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 379151958
 
Final Report Year 2024

Final Report Abstract

In the first funding period, it has been shown for the first time that the shadowgraph method allows the simultaneous determination of the Fick diffusion coefficient D11, the thermal diffusivity a, the Soret coefficient ST, and the kinematic viscosity ν of fluid mixtures in a single thermodiffusion experiment by the analysis of the dynamics of non-equilibrium fluctuations. Considering restrictions regarding ST and ν and refining the available experimental and data evaluation approach, the second funding period aimed at the accurate determination of D11 and a in binary mixtures exhibiting a broad range of ST and signal intensities. After a revision of the experimental setup to increase the accessible temperature and concentration gradients, studies on mixtures with systematically varied ST and refractive index differences of their pure components helped to achieve this goal. On this basis, 99 D11 and 140 a data for binary hydrocarbon mixtures were determined with average uncertainties of (12.9 and 8.0)% over a wide range of temperatures and pressures, from which structure-property relationships were derived.

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