Evaluation of the shadowgraph method for the determination of mutual and thermal diffusivities

Schmidt P, Rausch MH, Wu W, Fröba AP (2024)

Publication Language: English

Publication Type: Journal article, Original article

Publication year: 2024

Journal

Journal of Chemical Physics AIP Publishing

Book Volume: 161

Article Number: 044201

Journal Issue: 4

DOI: 10.1063/5.0218362

Abstract

The present work provides a systematic study on the influence of sample properties and experimental conditions on the reliable accessibility of Fick or mutual diffusion coefficients D11 and thermal diffusivities a in binary liquid mixtures using the shadowgraph method. For this, mixtures with varying magnitudes of the Soret coefficient ST and their optical contrast factors were studied at a temperature of 298.15 K and pressures between (0.1 and 0.65) MPa with varying magnitudes and orientations of the applied temperature and concentration gradients ∇T and ∇c. Experimental signals obtained in these investigations were analyzed with respect to the intensities of the signal contributions from non-equilibrium fluctuations (NEFs) in concentration and temperature, and the reliability of the determined D11 and a data was assessed by comparison to literature data. Larger signal intensities from NEFs and, therefore, a more reliable determination of diffusivities were given for sufficiently large magnitudes of ST, the optical contrast factors, and the applied ∇T and ∇c. At very small fluid layer thicknesses L ≤ 0.30 mm, the associated reduction of signal statistics outweighing the expected increase of signal intensities at larger magnitudes of ∇T and ∇c as well as the influence of confinement imposed limitations for the determination of diffusivities in some cases. Furthermore, an influence of the mixture composition on signal intensities from concentration-NEFs was identified, where too small mole fractions of one component can hinder the determination of D11 in mixtures with small magnitudes of the optical contrast factor (∂n/∂c)T,p

Authors with CRIS profile

Patrick Schmidt Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP) Michael Rausch Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP) Wenchang Wu Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP) Andreas Paul Fröba Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP)

Additional Organisation(s)

Erlangen Graduate School in Advanced Optical Technologies (SAOT)

Related research project(s)

Development of the shadowgraph method for the accurate determination of diffusivities of fluid mixtures under high pressures and high temperatures Feb. 1, 2021 - March 31, 2024

How to cite

APA:

Schmidt, P., Rausch, M.H., Wu, W., & Fröba, A.P. (2024). Evaluation of the shadowgraph method for the determination of mutual and thermal diffusivities. Journal of Chemical Physics, 161(4). https://doi.org/10.1063/5.0218362

MLA:

Schmidt, Patrick, et al. "Evaluation of the shadowgraph method for the determination of mutual and thermal diffusivities." Journal of Chemical Physics 161.4 (2024).

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