Analysis of Thermodynamic Complexes and Density Data for SF6 on the Saturation Line Near the Critical Point
DOI:
https://doi.org/10.24160/1993-6982-2025-2-91-101Keywords:
critical point, boundary line, liquid density, gas density, scaling model, sulfur hexafluorideAbstract
The article considers complexes containing the properties (liquid and gas densities) of sulfur hexafluoride on the saturation line and representing the order parameter, the average diameter, the ur = fd/fs complex, etc. A number of equations focused on thermophysical (TF) calculations in a wide neighborhood of the critical point (CP) for SF6 are studied
The purpose of the research is, first, to estimate the errors of data on SF6 in the range (2 10-8< τ <10-2). In so doing, it is planned to use reliable experimental values and recommendations of the critical phenomena scaling theory (ST). Second, it is planned to clarify the functions fs(τ), fd(τ), Dρl(τ), ... and to estimate numerically some thermodynamic complexes in the specified temperature range. In accordance with the chosen purpose, problems I–III were analyzed. From the methodological point of view, several stages were carried out:
- setting up of the initial data array containing reliable experimental data in the range
2 10-8< τ <0.3; - development of empirical equations Zl eff(x1, x2, τ), Zg eff(x1, x2, τ), which have a simple structure and contain the coefficients x1, x2 calculated by statistically processing the experimental data;
- elaboration of the methodology aimed at finding the coefficients x1, x
Within the framework of solving problems I and II, numerical information on the binodal shape was obtained when using the coordinates Dρl, |Dρg|, τ and Zl, Zg, urbas. Some advantages of the second version of coordinates over the first one are shown.
As a result of solving problem III, the empirical functions Zl eff(x1, x2, τ) and Zg eff(x1, x2, τ) are constructed. On their basis, numerical data are obtained, which confirm that these functions meet the requirements of ST in the CP neighborhood. Some applied calculations are performed, in which these empirical models are used.
The proposed methodological developments and the results of the performed calculations are of interest for specialists in thermal physics who work on CT problems, including those who perform various calculations focused on the thermodynamic properties of SF6 in the CT neighborhood.
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Для цитирования: Рыков С.В., Кудрявцева И.В., Устюжанин Е.Е., Очков В.Ф., Рыков В.А. Анализ термодинамических комплексов и данных о плотности на линии насыщения в окрестности критической точки SF6 // Вестник МЭИ. 2025. № 2. С. 91—101. DOI: 10.24160/1993-6982-2025-2-91-101
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Конфликт интересов: авторы заявляют об отсутствии конфликта интересов
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7. Vorob’ev V.S. e. a. Study of the Phase Boundary for C6F6 and SF6 under Microgravity. High Temp. 2020;58:333—341.
8. Lecoutre C. e. a. Near-critical Density Filling of the SF6 Fluid Cell for the ALI-R-DECLIC Experiment in Weightlessness. Proc. 68th Intern. Astronautical Congress. Adelaïde, 2017:1—11.
9. Oprisan A., Garrabos Y., Lecoutre C., Beysens D. Pattern Evolution During Double Liquid-vapor Phase Transitions Under Weightlessness. Molecules. 2017;22(6):947.
10. Weiner J., Langley K.H., Ford Jr.N.C. Experimental Evidence for a Departure from the Law of the Rectilinear Diameter. Phys. Rev. Lett. 1974;32:879—884.
11. Kurzeja N., Tielkes T., Wagner W. The Nearly Classical Behavior of a Pure Fluid on the Critical Isochore Very Near the Critical Point under the Influence of Gravity. Int. J. Thermophys. 1999;20:531—561.
12. Guder C., Wagner W. A Reference Equation of State for the Thermodynamic Properties of Sulfur Hexafluoride (SF6) for Temperatures from the Melting Line to 625 K and Pressures up to 150 MPa. J. Phys. Chem. Ref. Data. 2009;38(1):33—94
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For citation: Rykov S.V., Kudryavtseva I.V., Ustyuzhanin E.E., Ochkov V.F., Rykov V.A. Analysis of Thermodynamic Complexes and Density Data for SF6 on the Saturation Line Near the Critical Point. Bulletin of MPEI. 2025;2:91—101. (in Russian). DOI: 10.24160/1993-6982-2025-2-91-101
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Conflict of interests: the authors declare no conflict of interest
