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Titolo: The nearly classical behavior of a pure fluid on the critical isochore very near the critical point under the influence of gravity
Autore: Kurzeja, N; Tielkes, T; Wagner, W;
 Indirizzi:
 Ruhr Univ Bochum, Lehrstuhl Thermodynam, D44780 Bochum, Germany Ruhr UnivBochum Bochum Germany D44780 modynam, D44780 Bochum, Germany Deutsch Bahn AG, Forsch & Technol Zentrum, D80939 Munich, Germany DeutschBahn AG Munich Germany D80939 Zentrum, D80939 Munich, Germany
 Titolo Testata:
 INTERNATIONAL JOURNAL OF THERMOPHYSICS
fascicolo: 2,
volume: 20,
anno: 1999,
pagine: 531  561
 SICI:
 0195928X(199903)20:2<531:TNCBOA>2.0.ZU;2T
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 CRITICAL REGION; SUPPLEMENTARY MEASUREMENTS; SULFURHEXAFLUORIDE; HOMOGENEOUS REGION; CARBONDIOXIDE; DENSITY; GASES;
 Keywords:
 carbon dioxide; critical exponent; critical point; differential pressure; gravity; isothermal compressibility; multicell apparatus; sulfur hexafluoride;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Physical, Chemical & Earth Sciences
 Citazioni:
 22
 Recensione:
 Indirizzi per estratti:
 Indirizzo: Wagner, W Ruhr Univ Bochum, Lehrstuhl Thermodynam, D44780 Bochum, GermanyRuhr Univ Bochum Bochum Germany D44780 44780 Bochum, Germany



 Citazione:
 N. Kurzeja et al., "The nearly classical behavior of a pure fluid on the critical isochore very near the critical point under the influence of gravity", INT J THERM, 20(2), 1999, pp. 531561
Abstract
Comprehensive measurements of the isothermal compressibility along the critical isochore in the critical region of pure sulfur hexafluoride (SF6) andpure carbon dioxide (CO2) were carried out. All measurements were performed with a multicell apparatus, especially designed for ppT measurements in the critical region. The height of the measuring cells was either 30 or 11 mm. Independent of the cell height, we found for both fluids nearly "classical" values for the critical exponent gamma in the limiting approach to the critical point. However, at a certain distance from the critical point {(T  Tc) approximate to 90 mK or tau approximate to 2.82 x 10(4) for SF6 and(T  Tc) approximate to 55 mK or tau approximate to 1.81 x 10(4) for CO2}, we observed a transition to values of the critical exponents which nearly meet the predictions of the renormalizationgroup theory. Since in the fitting range (T  Tc greater than or equal to 1 mK) the correlation length (xi less than or equal to 0.5 mu m) is very much smaller than the geometrical dimensions of the measuring cells, we conclude that the reason for the different behavior is an explicit gravity effect governing the inner critical region. The two different loci of the transition points For sulfur hexafluoride and carbon dioxide can be attributed to the different gravity impacton the fluid corresponding to the different critical densities of the two substances.
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Documento generato il 05/04/20 alle ore 08:43:43