Negative nonlinearity in selected fluorocarbons

Cramer, M. S.

doi:10.1063/1.857514

Cited by 100 publications

(57 citation statements)

References 9 publications

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“…32 Yet the interpretation of the results presented in Refs. 5 and 32 has been challenged by Cramer, 33 Thompson, 29 Fergason et al 34,35 and the observed wavefield is now believed to be related to both critical point and two-phase nonclassical effects.…”

Section: Introductionmentioning

confidence: 99%

Molecular interpretation of nonclassical gas dynamics of dense vapors under the van der Waals model

Colonna

Guardone

2006

Physics of Fluids

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The van der Waals polytropic gas model is used to investigate the role of attractive and repulsive intermolecular forces and the influence of molecular complexity on the possible nonclassical gas dynamic behavior of vapors near the liquid-vapor saturation curve. The decrease of the sound speed upon isothermal compression is due to the well-known action of the van der Waals attractive forces and this effect is shown here to be comparatively larger for more complex molecules with a large number of active vibrational modes; for these fluids isentropic flows are in fact almost isothermal. Contributions to the speed of sound resulting from intermolecular forces and the role of molecular complexity are analyzed in details for both isothermal and isentropic transformations. Results of the exact solution to the problem of a finite pressure perturbation traveling in a still fluid are presented in three exemplary cases: ideal gas, dense gas and nonclassical gas behavior. A classification scheme of fluids based on the possibility of exhibiting different gas dynamic behaviors is also proposed.

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Section: Introductionmentioning

confidence: 99%

Molecular interpretation of nonclassical gas dynamics of dense vapors under the van der Waals model

Colonna

Guardone

2006

Physics of Fluids

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“…Starting from the pioneering work of Lambrakis and Thompson, 21 many studies [22][23][24][25] relied upon various thermodynamic models to compute the value of ⌫ for several commercially available fluids in order to identify the most promising ones for both applications and experiments. The fluids under investigation were organic compounds and belong to the class of the alkanes, the ethers, the perfluorocarbons, and the siloxanes.…”

Section: Introductionmentioning

confidence: 99%

Siloxanes: A new class of candidate Bethe-Zel’dovich-Thompson fluids

2007

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This paper presents a new class of Bethe-Zel'dovich-Thompson fluids, which are expected to exhibit nonclassical gasdynamic behavior in the single-phase vapor region. These are the linear and cyclic siloxanes, light silicon oils currently employed as working fluids in organic Rankine cycle turbines. State-of-the-art multiparameter equations of state are used to describe the thermodynamic properties of siloxanes and to compute the value of the fundamental derivative of gasdynamics ⌫, whose negative sign is the herald of nonclassical gasdynamics. Siloxane fluids starting from D 6 and cyclic siloxanes of greater complexity, and MD 3 M and linear siloxanes of greater complexity are predicted to exhibit a thermodynamic region in which ⌫ is negative and hence nonclassical wavefields are admissible. As an exemplary case, a nonclassical rarefaction shock wave propagating in fluid D 6 is studied to demonstrate the possibility of using siloxane fluids in nonclassical gasdynamic applications and to experimentally verify the existence of nonclassical wavefields in the vapor phase. The sensitivity of the present results to the considered thermodynamic model of the fluid is also briefly discussed.

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“…These complex equations, whose accuracy in computing the value of Γ has been discussed by Colonna et al (under review), have been applied to the selected linear and cyclic siloxane and perfluorocabons fluids listed in table 1, where relevant thermophysical properties are also reported for the reader's convenience. Additional information on the thermophysical properties of these fluids and their gasdynamic behaviour can be found in Nannan et al (2007) and Colonna et al ( , 2008b for siloxanes and Lambrakis & Thompson (1972), Cramer (1989Cramer ( , 1991 and Guardone & Argrow (2005) for perfluorocarbons. The minimum value of Γ obtained from the three thermodynamic models is also reported.…”

Section: Results For Selected Siloxanes and Perfluorocarbonsmentioning

confidence: 99%

“…These complex models include various thermophysical parameters, such as the acentric factor ω, in their functional forms, and therefore the number of active degrees of freedom, N, no longer represents molecular complexity, as discussed by Guardone & Argrow (2005). Therefore, the minimum value of the fundamental derivative in the vapour phase, Γ min , which occurs at a state point along the VLE line, is used in the following Stewart, Jacobsen & Penocello (1969), Lambrakis & Thompson (1972), Cramer (1989Cramer ( , 1991, Guardone & Argrow (2005), Nannan et al (2007) and Colonna et al ( , 2008b.…”

Section: Results For Selected Siloxanes and Perfluorocarbonsmentioning

confidence: 99%

Maximum intensity of rarefaction shock waves for dense gases

2009

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Modern thermodynamic models indicate that fluids consisting of complex molecules may display non-classical gasdynamic phenomena such as rarefaction shock waves (RSWs) in the vapour phase. Since the thermodynamic region in which non-classical phenomena are physically admissible is finite in terms of pressure, density and temperature intervals, the intensity of RSWs is expected to exhibit a maximum for any given fluid. The identification of the operating conditions leading to the RSW with maximum intensity is of paramount importance for the experimental verification of the existence of non-classical phenomena in the vapour phase and for technical applications taking advantage of the peculiarities of the non-classical regime. This study investigates the conditions resulting in an RSW with maximum intensity in terms of pressure jump, wave Mach number and shock strength. The upstream state of the RSW with maximum pressure drop is found to be located along the double-sonic locus formed by the thermodynamic states associated with an RSW having both pre-and post-shock sonic conditions. Correspondingly, the maximumMach thermodynamic and maximum-strength loci locate the pre-shock states from which the RSW with the maximum wave Mach number and shock strength can originate. The qualitative results obtained with the simple van der Waals model are confirmed with the more complex Stryjek-Vera-Peng-Robinson, Martin-Hou and Span-Wagner equations of state for selected siloxane and perfluorocarbon fluids. Among siloxanes, which are arguably the best fluids for experiments aimed at the generation and measurement of an RSW, the state-of-the-art Span-Wagner multiparameter equation of state predicts a maximum wave Mach number close to 1.026 for D 6 (dodecamethylcyclohexasiloxane, [O-Si-(CH 3 ) 2 ] 6 ). Such value is well within the capacity of the measurement system of a newly built experimental set-up aimed at the first-ever demonstration of the existence of RSWs in dense vapours.

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Negative nonlinearity in selected fluorocarbons

Cited by 100 publications

References 9 publications

Molecular interpretation of nonclassical gas dynamics of dense vapors under the van der Waals model

Molecular interpretation of nonclassical gas dynamics of dense vapors under the van der Waals model

Siloxanes: A new class of candidate Bethe-Zel’dovich-Thompson fluids

Maximum intensity of rarefaction shock waves for dense gases

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