Behavior of the heat capacity C V at the liquid-vapor critical point and in the two-phase region of a thermodynamic system

The prediction of phase equilibria for hydrocarbon/water blends in separators, is a subject of considerable importance for chemical processes. Despite its relevance, there are still pending questions. Among them, is the prediction of the correct number of phases. While a stability analysis using the Gibbs Free Energy of mixing and the NRTL model, provide a good understanding with calculation issues, when using HYSYS V9 and Aspen Plus V9 software, this shows that significant phase equilibrium uncertainties still exist. To clarify these matters, n-octane and water blends, are good surrogates of naphtha/water mixtures. Runs were developed in a CREC vapor–liquid (VL_ Cell operated with octane–water mixtures under dynamic conditions and used to establish the two-phase (liquid–vapor) and three phase (liquid–liquid–vapor) domains. Results obtained demonstrate that the two phase region (full solubility in the liquid phase) of n-octane in water at 100 °C is in the 10-4 mol fraction range, and it is larger than the 10-5 mol fraction predicted by Aspen Plus and the 10-7 mol fraction reported in the technical literature. Furthermore, and to provide an effective and accurate method for predicting the number of phases, a machine learning (ML) technique was implemented and successfully demonstrated, in the present study.

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Deposition of C60, C70 and C84 fullerene molecules, in benzene via a change of the fluid state, from a gas–liquid two phase region to the critical point

The Journal of Supercritical Fluids ◽

10.1016/j.supflu.2011.07.006 ◽

2011 ◽

Vol 58 (3) ◽

pp. 407-411 ◽

Cited By ~ 1

Author(s):

Takahiro Fukuda ◽

Yoshihiro Katsube ◽

Nami Watabe ◽

Shunji Kurosu ◽

Raymond L.D. Whitby ◽

...

Keyword(s):

Critical Point ◽

Phase Region ◽

Two Phase ◽

Fluid State

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Impurity effects on the two-phase isochoric heat capacity of fluids near the critical point

The Journal of Chemical Physics ◽

10.1063/1.1449457 ◽

2002 ◽

Vol 116 (10) ◽

pp. 4202-4211 ◽

Cited By ~ 16

Author(s):

A. Kostrowicka Wyczalkowska ◽

M. A. Anisimov ◽

J. V. Sengers ◽

Y. C. Kim

Keyword(s):

Heat Capacity ◽

Critical Point ◽

Isochoric Heat Capacity ◽

Impurity Effects ◽

Two Phase

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The admissibility domain of rarefaction shock waves in the near-critical vapour–liquid equilibrium region of pure typical fluids

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.197 ◽

2016 ◽

Vol 795 ◽

pp. 241-261 ◽

Cited By ~ 8

Author(s):

Nawin R. Nannan ◽

Corrado Sirianni ◽

Tiemo Mathijssen ◽

Alberto Guardone ◽

Piero Colonna

Keyword(s):

Shock Waves ◽

Critical Point ◽

Compressible Flows ◽

Three Dimensional ◽

Fundamental Equation ◽

Phase Region ◽

Liquid Equilibrium ◽

Two Phase ◽

Rarefaction Shock ◽

Equilibrium Region

Application of the scaled fundamental equation of state of Balfour et al. (Phys. Lett. A, vol. 65, 1978, pp. 223–225) based upon universal critical exponents, demonstrates that there exists a bounded thermodynamic domain, located within the vapour–liquid equilibrium region and close to the critical point, featuring so-called negative nonlinearity. As a consequence, rarefaction shock waves with phase transition are physically admissible in a limited two-phase region in the close proximity of the liquid–vapour critical point. The boundaries of the admissibility region of rarefaction shock waves are identified from first-principle conservation laws governing compressible flows, complemented with the scaled fundamental equations. The exemplary substances considered here are methane, ethylene and carbon dioxide. Nonetheless, the results are arguably valid in the near-critical state of any common fluid, namely any fluid whose molecular interactions are governed by short-range forces conforming to three-dimensional Ising-like systems, including, e.g. water. Computed results yield experimentally feasible admissible rarefaction shock waves generating a drop in pressure from 1 to 6 bar and pre-shock Mach numbers exceeding 1.5.

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The Role of Clustering in the Liquid-Vapor Transition of Mercury

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2014-0515 ◽

2014 ◽

Vol 228 (4-5) ◽

Cited By ~ 1

Author(s):

Friedrich Hensel ◽

Joshua Jortner

Keyword(s):

Binary Mixture ◽

Phase Region ◽

Single Line ◽

Two Dimensional ◽

Two Phase ◽

Liquid Mercury ◽

Dimensional Domain ◽

Liquid Vapor

AbstractThe paper attempts to analyze the implications for the liquid-vapor transition of the recent finding of the coexistence of metallic- and non-metallic domains in liquid mercury. In particular, it is shown that liquid mercury forms a “pseudo-binary” mixture, for which the liquid-vapor two phase region in the pressure-temperature plane is no longer a single line but a two dimensional domain.

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Method for constructing the fundamental equation of state that takes into account the peculiarities of the substance behaviour in a wide vicinity of the critical point

Journal of Physics Conference Series ◽

10.1088/1742-6596/2057/1/012112 ◽

2021 ◽

Vol 2057 (1) ◽

pp. 012112

Author(s):

S V Rykov ◽

I V Kudryavtseva

Keyword(s):

Heat Capacity ◽

Free Energy ◽

Equation Of State ◽

Critical Point ◽

Fundamental Equation ◽

Virial Coefficients ◽

Phenomenological Theory ◽

Phase Region ◽

Scale Functions ◽

Fundamental Equation Of State

Abstract On the basis of the phenomenological theory of the critical point and the Benedek hypothesis, an expression for the Helmholtz free energy F with scale functions in the density-temperature variables has been developed. The proposed free energy equation has been tested on the example of constructing the fundamental equation of state of 2,3,3,3-tetrafluoropropene (R1234yf). By comparison with the known experimental data on the equilibrium properties of R1234yf – density and pressure on the phase equilibrium line, p-ρ-T-data in the single-phase region, the second and third virial coefficients, isochoric heat capacity, isobaric heat capacity and the sound velocity – the operating range of the equation of state of R1234yf has been established according to temperature from 220 K to 420 K and pressure up to 20 MPa.

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Fundamental and Higher-Mode Density-Wave Oscillations in Two-Phase Flow

Journal of Heat Transfer ◽

10.1115/1.3449892 ◽

1972 ◽

Vol 94 (2) ◽

pp. 189-195 ◽

Cited By ~ 71

Author(s):

G. Yadigaroglu ◽

A. E. Bergles

Keyword(s):

Heat Capacity ◽

Atmospheric Pressure ◽

Single Phase ◽

Two Phase Flow ◽

Density Wave ◽

Phase Region ◽

Flow Instabilities ◽

Phase Flow ◽

Two Phase ◽

Density Wave Oscillations

This paper treats the oscillatory two-phase flow instabilities commonly referred to as density-wave oscillations. A dynamic analysis of the single-phase region of a boiling channel, accounting for wall heat capacity and the effect of pressure variations on the movements of the boiling boundary, is summarized. Experiments conducted with a Freon-113 channel at atmospheric pressure revealed the existence of “higher-mode” oscillations. These appeared at high subcoolings and low power levels and were characterized by unexpectedly short periods that were fractions of the transit time. The presence of the higher modes and other observations are explained in terms of the dynamic behavior of the boiling boundary.

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