Extended corresponding states model for fluids and fluid mixtures

Estela-Uribe, Jorge F.; Trusler, J. P. Martin

doi:10.1016/s0378-3812(02)00190-5

Cited by 18 publications

(24 citation statements)

References 89 publications

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“…(8) and (9) the T c,j and ρ c,j critical parameters coincide with T c,0 and ρ c,0 , respectively, since the target fluid and the reference fluid are the same. In the present case it follows that…”

Section: Extended Equation Of State Model: Mathematical Formulationmentioning

confidence: 89%

“…Lately, the ECS method was revisited by some authors [8][9][10][11][12]17], who independently determined the shape functions through a minimization procedure using experimental data of various properties for the fluid of interest, making the method similar to the classical multiproperty fitting approach [1][2][3]. In such a way both the shape functions become available as continuous analytical functions of temperature and density.…”

Section: Ecs Basic Modelingmentioning

confidence: 99%

“…In recent times, the extended corresponding states (ECS) modeling technique [4][5][6][7][8][9] was also extensively studied to verify whether it could be improved to obtain a further method for the development of wide-range fundamental EoSs. A new heuristic procedure descending from the conventional ECS technique was recently proposed for the haloalkanes in a predictive mode [10] and in a correlative mode [11]; moreover, a widerange fundamental EoS dedicated to fluoropropane (R227ea) was obtained [12].…”

Section: Introductionmentioning

confidence: 99%

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An Extended Equation of State Modeling Method I. Pure Fluids

et al. 2006

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A new technique is proposed here to represent the thermodynamic surface of a pure fluid in the fundamental Helmholtz energy form. The peculiarity of the present method is the extension of a generic equation of state for the target fluid, which is assumed as the basic equation, through the distortion of its independent variables by individual shape functions, which are represented by a neural network used as function approximator. The basic equation of state for the target fluid can have the simple functional form of a cubic equation, as, for instance, the Soave-Redlich-Kwong equation assumed in the present study. A set of nine fluids including hydrocarbons, haloalkane refrigerants, and strongly polar substances has been considered. For each of them the model has been regressed and then validated against volumetric and caloric properties generated in the vapor, liquid, and supercritical regions from highly accurate dedicated equations of state. In comparison with the underlying cubic equation of state, the prediction accuracy is improved by a factor between 10 and 100, depending on the property and on the region. It has been verified that about 100 density experimental points, together with from 10 to 20 coexistence data, are sufficient to guarantee high prediction accuracy for different thermodynamic properties. The method is a promising modeling technique for the heuristic development of multiparameter dedicated equations of state from experimental data. KEY WORDS: cubic equation of state; extended equation of state; feed forward neural network; fundamental equation of state; Helmholtz energy equation; pure fluids; thermodynamic properties.

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Section: Extended Equation Of State Model: Mathematical Formulationmentioning

confidence: 89%

Section: Ecs Basic Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Extended Equation of State Modeling Method I. Pure Fluids

et al. 2006

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“…The generalised shape-factor correlations of references [13,14] do have some limitations and, in order to obtain improved accuracy, we developed alternative substance specific parameters for key components of natural gases [1]. The results reported in our preceding paper [1] show that the ECS model represents a distinct improvement over a previous shape-factor correlation [5]; indeed, some of the results are comparable in accuracy to those obtained with modern reference equations of state.…”

Section: Introductionmentioning

confidence: 95%

“…In a previous paper [1] we reported an improved extended corresponding states (ECS) model for the thermodynamic properties of pure substances. The reference fluid for this model was methane and new equations were proposed to correlate the two shape factors which appear in the model.…”

Section: Introductionmentioning

confidence: 99%

Extended corresponding states model for fluids and fluid mixtures

Estela-Uribe

Mendoza

Trusler

2004

Fluid Phase Equilibria

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A fundamental equation of state for the (R134a + triethylene glycol dimethyl ether) mixture

Marchi

Scalabrin

Ihmels³

et al. 2007

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).The thermodynamic properties of the mixture of 1,1,1,2-tetrafluoroethane (R134a) and triethylene glycol dimethyl ether (TriEGDME) have been modeled with equations of state in an extended corresponding states format. A recent equation of state for pure R134a was assumed as the reference while the scale factors have been obtained in neural network form by regression of experimental data for the mixture. The modeling was focused on the liquid phase, considering the possible application of such a mixture in a refrigeration plant; since the vapor pressure of pure TriEGDME is negligible over the considered temperature range, the vapor phase of the mixture at vapor-liquid equilibrium condition is almost pure R134a. Two fundamental equations are proposed herein. The first one, developed from a limited amount of experimental data is valid for R134a mole fractions greater than 0.94. The second equation was obtained from a wider data base; it has a larger number of free parameters to regress and covers the R134a mole fractions greater than 0.59. 2007 American Institute of Chemical Engineers AIChE J, 53: [1349][1350][1351][1352][1353][1354][1355][1356][1357][1358][1359][1360][1361] 2007 Keywords: extended corresponding states, neural networks, R134a, refrigerant þ lubricant mixtures, thermodynamic properties, TriEGDME IntroductionThe environmental problems connected with the use of chlorofluorocarbon (CFC) refrigerants, in particular the depletion of the stratospheric layer of ozone, have imposed the phase-out of such substances and their replacement with less harmful fluids. Consequently, the study of alternative refrigerants and of their properties has become a fundamental task for scientific and technical research.Nowadays, the fluids mainly used in the refrigeration and air-conditioning plants are hydrofluorocarbons (HFC) that show better environmental behavior, thanks to the absence of chlorine atoms in their molecules. Among the substances of this family, 1,1,1,2-tetrafluoroethane (R134a) is widely used, because of its favorable thermodynamic performances in compression cycles and its compatibility with the existing refrigeration plants designed for CFC refrigerants.The identification of a suitable alternative refrigerant does not completely solve the technical problem: in fact, in the compression plants, the working fluid is not a pure refrigerant (or a mixture of refrigerants), but a certain amount of lubricant, compatible and soluble with the refrigerant, must be added. Because the mineral oils that were used with CFCs for years show low solubility in HFC refrigerants, it is necessary to propose alternative lubricants. The problems posed by the selection of the lubricant have been widely studied in recent years; a partial review is given by Marsh and Kandil.1 Guidance for the choice of the most efficient lubricant for specific technical applications, as for instance the design of a refrigeration plant, requires the knowledge of the thermophysical properties of t...

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Extended corresponding states model for fluids and fluid mixtures

Cited by 18 publications

References 89 publications

An Extended Equation of State Modeling Method I. Pure Fluids

An Extended Equation of State Modeling Method I. Pure Fluids

Extended corresponding states model for fluids and fluid mixtures

A fundamental equation of state for the (R134a + triethylene glycol dimethyl ether) mixture

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