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  • Articles  (20)
  • equation of state  (20)
  • Springer  (20)
  • American Chemical Society
  • 1995-1999  (20)
  • 1995  (20)
  • Physics  (20)
  • 1
    Electronic Resource
    Electronic Resource
    Application of a new selection algorithm to the development of a wide-range equation of state for refrigerant R134a (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 101-110 
    Details
    ISSN: 1572-9567
    Keywords: equation of state ; R 134a ; refrigerants ; simulated annealing ; stepwise regression ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Refrigerant R134a (1,1.1,2-tetrafuoroethane) is a leading substitute for refrigerant R12. As such, there has been worldwide activity to develop accurate wide-range equations of state for this fluid. In this study. we have developed a new selection algorithm for determining high-accuracy equations of state in the Helmholtz representation. This method combines least-squares regression analysis with simulated annealing optimization. Simulated annealing, unlike stepwise regression, allows for the controlled acceptance of random increases in the objective function. Thus, this procedure produces a computationally efficient selection algorithm which is not susceptible to the function-space local-minima problems present in a purely stepwise regression approach. Two equations are presented in this work and compared against experimental data and other high-accuracy equations of state for R134a. One equation was produced strictly by using stepwise a regression algorithm, while the other was produced using the simulated-annealing selection algorithm. In both cases the temperature dependence of the equations was restricted to have no terms whose exponents were greater than live.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438961
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  • 2
    Electronic Resource
    Electronic Resource
    Equations of state for the thermodynamic properties of R32 (difluoromethane) and R125 (pentafluoroethane) (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 79-89 
    Details
    ISSN: 1572-9567
    Keywords: difluoromethane (R32) ; equation of state ; pentafluoroethane (R125) ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thermodynamic properties of difluoromethane (R32) and pentafluoroethane (R125) are expressed in terms of 32-term modified Benedict-Webb-Rubin (MBWR) equations of state. For each refrigerant, coefficients are reported for the MBWR equation and for ancillary equations used to fit the ideal-gas heat capacity and the coexisting densities and pressure along the saturation boundary. The MBWR coefficients were determined with a multiproperty fit that used the following types of experimental data: PVT: isochoric, isobaric, and saturated-liquid heal capacities; second virial coefficients; and properties at coexistence. The respective equations of stale accurately represent experimental data from 160 to 393 K and pressures to 35 MPa for R32 and from 174 to 448 K and pressures to 68 MPa for R125 with the exception of the critical regions. Both equations give reasonable results upon extrapolation to 500 K and 60 MPa. Comparisons between predicted and experimental values are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438959
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  • 3
    Electronic Resource
    Electronic Resource
    A fundamental equation of state for 1,1-difluoroethane (HFC-152a) (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 91-100 
    Details
    ISSN: 1572-9567
    Keywords: equation of state ; Helmholtz free energy ; HFC-152a ; refrigeranis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A fundamental equation ofstale for HFC-152a ( 1,1-dilluorocthane) is presented covering temperatures between the triple-point temperature ( 154.56 K) and 435 K for pressures up to 311 M Pa. The equation is based on reliable (p, g, T) data in the range mentioned above. These are generally represented within ±0.1 % of density. Furthermore. experimental values of the vapor pressure, the saturated liquid density, and some isobaric heat capacities in the liquid were included during the correlation process. The new equation of state is compared with experimental data and also with the equation of state developed by Tamatsu et al. Differences between the two equations of state generally result from using different experimental input data. It is shown that the new equation of state allows an accurate calculation of various thermodynamic properties for most technical applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438960
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of thermodynamic properties from the speed of sound (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 663-673 
    Details
    ISSN: 1572-9567
    Keywords: equation of state ; speed of sound ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe methods by which all of the observable thermodynamic properties of a compressed gas, including the compressibility factor and the isochoric heat capacity, may be determined from sound speed data by numerical integration of a pair of partial differential equations. The technique may be employed over a wide range of conditions. Initial values are required. but we demonstrate that values specified on an isotherm close to the critical temperature are sufficient for application of the method to the entire homogeneous fluid region at subcritical densities. The method may also be extended to higher densities at temperatures above the critical. The effects of errors in both the initial values and the speed of sound are examined in detail by means of analytic and numerical results. The results indicate that all of the observable thermodynamic properties may be obtained with an uncertainty equal to or less than that achievable by the best available alternative techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438851
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular simulation and theory of associating chain molecules (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 705-713 
    Details
    ISSN: 1572-9567
    Keywords: associating fluids ; chain fluids ; computer simulations ; equation of state ; hydrogen bonding ; Lennard-Jones ; Monte Carlo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A closed-form statistical mechanical based equation of state for associating chain fluids is presented. A Lennard-Jones chain is used as a reference to account for the repulsive, dispersive and anisotropic (size) contributions, while the short-range directional attraction is treated as a perturbation expansion based on Wertheim's first-order theory of associating fluids. A model fluid composed of a chain of tangently bonded Lennard-Jones spheres with an associating square-well site at one of the end spheres is studied. Isobaric-isothermal Monte Carlo simulations were performed for this model at subcritical and supercritical temperatures at a association strength typical of hydrogen-bonding systems. The theory is seen accurately to predict the simulation results subject to the limitations of the equation of state of the reference fluid. The system studied has some of the main complexities found in associating chain molecules such as organic acids, alkanols, and primary amines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438855
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  • 6
    Electronic Resource
    Electronic Resource
    A new nonrandom lattice fluid model and its simplification by two-liquid theory for phase equilibria of complex mixtures (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 723-731 
    Details
    ISSN: 1572-9567
    Keywords: complex mixtures ; equation of state ; multiphase equilibria ; nonrandom lattice theory ; polymer solutions ; supercritical fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new riogorous equation of state (EOS) and its simplified version have been proposed by the present authors based on the full Guggenheim combinatorics ] of the nonrandom lattice hole theory. The simplified EOS. with the introduction of the concept of local composition, becomes similar to the density-dependent UNIQUAC model. However, im the present approach we have a volumetric EOS instead of the excess Gibbs function. Both EOSs were tested for their applicability in correlating the phase equilibria behavior of pure components and complex mixtures. Comparison of both models with experiment includes such systems as nonpolar nonpolar, nonpolar polar, and polar polar hydrocarbons, supercritical systems, and polymer solutions. With two parameters for each pure component and one binary interaction energy parameter, results obtained to date demonstrate that both formulations are quantitatively applicable to complex systems oer a wide range of temperatures, pressures, and concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438857
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  • 7
    Electronic Resource
    Electronic Resource
    Thermodynamic properties of the generalized Murnaghan equation of state of solids (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1009-1026 
    Details
    ISSN: 1572-9567
    Keywords: Anderson-Grüneisen ; bulk modulus ; equation of state ; expansivity ; high pressure ; Murnaghan equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the Murnaghan approximation, an isothermal relation between pressure (P) and volume (V) for solids is derived from the assumption that the isothermal bulk modulus (B) is a linear function ofP. This paper presents a thermodynamic analysis of a generalized form of the equation, based on treating all its various parameters [viz., V, B, and (∂B/∂P) T atP=0] as functions of temperature. Extending a previous study, the effect ofT upon (∂B/∂P) T is accounted for by using a dimensionless parameter introduced by us, which is used in formulating general expressions for the volume dependence of various thermophysical quantities,viz., the thermal expansion coefficient (α), the productαB, and the Grüneisen and Anderson-Grüneisen parameters. Some combinations of these parameters are identified, which show a simple dependence uponP. The new expressions are used in analyzing current approximations and the behavior of the solid in the low-compression range. In particular, an expression forα at highP is reported which generalizes the Anderson equation and previous results by us.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02093479
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  • 8
    Electronic Resource
    Electronic Resource
    Application of nonlinear regression in the development of a wide range formulation for HCFC-22 (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1155-1164 
    Details
    ISSN: 1572-9567
    Keywords: chlorodifluoromethane ; equation of state ; HCFC-22 ; nonlinear fitting ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An equation of state has been developed for HCFC-22 for temperatures from the triple point (115.73 K) to 550 K, at pressures up to 60 MPa. Based on comparisons between experimental data and calculated properties, the accuracy of the wide-range equation of state is ±0.1% in density, ±0.3% in speed of sound, and ±1.0% in isobaric heat capacity, except in the critical region. Nonlinear fitting techniques were used to fit a liquid equation of state based onP-ρ-T, speed of sound, and isobaric heat capacity data. Properties calculated from the liquid equation of state were then used to expand the range of validity of the wide range equation of state for HCFC-22.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081283
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  • 9
    Electronic Resource
    Electronic Resource
    Vapor-liquid equilibrium, coexistence curve, and critical locus for binary HFC-32/HFC-134a mixture (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1175-1184 
    Details
    ISSN: 1572-9567
    Keywords: binary interaction parameter ; critical density ; critical temperature ; equation of state ; R-32/134a mixture ; vapor-liquid coexistence curve ; vapor-liquid equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two kinds of equilibrium measurements of binary R-32/134a mixtures were carried out. The vapor-liquid equilibria were measured by the static method in the temperature range between 283 and 313 K. On the basis of the present experimental data, the temperature dependence of the binary interaction parameterk 12 for two equations of state, namely, the Soave-Redlich-Kwong equation and Carnahan-Starling-De Santis equation, was discussed. The vapor-liquid coexistence curve near the critical point was also measured by the observation of meniscus disappearance. The critical temperatures and critical densities of 30 and 70 wt% R-32 mixtures were determined on the basis of the saturation densities along the coexistence curve in the critical region. In addition, a correlation of the critical locus for this mixture is proposed as a function of composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081285
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  • 10
    Electronic Resource
    Electronic Resource
    The use of an MHV-2 equation of state for modeling the thermodynamic properties of refrigerant mixtures (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1165-1174 
    Details
    ISSN: 1572-9567
    Keywords: activity coefficient ; equation of state ; MHV-2 ; refrigerants ; R32 ; R134a ; R125 ; vapor-liquid equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper reports on the development and application of a thermodynamic model based on the second-order Modified Huron Vidal equation of state (MHV-2) to predict the properties of ternary mixtures of the refrigerants R32, R125, and R134a. The mixing rules of this equation of state have been used to incorporate directly an activity-coefficient model for the excess Gibbs free energy. The parameters for the activity-coefficient model have been derived from experimental VLE data for binary mixtures. This methodology has enabled the production of a thermodynamically consistent model which can be used to predict the phase equilibria of R32/R125/R134a mixtures. The input data used in the model are presented in the paper and the predictions of the model are compared with available experimental data. The model has been used to predict the behavior of ternary refrigerant blends of R32/R125/R134a in fractionation scenarios, such as liquid charging and vapor leakage, which are of direct interest to the refrigeration industry. Details of these applications and comparisons with experimental data are discussed, along with other general uses of the thermodynamic model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081284
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  • 11
    Electronic Resource
    Electronic Resource
    Prediction of multiphase equilibria in associating fluids by a contact-site quasichemical equation of state (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1287-1297 
    Details
    ISSN: 1572-9567
    Keywords: associating fluids ; contact-site model ; equation of state ; group contribution ; monomer fraction ; multiphase equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A contact-site quasichemical equation of state has been used Tor the modeling of different kinds of fluid phase equilibria (between a gas phase and one or more liquids) over a wide range of conditions. Among the systems of interest are the ternary mixtures water + alkanols + hydrocarbons (alkanes or alkynes), water + alkanols (or acetone)+ CO2, water + polyoxyethyleneglycol ethers + heavy alkanes. The model has been applied to describing the thermodynamic properties of the binary subsystems and to predict the phase behavior of the ternary systems. For longer-chain alkanols and hydrocarbons a group-contribution approach is implemented, which allows the modeling when no experimental data are available. The model gives reasonable predictions of phase behavior and the correct trends in the calculated phase diagrams in most cases. The concentrations of associates in liquid and gas phases are estimated by the model and compared with some experimental and computer simulation data. The predictive abilities of the model, its limitations, and possible ways of its improvement are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081296
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  • 12
    Electronic Resource
    Electronic Resource
    A New equation of state for square-well molecules (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1277-1286 
    Details
    ISSN: 1572-9567
    Keywords: equation of state ; molecular simulation ; perturbation theory ; second virial coefficient ; square-well molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper presents a new equation of state for the square-well fluid based on perturbation theory. This equation has the exact second virial coefficient behavior, converges to the correct mean-field behavior at high densities, and accurately interpolates between the two limits. Monte Carlo simulations were performed to evaluate the limiting behavior of the theory in the dilute-gas regime. Comparison of the theory with the simulation results shows excellent agreement between the equation-of-state predictions and the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081295
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  • 13
    Electronic Resource
    Electronic Resource
    Ideal-gas thermodynamic properties for natural-gas applications (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1381-1392 
    Details
    ISSN: 1572-9567
    Keywords: caloric properties ; equation of state ; ideal gas ; isobaric heat capacity ; natural gas ; speed of sound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Calculating caloric properties from a thermal equation of state requires information such as isobaric heat capacities in the ideal-gas state as a function of temperature. In this work, values for the parameters of thec p 0 correlation proposed by Aly and Lee were newly determined for 21 pure gases which are compounds of natural gas mixtures. The values of the parameters were adjusted to selectedc p 0 data calculated from spectroscopic data for temperatures ranging from 10 to 1000 K. The data sources used are discussed and compared with literature data deduced from theoretic models and caloric measurements. The parameters presented will be applied in a current GERG project for evaluating equations of state (e.g., the AGA 8 equation) for their suitability for calculating caloric properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02083547
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  • 14
    Electronic Resource
    Electronic Resource
    An analytical method of predicting Lee-Kesler-Plöcker equation-of-state binary interaction coefficients (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1393-1411 
    Details
    ISSN: 1572-9567
    Keywords: computer algorithm ; binary interaction coefficient ; equation of state ; mixture ; nonpolar and polar substances ; thermodynamic properties ; reduced properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analytical method is proposed for finding numerical values of binary interaction coefficients for the Lee-Kesler-Plöcker (LKP) equation of state. The method is based on solving simultaneous equations from Plöcker's mixing rules for pseudocritical parameters of a mixture and the Lee-Kesler equation for the saturation line. For mixtures of hydrocarbons containing from two to nine carbon atoms, the divergence between calculated and experimentally based interaction coefficients (ICs) is no more than ±0.4%. The method is extended to mixtures of polar substances. For polar mixtures, aneffective molar composition concept is introduced which takes into account the impact of dipole moments on the process of molecular associations. Formulas for finding the effective molar composition of mixtures containing polar and/or nonpolar constituents and the binary interaction coefficient (κ ij) based on this effective composition and pure component properties are shown. Calculatedκ ij values for 12 binary mixtures of polar substances differ by 0.4 % or less from correspondingκ ij values obtained by processing experimental data on saturated pressure (P s) and saturated temperature (T s) lines for these same mixtures. A simplified alternativeκ ij approximation method with an error (2–5 %) is also given for mixtures of polar substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02083548
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  • 15
    Electronic Resource
    Electronic Resource
    A corresponding-states principle for the equation of state of linear homonuclear fused-hard-sphere fluids (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1413-1419 
    Details
    ISSN: 1572-9567
    Keywords: equation of state ; corresponding states ; fused-hard-sphere fluids ; hard spheres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A theoretically based corresponding-states principle previously developed for the equation of state of hard-convex-body fluids is extended to rigid linear homonuclear fused-hard-sphere fluids. Effective volumes and shapes are introduced in order to account for the nonconvexity of the molecules. The excess compressibility factor, reduced by means of a parameter which can be determined analytically, is a common function of the effective packing fraction. The analytical expression for the function can be obtained from the equation of state of the hard-sphere fluid. Existing simulation data for diatomics, triatomics and tetraatomics show excellent agreement with the corresponding-states principle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02083549
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  • 16
    Electronic Resource
    Electronic Resource
    An analytical equation of state for molten alkali metals (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1429-1438 
    Details
    ISSN: 1572-9567
    Keywords: cohesive energy ; equation of state ; molten alkali metals ; statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper brings the molten alkali metals into the scope of a new statistical mechanical equation of state that is known to satisfy normal fluids over the whole range. As for normal fluids, the latent heat of vaporization and density at freezing temperature are the only inputs (scaling factors). The correspondingstates correlation of normal fluids is used to calculate the second virial coefficient,B 2(T), of alkali metals, which is scarce experimentally and its calculation is complicated by dimer formation. Calculations of the other two temperature-dependent constants,α(T) andb(T), follow by scaling. The virial coefficients of alkali metals cannot be expected to obey a law of corresponding states for normal fluids. The fact that two potentials are involved may be the reason for this. Thus, alkali metals have the characteristics of interacting through singlet and triple potentials so that the treatment by a single potential here is fortuitous. The adjustable parameter of the equation of state,γ, compensates for the uncertainties inB 2(T). The procedure used to calculate the density of liquids Li through Cs from the freezing line up to several hundred degrees above the boiling temperatures. The results are within 5 %.
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    URL: http://dx.doi.org/10.1007/BF02083551
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  • 17
    Electronic Resource
    Electronic Resource
    Equation of state for fluid alkali metals: Binodal (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 533-543 
    Details
    ISSN: 1572-9567
    Keywords: alkali metals ; binodal ; corresponding states ; equation of state ; fluid metals ; rectilinear diameter ; thermodynamic similarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The three-parameter generalized van der Waals equation of state for liquids and gases is analyzed. This equation contains the generalized expressiona/V" for the molecular pressure: here the parametern takes into account the specificity of intermolecular attractive forces for various substances. The equation is presented in the reduced form, from which follows the single-parameter law of corresponding states with the thermodynamic similarity parametern. 11 is established that for alkali metals the value of the parameter it is the same and does not depend on temperature substantially. From the given generalized equation, the expressions for the binodal (equilibrium curve of the liquid and vapor phases) are obtained. For cesium. rubidium, and potassium, the temperature dependence of density is calculated over the temperature range from their melting point to the critical point: the results of the calculations agree with experimental data. It is established that for alkali metals, the law of rectilinear diameter breaks down in the vicinity of the critical point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01441919
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  • 18
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    A thermodynamic property formulation for cyclohexane (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 519-531 
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    ISSN: 1572-9567
    Keywords: cyclohexane ; equation of state ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A formulation for the thermodynamic properties of cyclohexane is presented. The equation is valid for single-phase and saturation states from the melting line to 700 K at pressures up to 80 MPa. It includes a fundamental equation explicit in reduced Helmholtz energy with independent variables of reduced density and temperature. The functional form and coefficients of the ancillary equations were determined by weighted linear regression analyses of evaluated experimental data. An adaptive regression algorithm was used to determine the final equation. To ensure correct thermodynamic behavior of the Helmholtz energy surface the coefficients of the fundamental equation were determined with multiproperty fitting, Pressure-density-temperature (P-p-T) and isobaric heat capacity (C p -P-T) data were used to develop the fundamental equation, SaturationP-p-T values, calculated from the estimating functions, were used to ensure thermodynamic consistency at the vapor-liquid phase boundary. Separate functions were used for the vapor pressure, saturated liquid density, saturated vapor density. ideal-gas heat capacity. and pressure on the melting curve, Comparisons between experimental data and values calculated using the fundamental equation are given to verify the accuracy of the formulation. The formulation given here may be used to calculate densities within ±0.1 %, heat capacities to within ±2 %. and speed of sound to within ± 1 %, except near the critical point.
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    URL: http://dx.doi.org/10.1007/BF01441918
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  • 19
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    Describing vapor-liquid equilibria in methanol +n-alkane systems by means of an equation of state with association (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 227-236 
    Details
    ISSN: 1572-9567
    Keywords: association ; equation of state ; false liquid-liquid split ; methanol +n-alkane systems ; mixing rule ; vapor-liquid equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ability of an equation of state incorporating association to describe vapor-liquid equilibrium of methanol +n-alkane systems has been tested. An equation of state with association is divided into “physical” and “chemical” parts, where the Patel-Teja cubic equation of state is used for the description of the physical part and an association tenn forms the chemical part. Five two- and threeparameter mixing rules were tested and compared with an equation of state without association. On the average for the first eight n-alkanes, the improvement in fit of pressure using association was 30–50 % and the calculated vapor compositions were also much improved. In addition, there were lewer points with unstable liquid phase (false liquid-liquid split). Both with and without association, density-dependent mixing rules based on a local-composition concept gave the best result.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438973
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  • 20
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    The selection of international standards for the thermodynamic properties of HFC-134a and HCFC-123 (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 781-790 
    Details
    ISSN: 1572-9567
    Keywords: environmentally acceptable refrigerants ; equation of state ; thermodynamic properties ; international standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The objectives and activities of the International Energy Agency-Annex 18 are summarized. One of the goals of the Annex was to determine the formulations that best represent the thermodynamic properties of HFC-134a and HCFC-123. The formulations selected were those which accurately represented the experimental data and simultaneously exhibited thermodynamic consistency. Methods of comparison include analysis of the experimental data, statistical comparisons of values calculated from the property formulations to experimental values, and graphical analyses of the thermodynamic surface. The analytical methods used are summarized in this paper. The equations of state reviewed in these comparisons represented the most accurate formulations available in December 1992. Four equations of state were reviewed for HFC-I34a and three equations of state were considered for HCFC-123. These equations represented the work of independent researchers in Germany, Japan, and the United States. The formulations selected as international standards are presented.
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    URL: http://dx.doi.org/10.1007/BF01438863
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