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  • 1
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438863
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  • 2
    Electronic Resource
    Electronic Resource
    A thermodynamic property formulation for air. I. Single-phase equation of state from 60 to 873 K at pressures to 70 MPa (1990)
    Springer
    International journal of thermophysics 11 (1990), S. 169-177 
    Details
    ISSN: 1572-9567
    Keywords: air ; density ; equation of state ; fundamental equation ; heat capacity ; thermodynamic properties ; velocity of sound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A revised interim formulation for the thermodynamic properties of air has been developed for calculating properties of the vapor and estimating properties for the liquid at temperatures as low as 60 K. The formulation incorporates separate equations for the calculation of bubble-point and dew-point pressures and densities and for the ideal-gas heat capacity. A new fundamental equation of state is given for vapor and liquid states of air based upon available experimental data and predicted values of isochoric heat capacity for the liquid using corresponding states methods. Procedures for predicting C v are discussed. The fundamental equation for air is explicit in nondimensional Helmholtz energy. The terms of the fundamental equation were selected from a larger set of 75 proposed terms using a least-squares fitting procedure. Representative graphical comparisons of calculated property values to experimental measurements are given. The estimated accuracy of calculated densities is generally ± 0.2% except near the dew and bubble lines. Calculated heat capacities for the liquid must be considered only as estimates until substantiated by experimental measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503868
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  • 3
    Electronic Resource
    Electronic Resource
    A thermodynamic property formulation for air. II. Pressure and density estimation functions for the dew and bubble lines (1990)
    Springer
    International journal of thermophysics 11 (1990), S. 179-188 
    Details
    ISSN: 1572-9567
    Keywords: air ; bubble point ; dew point ; phase equilibrium ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As a companion to a new correlation for the thermodynamic properties of air in single-phase states, new values for the properties on the dew and bubble lines have been calculated. Phase equilibrium properties for air at low and moderate pressures were predicted from accurate equations of state for argon, nitrogen, and oxygen using extended corresponding-states (ECS) methods. For pressures near the critical pressure, property values were calculated using a modified Leung-Griffiths model for mixtures of argon, nitrogen, and oxygen. Available experimental data and newly predicted values have been used in developing new correlating functions for estimating density and pressure on the dew and bubble lines of air. Estimates of the accuracies of these correlations based upon comparisons of calculated properties to data from other sources are also included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503869
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  • 4
    Electronic Resource
    Electronic Resource
    A Reference Quality Equation of State for Nitrogen (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 1121-1132 
    Details
    ISSN: 1572-9567
    Keywords: caloric properties ; density ; equation of state ; nitrogen ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new formulation describing the thermodynamic properties of nitrogen has been developed. New data sets which have been used to improve the representation of the p–ρ–T surface of gaseous, liquid and supercritical nitrogen, including the saturated states are now available. New measurements on the speed of sound from spherical resonators have been used to improve the accuracy of caloric properties in gaseous and supercritical nitrogen. State-of-the-art algorithms for the optimization of the mathematical structure of the equation and special functional forms for an improved description of the critical region were used to represent even the most accurate data within their experimental uncertainty. The uncertainty in density of the new reference equation of state ranges from ±0.01% between 270 and 350 K at pressures less than 12MPa, within ±0.02% over all other temperatures less than 550 K and pressures less than 12 MPa, and up to a maximum of ±0.6% at the highest pressures. The equation is valid from the triple point to temperatures of 1000 K and pressures up to 2200 MPa. The new formulation yields a reasonable extrapolation up to the limits of chemical stability of nitrogen as indicated by comparison to experimental shock tube data. Constraints regarding the structure of the equation ensure reasonable extrapolated properties up to temperatures and pressures of 5000 K and 25 GPa. For typical calibration applications, the new reference equation is supplemented by a simple but also highly accurate formulation, valid only for supercritical nitrogen between 270 and 350 K at pressures up to 30 MPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022689625833
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamic Properties of Air from 60 to 2000 K at Pressures up to 2000 MPa (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 217-228 
    Details
    ISSN: 1572-9567
    Keywords: air ; equation of state ; fundamental equation ; high pressure ; high temperature ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A thermodynamic property formulation for standard dry air based upon experimental P–ρ–T, heat capacity, and speed of sound data and predicted values, which extends the range of prior formulations to higher pressures and temperatures, is presented. This formulation is valid for temperatures from the solidification temperature at the bubble point curve (59.75 K) to 2000 K at pressures up to 2000 MPa. In the absence of experimental air data above 873 K and 70 MPa, air properties were predicted from nitrogen data. These values were included in the fit to extend the range of the fundamental equation. Experimental shock tube measurements ensure reasonable extrapolated properties up to temperatures and pressures of 5000 K and 28 GPa. In the range from the solidification point to 873 K at pressures to 70 MPa, the estimated uncertainty of density values calculated with the fundamental equation for the vapor is ±0.1%. The uncertainty in calculated liquid densities is ±0.2%. The estimated uncertainty of calculated heat capacities is ±1% and that for calculated speed of sound values is ±0.2%. At temperatures above 873 K and 70 MPa, the estimated uncertainty of calculated density values is ±0.5%, increasing to ±1% at 2000 K and 2000 MPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021450818807
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  • 6
    Electronic Resource
    Electronic Resource
    A thermodynamic property formulation for nitrogen from the freezing line to 2000 K at pressures to 1000 MPa (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 503-511 
    Details
    ISSN: 1572-9567
    Keywords: equation of state ; nitrogen ; saturation properties ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new fundamental equation explicit in Helmholtz energy for thermodynamic properties of nitrogen from the freezing line to 2000 K at pressures to 1000 MPa is presented. A new vapor pressure equation and equations for the saturated liquid and vapor densities as functions of temperature are also included. The techniques used for development of the fundamental equation are those reported in a companion paper for ethylene. The fundamental equation and the derivative functions for calculating internal energy, enthalpy, entropy, isochoric heat capacity (C v), isobaric heat capacity (C p), and velocity of sound are also included in that paper. The property formulation using the fundamental equation reported here may generally be used to calculate pressures and densities with an uncertainty of ±0.1%, heat capacities within ± 2%, and velocity of sound values within ±2%. The fundamental equation is not intended for use near the critical point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502385
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of the critical liquid volume fraction to rectilinear-diameter methods for prediction of the critical density of ethylene and oxygen (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 513-524 
    Details
    ISSN: 1572-9567
    Keywords: coexistence densities ; critical density ; ethylene ; liquid volume fraction ; oxygen ; rectilinear diameter ; phase equilibria ; pure fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A comparison of the prediction of the critical density for ethylene and oxygen from available coexistence density values using three methods is presented. The conventional rectilinear diameter, the rectilinear diameter with an additional term to represent the postulated curvature near the critical point, and the critical liquid volume fraction were each utilized to predict critical density values for ethylene and oxygen. The correlating functions and fitted constants for the three techniques are given for different ranges of saturation density values. The accepted saturation lines for ethylene and oxygen calculated from new correlations of thermodynamic properties for these fluids were used in this study. The critical density of ethylene was predicted using coexistence density values from 220 to 230 K and from 220 to 282.34 K. Similarly, the critical density for oxygen was predicted using coexistence densities from 100 to 116 K, from 100 to 154.004 K, and from 100 to 154.571 K. Values of the critical density predicted using the three methods are compared with the accepted critical density values for these fluids. The ability of the three methods to predict accurate critical density values using saturation densities at temperatures removed from the critical point is assessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502386
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  • 8
    Electronic Resource
    Electronic Resource
    A Generalized Model for the Thermodynamic Properties of Mixtures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 825-835 
    Details
    ISSN: 1572-9567
    Keywords: cryogens ; equation of state ; hydrocarbons ; mixtures ; refrigerants ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A mixture model explicit in Helmholtz energy has been developed which is capable of predicting thermodynamic properties of mixtures containing nitrogen, argon, oxygen, carbon dioxide, methane, ethane, propane, n-butane, i-butane, R-32, R-125, R-134a, and R-152a within the estimated accuracy of available experimental data. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the compressibility (or real gas) contribution, and the contribution from mixing. The contribution from mixing is given by a single generalized equation which is applied to all mixtures studied in this work. The independent variables are the density, temperature, and composition. The model may be used to calculate the thermodynamic properties of mixtures at various compositions including dew and bubble point properties and critical points. It incorporates accurate published equations of state for each pure fluid. The estimated accuracy of calculated properties is ±0.2% in density, ±0.1 % in the speed of sound at pressures below 10 MPa, ±0.5% in the speed of sound for pressures above 10 MPa, and ±1% in heat capacities. In the region from 250 to 350 K at pressures up to 30 MPa, calculated densities are within ±0.1 % for most gaseous phase mixtures. For binary mixtures where the critical point temperatures of the pure fluid constituents are within 100 K of each other, calculated bubble point pressures are generally accurate to within ±1 to 2%. For mixtures with critical points further apart, calculated bubble point pressures are generally accurate to within ±5 to 10%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022627001338
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  • 9
    Electronic Resource
    Electronic Resource
    The prediction of high-density thermodynamic states using molecular shape factors (1988)
    Springer
    International journal of thermophysics 9 (1988), S. 975-983 
    Details
    ISSN: 1572-9567
    Keywords: corresponding states ; equation of state ; molecular shape factor ; vapor-liquid equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new extended corresponding-states method for the prediction of high-density states for pure fluids is presented. The method incorporates the use of molecular shape factors. This approach requires accurate equations for the saturated-liquid density and the vapor pressure for the fluid in question. In addition, an equation of state for the vapor phase is also required. With this information, the molecular shape factors are calculated on the saturated-liquid line of the fluid being predicted, and they are assumed to be constant in the high-density, single-phase region along isotherms. This property prediction method is well suited for application to any fluid that has an equation of state valid in the vapor phase. Modern equations of state for nitrogen and oxygen were used to define properties of reference fluids in the development and testing of this new method. Experimental data for liquid ethylene were used to verify the accuracy of the new prediction method. Tests have shown that this approach predicts high-density data accurately to approximately six times the critical pressure and up to 85 % of the critical temperature. The results of these tests are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133265
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  • 10
    Electronic Resource
    Electronic Resource
    An extended corresponding-states model for predicting thermodynamic properties of N2-Ar-O2 mixtures including vapor-liquid equilibrium (1994)
    Springer
    International journal of thermophysics 15 (1994), S. 1289-1298 
    Details
    ISSN: 1572-9567
    Keywords: binary interaction parameters ; extended corresponding states ; shape factors ; single-phaseP-p-T ; vapor-liquid equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A formulation developed previously for the prediction of the thermodynamic properties of single-phase states of binary and ternary mixtures in the nitrogen-argon-oxygen system has been revised to include the calculation of vapor-liquid equilibrium (VLE) properties. The model is based on the theory of extended corresponding states with van der Waals mixing rules. Binary interaction parameters have been determined with single-phaseP-p-T and vaporliquid equilibrium data to improve the accuracy of thermodynamic property predictions. The model accurately represents single-phase and vapor-liquid equilibrium properties over a wide range of compositions for binary and ternary mixtures. Comparisons of calculated properties to selected mixture data for both single-phase and VLE states are included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01458837
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