An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is ... more An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is valid from the triple-point temperature 216.37 K to 650 K with a maximum pressure of 1000 MPa and allows for the calculation of all thermodynamic properties in the vapor and liquid phase, in the supercritical region, and in equilibrium states. In the homogeneous liquid phase, the uncertainty in density is 0.03% at atmospheric pressure. For pressures up to 200 MPa and temperatures between 270 and 440 K, density is described with an uncertainty of 0.1%. Outside this region, the uncertainty in the liquid phase increases to 0.5%. Densities in the vapor phase are estimated to be accurate within 0.5%. The uncertainty in vapor pressure depends on the temperature range and varies from 0.02% to 0.4%. Speed of sound in the liquid phase at temperatures below 500 K is described with an uncertainty of 0.1% or less. The isobaric heat capacity in the liquid phase can be calculated with an uncertainty o...
Journal of Physical and Chemical Reference Data, 1996
This work reviews the available data on thermodynamic properties of carbon dioxide and presents a... more This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single-phase region (pρT) and (b) of the liquid-vapor saturation curve (ps, ρ′, ρ″) including the Maxwell criterion, (c) speed of sound w and (d) specific isobaric heat capacity cp of the single phase region and of the saturation curve, (e) specific isochoric heat capacity cv, (f) specific enthalpy h, (g) specific internal energy u, and (h) Joule–Thomson coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimen...
Multiparameter equations of state allow for a highly accurate description of properties of experi... more Multiparameter equations of state allow for a highly accurate description of properties of experimentally well investigated fluids. For selected pure fluids reference equations of state are available, which represent all data available for thermodynamic properties within their experimental uncertainty. Recent multiparameter mixture approaches enable an accurate description of properties of mixtures over wide ranges of temperature and pressure as well. The availability of software allowing for an application of multiparameter equations of state on very different computer platforms and in different user environments makes accurate multiparameter property models an everyday tool for engineers and natural scientists. This chapter explains the fundamentals of empirical multiparameter models explicit in pressure and Helmholtz energy, as well as some historical aspects of their development with special focus on the representation of volumetric properties and phase equilibria. References are given for more extensive studies.
An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is ... more An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is valid from the triple-point temperature 216.37 K to 650 K with a maximum pressure of 1000 MPa and allows for the calculation of all thermodynamic properties in the vapor and liquid phase, in the supercritical region, and in equilibrium states. In the homogeneous liquid phase, the uncertainty in density is 0.03% at atmospheric pressure. For pressures up to 200 MPa and temperatures between 270 and 440 K, density is described with an uncertainty of 0.1%. Outside this region, the uncertainty in the liquid phase increases to 0.5%. Densities in the vapor phase are estimated to be accurate within 0.5%. The uncertainty in vapor pressure depends on the temperature range and varies from 0.02% to 0.4%. Speed of sound in the liquid phase at temperatures below 500 K is described with an uncertainty of 0.1% or less. The isobaric heat capacity in the liquid phase can be calculated with an uncertainty o...
Journal of Physical and Chemical Reference Data, 1996
This work reviews the available data on thermodynamic properties of carbon dioxide and presents a... more This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single-phase region (pρT) and (b) of the liquid-vapor saturation curve (ps, ρ′, ρ″) including the Maxwell criterion, (c) speed of sound w and (d) specific isobaric heat capacity cp of the single phase region and of the saturation curve, (e) specific isochoric heat capacity cv, (f) specific enthalpy h, (g) specific internal energy u, and (h) Joule–Thomson coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimen...
Multiparameter equations of state allow for a highly accurate description of properties of experi... more Multiparameter equations of state allow for a highly accurate description of properties of experimentally well investigated fluids. For selected pure fluids reference equations of state are available, which represent all data available for thermodynamic properties within their experimental uncertainty. Recent multiparameter mixture approaches enable an accurate description of properties of mixtures over wide ranges of temperature and pressure as well. The availability of software allowing for an application of multiparameter equations of state on very different computer platforms and in different user environments makes accurate multiparameter property models an everyday tool for engineers and natural scientists. This chapter explains the fundamentals of empirical multiparameter models explicit in pressure and Helmholtz energy, as well as some historical aspects of their development with special focus on the representation of volumetric properties and phase equilibria. References are given for more extensive studies.
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