A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple-Point Temperature to 1100 K at Pressures up to 800 MPa
- Lehrstuhl fuer Thermodynamik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)
This work reviews available data on thermodynamic properties of carbon dioxide and presents a new equation of state as a fundamental equation explicit in the Helmholtz free energy. Function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of single-phase region ({ital p}{rho}{ital T}) and (b) liquid-vapor saturation curve ({ital p}{sub s}, {rho}{prime}, {rho}{double_prime}) including the Maxwell criterion, (c) speed of sound {ital w} and (d) specific isobaric heat capacity {ital c}{sub {ital p}} of single phase region and saturation curve, (e) specific isochoric heat capacity {ital c}{sub {ital v}}, (f) specific enthalpy {ital h}, (g) specific internal energy {ital u}, and (h) Joule{endash}Thomson coefficient {mu}. By applying modern strategies for optimizing the mathematical form of the equation of state and for simultaneous nonlinear fit to the data of all these properties, resulting formulation is able to represent even the most accurate data to within experimental uncertainty. In the technically most important region up to pressures of 30 MPa and up to temperatures of 523 K, estimated uncertainty of the equation ranges from {+-}0.03% to {+-}0.05% in the density, {+-}0.03% to {+-}1% in the speed of sound, and {+-}0.15% to {+-}1.5% in the isobaric heat capacity. Special interest has been focused on the description of the critical region and the extrapolation behavior of the formulation. Without a complex coupling to a scaled equation of state, the new formulation yields a reasonable description even of the caloric properties in the immediate vicinity of the critical point. At least for the basic properties such as pressure, fugacity, and enthalpy, the equation can be extrapolated up to the limits of the chemical stability of carbon dioxide. (Abstract Truncated)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 402357
- Journal Information:
- Journal of Physical and Chemical Reference Data, Vol. 25, Issue 6; Other Information: PBD: Nov 1996
- Country of Publication:
- United States
- Language:
- English
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