An International Standard Equation of State for Difluoromethane (R-32) for Temperatures from the Triple Point at 136.34 K to 435 K and Pressures up to 70 MPa
- Institut fuer Thermodynamik, Universitaet Hannover, Callinstrasse 36, 30167, Hannover (Germany)
- DuPont Chemicals, Fluorochemicals Laboratory, Chestnut Run Plaza, P.O. Box 80711, Wilmington, Delaware 19880-0711 (United States)
A fundamental equation of state for the Helmholtz free energy of R-32 (difluoromethane) is presented which is valid from the triple point at 136.34 K to 435 K and pressures up to 70 MPa. It is based on accurate measurements of pressure-density-temperature (p,{rho},T), speed of sound, heat capacity, and vapor pressure currently available. New values for the isobaric heat capacity c{sub p}{sup {circ}} of the ideal gas calculated from spectroscopic data taking into account also first order anharmonicity corrections are presented. The Helmholtz free energy equation of state has 19 coefficients and represents all selected experimental data within their estimated accuracy with the exception for heat capacities and speed of sound in the region close to the critical point. Typical uncertainties are {plus_minus}0.05{percent} for density, {plus_minus}0.02{percent} for the vapor pressure and {plus_minus}0.5{percent}{endash}1{percent} for the heat capacity. This equation of state has been compared to equations developed by other research groups by Annex 18 of the International Energy Agency and has been selected as an international standard formulation for the thermodynamic properties of R-32 by this group. {copyright} {ital 1997 American Institute of Physics and American Chemical Society.}
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 564885
- Journal Information:
- Journal of Physical and Chemical Reference Data, Vol. 26, Issue 6; Other Information: PBD: Nov 1997
- Country of Publication:
- United States
- Language:
- English
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