摘要:

A fundamental equation of state for the Helmholtz free energy of R 134a (1,1,1,2‐tetrafluoroethane) is presented which is valid for temperatures between 170 K and 455 K and pressures up to 70 MPa. It is based on the most accurate measurements of pressure‐density‐temperature (p,&rgr;,T), speed of sound, heat capacity, and vapor pressure which are currently available. A linear regression analysis and a nonlinear least squares fitting technique, based on the selected measurements, were used to determine the structure of the fundamental equation of state and the values of its 21 coefficients. The equation represents nearly all selected experimental data within their estimated accuracy with the exception of heat capacities and speed of sound in the region close to the critical point. Typical accuracies are ±0.05% for density, ±0.02% for the vapor pressure, or ±0.5 and ±1% for the heat capacity. This equation of state has been compared to equations established by other research groups by Annex 18 of the International Energy Agency (IEA) and has been selected as an international standard formulation for the thermodynamic properties of R 134a by this group.

ISSN:0047-2689    

DOI:10.1063/1.555958

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A modified Benedict–Webb–Rubin (MBWR) equation of state has been developed for Refrigerant 123 (2,2‐dichloro‐1,1,1‐trifluoroethane) based on recently measured thermodynamic property data and data available from the literature. Single‐phase pressure‐volume‐temperature (PVT), heat capacity, and sound speed data, as well as second virial, vapor pressure, and saturated liquid and saturated vapor density data, were used with multiproperty linear least squares fitting techniques to fit the 32 adjustable coefficients of the MBWR equation. Coefficients for the equation of state and for ancillary equations representing the vapor pressure saturated liquid and saturated vapor densities, and ideal gas heat capacity are given. While the measurements cover differing ranges of temperature and pressure, the MBWR formulation is applicable along the saturation line and in the liquid, vapor, and supercritical regions at temperatures from 166 to 500 K with pressures to 40 MPa and densities to 11.6 mol/L (1774 kg/m3). This formulation has been selected as an international standard based on an evaluation of the available equations of state by a group working under the auspices of the International Energy Agency.

ISSN:0047-2689    

DOI:10.1063/1.555950

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A comprehensive review of the vapor to liquid homogeneous nucleation experiment literature from 1968 to 1992 is presented. The review identifies and presents in tabular format experimental nucleation data dealing specifically with: (1) critical supersaturation measurements in both unary and binary systems; (2) nucleation rate measurements in both unary and binary systems; (3) photoinduced nucleation experiments; and, (4) ion‐induced nucleation experiments. The data tables identify the substance under investigation; the experimental method used in each investigation; the background gas and, when available, the pressure range of the background gas used in each investigation; a brief summary of the key results of each investigation; and literature references where more detailed information concerning each investigation can be found. The review contains a brief description of the operation of the experimental devices referenced in the tables. The review also contains an assessment of the various experimental devices currently capable of quantitative nucleation rate measurements.

ISSN:0047-2689    

DOI:10.1063/1.555951

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

For the use of a mercury column for precise pressure measurements—such as the pressurized 30 meter mercury‐in‐steel column used at the Van der Waals–Zeeman Laboratory for the calibration of piston gauges up to nearly 300 MPa—it is highly important to have accurate knowledge of such properties of mercury as density, isobaric secant and tangent volume thermal expansion coefficients, and isothermal secant and tangent compressibilities as functions of temperature and pressure. In this paper we present a critical assessment of the available information on these properties. Recommended values are given for the properties mentioned and, in addition, for properties derived from theses such as entropy, enthalpy, internal energy, and the specific heat capacities.

ISSN:0047-2689    

DOI:10.1063/1.555952

出版商:AIP    

年代:1994

数据来源: AIP