Translated Abstract
The Montreal Protocol and its subsequent amendments have created a schedule to phase out the uses of hydrochlorofluorocarbons (HCFCs) which have been widely used in many applications, such as refrigerant system, energy-conversion system, blowing agent and fire extinguishing agent, etc. The scientific researchers and engineers from different countries are now dealing with the challenge of searching new promising substitutes with zero depletion potential. The thermodynamic properties especially the pvT properties of fluid are indispensable for the selection of the promising alternates, and those properties are also the most fundamental and essential properties to clarify the thermodynamic property of fluid. Dimethyl ether (DME) and fluorinated propane are now considered as alternative refrigerants, working fluids for high temperature pump, bolwing agent and so on. In this work, a high precision measurement system for the pvT properties of fluids has been developed. The pvT properties of DME, 1,1,1,3,3-pentafluoropropane (HFC-245fa) and 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) have been investigated and the high precison data and correlations were obtained.A high precision experimental measurement system for the gaseous pvT properties was developed. A temperature measurement system (range: 0~419.527 ℃，the uncertainty is better than ±1 mK), an automatic pressure measurement system (range: 0~13.8 MPa，the expanded (k=2) uncertainty was estimated to be within: ±160 Pa (0~1.38 MPa)，±800 Pa (1.38~6.9 MPa)，±1600 Pa (6.9~13.8 MPa)) and a high vaccum system (a turbo-molecular pump, the ultimate pressure is 1.0×10-5 Pa) were developed. The gaseous pvT properties apparatus was modified and the accuracy and reliability of the system were significantly enhanced.A high pressure vibrating tube densimeter system for the measurements of the densities of compressed liquids in the temperature up to 100 ℃ and pressure up to 100 MPa was developed. The core component of the system is a commercial vibrating tube densimeter Anton Paar HPM. The system was calibrated using water and the vacuum condition. The expanded (k=2) measurement uncertainty for temperature, pressure and density was better than ±16 mK, ±0.13 MPa and ±0.6 kg•m-3, respectively.The gaseous pvT properties of DME were measured via the Burnett-isochoric method. The second and third virial coefficients as well as a truncated viral equation of state were obtained. A new designed apparatus for the measurement of the saturated vapor pressure was constructed and the saturated vapor pressure of DME was measured. A Wagner-type vapor pressure equation valid up to the critical temperature of DME was developed. The normal boiling point and acentric factor were also determined.The compressed liquid densites of DME were investigated in the temperature range between (293 and 373) K with pressure up to 70 MPa using the vibrating tube densimeter system. The data were correlated well with a Tait equation, and the isothermal compressibilities and isobaric thermal expansivities were calculated from the density data. The capability and stability of the densimeter were proved by the existing data of DME, and on the other hand, with the new data the pressure range was extended up to 70 MPa.The high pressure densimeter system was also used to measure the compressed liquid densites of HFC-245fa and HFC-236fa. The experimental data for both fluids were measured for the temperature range from 293 K to 373 K and pressure up to 70 MPa. All the data were correlated with the Tait equation. The isothermal compressibilities and isobaric thermal expansivities of HFC-245fa and the isothermal compressibilities of HFC-236fa were also calculated. This work provided the first information for the liquid density data of HFC-236fa at pressures higher than 7 MPa.
Translated Keyword
[pvTDensityBurnett-isochoricVibrating tubeAlternative refrigerant]
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