Currently Reliable Property Values And Simple Equation For Pure Hydrofluorocarbons

In 1994, the JSRAE published JARef, Vol. 1, ‘HFCs and HCFCs,’ JAR Thermodynamic Tables, Vol. 1, Version 1.0, which provides the thermodynamic properties of 12 refrigerants by a printed form and a software. At the time reliable experimental data for new alternative refrigerants were qualitatively and quantitatively limited, some of the properties had to be estimated. Many reliable experimental data and theoretical information have been accumulated till present especially for pure hydrofluorocarbons (HFCs), e.g., the ideal gas heat capacity was derived experimentally and theoretically with an uncertainty of ±0.1 %, and many transport properties were reported. In addition, the new molar gas constant and molar masses were defined recently as the international standards. The review of the thermodynamic and transport properties is conducted mainly for HFCs in the JSRAE. Recommended critical parameters and simple equations of the vapor pressures, saturated liquid density, virial coefficients, surface tension, viscosity, and thermal conductivity are introduced and compared with selected experimental data. The information on material compatibility is also provided. INTRODUCTION Regarding the refrigerant mixtures, the JSRAE book by Tillner-Roth et al. (1998) is a unique complete compilation not only for refrigerant mixtures including R404, R407, R410, and R507 but also for the pure refrigerants of R32, R125, R134a, and R143a. The JSRAE book was calculated on the basis of the complicated Helmholtz thermodynamic equations of state. On the other hand, the JARef, (JAR Thermodynamic Tables 1994), was published for providing the thermodynamic properties of pure HFCs and HCFCs (hydrochlorofluorocarbones) as a convenient engineering tool by means of a booklet and a software in a floppy disk. The JARef provided simple correlations, which can calculate reliable property values; and a lot of Figures, which compare with selected experimental data for confirming the reliability of calculation results. Simultaneously, the complete list of experimental information was summarized in Tables and the literature survey was provided. The members of the JARef Project on the Properties of Refrigerants are preparing a new version of JARef at present. The members introduce the current situation on the properties of pure refrigerants including HFC refrigerants of R32, R125, R134a, R143a, and R152a in this report. INTERNATIONAL EQUATIONS OF STATE Regarding the International Standard values, the International Energy Agency (IEA) set up a working group on ‘Thermophysical Properties of Environmentally Acceptable Refrigerants’ as an Annex 18 in March 1990. After nearly ten years of activity till June 1998, the Annex 18 established the International equations of state for R32 (Tillner-Roth and Yokozeki 1997), R123 (Younglove and McLinden 1994), R125 (Piao and Noguchi 1998), R134a (Tillner-Roth and Baehr 1994), and R143a (Lemmon and Jacobsen 2000). These equations can provide only the thermodynamic properties such as enthalpy and entropy but not the transport properties such as thermal conductivity and viscosity. The behavior of heat capacities of vapor at low temperatures near the saturation was still uncertain with several percentages as being pointed out by Narukawa et al. (2000). PHYSICAL CONSTANTS, MOLAR MASSES, ODP, AND GWP Based on the International Standards of physical constants (CODATA, Mohr and Taylor 1999) and molar masses (IUPAC, Vocke 1999), the properties of refrigerants were calculated. The molar gas constant is 8.314 472 J⋅K⋅mol; Avogadro constant is 6.022 141 99 × 10 mol; and Boltzmann constant is 1.380 6503 × 10 J⋅K. The molar mass, ozone depleting potential (ODP) and the global warming potential (GWP) (Sand, et al. 1998), are summarized for important pure refrigerants in HCFC refrigerants which include chlorine atom Protocol. CRIT The importance of the critical parameters is not necessary to be emphasized here. The recommended values of the critical parameters for six HFC refrigerants, R23, R32, R125, R134a, R143a, and R152a listed in Table 2 were determined from the experimental results reported in the literatures by taking into account the experimental process and the data processing; sample purity; claimed experimental uncertainty; reproducibility of me Table 1. Molar Mass, GWP, and ODP of Important Refrigerants Refrigerant Molar mass g⋅mol GWP ODP R12(CFC) 120.913 8500 1.0 R22(HCFC) 86.468 1700 0.055 R23(HFC) 70.014 11700 0 R32(HFC) 52.023 650 0 R123(HCFC) 152.930 93 0.02 R125(HFC) 120.021 2800 0 R134a(HFC) 102.031 1300 0 R143a(HFC) 84.040 3800 0 R152a(HFC) 66.050 140 0 Table 1. Refrigerants shown with shadows in Table 1 are CFC or s and has already been or been scheduled to be banned in Montreal

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