Liquid-Phase Thermodynamic Properties of New Refrigerants: Pentafluoroethyl Methyl Ether and Heptafluoropropyl Methyl Ether

In the present paper, we report an experimental study on the liquid-phase thermodynamic properties of the new-generation alternative refrigerants, pentafluoroethyl methyl ether, CF 3 CF 2 OCH 3 (245cbEβγ), and heptafluoropropyl methyl ether, CF 3 CF 2 CF 2 OCH 3 (347sEγδ). The measurements of vapor pressures and saturated- and compressed-liquid densities were performed by means of a magnetic densimeter coupled with a variable-volume cell mounted with a metallic bellows for temperatures from 260 to 370 K (for CF 3 CF 2 OCH 3 ) and from 250 to 370 K (for CF 3 CF 2 CF 2 OCH 3 ) and pressures up to 3 MPa. The experimental uncertainties of the temperature, pressure, and density measurements were estimated to be within ±8 mK, ±1.9 kPa (single-phase measurements) and ±2.5 kPa (two-phase vapor pressure measurements), and ±2 kg·m - 3, respectively. The purities of the samples used throughout the measurements were 99.99 mass % for CF 3 CF 2 CF 2 OCH 3 and 99.9 mass % for CF 3 CF 2 CF 2 OCH 3 . On the basis of these measurements and the available data reported by other investigators, the thermodynamic behaviors with respect to vapor pressures and saturated- and compressed-liquid densities are discussed in terms of vapor pressure and saturated liquid density correlations optimized and a liquid-phase equation of state. By examining the thermodynamic behavior of the derived properties such as the specific isochoric and isobaric heat capacities, speeds of sound, and Joule−Thomson coefficients, the range of validity for the optimized simple correlations and their physical soundness will be discussed.