3-Heptafluoropropane (R227ea) is considered an alternative fluid in the refrigeration and air conditioning industry to replace traditional CFC refrigerants. Limited information is available in the literature about the PFT behavior of this fluid, so the purpose of the experimental analysis described in the present paper is to provide a set of compressed liquid density data. A vibrating tube densimeter (Anton Paar DMA 512) was used to measure the density of R227ea along six isotherms between (283.15 and 333.15) K and up to 35 MPa, with an estimated uncertainty of about 0.05 %. Saturated liquid densities were extrapolated from the measured data using a polynomial. The results of the compressed liquid density measurements and the extrapolated values of saturated liquid density were correlated with fitting equations and compared to existing experimental data sets.

The compatibility of carbon dioxide with synthetic oils, employed as lubricants for compressors in the refrigeration and air conditioning plants, is a fundamental and still unsolved problem. Mutual solubility with the refrigerant is one of the properties that influences the choice of a particular lubricant for a specific application. A systematic study of the solubility of carbon dioxide in polyolester oils (POE) has been started at our laboratories with the aim to investigate the dependence of this property on various parameters, such as pressure, temperature, and oil chemical structure. In this paper, experimental measurements of solubility of carbon dioxide in pentaerythritol hexanoate (PEC6), which is a precursor of polyol ester based lubricants, are presented in a temperature range of (243 to 343) K and pressures up to about 10 MPa. The uncertainty in the liquid composition measurements was estimated to be from 0.002 (high CO 2 molar fraction) to 0.02 (low CO 2 molar fraction). The experimental data were correlated by means of the Peng-Robinson equation of state with the Huron Vidal mixing rules in which the excess Gibbs energy at infinite pressures was represented by the UNIQUAC equation.

Carbon dioxide (CO 2 ) is one of the most promising natural refrigerants that can be employed as an alternative to hydrofluorocarbons (HFC), due to its low global warming potential (GWP). Nevertheless, CO 2 presents several technical problems when employed as a working fluid in refrigeration systems. In particular, the selection of the most suitable lubricant for each application is far from being resolved. The thermodynamic behavior of a CO 2 + lubricant system must be well-known for a correct oil selection. This work is part of a research project to study the solubility of CO 2 in commercial oils and their precursors. Here, solubility measurements of CO 2 in pure pentaerythritol tetrabutyrate (PEC4) between 243 K and 343 K are presented and compared with miscibility data of CO 2 in pentaerythritol tetrahexanoate (PEC6) and pentaerythritol tetraoctanoate (PEC8). The experimental data were correlated with a thermodynamic model based on a cubic equation of state with Huron-Vidal mixing rules and the UNIQUAC equation for the excess Gibbs energy at infinite pressure.