New experimental densities are reported for squalane and for branched pentaerythritol tetra(2ethylhexanoate), PEB8, in the compressed liquid state over the temperature range from (278.15 to 353.15) K and for pressures up to 45 MPa. The reliability of the technique and the procedure up to 25 MPa has been verified in our previous works, and in the present work they were checked up to 45 MPa by comparing our experimental densities for heptane with literature data. A total of 297 density values have been measured with a high-pressure vibrating tube densimeter. The correction factor for density due to the sample viscosity has been considered. This factor ranges from 1 × 10 -4 to 1 × 10 -3 g‚cm -3 for PEB8 and from 4 × 10 -5 to 6 × 10 -4 g‚cm -3 for squalane over the entire Tp interval. The pressure and temperature dependencies of squalane and PEB8 densities could be accurately represented by the Tammann-Tait equation with standard deviations of 3 × 10 -5 g‚cm -3 for squalane and 9 × 10 -5 g‚cm -3 for PEB8. These density data were used to analyze the isothermal compressibility, the isobaric thermal expansivity, and the internal pressure of squalane and PEB8.

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Knowledge of proper lubricant selection and its handling can substantially influence the reliability of a refrigeration system. In this sense the awareness of several thermophysical properties of refrigerants, lubricants, and their mixtures under different conditions of pressure and temperature is highly important for designing refrigeration systems. Polyol ester oils have been proposed as lubricant candidates for refrigeration systems. In this work, we have studied the density of two polyol esters, pentaerythritol tetraheptanoate and pentaerythritol tetranonanoate, in the range 278.15 ¡ T/K ¡ 353.15 and 0.1 ¡ p/MPa ¡ 45. In addition, the behaviour of two other essential volumetric properties, namely the thermal expansion coefficient and the isothermal compressibility coefficient, as well as the internal pressure have been analysed.

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New experimental densities in the compressed liquid state are reported for pentaerythritol tetrapentanoate (PEC5) over the temperature range of 278.15−353.15 K and for pressures up to 45 MPa. Density values (99 experimental data) have been measured with a high-pressure vibrating tube densimeter. A correction factor that was due to the viscosity of the sample was applied to the experimental density values. These data were used to determine isothermal compressibilities, isobaric thermal expansion coefficients, and internal pressures for this compound. Furthermore, the density data corresponding to the homologous series:  dialkyl sebacates, 1,10-decanediol diesters, triglycerides, trimethyolethane triesters, pentaerythritol tetraesters, and linear oligomer esters of poly(hexamethylene sebacate) were predicted using the Sako−Wu−Prausnitz (SWP) equation of state (EoS), which is linked to the group contribution approach of Elvassore et al. [Ind. Eng. Chem. Res. 1999, 38, 2110] and compared with experimental data in the literature. In addition, other two EoSthe Soave−Redlich−Kwong (SRK) and Peng−Robinson (PR) equationswere used to predict the densities of some pentaerythritol tetraesters, for which the critical constants and acentric factors have been published in the literature.