Determination of derived volumetric properties and heat capacities at high pressures using two density scaling based equations of state. Application to dipentaerythritol hexa(3,5,5-trimethylhexanoate)

Scaling based EoSs describe the complex behavior of derived properties for broad temperature and pressure ranges from diPEiC₉ experimental densities.

Thermodynamic properties of 1,1,1,2-tetrafluoroethane + polyether mixtures up to 60 MPa

In this work we report several derived thermodynamic properties, the isothermal compressibility (κT), the isobaric thermal expansion coefficient (αp), and the internal pressure (π), and their excess functions (κTE, αpE, and πE) for the refrigerant + lubricant mixtures HFC-134a + triethylene glycol dimethyl ether and HFC-134a + tetraethylene glycol dimethyl ether. These properties have been determined in wide temperature (293.15–373.15 K) and pressure (10–60 MPa) ranges in an effort to better understand the behaviour of these kinds of mixtures and their thermophysical properties as functions of temperature, pressure, and composition. The analysis of the thermodynamic excess properties (negative values for κTE and αpE, positive values for πE) for both systems shows a high degree of interaction between the refrigerant and the synthetic lubricant molecules. Key words: HFC-134a, high pressure, internal pressure, isobaric thermal expansion coefficient, isothermal compressibility, polyglycol ethers, refrigerant–lubricant mixtures.

UNIFAC calculation of thermodynamic properties of binary 1-chloroalkane + alkane and α,ω-dichloroalkane + alkane mixtures: Comparison with Nitta–Chao and DISQUAC predictions

Data available in the literature for vapor–liquid equilibria, activity coefficients at infinite dilution, and enthalpies of mixing for binary mixtures of 1-chloroalkanes or dichloroalkanes with alkanes are used to determine interaction parameters for three versions of the UNIFAC model – the Tassios et al., Larsen et al., and Gmehling et al. versions. The interaction parameters for chlorine and methyl or methylene groups are calculated using data for the thermodynamic properties of 1-chloroalkane + alkane mixtures. In the case of the Gmehling version, the geometrical parameters for chlorine are also determined. In addition, structure-dependent interaction parameters for α,ω-dichloroalkane + alkane mixtures are presented, taking into account the proximity effect. When the two chlorine atoms of the dichloroalkane are more separated, they become more independent, and the reported values of the interaction parameters approach those of 1-chloroalkane. For all of the properties studied the mean deviation obtained with the new parameter values is lower than that obtained with older values. The results for the thermodynamic properties obtained using the new parameters of the three versions of UNIFAC are compared with those of DISQUAC and Nitta–Chao models. Key words: alkanes, chloroalkanes, DISQUAC, excess thermodynamic properties, proximity effect, UNIFAC.

Excess molar volumes of liquid 1-bromoalkane + alkane mixtures. Nitta–Chao characterization of the bromine–bromine and bromine–methylene interactions in binary 1-bromoalkane + alkane mixtures

Excess molar volumes at 298.15 K for the binary mixtures of a 1-bromoalkane with a n-alkane are reported. The VE values were obtained from measurements of the density with an Anton Paar densimeter. Literature data of excess Gibbs energies, excess enthalpies, excess volumes, and activity coefficients at infinite dilution for this kind of mixtures together with molar volumes and vaporization enthalpies of pure bromoalkanes were used to calculate the characteristic parameters of the Nitta-Chao group contribution model. With the obtained parameters, this model consistently describes the experimental data of the 1-bromoalkane + n-alkane mixtures. Furthermore, we have determined the energetic parameters for the Larsen version of the UNIFAC model.Key words: liquids, mixtures, thermodynamics, group contributions.