Isochoric Specific Heat in the Dual Model of Liquids

We continue in this paper to illustrate the implications of the dual model of liquids (DML) by deriving the expression for the isochoric specific heat as a function of the collective degree of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks have been accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression has been compared with the analogous one obtained in another theoretical dual model of the liquid state, the phonon theory of liquid thermodynamics. This comparison allows providing interesting insights about the number of collective degrees of freedom available in a liquid and the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework.

Isochoric Specific Heat in the Dual Model of Liquids

We continue in this paper to illustrate the implications of the Dual Model of Liquids (DML) by deriving the expression for the isochoric specific heat as function of the collective degrees of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks will be accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression will be compared with the analogous one obtained in another theoretical dual model of the liquid state, the Phonon Theory of Liquid Thermodynamics. This comparison will allow to get interesting insights about the number of collective degrees of freedom available in a liquid and on the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework.

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.

A study on excess functions and thermodynamic parameters of some bromoform- containing binary mixtures

Densities and viscosities have been determined for six binary mixtures of bromoform, aniline, n-hexane, benzonitrile, butyronitrile, and benzylnitrile at different mole fractions and temperatures. The excess volumes VE, apparent excess values of viscosity δη, excess Gibbs energy of activation of flow ΔG*E, and partial molar volumes Vi have been calculated from the experimental data. Furthermore, attempts were made to calculate theoretically the excess isobaric thermal expansion coefficient δα, of the mixtures using the refractive index mixture rules. These results are in good agreement with the experimental data obtained from densities. Various excess functions and thermodynamic parameters have been used in the discussion of results to understand the nature and type of interactions in binary mixtures. Keywords: excess volume, refractive index mixture rules, interactions, bromoform, density, viscosity.