New functional forms have been developed for multiparameter equations of state for non- and weakly polar fluids and for polar fluids. The resulting functional forms, which were established with an optimization algorithm which considers data sets for different fluids simultaneously, are suitable as a basis for equations of state for a broad variety of fluids. The functional forms were designed to fulfil typical demands of advanced technical application with regard to the achieved accuracy. They are numerically very stable and their substance-specific coefficients can easily be fitted to restricted data sets. In this way, a fast extension of the group of fluids for which accurate empirical equations of state are available is now possible. This article deals with the results found for the polar fluids CFC-11 (trichlorofluoromethane), CFC-12 (dichlorodifluoromethane), HCFC-22 (chlorodifluoromethane), HFC-32 (difluoromethane), CFC-113 (1,1,2-trichlorotrifluoroethane), HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane), HFC-125 (pentafluoroethane), HFC-134a (1,1,1,2-tetrafluoroethane), HFC-143a (1,1,1-trifluoroethane), HFC-152a (1,1-difluoroethane), carbon dioxide, and ammonia. The substance-specific parameters of the new equations of state are given as well as statistical and graphical comparisons with experimental data. General features of the new class of equations of state such as their extrapolation behavior or their numerical stability and results for non- and weakly polar fluids have been discussed in preceding articles.

Equations of state for technical applications. III. Results for polar fluids

A compendium of phase change enthalpies published in 2010 is updated to include the period 1880–2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C1-C10

Cubic crossover equation of state

We have developed a predictive corresponding states model for the thermophysical properties of pure refrigerants and refrigerant mixtures. The bulk phase properties such as the density, enthalpy and entropy are predicted using the principle of extended corresponding states, incorporating a recent 32-term modified Benedict-Webb-Rubin correlation for the R134a (1,1,1,2-tetrafluoroethane) reference fluid. This theoretically based model uses shape factors to ensure conformality among the various components. A correlation for the shape factors was found by mapping saturation boundaries of the fluids of interest onto the reference fluid and then fitting the results to an empirical correlation. In this work we present the coefficients for density-independent shape-factor correlations for 21 refrigerants, and a set of universal coefficients that can be used with any refrigerant given only the critical parameters and the acentric factor. We show comparisons with experimental density data for each of the 21 refrigerants. We also demonstrate the use of generalized coefficients for shape factors where only the critical parameters and acentric factors are known. In addition, we present comparisons of the volume prediction for two binary refrigerant mixtures and one ternary refrigerant mixture.

A predictive extended corresponding states model for pure and mixed refrigerants including an equation of state for R134a

Vle have developed a predictive corresponding states model for the thermo· physical properties of pure refrigerants and refrigerant mixtures. The bulk phase properties such as the density, enthalpy and entropy are predicted using the prin· ciple of extended corresponding states. This theoretically based model uses shape factors to insure conformality among the various components and R134a is used as the reference fluid. The shape factors are found by mapping saturation boundaries of the fluids of interest onto the reference fluid. In the case where no saturation data are available, the shape factors are predicted. In addition to equilibrium properties, a one-fluid corresponding states model is used to predict the viscosity and thermal conductivity. Phase equilibria is predicted using a Peng-Robinson equation of state. The corresponding states model is contained in an interactive microcomputer program, PROZPER, (PRoperties of OZone Protecting Environmentally acceptable Refrigerants). The program performs various vapor-liquid equilibria calculations-dew point and bubble point pressures and temperatures, isothermal, isenthalpic and isentropic flashes-and gives the bulk phase properties (such as density, enthalpy, entropy, Joule-Thomson coefficient, Cp, Cp/Cv, sound speed, viscosity and thermal conductivity) of the coexisting phases. Calculations may be performed on pure fluids or on mixtures of up to 20 components. A built-in database contains many common refrigerants including fully-halogenated CFC's (for example Rll, Rl14, R12 and R13) as well as environmentally acceptable alter· natives (such as R123, R134a and others). In addition, the program can "learn" new components using only a minimum amount of information-the molecular weight, the normal boiling point and the critical parameters of the chemical species. Additional information such as vapor pressures, saturated liquid densities, saturated liquid thermal conductivities and viscosities may be input to improve the predictive capability of the model.

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P. F. Malbrunot

Papers

Pressure-volume-temperature behavior of difluoromethane

Pressure-volume-temperature behavior of a mixture of difluoromethane and pentafluoromonochloroethane