In a preceding project, functional forms for “short” Helmholtz energy equations of state for typical nonpolar and weakly polar fluids and for typical polar fluids were developed using simultaneous optimization. In this work, the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbon monoxide, carbonyl sulfide, decane, hydrogen sulfide, 2-methylbutane (isopentane), 2,2-dimethylpropane (neopentane), 2-methylpentane (isohexane), krypton, nitrous oxide, nonane, sulfur dioxide, toluene, xenon, hexafluoroethane (R-116), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), octafluoropropane (R-218), 1,1,1,3,3-pentafluoropropane (R-245fa), and fluoromethane (R-41). The 12 coefficients of the equations of state were fitted to substance specific data sets. The results show that simultaneously optimized functional forms can be applied to other fluids out of the same class of fluids for which they were optimized without significant loss of a...

Short Fundamental Equations of State for 20 Industrial Fluids

A formulation for the thermodynamic properties of ethanol (C2H5OH) in the liquid, vapor, and saturation states is presented. The formulation is valid for single-phase and saturation states from 250 to 650 K at pressures up to 280 MPa. The formulation includes a fundamental equation and ancillary functions for the estimation of saturation properties. The experimental data used to determine the fundamental equation include pressure-density-temperature, ideal gas heat capacity, speed of sound, and vapor pressure. Saturation values computed from the ancillary functions were used to ensure thermodynamic consistency at the vapor-liquid phase boundary. Comparisons between experimental data and values computed using the fundamental equation are given to verify the uncertainties in the calculated properties. The formulation presented may be used to compute densities to within ±0.2%, heat capacities to within ±3%, and speed of sound to within ±1%. Saturation values of the vapor pressure and saturation densities are represented to within ±0.5%, except near the critical point.

A Fundamental Equation for Calculation of the Thermodynamic Properties of Ethanol

The Flory theory of solution thermodynamics is used to predict exess volumes for systems containing a series of n-alkanes mixed with liquids of higher P* parameter and internal pressure, i.e., cyclopentane, cyclohexane, carbon tetrachloride, benzene and dioxane as well as of lower P*, i.e., decamethyltetrasiloxane. Trends of V E , e.g. changes of sign with alkane carbon number are well predicted and indicate the importance of the P* contribution in V E . Mixtures of hexane isomers with liquids of much higher P* typically have large excess enthalpies through zero as an S-shaped curve against composition which is negative on the side of the high P* component. This behaviour is interpreted as arising from increasingly large negative P* contributions in V E .

Volumes of mixing and theP* effect: Part II. Mixtures of alkanes with liquids of different internal pressures

The velocity of sound in ethanol has been measured in the temperature range between 273.15 and 333.15 K and at pressures up to 280 MPa using the phase comparison pulse-echo method with two reflectors, which has been described previously. The density, isothermal compressibility, isobaric thermal expansion and the specific heat at constant pressure of ethanol have been evaluated from the measured sound velocity, using an improved method of computation.

Acoustic and Thermodynamic Properties of Ethanol from 273.15 to 333.1 5 K and up to 280 MPa

An isothermal flow calorimeter suitable for measuring heats of reaction and heats of mixing at high pressure is described. With the calorimeter endothermic or exothermic processes can be studied from 0 to 70 °C and from 1 to 400 atm. Energy effects from 0.15 to 30 J/min are measured with a precision of ±0.4% at a constant temperature through the use of an automatic controlled variable heater and a constant cooling Peltier device. A complete heat‐of‐mixing curve can be generated from a single run. The calorimeter was tested by measuring the heats of neutralization of HClO4–NaOH and HClO4–TRIS and the heat of mixing of n‐hexane‐cyclohexane, and was found to produce data in very good agreement with published literature values.

Avinash C. Gupta

Papers

Calculation of Isothermal Vapor-Liquid Equilibrium Data for Binary Mixtures from Heats of Mixing

Liquid phase PVT data for binary mixtures of toluene with nitroethane and acetone, and benzene with acetonitrile, nitromethane, and ethanol

Liquid phase PVT data, excess volume data, constant volume excess thermodynamic functions, and thermal pressures for ten binary mixtures