James F. Ely

Thermophysical properties of fluids. II: Methane, ethane, propane, isobutane, and normal butane

Tables of methane, ethane, propane, isobutane, and normal butane thermodynamic and transport properties are presented. The mathematical relations from which these thermophysical properties are obtained are described. The tables list pressure, density, temperature, internal energy, enthalpy, entropy, specific heat at constant pressure and at constant volume, sound speed, viscosity, thermal conductivity, and dielectric constant.

Thermophysical Properties of Methane

New correlations for the thermophysical properties of fluid methane are presented. The correlations are based on a critical evaluation of the available experimental data and have been developed to represent these data over a broad range of the state variables. Estimates for the accuracy of the equations and comparisons with measured properties are given. The reasons for this new study of methane include significant new and more accurate data, and improvements in the correlation functions which allow increased accuracy of the correlations especially in the extended critical region. For the thermodynamic properties, a classical equation for the molar Helmholtz energy, which contains terms multiplied by the exponential of the quadratic and quartic powers of the system density, is used. The resulting equation of state is accurate from about 91 to 600 K for pressures <100 MPa and was developed by considering PVT, second virial coefficient, heat capacity, and sound speed data. Tables of coefficients and equatio...

Simplified crossover SAFT equation of state for pure fluids and fluid mixtures

A simplified modification of the crossover statistical associating fluid theory (SAFT) EOS is used to describe thermodynamic properties of pure fluids and binary mixtures over a wide range of parameters of state including the nearest vicinity of the critical point. For pure fluids, the simplified crossover (SCR) SAFT model contains only three adjustable parameters but allows an accurate prediction of the critical parameters of pure fluids and yields a better representation of the thermodynamic properties of pure fluids than the original SAFT equation of state. For binary mixtures, simple mixing rules with only one adjustable parameter are used. A comparison is made with experimental data for pure refrigerants R12, R22, R32, R125, R134a, R143a, and mixtures R22CR12, R32CR134a and R125 C R32 in the one- and two-phase regions. The SCR SAFT EOS reproduces the saturated pressure data with an average absolute deviation (AAD) of about 1.1% and the saturated liquid densities with an AAD of about 0.9%. In the one-phase region, the SCR SAFT equation represents the experimental values of pressure with an AAD of about 2.2% in the range of temperatures and density bounded by T T c and 2c.

Thermal conductivity of molten alkali halides from equilibrium molecular dynamics simulations

The thermal conductivity of molten sodium chloride and potassium chloride has been computed through equilibrium molecular dynamics Green-Kubo simulations in the microcanonical ensemble (N,V,E). In order to access the temperature dependence of the thermal conductivity coefficient of these materials, the simulations were performed at five different state points. The form of the microscopic energy flux for ionic systems whose Coulombic interactions are calculated through the Ewald method is discussed in detail and an efficient formula is used by analogy with the methods used to evaluate the stress tensor in Coulombic systems. The results show that the Born-Mayer-Huggins-Tosi-Fumi potential predicts a weak negative temperature dependence for the thermal conductivity of NaCl and KCl. The simulation results are in agreement with part of the experimental data available in the literature with simulation values generally overpredicting the thermal conductivity by 10%-20%.

Prediction of the thermal conductivity of refrigerants and refrigerant mixtures

Abstract We use an extended corresponding states model to predict the thermal conductivity of pure halocarbon refrigerants and refrigerant mixtures. The model uses R134a (1,1,1,2-tetrafluoroethane) as the reference fluid, and we present a correlation, including critical enhancement, for the thermal conductivity of R134a. We give sample results comparing the model predictions with experimental data for pure halocarbon refrigerants and refrigerant mixtures; typically, the uncertainty of the predictions is 5–10 percent.

Generalized corresponding states model for bulk and interfacial properties in pure fluids and fluid mixtures

We have formulated a general approach for transforming an analytical equation of state (EOS) into the crossover form and developed a generalized cubic (GC) EOS for pure fluids, which incorporates nonanalytic scaling laws in the critical region and in the limit ρ→0 is transformed into the ideal gas equation EOS. Using the GC EOS as a reference equation, we have developed a generalized version of the corresponding states (GCS) model, which contains the critical point parameters and accentric factor as input as well as the Ginzburg number Gi. For nonionic fluids we propose a simple correlation between the Ginzburg number Gi and Zc, ω, and molecular weight Mw. In the second step, we develop on the basis of the GCS model and the density functional theory a GCS-density functional theory (DFT) crossover model for the vapor–liquid interface and surface tension. We use the GCS-DFT model for the prediction of the PVT, vapor–liquid equilibrium (VLE) and surface properties of more than 30 pure fluids. In a wide range...

Prediction of viscosity of refrigerants and refrigerant mixtures

Abstract We have developed a predictive corresponding states model for the viscosity of pure refrigerants and refrigerant mixtures. The model uses extended corresponding states with R134a (1,1,1,2-tetrafluoroethane) as the reference fluid. The model uses equilibrium shape factors and an equivalent substance reducing ratio (ESRR) for the viscosity which involves the molecular mass. The “mass” ESRR is found using viscosity data along the saturation boundary. We have fit these mass ESRRs to a general form involving reduced temperature and a structural factor. In addition, we have determined a set of universal coefficients for the mass ESRR that can be used to predict the viscosity of any halocarbon refrigerant given the critical parameters and the structural parameter. We give sample results comparing the model predictions with experimental data for pure fluids and a refrigerant mixture.

The Viscosity and Thermal Conductivity Coefficients of Dilute Nitrogen and Oxygen

The viscosity and thermal conductivity coefficients of dilute oxygen and nitrogen are discussed and tables of values are presented for temperatures between 80 and 2000 K. The oxygen viscosity tables are estimated to be accurate to two percent for temperatures up to 400 K and four percent above that temperature; the nitrogen viscosity tables are estimated to be reliable to one percent in the range 100–1000 K, increasing to two percent above 1000 K and below 100 K. The error assigned to the thermal conductivity is three percent below 400 K and five percent above 400 K for both gases. The tables were calculated from the appropriate kinetic theory equations using the m‐6–8 model potential with nonspherical contributions. The approximations to the equations are discussed. It is emphasized that the available data for oxygen viscosity are generally poor and that the thermal conductivity data for both oxygen and nitrogen cannot be considered reliable at high temperatures. No oxygen data exist for temperatures abo...

A crossover equation of state for associating fluids

In this work we extend the crossover (CR) modification of the statistical-associating-fluid-theory (SAFT) equation of state (EOS), recently developed and applied for non-associating systems [Ind. Eng. Chem. Res. 38 (1999) 4993] to associating fluids. Unlike the previous crossover EOS that was based on the parametric linear model for the universal crossover function Y, the new CR SAFT EOS is based on Fisher’s recent parametric sine model. This model can be extended into the metastable region and gives analytically connected van der Waals loops in the two-phase region. We show that for associating fluids the new CR SAFT EOS not only yields a better description of the PVT and VLE properties of fluids in the critical region, but also improves the representation of the entire thermodynamic surface. A comparison is made with experimental data for pure normal methanol, ethanol, propanol, butanol, pentanol, and hexanol in the one- and two-phase regions. The CR SAFT EOS reproduces the saturated pressure and liquid density data with an average absolute deviation (AAD) of about 1%. In the one-phase region, the CR SAFT equation represents the experimental values of pressure with an AAD less than 1% in the critical and supercritical region and the liquid densities with an AAD of about 2%.

Isochoric (p, v, T) measurements on CO2 and (0.98 CO2+0.02 CH4) from 225 to 400 K and pressures to 35 MPa

Comprehensive isochoric (p, v, T) measurements have been obtained for (0.98 CO2+0.02 CH4) at densities from 1 to 26mol·dm−3. Supplemental isochoric (p, v, T) measurements have been obtained for high-purity CO2 at densities from 12 to 24 mol·dm−3. Measurements of p(T) cover a broad range of temperature, 225 to 400 K, at pressures to 35 MPa. Comparisons have been made with independent sources and with a predictive method based on corresponding states.