Saturated Liquid Density Data Research Articles

Equation of state for pure sodium chloride

Abstract An equation of state for pure sodium chloride has been developed on the basis of experimental data and results of Monte Carlo simulations for the restricted primitive model (RPM). The experimental data base included limited vapor pressure and saturated liquid density data as well as dimerization equilibrium constants. The liquid densities have been extrapolated to the supercooled region using liquid-phase Monte Carlo data. For this purpose, the parameters of the primitive model have been calculated by assuming that sodium chloride and RPM obey the corresponding states principle over a limited range of conditions. In the near-critical region Monte Carlo data as well as results of cluster calculations have been used with parameters scaled to reproduce the critical temperature obtained by extrapolating saturation data. The RPM parameters employed in the calculations are close to those for crystalline NaCI. The experimental and scaled Monte Carlo data have been reproduced within their accuracy using a van der Waals-type equation of state with two temperature-dependent parameters a and b. The functions representing the temperature dependence of the parameters have been designed to ensure reliable extrapolation to lower and higher temperatures. Formation of Na 2 Cl 2 clusters has been allowed for by using a closed-form term representing the effect of association on the compressibility factor. The performance of the equation has been additionally verified by predicting compressibility factors at low reduced temperatures outside the saturation region and comparing them with scaled Monte Carlo data.

Modification of the Kumar-Starling five-parameter cubic equation of state and extension to mixtures

Abstract Chu, J.-Z., Zuo, Y.-X. and Guo, T.-M., 1992. Modification of the Kumar-Starling five-parameter cubic equation of state and extension to mixtures. Fluid Phase Equilibria 77: 181-216. For extending the five-parameter cubic equation of state (KS EOS) proposed by Kumar and Starling (1982) (Ind. Eng. Chem. Fundam, 21:255-262) to polar substances, and improving the phase behavior description of heavy hydrocarbons, the generalized correlations of parameters A2 and A5 were modified, and new orientation parameters were determined. In the near critical region, transition functions for parameters A22, A5 and A5 were introduced, in which the experimental critical compressibility factor was incorporated. The parameters of the modified Kumar-Starling equation of state (MKS EOS) were determined by fitting the vapor pressure and saturated liquid density data simultaneously. The proposed MKS EOS was tested on 127 pure non-polar and polar substances. Extensive comparisons with nine other well-known cubic EOS indicate that the modified version of the KS EOS significantly improved the representation of the phase behavior of pure substances in various regions. The MKS EOS was further extended to mixtures by rearranging its form into conventional van der Waals (VDW) form, and the simple VDW one-fluid mixing rules were applied to the new EOS parameters. The test results on 97 binary and multicomponent mixtures indicate that, as compared with other equations of state, the MKS EOS predicts comparable bubble point pressures, but much more accurate saturated liquid densities.

Densities of tetramethylsilane, tetraethylsilane, and tetraethoxysilane under high pressures

Accurate density data for tetramethylsilane, tetraethylsilane, and tetraethoxysilane in the temperature range from 283.15 to 333.15 K under pressure up to 100 MPa have been measured in order to test existing correlation methods. We have also measured the saturated liquid densities of tetramethylsilane, tetraethylsilane, and tetraethoxysilane in the temperature range from 283 to 343 K. The modified Rackett equation and the COSTAD correlation were used to correlate the saturated liquid density data. The Tait equation and a modified van der Waals equation of state were used to correlate the liquid density data under pressure. It was found that the average absolute deviations of the experimental values from those calculated with the Tait equation and the modified van der Waals equation of state were less than 0.01 and 0.21%, respectively. The effective hard sphere diameters for these three silane compounds were determined from the modified van der Waals equation of state parameter. It was found that the effective hard-sphere diameter decreases with temperature.

A three-parameter cubic equation of state for reservoir fluids

A new three-parameter cubic equation of state (EOS) was developed with special attention to the application for reservoir fluids. The EOS parameters were fit to the saturated vapor pressure and liquid density data of hydrocarbons up to C 40. In the extension to reservoir fluid mixtures, two characterization methods for the plus fraction (defined as the heaviest fraction in the wellstream composition analysis), the effects of the choice of T C-P C-w correlations, and the number of lumped pseudo-components were studied. The new model has been tested on 27 reservoir crude oils and 12 gas condensates. Satisfactory predictions of phase behavior and oil enthalpy data were obtained.

Calculation of vapor—liquid equilibria at elevated pressures by means of an equation of state incorporating association

A previously proposed simple equation of state incorporating association is applied to calculate vapor—liqud equilibria (VLE) at elevated pressures for systems formed by polar compounds and hydrocarbons. The pure-component parameters are calculated from experimental saturated vapor pressure and liquid density data. Such parameters are sufficient for the prediction of VLE with reasonable accuracy in binary systems formed by hydrogen sulfide, ammonia, carbon dioxide, carbon monoxide or sulfur dioxide with aliphatic hydrocarbons. All 26 systems formed by various hydrocarbons with the polar compounds analyzed in this paper can be represented within experimental accuracy when only one adjustable binary parameter is introduced. The binary parameter is generalized in terms of the critical temperature, pressure and acentric factor of the nonpolar (aliphatic or aromatic hydrocarbon) component. The equation also predicts saturated liquid and vapor densities with good accuracy.

Saturated liquid density of 1,1[sbnd]difluoroethane(R 152a) and thermodynamic properties along the vapor[sbnd]liquid coexistence curve

Saturated liquid densities of 1,1-difluoroethane(CH 3CHF 2) are measured at temperatures from 223 K to 363 K with the estimated uncertainty of 0.2 % by magnetic densimetry. The experimental results are compared with the available experimental data and some correlations and equations of state. A simple correlation for the saturated liquid density is developed as a function of temperature. This correlation covers the temperature range up to the critical point which reproduces the present experimental results with the percent mean deviation of 0.11 %.Adding the available experimental data with respect to the vapor pressure, critical parameters, saturated vapor density, and the second virial coefficient to the present saturated liquid density data, the parameters of the Redlich-Kwong-Soave equation of state are determined and the thermodynamic properties along the vaporliquid coexistence curve are derived.

Determination of the bulk-saturated liquid condition for maximum heat fluxes at boiling crises

In this paper is presented a method of predicting the thermodynamic state of the bulk-saturated liquid at which peak nucleate boiling and minimum film boiling heat fluxes attain a maximum in pool boiling. The data in the form of saturated pressure and temperature in both absolute and reduced quantities are listed for several cryogenic liquids, hydrocarbons and halocarbon refrigerants. It is observed that the bulk liquid condition for a maximum in critical heat flux in nucleate boiling corresponds to intermolecular separation at maximum attractive potential, which in turn can be determined from saturated liquid density data. The predictions are fairly well corroborated by experimental data available in literature.

A thermodynamic property formulation for ethylene from the freezing line to 450 K at pressures to 260 MPa

A new thermodynamic property formulation based upon a fundamental equation explicit in Helmholtz energy of the form A=A(ρ, T) for ethylene from the freezing line to 450 K at pressures to 260 MPa is presented. A vapor pressure equation, equations for the saturated liquid and vapor densities as functions of temperature, and an equation for the ideal-gas heat capacity are also included. The fundamental equation was selected from a comprehensive function of 100 terms on the basis of a statistical analysis of the quality of the fit. The coefficients of the fundamental equation were determined by a weighted least-squares fit to selected P-ρ-T data, saturated liquid and saturated vapor density data to define the phase equilibrium criteria for coexistence, C v data, velocity of sound data, and second virial coefficients. The fundamental equation and the derivative functions for calculating internal energy, enthalpy, entropy, isochoric heat capacity (C v), isobaric heat capacity (C p), and velocity of sound are included. The fundamental equation reported here may be used to calculate pressures and densities with an uncertainty of ±0.1%, heat capacities within ±3 %, and velocity of sound values within ±1 %, except in the region near the critical point. The fundamental equation is not intended for use near the critical point. This formulation is proposed as part of a new international standard for thermodynamic properties of ethylene.

Thermodynamic Properties of Nitrogen from the Freezing Line to 2000 K at Pressures to 1000 MPa

A new fundamental equation explicit in Helmholtz energy for thermodynamic properties of nitrogen from the freezing line to 2000 K at pressures to 1000 MPa is presented. New independent equations for the vapor pressure and for the saturated liquid and vapor densities as functions of temperature are also included. The fundamental equation was selected from a comprehensive function of 100 terms on the basis of a statistical analysis of the quality of the fit. The coefficients of the fundamental equation were determined by a weighted least-squares fit to selected P-ρ-T data, saturated liquid, and saturated vapor density data to define the phase equilibrium criteria for coexistence, and velocity of sound data. The fundamental equation and the derivative functions for calculating internal energy, enthalpy, entropy, isochoric heat capacity (Cv), isobaric heat capacity (Cp), and velocity of sound are included. Tables of thermodynamic properties of nitrogen are given for liquid and vapor states within the range of validity of the fundamental equation. The fundamental equation reported here may generally be used to calculate pressures and densities with an uncertainty of ±0.1%, heat capacities within ±3%, and velocity of sound values within ±1%. Comparisons of calculated properties to experimental data are included to verify the accuracy of the formulation.

Thermodynamic Properties of Ethylene from the Freezing Line to 450 K at Pressures to 260 MPa

A new fundamental equation explicit in Helmholtz energy for thermodynamic properties of ethylene from the freezing line to 450 K at pressures to 260 MPa is presented. Independent equations for the vapor pressure for the saturated liquid and vapor densities as functions of temperature, and for the ideal gas heat capacity are also included. The fundamental equation was selected from a comprehensive function of 100 terms on the basis of a statistical analysis of the quality of the fit. The coefficients of the fundamental equation were determined by a weighted least-squares fit to selected P-ρ-T data, saturated liquid, and saturated vapor density data to define the phase equilibrium criteria for coexistence, Cv data, velocity of sound data, and second virial coefficient data. The fundamental equation and the derivative functions for calculating internal energy, enthalpy, entropy, isochoric heat capacity (Cv), isobaric heat capacity (Cp), and velocity of sound are included. Tables of thermodynamic properties of ethylene are given for liquid and vapor states within the range of validity of the fundamental equation. The fundamental equation reported here may generally be used to calculate pressures and densities with an uncertainty of ±0.1%, heat capacities within ±3%, and velocity of sound values within ±1%. Comparisons of calculated properties to experimental data are included to verify the accuracy of the formulation.

THE APPLICATIONS OF A GENERALIZED EQUATION OF STATE TO THE CORRELATION AND PREDICTION OF PHASE EQUILIBRIA∗

Two methods of generalizing an equation of state are demonstrated and their limitations are outlined. One method involves the correlation of the equation of state constants and the second method involves a recently proposed Generalized Corresponding States Principle based on the properties of two (nonspherical) reference fluids. The PVT properties of pure fluids are represented by a new cubic equation of slate with four parameters which are obtained from vapor pressure and saturated liquid density data. It is demonstrated how a limited amount of data on key components may be used to obtain phase equilibria in mixtures.

Densities of the Liquid and Dense Phase Regions.

T h e expansion factor correlation introduced i n 1913 by Watson (21) h a s received considerable interest and application for t h e calculation of thermodynamic properties and dens i t ies of t h e liquid s ta te . In t h i s connection, t h e saturated liquid density data of Young (23) for isopentane and t h e high pressure data of Sage a n d Lacey (18, 19) for propane and n-pentane were used t o ca lcu la te values of t h e expansion factor, defined a s :