Density calculation of liquid organic compounds using a simple equation of state up to high pressures (original) (raw)
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A simplified method for calculating saturated liquid densities
Fluid Phase Equilibria, 2004
A simplification for the Nasrifar-Moshfeghian (NM) liquid density correlation has been developed. A replacement for the Mathias and Copeman temperature-dependent term with the original Soave-Redlich-Kwong equation of state (SRK EOS) temperature-dependent term has been done. This replacement has overcome the limitations in use for the original model due to the Mathias and Copeman vapor pressuredependent parameters. The new correlation uses one characteristic parameter for each compound and suggests a value of zero for generalization purpose. The revised model has been tested for pure compounds liquid density prediction of different types including paraffins, cycloparaffins, olefins, diolefins, cyclic olefins, aromatics, ethers, liquefied inorganic gases and alcohols. The average absolute percent deviation for 76 compounds consisting of 2379 experimental data points was found to be 0.58%. The simplified method was then used to predict the saturated liquid density of multi-component systems. The average absolute percent deviation for 58 multi-component systems consisting of 978 experimental points was found to be 0.67%. Generalizing the correlation, by setting a value of zero for the characteristic parameter, gave average absolute percent deviation of 2.01% for the same pure compounds and 1.57% for the 58 multi-component systems. The accuracy of the simplified model has been compared with other correlations and equations of states. (M. Moshfeghian). 1 Present address: Coiled Tubing Services, Well Services, Schlumberger. though correlations are the most accurate and reliable way for the prediction of saturated liquid density, they suffer from shortcomings. For example, corresponding state liquid density, COSTALD [3], and Spencer-Danner [4] modification of Rackett [5], Rackett-Spencer-Danner (RSD), give poor results for the calculation of liquid density of He and H 2 as well as high deviation from the experimental data for multicomponent systems. Nasrifar and Moshfeghian [6] presented a correlation which works in conjunction with the predictive-Soave-Redlich-Kwong (PSRK) EOS [7]. Their correlation requires three parameters for the Mathias and Copeman [8] temperature-dependent term used in the PSRK EOS for each compound. In addition, the complexity in the calculation arises from the use of three different parameters for each compound. These parameters are not readily available for all compounds. The Mathias and Copeman parameters [8] are normally determined by regression of the vapor pressure data 0378-3812/$ -see front matter
Compressed and Saturated Liquid Densities for 18 Halogenated Organic Compounds †
Journal of Chemical & Engineering Data, 1997
The pressure-density-temperature P(F,T) behavior of 18 liquids that are potential working fluids in thermal machinery has been measured using a vibrating tube densimeter. For each liquid, the data were taken on isotherms spaced at intervals of 5 K to 10 K spanning the temperature range 245 K to 370 K. The pressures ranged from just above the vapor pressure (or the critical pressure) to 6500 kPa. The results of measurements at more than 12 000 thermodynamic points are summarized by correlating functions. Comparison with data from other laboratories indicates that the relative expanded uncertainty in the measured densities is less than 0.05%, except in the critical region. The repeatability of the measured densities is on the order of 0.005%. For each liquid, the P(F,T) data were extrapolated to the vapor pressure to obtain the density of the liquid at the vapor pressure. The fluids studied (and their designations by the refrigeration industry) were trichlorofluoromethane (pentafluoropropane (R245fa), and propane (R290). † Brand names and commercial sources of materials and instruments, when noted, are given for scientific completeness. Such information does not constitute a recommendation by the National Institute of Standards and Technology nor does it suggest that these products or instruments are the best for the described application.
Representation and Validation of Liquid Densities for Pure Compounds and Mixtures
Journal of Chemical & Engineering Data, 2015
Reliable correlation and prediction of liquid densities are important for designing chemical processes at normal and elevated pressures. A corresponding-states model from molecular theory was extended to yield a robust method for quality testing of experimental data that also provides predicted values at unmeasured conditions. The model has been shown to successfully represent and validate the pressure and temperature dependence of liquid densities greater than 1.5 of the critical density for pure compounds, binary mixtures, and ternary mixtures from the triple to critical temperatures at pressures up to 10 6 kPa. The systems include the full range of organic compounds, including complex solutions, and ionic liquids. Minimal data are required for making predictions.
A Note on the Relationship between Organic Solid Density and Liquid Density at the Triple Point
Journal of Chemical & Engineering Data, 2004
A simple relationship between the solid density of organic compounds and the liquid density at the triple point is presented as an extension of a previous relationship used internally by the DIPPR 801 database project. The relationship allows estimation of solid density (of the solid phase most stable at the triple point) for organic compounds over a wide range of temperatures with an average uncertainty of approximately 6%.
Liquid Density of Pure Alkanes and Halogenated Alkanes in a Corresponding States Format
1998
The development of a three parameters Corresponding States (CS) model is here proposed aiming at the prediction of the saturated and compressed liquid density of pure fluids pertaining to the two conformal families of alkanes (A) and hydrofluorocarbons (HFC) which are widely used as refrigerants. Two fluids of the same family are chosen for both their acentric factor value and for the saturated and compressed liquid density dedicated equations availability and, on the basis of the Teja et al. three parameters CS model, the saturated and compressed liquid density of a fluid of interest is obtained in reduced variables. Assuming experimental data of saturated liquid density for several components of each of the two families of fluids an improvement is introduced substituting the acentric factor with a new constant scaling factor. As a final result both the saturated and the compressed liquid models are predictive methods. The reached prediction accuracy of the proposed method is similar to that of the dedicated equations for all the fluids of a family. The result is particularly satisfactory for the application requirements in refrigeration.
Industrial & Engineering Chemistry Research, 2013
Experimental density data for o-xylene, m-xylene, p-xylene, and 2-methylnaphthalene, are reported at pressures (P) to 265 MPa and temperatures (T) to 525 K using a variable-volume, high-pressure cell. The reported data agree to within ±0.4% of available literature data. o-Xylene has the largest densities and p-xylene has the smallest densities in the P−T range investigated in this study although the 525 K isotherms for all three aromatics virtually superpose at high pressures. The aromatic densities are modeled using the Peng−Robinson (PR), high-temperature, high-pressure, volume-translated Peng−Robinson (HTHP VT-PR), and perturbed chain statistical associating fluid theory (PC-SAFT) equations of state (EoS). Generally, the PC-SAFT EoS gives the best predictions of the HTHP density data with mean absolute percent deviations (δ) within 1.0%, even though the pure-component parameters are fitted to low-pressure vapor pressure and saturated liquid density data. δ decreases to 0.4% for calculations with a new set of PC-SAFT parameters obtained from a fit of the HTHP experimental density data obtained in this study.
A compressed liquid density correlation
Fluid Phase Equilibria, 2000
A new correlation is developed for calculation of the compressed liquid density of pure compounds and Ž . mixtures. This correlation is used together with the Hankinson-Thomson COSTALD correlation of saturated liquid density and the Riedel equation for the calculation of vapor pressures. The range of application of this correlation is quite wide; from freezing point temperature to critical point temperature and from saturation pressure to 500 MPa. The average of error for the prediction of the compressed liquid volume of 31 compounds consisting of 3324 experimental data points is 0.77% with y0.24% bias from the experimental data. For mixtures, the average of error for the prediction of the compressed liquid volume of 13 mixtures consisting of 2101 experimental data points is 1% with y0.22% bias from the experimental data. The comparison with other correlations shows that the new correlation is somewhat better and quite reliable to very high pressures. q
Liquid Density of Alkanes and Halogenated Alkanes Mixtures in a Corresponding States Format
1998
The Corresponding States (CS) density models for mixture proposed here, one for saturated and one for compressed liquid, are analytically similar to the pure fluid liquid density exposed in the former paper, but now with critical constants and 8,, replacing wm , as from the mixing rules. The mixing rules present two adjustable interaction coefficients for each binary pair, but they are set to unity making the two models completely predictive: both in fact do not preliminarily require any density data for the mixture of interest. To improve the prediction accuracy a correlative mode is here proposed in which the om parameter is substituted with a 8,, (x) function which parameters are regressed from saturated liquid data, when available, for the binary mixture of interest. The two models are validated with mixtures experimental data for the families of alkanes and hydrofluoroalkanes (HFC) and the prediction accuracy obtained is significatively better with respect to the existing predictive liquid density models for mixtures. The result is particularly useful for the studies about the new generation refrigerants applications.
Materials Chemistry and Physics, 1985
Molar or specific volumes, isobaric expansivities and/or isothermal compressibilities have been determined by the piezometric method for: n-nonane, 3,3diethylpentane (DEP), 5,5-dibutylnonane, 4,4-dipropylheptane (DPH), n-heptadecane, tetraethylsilane, tetraethylammonium tetrapropylborate (TETP), tetra-propylam~nium tetraethylborate (TPTE), tetrapropyla~onium tetrabutylborate TPTB), equimolar mixtures of DEP and DPH, and water. The temperature interval covered was in most cases 30-15O"C, pressures O-800 J-cmq3. Normal melting temperatures were determined: 353 K for TETP, 382 K for TPTE and 383 K for TPTB. A formula relating the liquid isothermal compressibility to both temperature and pressure has been proposed and successfully tested; it is applicable to inorganic as well as organic materials.