Measurements of the viscosity of n-heptane + n-undecane mixtures at pressures up to 75 MPa

New absolute measurements of the viscosity of binary mixtures of n-heptane and n-undecane are presented. The measurements, performed in a vibrating-wire instrument, cover the temperature range 295–335 K and pressures up to 75 MPa. The concentrations studied were 40 and 70%, by weight, of n-heptane. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to predict successfully both the thermal conductivity and the viscosity of these mixtures, as a function of composition, temperature, and pressure.     

Mutual diffusivity in binary mixtures of n-heptane with n-hexane isomers

This paper presents a study of the influence of branching in the binary diffusion coefficients of n-heptane + n-hexane isomers, in the liquid state. The measurements have been made with the Taylor dispersion technique, at several compositions, at 283 and 298 K, for the X + n-heptane mixtures, where X= n-hexane, 3-methylpentane, 2, 3-dimethylbutane, and 2, 2-dimethylbutane. The results show a very interesting behavior of the composition dependence of the binary diffusion coefficients, presenting a maximum, for compositions about a molar fraction of n-heptane of 0.5, which increases with the increase in the degree of branching, suggesting the possibility of order-disorder effects caused by stereochemically favored packing in the liquid phase and energetically favored segment interaction in the liquid mixtures. An attempt to apply the van der Waals model to these data could not predict the experimental binary diffusion coefficients of these systems within the experimental accuracy.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Composition dependence of binary diffusion coefficients in alkane mixtures

The binary diffusion coefficients of mixtures of n-heptane with n-hexane and 2,2,4-trimethylpentane with n-hexane have been measured at various compositions at 308.1, 312.2, and 316.5 K using the Taylor dispersion technique. The experimental results for the n-hexane/n-heptane system were in good agreement with the literature values (<1.5%). The observed binary diffusion coefficients for this system exhibit a linear dependence on composition. On the contrary, the results of the n-hexane/2,2,4-trimethylpentane system reveal an interesting behavior of the composition dependence of the binary diffusion coefficients, presenting a slight maximum, for composition at a molar fraction of n-hexane of 0.86. In order to explain this difference in behavior, the influence of branching of molecules on diffusion is discussed. It was found that although the Enskog hard-sphere model for binary diffusion can reproduce the experimental results for the n-hexane/n-heptane system within 3%, it failed to predict the composition dependence of the n-hexane/2,2,4-trimethylpentane system within the experimental accuracy. The results showed that there is significant effect of branching in alkane molecules on the diffusion coefficient. This effect has been quantified using the roughness parameter, which represents the magnitude of coupling between translational and rotational motions.     

Viscosity and thermal conductivity of binary n-heptane + n-alkane mixtures

New absolute measurements of the viscosity of binary mixtures of n-heptane with n-hexane and n-nonane are presented. The measurements, performed in a vibrating-wire instrument, cover a temperature range 290–335 K and pressures up to 75 MPa. The concentrations studied are 40 and 70% by weight of n-heptane. The accuracy of the reported viscosity data is estimated to be ±0.5%. The present measurements, together with other n-heptane + n-alkane viscosity and thermal-conductivity measurements, are used to develop a consistent semiempirical scheme for the correlation and prediction of these mixture properties from those of the pure components.     

Viscosities of nonelectrolyte liquid mixtures. II. Binary mixtures ofn-hexane with alkanoates and bromoalkanoates

Viscosity measurements are reported for mixtures of ethyl ethanoate, ethyl propionate, ethyl butyrate, ethyl-2-bromopropionate, ethyl-3-bromopropionate, ethyl-2-bromobutyrate, and ethyl-4-bromobutyrate withn-hexane at 303.15 K. The viscosity data have been correlated with equations of Grunberg and Nissan, of McAllister, and of Auslaender. Furthermore, excess Gibbs energies of activationG ^*E of viscous flow have been calculated with Eyring's theory of absolute reaction rates and values ofG ^*E for the present binary mixtures have been explained in terms of the dipole-dipole interaction in alkanoates and the intramolecular Br...O interaction in bromoalkanoates.     

Correlation and prediction of dense fluid transport coefficients. III. n-alkane mixtures

Viscosity and thermal conductivity coefficients for binary, ternary, and quaternary n-alkane mixtures are predicted over extended ranges of temperature and pressure, in excellent agreement with experiment, by extension of a method recently described for the correlation of n-alkane transport coefficients. The outstanding advantage of this approach is that there are no adjustable parameters. Furthermore, in contrast with other mixture viscosity equations, this scheme does not require experimental viscosity coefficient data for the pure components under the same conditions of temperature and pressure.     

Densities, Sound Speeds, Excess Volumes, and Excess Isentropic Compressibilities of Methyl Acrylate + 1-Propanol (or 1-Butanol) + Hydrocarbons(n-Hexane, n-Heptane, Cyclohexane, Benzene, and Toluene) at 308.15 K

Densities and sound speeds of ten ternary mixtures of methyl acrylate (1)+1-propanol (2) or 1-butanol (2)+n-hexane (3), +n-heptane (3), +cyclohexane (3), +benzene (3), and +toluene (3) have been measured at 308.15 K. The excess volumes, V ^E , and excess isentropic compressibilities, ^E _s , have been estimated. These two experimentally derived excess functions were also compared with those predicted by empirical equations of Redlich–Kister, Kohler, and Tsao–Smith. A qualitative analysis of V ^E and ^E _s data of ternary mixtures reveals that in MA (1)+1-alcohols (2)+n-hexane (3), +n-heptane (3), and +cyclohexane (3), structure disruptions are more predominant while in MA (1)+1-alcohols (2)+benzene (3) or +toluene (3) mixtures, the weak but specific structure making interactions dominate. A perusal of deviations between the experimental and calculated V ^E and ^E _s results shows that the predictive expressions give only a rough estimate of the functions for the ten studied mixtures.     

Measurements of the viscosity of n-heptane,n-nonane,and n-undecane at pressures up to 70 MPa

New absolute measurements of the viscosity of n-heptane, n-nonane, and n-undecane are presented. The measurements were performed with a vibrating-wire instrument at temperatures of 303.15 and 323.15 K and pressures up to 70 MPa. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%. A recently developed semiempirical scheme for the correlation and prediction of the thermal conductivity, viscosity, and self-diffusion coefficients of n-alkanes is applied to the prediction of the viscosity of n-heptane, n-nonane, and n-undecane. The comparison of these predicted values with the present high-pressure measurements demonstrates the predictive power of this scheme.     

Empirical and Semi-theoretical Methods for Predicting the Viscosity of Binary <Emphasis Type="Italic">n</Emphasis>-Alkane Mixtures

In this study, empirical and semi-theoretical methods for predicting the viscosity of binary mixtures of n-alkanes are presented at atmospheric pressure and in the temperature range from 288 to 333 K. In the empirical viscosity calculation method, a modified version of the Andrade equation and a simple mixture rule are used. The proposed semi-theoretical method employs both the Enskog’s hard-sphere theory for dense fluids and the principle of corresponding states. The viscosities of binary mixtures of n-heptane with n-hexane and n-nonane covering different compositions were calculated using these methods which require only critical properties and the normal boiling point as input data. The predictions were compared with accurate experimental data in the literature. Highly satisfactory results were obtained. The percent average absolute deviations amount to 1.2 and 0.9% utilizing the empirical and semi-theoretical viscosity methods, respectively, for 27 data points. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

The transport properties of ethane. I. Viscosity

A new representation of the viscosity of ethane is presented. The representative equations are based upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory in the zero-density limit, vapor phase, and critical region. The representation extends over the temperature range from 100 K to the critical temperature in the liquid phase and from 200 K to the critical temperature in the vapor phase. In the supercritical region, the temperature range extends to 1000 K for pressures up to 2 MPa and to 500 K for pressures up to 60 MPa. The ascribed accuracy of the representation varies according to the thermodynamic state from ±0.5 % for the viscosity of the dilute gas near room temperature to ±3.0% for the viscosity at high pressures and temperatures. Tables of the viscosity, generated by the relevant equations, at selected temperatures and pressures and along the saturation line, are also provided.     

Viscosity of binary mixtures. IV. Triethylamine with alkanes and monoalkylamines at 303.15 and 313.15 K

Viscosities and densities of seven binary mixtures of n-hexane, n-octane, isooctane, n-propylamine, n-butylamine, n-hexylamine, and n-octylamine with triethylamine have been measured at 303.15 and 313.15 K. Deviations of viscosities from a linear dependence on the mole fraction and values of excess Gibbs energy of activation G ^*E of viscous flow are attributable to the H-bonding and to the size of the alkylamine and alkane molecules.     

Viscosity and density of liquid mixtures ofn-alkanes with squalane

Viscosity and density measurements are reported for binary liquid mixtures ofn-butane andn-hexane with squalane in the temperature range from 273 to 333 K. The viscosity measurements have been carried out by using a capillary viscometer calibrated with standard liquids. that is. JS5, JSIO, JS20, and water. The uncertainty in the viscosity data was estimated to be ± 1.7%. The density needed for the calculation of the viscosity has been measured by using a glass pycnometer within an accuracy of ±0.04%. In the prediction of the viscosity, the scheme of Assael et al. fails for mixtures of this type differing greatly in size.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, U.S.A.     

Excess volumes and excess viscosities of binary mixtures of some cyclic ethers + bromocyclohexane at 298.15 and 313.15 K

Excess Volumes,V ^E, and excess viscosities, ^E, at 293.15 and 313.15 K are reported for binary mixtures of some cyclic ethers (tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran and 2,5-dimethyltetrahydrofuran) + bromocyclohexane. These properties were obtained from density and viscosity measurements. ^E and ^E show negatives values for all the mixtures.     

Extended corresponding states as a tool for the prediction of the thermodynamic properties of mixtures

The principle of corresponding states, with one of its many extensions, is used to predict the thermodynamic properties of the binary mixtures N₂-CH₄ and CH₄-C₂H₆. Comparisons of the predicted properties with experimental data are given to illustrate some of the powers and problems associated with the method. Problems encountered in modeling mixtures, which are not necessarily associated with the mathematical model of the equation of state, are also discussed. Wide-range equations of state for the two binary systems mentioned above are presented.Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Absolute measurement of the thermal conductivity of alcohol + n-hexane mixtures

New absolute measurements, by the transient hot-wire technique, of the thermal conductivity of binary mixtures of n-hexane with methanol, ethanol, and hexanol are presented. The temperature range examined was 295–345 K and the pressure atmospheric. The concentrations studied were 75% by weight of methanol and 25, 50, and 75% by weight of ethanol and hexanol. The overall uncertainty in the reported thermal conductivity data is estimated to be ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to correlate and predict the thermal conductivity of these mixtures, as a function of both composition and temperature.     

Nonequilibrium Molecular Dynamics Simulations of Shear Viscosity: Isoamyl Alcohol, n-Butyl Acetate, and Their Mixtures

Nonequilibrium, NVT, molecular dynamics (NEMD) simulations were used to obtain the shear viscosity, , of isoamyl alcohol, n-butyl acetate, and their binary mixtures at 35°C and 0.1 MPa. The fluids were modeled using rigid bonds, rigid bond angles, appropriate torsional potentials, pairwise-additive Lennard–Jones dispersion interactions between united-atom sites, and partial point charges located at atomic centers. Simulations were performed at different shear rates, , and values obtained at =0 are compared to experimental values. Two methods are commonly used to extrapolate pure-fluid simulated data to zero shear, (0). The applicability of these two methods to mixtures of polar fluids was examined in this study. It was found that linear extrapolation with respect to ^1/2 can lead to ambiguous (0) results for some mixtures because of a curvature in the data that shows no observably distinct change in rheology. On the other hand, a log–log plot of () versus is consistently very linear with a distinct change from shear-thinning to Newtonian rheology at lower shear rates. The latter method is recommended for consistency sake, even though agreement between experiment and (0) values was better with the former method. This agreement was 12 and 21% for the two methods, respectively. A negative bias in the simulated values is attributable to the united-atom model.     

Viscosity and Liquid Density of Asymmetric Hydrocarbon Mixtures

Although a large body of viscosity data exists for simple mixtures of lighter n-alkanes, available information for heavy or asymmetric systems is scarce. Experimental measurements of viscosity and liquid densities were performed, at atmospheric pressure, in pure and mixed n-heptane, n-hexadecane, n-eicosane, n-docosane, and n-tetracosane from 293.15 K, or above the melting point, up to 343.15 K. The measured densities were correlated using the Peng–Robinson equation of state, and viscosities were modelled using the friction theory.     

The thermal conductivity of n-hexadecane+ ethanol and n-decane+butanol mixtures

New absolute measurements, by the transient hot-wire technique, of the thermal conductivity of n-hexadecane and binary mixtures of n-hexadecane with ethanol and n-decane with butanol are presented. The temperature range examined was 295–345 K and the pressure atmospheric. The concentrations of the mixtures studied were 92% (by weight) of n-hexadecane and 30 and 70% (by weight) of n-decane. The overall uncertainty in the reported thermal conductivity data is estimated to be ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to correlate and predict the thermal conductivity of these mixtures, as a function of both composition and temperature.     

Local composition modelling of the thermodynamic properties of refrigerant and oil mixtures

Six local composition models of the thermodynamic behaviour of mixtures are described. Using data from the literature and a non-linear regression analysis, a comparison of the predictive abilities of the models is undertaken for R12, R22, R134a and R125 with various oils. The Wilson and Heil equations provide the most consistent results, with the Heil equation providing a modest improvement over the Wilson model. Using a 95% confidence interval, the Heil equation predicted the behaviour of R12 with a paraffinic mineral oil to within 3.1%; its worst-case 2-σ error was 10.4% (R22 with a polyol ester oil), and its average 2-σ error for all of the mixtures was 6.2%. Using model parameters and error estimates from the regression analyses, pressure-temperature-concentration behaviour for these mixtures can be predicted for system design and simulation.     

Viscosity of liquidn-heptane by dynamic light scattering

The dynamic viscosity of liquidn-heptane was measured in the temperature range 293–353 K by dynamic light scattering employing a newly designed optical setup. Commercial stearyl-coated silica particles were used as a seed, where a calibration of particle sizes to obtain absolute viscosity values was performed in other alkanes. The measurements included experimental runs at various particle concentrations and scattering vectors and in both a heating and a cooling cycle with a total standard deviation of 0.8–0.9%. As established reference values exist for alkane viscosities, from which the deviations were below 1% over the whole range of relevant temperatures, the experiments may also be regarded as a successful test of the accuracy of the method.