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.     

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.     

The thermal conductivity of n-hexane,n-heptane,and n-decane by the transient hot-wire method

New absolute measurements of the thermal conductivity of liquid n-hexane, n-heptane, and n-decane are reported. The measurements have been carried out in the temperature range 300–370 K at atmospheric pressure in a transient hotwire instrument. The accuracy of the measurements is estimated to be ±0.5%. The density dependence of the thermal conductivity of n-hexane and n-heptane is found to be well described by a universal equation for the hydrocarbons based on a rough hard-sphere model. The measurements of the three hydrocarbons studied are also employed to generate more accurate effective core volumes, which are the only parameters characteristic of the fluid required for the application of the proposed universal scheme.     

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.     

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.     

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 viscosity of five liquid hydrocarbons at pressures up to 250 MPa

This paper reports new measurements of the viscosity of toluene, n-pentane, n-hexane, n-octane, and n-decane at pressures up to 250 MPa in the temperature range 303 to 348 K. The measurements were performed with a vibrating-wire viscometer and with a relative method of evaluation. Calibration of the instrument was carried out with respect to reference values of the viscosity of the same liquids at their saturation vapour pressure. The viscosity measurements have a precision of ±0.1% but the accuracy is limited by that of the calibration data to be ±0.5%. The experimental data have been represented by polynomial functions of pressure for the purposes of interpolation. The data are also used as the most precise test yet applied to a representation of the viscosity of liquids based upon hard-sphere theory.     

Accurate measurement of the thermal conductivity and thermal diffusivity of toluene andn-heptane

Accurate and simultaneous measurements of the thermal conductivity and thermal diffusivity of toluene andn-heptane were made with an improved transient hot-wire method by using a transfer function having a feedback loop, in the temperature range of 0 to 45°C at atmospheric pressure. The accuracy of the empirical equations as a function of temperature is estimated to be 0.4 to 0.5% for the thermal conductivity and about 4% for the thermal diffusivity. Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5–8, 1995, Tokyo, Japan.     

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.     

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.     

Correlation and prediction of dense fluid transport coefficients. VI.n-alcohols

A previously described method, based on considerations of hard-sphere theory, is used for the simultaneous correlation of the coefficients of viscosity, self-diffusion, and thermal conductivity for then-alcohols, from methanol ton-decanol, in excellent agreement with experiment, over extended temperature and pressure ranges. Generalized correlations are given for the roughness factors and the characteristic volume. The overall average absolute deviations of the experimental viscosity, self-diffusion, and thermal conductivity measurements from those calculated by the correlation are 2.4, 2.6, and 2.0%, respectively. Since the proposed scheme is based on accurate density values, a Tait-type equation was also employed to correlate successfully the density of then-alcohols. The overall average absolute deviation of the experimental density measurements from those calculated by the correlation is ±0.05%.     

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.     

Correlation and prediction of dense fluid transport coefficients. I. n-alkanes

Recent accurate measurements of the self-diffusion coefficient for n-hexadecane and n-octane and of the viscosity coefficient for n-heptane, n-nonane, and n-undecane over wide pressure ranges have been used to provide a critical test of a previously described method, based on consideration of hard-sphere theory, for the correlation of transport coefficient data. It is found that changes are required to the universal curve for the reduced viscosity coefficient as a function of reduced volume and, also, to the parameters R _D, R , and R which were introduced to account for effects of nonspherical molecular shape. The scheme now accounts most satisfactorily for the self-diffusion, viscosity, and thermal conductivity coefficient data for all n-alkanes from methane to hexadecane at densities greater than the critical density.     

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.     

Thermal conductivity of water and 2-n-butoxyethanol and their mixtures in the temperature range 305–350 K at pressures up to 150 MPa

The thermal conductivity of binary liquid mixtures of water and 2-n-butoxyethanol has been measured within the temperature range 305–350 K at pressures up to 150 MPa. The measurements have been carried out with a transient hotwire instrument suitable for electrically conducting liquids and have an estimated accuracy of ±0.3%. The liquid mixture has a closed-loop solubility and reveals a lower critical solution temperature for a mole fraction of 2-n-butoxyethanol of 0.0478 at a temperature of 322.25 K. The results of the measurements reveal a small, but discernible, enhancement of the thermal conductivity of the solution at the critical composition.Paper presented at the Twelfth Symposium on Thermophysical Properties. June 19–24, 1994, Boulder, Colorado, U.S.A.     

Measurements of the Liquid Viscosities of Mixtures of n-Butane, n-Hexane, and n-Octane with Squalane to 30 MPa

The viscosities of liquid mixtures of n-butane, n-hexane, and n-octane with squalane that represent model mixtures of refrigerants with refrigeration oil were measured at temperatures between 273.15 and 333.15 K, and at pressures from 0.1 to 30 MPa, by using a falling body viscometer. The uncertainty of the measurements was estimated to be no larger than 2.9%. The experimental viscosity values were fitted to a Tait-like equation within 2.8%. There are larger deviations between the experimental data and calculated values predicted by the equation of Kanti et al., which is derived from the Flory theory. By introducing an interaction parameter of the energetic mixing rule into the equation, the deviations were significantly reduced.     

Modeling the Thermal Conductivity of Pure and Mixed Heavy n-Alkanes Suitable for the Design of Phase Change Materials

Recent interest in the use of paraffin waxes is related to energy management provided by phase change materials (PCMs) where a tunable melting temperature range is used to store or release latent heat by means of the solid–liquid phase change. Thermal conductivity is an essential property for the correct design of these new materials, with applications as different as household heating and insulation, clothes for athletes and campers, or solar energy storage. As the interest in most of these heavier n-alkanes was small until recently, the available data are particularly limited. The purpose of this work was to develop a simple and accurate model to estimate the liquid thermal conductivity of heavy n-alkanes suitable for the design of efficient PCMs. Corresponding states theory was selected, based on previous improvements for equilibrium and transport properties of pure and mixed heavy n-alkanes, using a second-order perturbation model on the Pitzer acentric factor. Results for the n-alkane series show that this new model is able to predict thermal conductivities in a broad temperature and pressure range with a deviation of 3%, whereas common deviations using a linear perturbation model are close to 16%. Results for one ternary and five binary mixtures indicate that the extension to mixtures is straightforward with the best results obtained using a mixing rule previously proposed for viscosity.     

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.     

Density and Viscosity of Mixtures of n-Hexane and 1-Hexanol from 303 to 423 K up to 50 MPa

Experimental results for the density and viscosity of n-hexane+1-hexanol mixtures are reported at temperatures from 303 to 423 K and pressures up to 50 MPa. The binary mixture was studied at three compositions, and measurements on pure 1-hexanol are also reported. The two properties were measured simultaneously using a single vibrating-wire sensor. The present results for density have a precision of ±0.07% and an estimated uncertainty of ±0.3%. The viscosity measurements have a precision of ±1% and an estimated uncertainty of ±4%. Representations of the density and viscosity of the mixture as a function of temperature and pressure are proposed using correlation schemes.     

Thermal conductivity of n-tridecane at pressures up to 500 MPa in the temperature range 35–75°C

Thermal conductivity coefficients are reported for liquid n-tridecane along three isotherms, 35, 48, and 73°C, and for pressures from 20 to 500 MPa. The measurements have been made with a transient hot-wire instrument, and the results, when corrected for the effects of radiation absorption, have an estimated uncertainty of ±0.7%. The thermal conductivity as a function of density along isotherms can be represented by means of the same form of equation as that found suitable for other normal alkanes, and this is based upon a heuristic modification of the van der Waals theory of liquids.