A correlation of thermal conductivity data for helium

A correlation for the thermal conductivity of helium has been developed which covers the temperature range from temperatures just above the lambda line to 830 K, and densities up to about 160 kg m⁻³. The data used incorporate some recent experimental results which cover the temperature range from 4 K to 20 K including the critical region. The correlation gives an equation which generally fits the experimental data within ± 5%. However, at low temperature, the experimental data deviate up to about 10% from predictions based upon viscosity measurements or molecular dynamics calculations.     

Reference Correlation for the Viscosity of Liquid Cyclopentane from 220 to 310 K at Pressures to 25 MPa

A correlation in terms of temperature and molar volume is recommended for the viscosity of liquid cyclopentane as a reference for low-temperature, high-pressure viscosity measurements. The temperature range covered is from 220 to 310 K and the pressure range from atmospheric up to 25 MPa. The standard deviation of the proposed correlation, within a 95% confidence limit, is 1%.     

The viscosity of gaseous propane and its initial density dependence

Results of five series of high-precision viscosity measurements on gaseous propane, each differing in density, are reported. The measurements were performed in a quartz oscillating-disk viscometer with small gaps from room temperature up to about 625 K and for densities between 0.01 and 0.05 mol · L^–1. The experimental data were evaluated with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficients deduced from the zero-density and initial-density viscosity coefficients for propane and for furthern-alkanes are in close agreement with the theoretical representation of the Rainwater-Friend theory for the potential parameter ratios by Bich and Vogel. A new representation of the viscosity of propane in the limit of zero density is provided using the new experimental data and some data sets from literature. The universal correlation based on the extended principle of corresponding states extends over the temperature range 293 to 625 K with an uncertainty of ±0.5 % and deviates from earlier representations by about 1 % at the upper temperature limit.     

Saturated Liquid Viscosity and Surface Tension of Alternative Refrigerants

Light scattering by thermally excited capillary waves on liquid surfaces or interfaces can be used for the investigation of viscoelastic properties of fluids. In this work, we carried out the simultaneous determination of the surface tension and the liquid kinematic viscosity of some alternative refrigerants by surface light scattering (SLS) on a gas–liquid interface. The experiments are based on a heterodyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). R23 (trifluoromethane), R32 (difluoromethane), R125 (pentafluoroethane), R143a (1,1,1-trifluoroethane), R134a (1,1,1,2-tetrafluoroethane), R152a (1,1-difluoroethane), and R123 (2,2-dichloro-1,1,1-trifluoroethane) were investigated under saturation conditions over a wide temperature range, from 233 K up to the critical point. It is estimated that the uncertainty of the present surface tension data for the whole temperature range is less than ±0.2 mN·m^–1. For temperatures up to about 0.95T _c, the kinematic viscosity of the liquid phase could be obtained with an absolute accuracy of better than 2%. For the highest temperatures studied in this work, measurements for the kinematic viscosity exhibit a maximum uncertainty of about ±4%. Viscosity and surface tension data are represented by a polynomial function of temperature and by a van der Waals-type surface tension equation, respectively. The results are discussed in detail with comparison to literature data.     

The Viscosity of Toluene in the Temperature Range from 210 to 370 K at Pressures up to 30 MPa

The paper presents new measurements of the viscosity of toluene over a temperature range from 210 to 370 K, from the saturation line up to pressures of 30 MPa. The measurements were performed with a vibrating-wire viscometer. The uncertainty of the measurements, confirmed above room temperature with the measurement of the viscosity of water, is estimated to be ±0.5%.     

Measurements of the viscosity of toluene + mesitylene mixtures at pressures up to 55 MPa

New absolute measurements of the viscosity of mesitylene and binary mixtures of toluene + mesitylene are presented. The measurements were performed in a vibrating-wire instrument and cover a temperature range of 295–330 K and pressures up to 55 MPa. The concentrations studied were 40 and 70%, by weight, of toluene. The overall uncertainty in the reported data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the viscosity of mixtures from the pure components is used to predict successfully the viscosity of these mixtures, as a function of composition, temperature, and pressure.     

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.     

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.     

Density and Viscosity Measurements of Dimethoxymethane and 1,2-Dimethoxyethane from 243 K to 373 K up to 20 MPa

Measurements of the density and viscosity of dimethoxymethane and 1,2-dimethoxyethane are reported over the temperature range from 243 K to 373 K and at pressures up to 20 MPa. The measurements were performed simultaneously using a vibrating-wire instrument operated in the forced mode of oscillation. The overall uncertainties of these results are 2.0% in viscosity and 0.2% in density. The measurements were correlated with a Tait-type equation for density and a hard-sphere model for viscosity. The maximum absolute deviation and the average absolute deviation (AAD) of the density measurements from the correlation for dimethoxymethane are 0.065% and 0.012%, respectively, and for 1,2-dimethoxyethane, are 0.16% and 0.044%. With regard to viscosity, the maximum absolute deviation and the AAD of the present results from the correlation for dimethoxymethane are 1.55% and 0.40%, respectively, and for 1,2-dimethoxyethane, are 1.05% and 0.26%. Comparisons of the experimental data and measurements from the literature with values calculated by the correlations at different temperatures and pressures are presented.     

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.     

Vapor-phase viscosity of phenol

New measurements of the vapor-phase viscosity of phenol were performed from 437 up to 624 K and for densities between 0.006 and 0.023 mol · L^–1 in an all-quartz oscillating-disk viscometer with small gaps. Thus, including our own measurements reported earlier, experimental data are available in the temperature range between 376 and 639 K and in the density range from 0.001 up to 0.023 mol · L^–1. The data were evaluated with a density series for the viscosity in which only a linear density contribution is included. The values of the second viscosity virial coefficient obtained for phenol as well as for benzene, toluene, and p-xylene were compared with results of the Rainwater-Friend theory and of the modified Enskog theory on the basis of the Lennard-Jones 12-6 potential. The agreement is reasonable, when the potential parameter ratios determined by Bich and Vogel are used. The influence of bound dimers seems to be already taken into account in the three-monomer contribution according to Hoffman and Curtiss.Paper dedicated to Professor Joseph Kestin.     

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.     

A New Apparatus for Combined Measurements of the Viscosity and Density of Fluids for Temperatures from 233 To 523 K at Pressures up to 30 Mpa

A new apparatus for measuring the viscosity and density of fluids is presented. The main element of the instrument is an electronically controlled magnetic suspension coupling. For the density measurement (buoyancy principle according to the single-sinker method), this coupling is used for the contactless transfer of the forces acting on a sinker in the measuring cell to an analytical balance. The coupling also serves as a frictionless bearing for a slender rotating cylindrical body which is slowed down due to the viscous drag of the fluid surrounding the cylinder. The viscosity of the fluid can be directly determined from the decay rate of the rotational frequency. The new combined viscometer-densimeter covers a viscosity range of 5 to 150 Pa·s and a density range from 20 to 2000 kg·m^–3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Test measurements on the viscosities and densities of nitrogen and carbon dioxide at 253, 293, and 523 K at pressures up to 30 MPa show an estimated total uncertainty of ±0.6 to ±1.0% in viscosity and of ±0.02 to ±0.05% in density.     

An improved correlation for the thermal conductivity of HCFC123 (2,2-dichloro-1,1,1-trifluoroethane)

An updated survey of the existing thermal conductivity data for HCFC123 is presented. In addition, new wide-ranging thermal conductivity measurements, which have been carried out at NIST, are summarized. These results supplement the existing database and are used for an improved correlation of the thermal conductivity of HCFC123. The correlation covers the temperature range from 180 to 480 K with pressures up to 67 MPa or densities up to 1900 kg m⁻³. The correlation includes an empirical critical enhancement term of a form suitable for industrial use and represents the NIST dataset within ±2.22% at the 95% confidence level.     

High-Pressure Viscosity Measurements for the Ethanol + Toluene Binary System

The viscosity of the ethanol + toluene binary system has been measured with a falling-body viscometer for seven compositions as well as for the pure ethanol in the temperature range from 293.15 to 353.15 K and up to 100 MPa with an experimental uncertainty of 2%. At 0.1 MPa the viscosity has been measured with a classical capillary viscometer (Ubbelohde) with an uncertainty of 1%. A total of 209 experimental measurements have been obtained for this binary system, which reveals a non-monotonic behavior of the viscosity as a function of the composition, with a minimum. The viscosity behavior of this binary system is interpreted as the result of changes in the free volume, and the breaking or weakening of hydrogen bonds. The excess activation energy for viscous flow of the mixtures is negative with a maximum absolute value of 335 J · mol⁻¹, indicating that this binary system is a very weakly interacting system showing a negative deviation from ideality. The viscosity of this binary system is represented by the Grunberg–Nissan and the Katti–Chaudhri mixing laws with an overall uncertainty of 12% and 8%, respectively. The viscosity of methanol (23 point) has also been measured in order to verify the calibration of the falling-body viscometer within the considered T, P range.     

Thermal conductivity of carbon tetrachloride in the temperature range 310 to 364 K at pressures up to 0.22 GPa

The paper reports new measurements of the thermal conductivity of carbon tetrachloride in the temperature range 310 to 364 K at pressures up to 0.22 GPa. The experimental data have an estimated uncertainty to ±0.3%. The hard-sphere theory of transport in dense fluids is employed to formulate a correlation scheme for the thermal conductivity as a function of density. A single equation represents the dependence of the thermal conductivity on density for all isotherms, the isotherms being distinguished by a characteristic value of the molar volume. It is shown that earlier measurements of the viscosity and self-diffusion coefficient of carbon tetrachloride may be represented in a similar fashion using consistent values of the characteristic volume.     

The viscosity and thermal conductivity of ethane in the limit of zero density

New representations of the viscosity and thermal conductivity of ethane in the limit of zero density are provided. The correlation for the viscosity extends over the temperature range 200 to 1000 K, whereas that for thermal conductivity extends from 225 to 725 K. The behavior of each property is represented by an independent correlation of the appropriate effective collision cross section as a function of temperature. The final results are compared with experimental data as well as with earlier correlations. The accuracy of the viscosity correlation is estimated to be ±0.5 % in the temperature range 300 KT600 K, increasing to ±1.5 and ±2.5% at 200 and 1000 K, respectively. The uncertainty associated with the thermal conductivity correlation is ±2 % in the temperature range 300 KT500 K, increasing to ±3% at either end. The results of this study indicate that there is an urgent need for additional high-precision measurements of thermal conductivity especially for temperatures above 400 K.     

An Absolute Viscometer-Densimeter and Measurements of the Viscosity of Nitrogen, Methane, Helium, Neon, Argon, and Krypton over a Wide Range of Density and Temperature

An apparatus for the simultaneous measurement of viscosity and density of fluids is presented. The viscometer-densimeter covers a viscosity range up to 150 µPas and a density range up to 2000 kgm^–3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Very accurate density measurements with uncertainties of ±0.02 to ±0.05% have always been carried out with this apparatus, although in its first version it was necessary to calibrate the viscosity measuring system on a reference fluid in order to achieve uncertainties of ±0.6 to ±1.0% in viscosity. After significant improvements, the apparatus now achieves uncertainties in viscosity of less than ±0.15% in the dilute gas region and less than ±0.4% for higher densities. Moreover, the viscosity measuring system can be described in an absolute way; calibration is no longer necessary. In order to test the advanced apparatus and to determine viscosity-density values of very high quality, comprehensive measurements on nitrogen, argon, and methane were carried out in the entire working range of the viscometer-densimeter. In addition, viscosity-density measurements on helium, neon, and krypton were made on two selected isotherms each. All measurements show that the estimated total uncertainty of ±0.15 to ±0.4% in viscosity and of ±0.02 to ±0.05% in density is clearly met. In order to verify the results of the combined viscometer-densimeter, a new apparatus for very accurate viscosity measurements was designed. While the working range of this apparatus is restricted to the dilute gas region, it yields uncertainties of less than ±0.07% in viscosity. Measurements carried out with this apparatus confirmed the previously measured values of the combined viscometer-densimeter within ±0.03%.     

Viscosity of Toluene+Cyclopentane Mixtures: Measurements and Prediction

New measurements of the viscosity of binary mixtures of toluene+cyclopentane are presented. The measurements, performed in a vibrating-wire viscometer, cover the temperature range from 210 to 310 K at pressures up to 25 MPa. The concentrations studied are 60 and 30%, by weight, toluene. The uncertainty of the measurements, confirmed at room temperature and higher temperatures with the measurement of the viscosity of water, is estimated to be ±0.5%, increasing to ±1% at temperatures below 240 K. The present measurements are employed to examine the predictive power of two recent theoretically based schemes proposed for the calculation of the viscosity of mixtures.     

High-Pressure Measurements of the Viscosity and Density of Two Polyethers and Two Dialkyl Carbonates

The viscosity and density of four pure liquid compounds (dimethyl carbonate, diethyl carbonate, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether) were measured at several temperatures between 283.15 and 353.15 K. The density measurements were performed up to 60 MPa with an uncertainty of 1×10^–4g·cm^–3. The viscosity at atmospheric pressure was measured with an Ubbelohde-type glass capillary tube viscometer with an uncertainty of ±1%. At pressures up to 100 MPa the viscosity was determined with a falling ball viscometer with an uncertainty of ±2%. The density (410 experimental values) and viscosity data (184 experimental values) were fitted to several correlation equations.