J. Kestin

On the density expansion for viscosity in gases

Abstract The paper presents the results of new, precise measurements of the viscosity of nitrogen, argon, and helium at 25°C. The measurements were performed over a nominal range of pressures 1–100 atm and at very closely spaced density intervals. The data were subjected to a stringent statistical analysis in order to determine whether the density expansion consists of a pure polynomial or whether a term of the form ϱ2 ln ϱ must be included in it. The existence of such a term was discovered theoretically by several investigators. The analysis indicates that if such a term exists, its factor must be very small. Moreover, the statistically significant interval of values which this factor can assume includes zero in it. This result is interpreted as indicating that correlations which extend over distances of the order of a mean free path are negligible when compared with correlations which extend over distances of the order of the range of molecular interactions.

Viscosity of He–Ar and He–Kr Binary Gaseous Mixtures in the Temperature Range 25–720°C

Measurements were made of the viscosity of helium, argon, krypton, and the mixture pairs helium–argon and helium–krypton to elevated temperature. The viscosity of the pure gases was measured to a temperature of about 850°C, whereas that of the mixtures was measured to 720°C. The instrument used was that of an oscillating‐disk type, and absolute measurements were obtained. The data on the pure gases showed good agreement with previous work on oscillating viscometers but did not agree well with the older capillary‐flow measurements. It is contended that the present results enjoy a higher confidence level. The pure‐gas results were used to find optimum force parameters for the interaction potential. It was found that argon and krypton are best represented by the conventional Lennard‐Jones (6–12) potential, but helium is best represented by a (6–9.5) potential model. Due to the extremely shallow depth of the potential well for helium, the present viscosity data are inadequate to yield meaningful values for th...

Viscosity and Diffusion Coefficient of Six Binary Mixtures

The paper contains the results of measurements of the viscosity of six binary mixtures: CO2–Kr; H2–N2; He–O2; CH4–CO2; CH4–C4H10; H2–He. Measurements were made in an oscillating‐disk viscometer at 20° and 30°C and at pressures from 1–25 atm, approximately; they were evaluated by the relative method. An analysis of the data shows that the interaction quantity μ12 which appears in the Chapman–Enskog theory for low densities is sensibly independent of composition. Although no direct check on the accepted mixing rules can be made owing to the narrowness of the temperature range covered, it is concluded that a knowledge of the viscosities μ1 and μ2 of the pure components together with that of μ12 at each temperature is sufficient to determine the dependence of the viscosity of the mixture on composition with the aid of the Chapman–Enskog theory. This dependence is reproduced well by the theory at virtually zero density and at a constant temperature. The experimental values of μ12 are used to calculate the bina...

Viscosity, Thermal Conductivity, and Diffusion Coefficient of Ar–Ne and Ar–Kr Gaseous Mixtures in the Temperature Range 25–700°C

The paper presents new relative measurements of the viscosity of argon, neon, and krypton and of the binary mixtures Ar–Ne and Ar–Kr, all at atmospheric pressure, in the nominal temperature range 25–700°C, and with a precision of ±u20090.1%. The oscillating‐disk method was employed. The experimental data were used to calculate the binary diffusion coefficient for the mixtures, and the thermal conductivity of the pure gases as well as the mixtures. The data for the pure gases can be correlated separately with the aid of a suitable potential of the 6‐n family, and optimum values of the parameters σ, e, and n are given for each of them. The same data can be correlated equally well with the aid of a universal, empirical expression for the collision integral with two individual parameters, s and p, being adequate to describe each gas separately. The conventional combination rules as well as those proposed by Kalelkar and Kestin [J. Chem. Phys. 52, 4268 (1970)] have been tested, and it was found that the latter rep...

A high-temperature oscillating-disk viscometer

Abstract The paper describes a new, high-precision, oscillating-disk viscometer in which it is possible to make absolute determinations of the viscosity of gases at atmospheric pressure in a temperature range 20–950°C, approximately. The effect of differential thermal expansion on the spacing between the disk and the fixed plates as well as that of high internal damping in the wire, both of which precluded the use of this method at high temperatures in the past, has been eliminated by making all such parts, including the suspension strand, of fused quartz. This was made possible by a novel method of drawing the strand. Estimates of precision and tests of reproducibility suggest that the measurements are accurate to ±0.1%. Preliminary results on pure nitrogen up to 500°C are presented. Excellent agreement with the most reliable determinations, which are available up to 75°C, is obtained, thus inspiring confidence in the results at higher temperatures.

A relative determination of the viscosity of several gases by the oscillating disk method

Synopsis New measurements are reported of the viscosity of argon, carbon dioxide, helium, neon and nitrogen in the range of temperatures 25–270°C and in the range of pressures 1–150 atm. The measurements are relative to nitrogen at 22°C; they have been performed by the use of an oscillating disk viscometer. The paper provides empirical correlations and correlations based on the use of a Lennard-Jones 6–12 and a Buckingham exp-6 potential. Except for helium, either potential gives a reasonable fit; in the case of helium the fit provided by the exp-6 potential is preferable.

The viscocity of carbon dioxide in the neighbourhood of the critical point

Abstract The paper contains the results of a new determination of the viscosity of carbon dioxide in the single-phase region surrounding the critical dome. The determination was performed in a modified oscillating-disk viscometer used earlier for the determination of the viscosity of several noble gases and steam. The results show that the anomalies in the dynamic viscosity of carbon dioxide are rather mild, and several orders of magnitude lower than those reported by A. Michels, A. Botzen and W. Schuurman. The kinematic viscosity, however, exhibits a region of very rapid change with pressure at constant temperature. At attempt was made to provide a very crude estimate of the effect of density stratification in the terrestrial gravitational field in the neighborhood of the critical dome.

The viscosity of argon-helium mixtures

Synopsis The paper describes the details and results of a precise, absolute determination of the viscosity of argon-helium mixtures at 20°C and at 30°C, both from 1 to 50 atm pressure. The accuracy of the measurements is estimated to be ± 0.2% at worst, but the relative values with respect to the pure gases are thought to be precise to ± 0.04. It is found that the excess viscosity of all mixtures is a unique function of density, p, certainly to order p, and approximately, but with an error comparable to that of the determination, also to order p2.

Viscosity of the Binary Gaseous Mixtures of Nitrogen with Argon and Krypton

This paper presents new measurements of the viscosity of the binary mixtures N2–Ar and N2–Kr both at zero density and in the temperature range 25–500°C. The measurements are compared with extensive calculations based on the extended law of corresponding states proposed by Kestin, Ro, and Wakeham. It is found that the calculations represent all data with a standard deviation of 0.33% and a maximum deviation of less than 0.5%. This is taken as new and additional evidence for the validity of the law of corresponding states. The latter is used as a device for the interpolation and extrapolation of the data in the form of tables ranging from 0°C to 2000°C for the mole fractions 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 for each system.

The viscosity of helium

Abstract The paper describes measurements of the viscosity of helium in the range of pressures of 1137 atm and in the range of temperatures of 25237C with an accuracy of from 0.2% at lower temperatures to 0.5% at higher temperatures. The method used was that of a disk oscillating between two plates with moderate gaps, and the measurements were relative to nitrogen. The results show no significant pressure effect. The temperature effect has been correlated empirically by the use of Keesoms and Keyes formulae as well as by the use of the methods of statistical mechanics, i.e. with the aid of the Lennard-Jones, 612, and the modified Buckingham, exp-6, potentials. It appears that the best fit is obtained with the aid of the exp-six potential. If an accuracy of 1 % only is required then there is little to choose between the various schemes up to 800C. Keesoms formula spans the widest range of temperatures.