W. A. Wakeham

Viscosity of liquid water in the range −8 °C to 150 °C

The paper re‐analyzes the results of earlier, very precise measurements of the viscosity of water at essentially atmospheric pressure. This is done in terms of a new, theoretically‐based equation for the operation of a capillary viscometer rather than in terms of semi‐empirical equations used by the original authors. The new analysis eliminates possible systematic errors and permits the establishment of realistic error bounds for water in its role as a standard reference substance for viscosity. The latter are smaller than those embodied in the most recent International Formulation. Standard values of the ratio of viscosity at a temperature T to its value at 20u2009°C have been derived from the re‐analyzed data because the uncertainty of this ratio is an order of magnitude smaller than that of the absolute values. The ratios are used to generate absolute values with the aid of the standard NBS datum μ=1002.0 μPa s at 20u2009°C. The viscosity ratios have been correlated with the aid of two empirical equations. The...

Viscosity of the Noble Gases in the Temperature Range 25–700°C

New relative measurements of the viscosity of xenon at a pressure P=1 atm and in the temperature range T=25–700°C are reported. The viscosity of argon has also been remeasured. A careful analysis of the long‐term reproducibility of the oscillating‐disk viscometer employed in the work is presented together with best estimates of the viscosity of all the noble gases. Standard reference values of the viscosity of the gases at atmospheric pressure and at zero density at 25°C are given. The data for all the monatomic gases are represented by means of a single empirical correlation.

An extended law of corresponding states for the equilibrium and transport properties of the noble gases

Abstract This paper proposes a new law of corresponding states which provides us with a thermodynamically consistent and accurate correlation of the properties B , μ, k , b , D , μ 12 , k 12 , D 12 , B 12 for the monatomic gases and their binary mixtures. The law of corresponding states, based on the hypothesis that all monatomic gases obey the same two-parameter pair potential, leads to the empirical determination of a number of universal functionals which replace the corresponding integrals of the Chapman-Enskog theory. The use of these functionals together with a list of empirically determined scaling factors for pure gases and binary mixtures allows us to compute the above quantities over an unusually large range of temperatures and a modest range of pressures, thus making it possible to employ measurements of a limited class of properties in a limited range of states to compute all others over wider ranges of states, as well as utilizing data on one gas, to generate them for another. Judged from the practical point of view of a user, the correlation is accurate and complete as far as monatomic gases and their binary mixtures are concerned, except for the evaluation of the pressure effect on the transport properties of mixtures. Taking into account the fact that the specific heat, c v , (or, equivalently, c v ) is a constant, and that it together with the equation Pv = RT + BP [or, equivalently, Pv = RT (1 + B/v )] fully determines all equilibrium properties of a monatomic gas in a reasonable range of pressures and a wide range of temperatures, the paper provides the basis for a thermodynamically consistent formulation of equilibrium as well as transport properties of the monatomic gases and their binary mixtures. The law of corresponding states provides us also with a sharp criterion which permits us to disqualify guessed analytic forms of the pair potential. It turns out that no member of the ( n -6) family of potentials is adequate, but that the (11-6-8) potential proposed by Klein and Hanley is acceptable as a correlator of data (for 1 ≤ T ∗ ≤ 20), even though it leads to considerably more complex numerical calculations. Even this potential fails for helium at high reduced temperatures.

The viscosity and diffusion coefficients of eighteen binary gaseous systems

The paper reports accurate measurements of the viscosity of the eighteen binary gaseous systems: CF4 with He, Ne, Ar, N2, CO2, CH4; SF6 with He, Ne, Ar, N2, CO2, CH4, CF4 and O2 with He, Ne, CO2, CF4, SF6. The measurements were performed in a high-precision oscillating-disk viscometer at atmospheric pressure and in the temperature range 25–200°C for the systems containing CH4 or SF6 and in the temperature range 25–400°C for the remainder. The reported viscosities are believed to be accurate to within ±0.1% at room temperature and to within ±0.2% at 400°C.

Viscosity of the Binary Gaseous Mixtures He–Ne and Ne–N2 in the Temperature Range 25–700°C

The paper presents new relative measurements of the viscosity of the binary mixtures He–Ne and Ne–N2, as well as repeated determinations of the viscosity of the pure gases. The experiments were performed using an oscillating‐disk viscometer; they were made at atmospheric pressure and in the nominal temperature range 25–700°C. The accuracy of the measurements is one of ± 0.1% at 25°C, deteriorating to ± 0.3% at 700°C. Tables of the thermal conductivity of the monatomic‐gas mixture are provided together with values for pure nitrogen. The binary diffusion coefficients for the mixtures have also been computed.

Viscosity of the Binary Gaseous Mixture Helium‐Nitrogen

The paper presents new relative measurements of the viscosity of binary mixtures of helium and nitrogen, together with repeated determinations of the viscosity of the pure gases. The experiments were performed, using an oscillating disk viscometer; they were made at atmospheric pressure and in the nominal temperature range 25–700°C, the precision being one of ±0.1%. Tables of thermodynamically consistent values of the thermal conductivity of the pure gases are given. The binary diffusion coefficient for the mixture has also been computed.

Theory of capillary viscometers

The purpose of this work is to analyze the various kinds of capillary viscometers that have been used in the past, and to formulate the relation between the measured quantities and the viscosity of the fluid. Three kinds of capillary viscometers are discussed: the steady-state capillary, two capillaries in tandem and the Rankine viscometer. Improved working formulae are derived for every case. Throughout the work the fluid is assumed to be incompressible. However, a short discussion of the correction for compressibility is also provided.

The viscosity and diffusion coefficients of the binary mixtures of xenon with the other noble gases

This paper presents new experimental data for the viscosity of binary mixtures of xenon with the remaining monatomic gases, helium, neon, argon, and krypton. The measurements have been performed in a high precision oscillating-disk viscometer at atmospheric pressure and within the temperature range 25–500°C. The data have an estimated uncertainty of ±0.1% at 25°C increasing to ±0.3% at 500°C. The collision integrals for the interactions of xenon with the other monatomic species conform to the extended law of corresponding states formulated by Kestin, Ro and Wakeham. For each binary interaction the scaling parameters σij and ∈ij have been obtained. The ensemble of experimental results can be correlated by means of the appropriate kinetic theory expressions reinforced by the extended law of corresponding states. The deviations do not exceed 0.5%. The binary diffusion coefficients were calculated from the measured mixture viscosity and compared with the available experimental results. The standard deviation was estimated as ±2% which is within the mutual uncertainty of the two sets.

Viscosity of Carbon Dioxide in the Temperature Range 25–700°C

The paper presents new relative measurements of the viscosity of carbon dioxide at a pressure P=1 atm and in the temperature range 25–700°C. The accuracy of the reported viscosity data is estimated as ±0.1% at 25°C and ±0.3% at 700°C. The rotational collision number for carbon dioxide is computed with the aid of the kinetic theory for polyatomic gases and reliable thermal conductivity data.

Viscosity of the Binary Gaseous Mixture Neon‐Krypton

The paper presents new relative measurements of the viscosity of binary mixtures of neon and krypton, and repeated determinations of the viscosity of the pure gases neon, krypton, and argon. The experiments were performed using an oscillating disk viscometer; the measurements were made at atmospheric pressure and in the nominal temperature range 25–700°C and with a precision of ±0.1%. Tables of consistent values of the thermal conductivity of the mixture as well as of the pure gases are given. The binary diffusion coefficient for the mixture has also been computed.