The viscosity of fluid mercury to 1520 K and 1000 bar

Abstract

The viscosity of liquid and gaseous mercury has been measured at saturation conditions and in the expanded gas phase to 1520 K and nearly 1000 bar. Measurements were performed with an oscillating cup viscometer. Small cylindrical, closed autoclaves (“cups”) of tungstenrhenium or pure molybdenum were suspended inside a heated vacuum chamber on tungsten rhenium wires. The viscosity at 1520 K is 0.58mPa · s in the saturated liquid and 0.16 mPa · s in the saturated gas phase as compared with 2.0 mPa · s for liquid Hg at the melting point. Results are discussed in terms of a modified Enskog hard‐sphere transport theory for dense fluids. An internally consistent description of data is obtained with temperature‐dependent hard‐sphere diameters of Hg atoms and ions derived from PVT and neutron scattering data. A viscosity curve for mercury along the whole coexistence line to the critical point (Tc = 1760 K) is given. The analysis is applied to correlate data for fluid Hg, Pb and Na.

Molecular simulation of the shear viscosity and the self-diffusion coefficient of mercury along the vapor-liquid coexistence curve

“…The experimental data for shear viscosity are mainly re-stricted to temperatures below 900 K. Only a few experimental results 17,21 are available at higher temperatures and these data are inconsistent with each other. In addition to the experimental investigation of the shear viscosities, Tippelkirch et al 21 also used an empirical modification of the Enskog theory that employs the experimental data of the VLE to calculate the shear viscosity curve of mercury along the whole coexistence line. As they found their calculation to be in reasonable agreement with experiment, it provides a useful comparison with our simulation results for the tempera- …”

“…Tippelkirch et al 21 interpreted the product of the characteristic length and the collision integral ⍀ ͑2 , 2͒ * as a measure of an effective cross section Tippelkirch et al 21 interpreted the product of the characteristic length and the collision integral ⍀ ͑2 , 2͒ * as a measure of an effective cross section…”

“…The Enskog theory cannot be directly employed for the calculation of shear viscosities at liquid densities because it assumes that the autocorrelation functions decay exponentially. Furthermore, Tippelkirch et al 21 determined a different temperature dependence of the effective hard-sphere diameter for the liquid phase to be eff L = 2.81 Åͩ 234 K Furthermore, Tippelkirch et al 21 determined a different temperature dependence of the effective hard-sphere diameter for the liquid phase to be eff L = 2.81 Åͩ 234 K…”

“…[2][3][4] Hensel and co-workers 2-4,21 pointed out that even if it is possible to describe the properties of mercury by an effective pair potential, its nature has to change with density, whereas our empirical multibody contribution only involves a linear temperature dependence. Additionally, a similar procedure to that used by Tippelkirch et al 21 for the shear viscosity of mercury can be used to calculate the self-diffusion coefficient along the whole VLE saturation line. In this region, glue-model approaches, 29,30 that include correlations induced by electron-ion interactions and which have been applied to simulate alkali-fluid properties, may yield a better description.…”

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“…The density dependence of these results is well compatible with the α-values denoted by the open circles, which were measured by Hunter et al [34] at 90 MHz, though one must be careful because the relative experimental error in α, α/α, increases at high densities where α becomes small. We have estimated the shear viscosity contribution to α/f 2 from experimental values of η [35] as shown by the dashed line in figure 9. Compared with the measured α/f 2 , Figure 9.…”