The viscosity of the alkali metal vapors

An experimental installation has been developed to study the viscosity of alkali metal vapor in a wide range of high (up to 2000 K) temperatures, which implements the method from a viscometer with an annular channel. The design of the viscometer of the measuring cell makes it possible to directly measure the temperature of the working element of the viscometer. This provides an accurate determination of the temperature of the investigated alkali metal vapor in the working gap. The original method of stabilization of the steam generator operation mode was applied, which allowed to ensure the stationary flow of the investigated alkali metal vapor in the working element of the viscometer. Distinctive features of the created installation are high stability of modes of its work and considerable resource. An experimental study of the viscosity of rubidium and cesium in the gas phase was carried out by the method of a viscometer with an annular channel at the following values of the state parameters: for cesium T = 900 ... 1770 K, P = 12 ... 135 kPa; for rubidium T = 990 ... 1750 K, P = 39 ... 135 kPa. Most of the experimental data obtained are in the temperature range above 1200 K. The average error of the experimental data is 3%. From the experimental data on the viscosity of cesium and rubidium in the gas phase, the values of the effective cross sections of the «atom-atom» collisions and the relative cross-sections of the «atom-molecule» collisions were obtained. Calculated equations and tables of viscosity and thermal conductivity of cesium and rubidium vapor in the temperature range 700-2000 K and pressures 1-1500 kPa, including the saturation line, have been developed. An experimental study of the viscosity of rubidium and cesium vapor at high temperatures have been conducted with implementation of the method from a viscosimeter with an annular channel. From the experimental data on the viscosity of cesium and rubidium in the gas phase, the values of the effective cross sections of the «atom-atom» collisions and the relative cross-sections of the «atom-molecule» collisions were obtained. Calculated equations and tables of viscosity and thermal conductivity in a wide range of temperatures and pressures have been developed.

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“…The effect of pressure [19] at T > 1050 K corresponds β 12 2 ≥ 2, and its positive sign at T > 1080 K -β 12 2 < 1,2. Rubidium.…”

Section: Generalization Of the Experimental Resultsmentioning

confidence: 95%

“…In [19] Bonilla C.F., Lee D.I. eliminating the shortcomings and methodological inaccuracies of the installation, diskovered during the experiments with the cesium vapor, conducted a study of the viscosity of the rubidium vapor in the temperature range of 930 ... 1230 K at pressures of 47 ... 200 kPa.…”

Section: Generalization Of the Experimental Resultsmentioning

confidence: 99%

Viscosity and Thermal Conductivity of Rubidium and Cesium in the Gas Phase

Dzis

Dyachynska

2022

Global Trends and Prospects of Socio-Economic Development of Ukraine

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“…Liquid sodium is used alongside water as coolant in nuclear reactors [49] and therefore, as for the case of water, it is important to study its behaviour in conditions when nuclear reactions generate enough heat to cause the fluid to boil; the fluid is also used in single-phase liquid and phase-change receivers of solar power plants [50]. The properties of saturated sodium [51,52] in conditions typical of its industrial applications are listed in Initial conditions of the simulation were computed with Scriven's theory at 4 ms into bubble growth (in this case 𝜏 ≈ 0.2 𝑚𝑠), corresponding to an initial radius 𝑅 Q of 2 mm and initial liquid thermal boundary layer thickness of 0.386 mm. As for the previous case of water, agreement with the analytical solution is observed as the grid is increasingly refined, as shown in Figure 11.…”

Section: Modelled Bubble Growth Vs Analytical Solution -Sodiummentioning

confidence: 99%

A method for simulating interfacial mass transfer on arbitrary meshes

2021

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This paper presents a method for modelling interfacial mass transfer in Interface Capturing simulations of two-phase flow with phase change. The model enables mechanistic prediction of the local rate of phase change at the vapour-liquid interface on arbitrary computational meshes and is applicable to realistic cases involving two-phase mixtures with large density ratios. The simulation methodology is based on the Volume Of Fluid (VOF) representation of the flow, whereby an interfacial region in which mass transfer occurs is implicitly identified by a phase indicator, in this case the volume fraction of liquid, which varies from the value pertaining to the 'bulk' liquid to the value of the bulk vapour. The novel methodology proposed here has been implemented using the Finite Volume framework and solution methods typical of 'industrial' CFD practice. The proposed methodology for capturing mass transfer is applicable to arbitrary meshes without the need to introduce elaborate but artificial smearing of the mass transfer term as is often done in other techniques. The method has been validated via comparison with analytical solutions for planar interface evaporation and bubble growth test cases, and against experimental observations of steam bubble growth.

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“…For this procedure the Lennard-Jones (6-12) parameters of Table 2 have been employed. In Figure 10, a comparison between our prediction and a few sets of available experimental results [29][30][31][32] is provided. Differences between theory and experiments may come from the presence of molecules or ions in the vapours.…”

Section: B Transport Properties Of the Ablated Vapourmentioning

confidence: 99%

Aerothermodynamic modelling of meteor entry flows in the rarefied regime

Bariselli

Boccelli

Magin

et al. 2018

2018 Joint Thermophysics and Heat Transfer Conference

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Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes, above 80 km, where the atmosphere is rarefied. Ground radio stations are able to detect the free electrons concentration in the meteoroid wake, which is produced by hyperthermal collisions of the ablated species with the free-stream. The interpretation of radio data, however, currently relies on phenomenological methods, derived under the assumption of free molecular flow, hence, poorly accounts for the dynamics of the vapour, chemistry, and diffusion in the meteor trail. In this work, we aim to provide a detailed description of the flowfield around a meteoroid by means of Direct Simulation Monte Carlo and to obtain the evolution of the free electrons in the meteor wake via an extended trail simulation. An evaporation boundary condition is developed in the framework of an open source DSMC software. The material is assumed to be composed by a mixture of metal oxides which are typically present in ordinary chondritic meteorites. The transport properties of the ablated vapour are computed following the Chapman-Enskog theory and the DSMC phenomenological parameters are retrieved by fitting the collision integrals over a wide range of temperatures. As a last step, chemical and diffusion processes in the trail are computed. Starting from the baseline DSMC solution, our approach marches in time along the precomputed streamlines, calculating chemistry and radial diffusion for metals and free electrons. As study case, the flow around a 1 mm evaporating meteoroid is analysed at different altitudes. A high level of thermal nonequilibrium is appreciated in the head of the meteor, whereas in the trail, after a few diameters, the flow equilibrates. At lower densities, the vapour can travel upstream without interacting much with the incoming jet. On the other hand, at lower altitudes, re-condensation plays a significant role in the stagnation region. Finally, a trail, several meters long and formed by metallic species, generates behind the body. Ionization of sodium turns out to be the dominant process in the production of free electrons, whereas radial diffusion seems to prevail over recombination as depletion mechanism.

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The viscosity of the alkali metal vapors

Cited by 18 publications

References 16 publications

Viscosity and Thermal Conductivity of Rubidium and Cesium in the Gas Phase

Viscosity and Thermal Conductivity of Rubidium and Cesium in the Gas Phase

A method for simulating interfacial mass transfer on arbitrary meshes

Aerothermodynamic modelling of meteor entry flows in the rarefied regime

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