Binary Mixtures Of Helium Research Articles

Revisiting acoustical gas-mixture separation.

This study experimentally investigated acoustically driven gas-mixture separation. Acoustic wave propagation in a narrow tube can induce gas-mixture separation. A binary mixture of helium and argon was used as the gas mixture. The pressure amplitude of the acoustic wave and initial molar fraction of the helium gas were investigated. The obtained experimental data indicated that the molar fraction initially increased with increasing pressure amplitude, whereas the saturated molar fraction did not show a clear dependence on the pressure. Although the degree of separation was smaller with purer helium, gas-mixture separation occurred under all conditions within the experimental range.

Measurement of the ([formula omitted], [formula omitted], [formula omitted]) behavior of Helium, Neon, and their mixtures at temperatures from (100 to 283.15) K and pressures up to 10.0 MPa

Densities of three binary mixtures of helium and neon were measured along six isotherms in the supercritical temperature range of (100 to 233.15) K at pressures of up to 10.0 MPa using a low-temperature single-sinker magnetic-suspension densimeter. The three mixtures were prepared gravimetrically with molar helium fractions of approximately 0.75, 0.50, and 0.25. In addition, densities of pure helium and neon were measured at temperatures from (100 to 283.15) K. In total, results for 108 and 64 (p, ρ, T) state points are presented for the binary mixtures and pure fluids, respectively. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be between (0.024 and 0.157) % for the binary mixtures and within (0.015 and 0.305) % for the pure fluids. The main uncertainty contributions are the weighings of the sinker and the composition of the gas mixtures for most state points. The new experimental results for the binary mixtures were compared with a new mixture model of Tkaczuk et al. for binary mixtures composed of helium, neon, and argon, as well as with a preliminary equation of state by Lemmon for mixtures of helium and neon. The relative deviations to the model of Tkaczuk et al. range from (−2.71 to −0.06) % while the deviations to the model of Lemmon are between (−0.68 and 0.78) %. The relative deviations of the pure substances to the respective reference equations are less than ±0.03 % for helium and within (−0.12 to 0.01) % for neon.

Study of reverse Brayton cryocooler with Helium-Neon mixture for HTS cable

As observed in the earlier studies, helium is more efficient than neon as a refrigerant in a reverse Brayton cryocooler (RBC) from the thermodynamic point of view. However, the lower molecular weight of helium leads to higher refrigerant inventory as compared to neon. Thus, helium is suitable to realize the high thermodynamic efficiency of RBC whereas neon is appropriate for the compactness of the RBC. A binary mixture of helium and neon can be used to achieve high thermodynamic efficiency in the compact reverse Brayton cycle (RBC) based cryocooler. In this paper, an attempt has been made to analyze the thermodynamic performance of the RBC with a binary mixture of helium and neon as the working fluid to provide 1 kW cooling load for high temperature superconductor (HTS) power cables working with a temperature range of 50 K to 70 K. The basic RBC is simulated using Aspen HYSYS V8.6®, a commercial process simulator. Sizing of each component based on the optimized process parameters for each refrigerant is performed based on a computer code developed using Engineering Equation Solver (EES-V9.1). The recommendation is provided for the optimum mixture composition of the refrigerant based on the trade-off factors like thermodynamic efficiency such as the exergy efficiency and equipment considerations. The outcome of this study may be useful for recommending a suitable refrigerant for the RBC operating at a temperature level of 50 K to 70 K.

РАВНОВЕСИЕ ЖИДКОСТЬ–ПАР В БИНАРНЫХ СМЕСЯХ ГЕЛИЯ С ОСНОВНЫМИ КОМПОНЕНТАМИ ВОЗДУХА

Compiled equations describing the experimental data of the liquid-vapor phase equilibrium in binary mixtures of helium with nitrogen, oxygen and argon. Equations represents the dependence of liquid or vapor pressure from temperature and composition. At their compiling selected automaticaly most significant coefficients of equation. Standard deviations of the experimental values of the pressure from calculated are equal from 3,5 to 4,5 %. Equations permits to determine the composition or temperature of phases at known values of other parameters of the phase equilibrium.

Mixture Working Gases in Thermoacoustic Engines for Different Applications

For working gases in thermoacoustic engines, the most important characteristics are low Prandtl number and high ratio of specific heats. These properties change a lot with pressure for some gases, which makes selecting a working gas under high pressure different from that under normal pressure. This article presents optimization calculations for gas mixtures under different pressures. Results show that binary mixtures of helium and xenon can reach the lowest Prandtl number and highest ratio of specific heats when the pressure is lower than 4.5MPa. When the pressure is higher than 4.5MPa, however, the lowest Prandtl number is obtained with a mixture of helium and krypton. It is found that ternary mixtures may be better working gases than binary mixtures in thermoacoustic engines, especially under high pressure. For example, a helium–argon–xenon ternary mixture can be used to obtain a relatively low Prandtl number and high ratio of specific heats. In addition, this article shows that mixtures containing carbon dioxide and other gases can also result in useful working gases. This suggests that it is possible to replace the expensive xenon gas with cheap carbon dioxide for some applications. Finally, the effect of temperature on the Prandtl number, the ratio of specific heats, and the thermal penetration depth is also studied, and a more reasonable construction of the thermoacoutic couple is presented. The results of this study should be useful for helping select working gases in thermoacoustic engines for different applications and design goals.

UV emission from capacitive discharge in inert gas-iodine vapor mixture

We have studied the optical characteristics of capacitive discharge in binary mixtures of helium, neon, argon, and krypton with iodine vapor in a spectral range of 180–300 nm. It is established that the main power of UV radiation from the discharge plasma is concentrated in the emission lines at 183.0 and 206.2 nm. The intensity of emission due the spectral lines of iodine atom was optimized with respect to the inert gas type and partial pressure. The optimum results were obtained using He-I2 mixture with partial pressures of helium within 0.8–2.0 kPa and iodine vapor below 50–60 Pa. Being excited with a trains of nanosecond current pulses at a repetition rate of 10–100 Hz, the capacitive discharge emitted pulses with duration not exceeding 400–500 ns.

Ab initio study of interaction-induced NMR shielding constants in mixed rare gas dimers

The interaction-induced contribution to the NMR shielding constants in homonuclear A2 and heteronuclear AB (A,B=He,Ne,Ar) dimers is obtained ab initio by employing a coupled cluster singles and doubles with perturbative treatment of triples wave function model and extended correlation-consistent basis sets. The second virial coefficients entering the expansion of the property with the density are then computed in a fully quantum mechanical approach, for temperatures ranging from the limit of dissociation of the dimer to well above standard conditions. The results can be used to describe the density and temperature dependence of the shielding constants in binary mixtures of helium, neon, and argon. The predicted effects should be observable for the interaction of 21Ne with other rare gases.

Density dependence of electric properties of binary mixtures of inert gases

A computational study of the density dependence of the refractivity and dielectric constants, the electric-field induced second harmonic generation (ESHG) hyperpolarizabilities and of the Kerr constants of binary mixtures of helium, neon and argon is presented. Potentials and interaction properties of the homonuclear A2 and heteronuclear AB dimers (A, B=He, Ne, Ar) are taken from a previous study [J. López Cacheiro, B. Fernández, D. Marchesan, S. Coriani, C. Hättig, A. Rizzo. Molec. Phys., 102, 101 (2004)]. Dispersion coefficients for the second virial coefficients allow for the determination of the density dependence at any frequency far from the lowest resonance. Fully quantum mechanical results are presented and a comparison with the corresponding classical estimates is discussed. Deep minima are predicted to occur in the ESHG second virial coefficient curve drawn as a function of the molar fraction of one of the components in binary mixtures of He/Ar and Ne/Ar. This phenomenon, observed over a wide range of temperatures, should be easily verifiable experimentally.

High-temperature vapor-liquid equilibria of helium + 1-methylnaphthalene and helium + n-hexadecane

Vapor-liquid equilibria were experimentally determined for binary mixtures of helium + 1-methylnaphthalene and helium + n-hexadecane at temperatures up to 705 K and pressures to 153 bar. The measurements were made in a flow apparatus to minimize thermal decomposition of chemicals at high temperatures. The equilibrium data were compared with calculated results from several equations of state.

Estimation of Prandtl numbers in binary mixtures of helium and other noble gases

This paper describes two different theoretical methods of calculating Prandtl numbers for mixtures of noble gases at moderate temperatures and pressures. In order to limit the scope and length of this work, only binary mixtures containing helium and one other noble gas (neon, argon, krypton, or xenon) were considered during this study. However, with relatively slight modifications, the methods described in this work for calculating Prandtl numbers should be applicable to other binary noble gas systems. In addition, theoretical gas mixture viscosities and thermal conductivities were compared with the corresponding experimentally measured values at 20.0 °C in order to provide a better assessment of the quality of the Prandtl number calculations. The results of this study should be useful to researchers and design engineers involved in optimizing the operation of acoustic refrigeration systems.

Quantum-Statistical Modeling of Mixed Inert Gas ICPs

Relative populations of excited neutral and ionic states in reduced-pressure ICPs supported by a binary mixture of helium and an additional inert gas have been shown to obey Fermi-Dirac statistical counting. A single thermodynamic temperature of 2000 K is sufficient to define the distribution of both neutral and ionic state populations. High-energy states of ionic species exhibit a “blending” between Fermi-Dirac and Boltzmann behavior. Agreement between measured relative populations and the Fermi-Dirac distribution is ∼1% overall.

Thermal conductivity of three noble gases with carbon monoxide

Abstract The paper reports the results of new measurements of the thermal conductivity of binary mixtures of helium, neon and argon with carbon monoxide at 27.5°C and in the pressure range 0.7–12 MPa. The viscosity of these mixtures had been measured previously. The availability of their interaction viscosity allows us to calculate the contribution of the internal degrees of freedom. The Monchick-Pereira-Mason equation provides a reasonable, but far from perfect, basis for a correlation. Even though the low-density viscosity of the present mixtures was essentially the same as the corresponding mixtures with nitrogen, the thermal conductivity is different, pointing to a significant contribution from the rotational degrees of freedom. A comparison between a calculation of the density effect based on a modification of the Thorne-Enskog theory due to Mason et al. shows the same reasonable agreement (of order 2%) as that ascertained in earlier measurements on other mixtures.

Thermal conductivity of some mixtures of monatomic gases at room temperature and at pressures up to 15 MPa

Abstract The paper reports measurements of the thermal conductivity of eight gaseous mixtures of monatomic gases. The group of systems studied consists of three binary mixtures of neon and argon, four binary mixtures of helium and argon and a ternary mixture of neon, argon and krypton. The measurements have been carried out in a transient hot-wire instrument at 27.5°C and within the pressure range 0.5–15 MPa. The accuracy of the experimental data is estimated to be one of ±0.2%. The experimental data for each mixture as a function of density are represented, within their uncertainty, by a polynomial of second degree in density. The thermal conductivity data in the limit of zero density for the Ne-Ar and Ne-Ar-Kr systems can be represented by the first-order kinetic theory formulae together with the universal functional of the extended law of corresponding states developed by Kestin, Ro and Wakeham. Furthermore, for Ne-Ar the data are shown to be thermodynamically consistent with viscosity measurements on the same system. However, in the case of He-Ar, a similar representation of the experimental data is found to be inadequate. This result is attributed to the poor convergence of the kinetic theory formulae for the thermal conductivity of a binary gas mixture composed of species having a large molecular mass ratio.

Antagonism of membrane compression effects by high pressure gas mixtures in a phospholipid bilayer system

Binary mixtures of helium with nitrogen, xenon or nitrous oxide were applied to suspensions of phosphatidylcholine-cholesterol vesicles to determine those mixtures of lipid soluble gases which would exactly antagonize the membrane rigidifying effect of 100 ATA compression. A previous study has shown that the initial application of 100 ATA compression by gas produces a significant reduction in the fluidity of the phospholipid bilayer. However, as the high pressure gas dissolves into the lipid region it creates disorder and increases fluidity. Fluidity of the bilayer at equilibrium represents the sum of the compression-ordering and dissolved-gas disordering effects and is dependent on the gas/lipid partition coefficient of the particular gas. The beneficial effect of a narcotic gas added to Trimix mixtures to ameliorate HPNS in deep divers may be due to a balance of compression-ordering and solubility-disordering effects achieved within the nerve membrane. It is therefore valuable to determine those gas mixtures which achieve balance of these two effects and result in zero net change in phospholipid bilayer fluidity at an established pressure of 100 ATA. Binary mixtures of helium with 88% nitrogen, 3.8% xenon or 2.8% nitrous oxide resulted in zero net change in bilayer fluidity with our model system at 100 ATA. A graph of the percent of narcotic gas needed to produce zero net effect as a function of pressure, however, was nonlinear. This would suggest the ratio of gases in Trimix must be varied as a function of pressure. While the phosphatidylcholine-cholesterol bilayer is a good model for certain components of the nerve membrane, it does not allow for study of protein-lipid or gas-protein interactions. The data presented thus aid in our understanding of HPNS but are yet incomplete for precise use in predicting diving mixtures.

Mutual diffusion of binary mixtures of helium, argon and xenon at different temperatures

Synopsis The coefficient of mutual diffusion of the binary gas mixtures A-He, A-Xe and He-Xe has been determined at 0, 15, 30 and 45C by allowing the diffusion to take place between two bulbs through a precision capillary tube. A differential conductivity analyser has been used to analyse the samples of the gas withdrawn from one of the bulbs at different times. These experimentally determined diffusion coefficients have been utilised for calculating the unlike potential parameters 12 /k and 12 on the Lennard-Jones 12:6 model and compared with the values obtained previously from thermal diffusion data and also from the usual combination rules. The agreement seems to be quite satisfactory. These experimentally determined values of 12 /k and 12 have been further used for calculating D 12 and are found to reproduce the experimental data satisfactorily.

Thermal diffusion in mixtures of the inert gases

Since the independent prediction of the thermal diffusion effect by Chapman (1916) and by Enskog (1911) and its experimental verification by Chapman and Dootson (1917), the general nature of the phenomenon has been extensively studied by a number of workers, and its power in giving information on intermolecular fields has been demonstrated. The present work deals with all the binary mixtures of helium, neon, argon, krypton and xenon. These mixtures of inert gases are of special interest owing to the simplicity of the monatomic molecules. A few pairs of these gases had previously been examined by us (Ibbs and Grew 1931) as part of the general investigation of the effect, but it seemed desirable to work through the whole group systematically so that the behaviour could be studied under practically identical conditions.