Polyatomic Gas Mixtures Research Articles

Diffusio-birefringence in binary gas mixtures

It is shown theoretically that diffusion can give rise to birefringence in binary mixtures of poly-atomic gases. In particular, mixtures of linear molecules with noble-gas atoms are studied. By use of the transport-relaxation equations obtained from the linearized Waldmann-Snider equation an expression is derived for the coefficient of diffusio-birefringence. It depends essentially on the collision integral which describes the coupling between velocity and Kagan polarization. All the other ensuing collision integrals can be inferred from measurements of the magnetic-field influence on the viscosity and the heat conductivity; such data are indeed available for mixtures of N 2 and HD with He, Ne and Ar. For these mixtures the concentration dependence of the coefficient of birefringence is discussed.

Kinetics of the thermal dissociation of diatomic molecules. II. Single-component system and mixtures of polyatomic gases

Kinetics of the thermal dissociation of diatomic molecules. II. Single-component system and mixtures of polyatomic gases

The Viscosity of Nine Binary and Two Ternary Mixtures of Gases at Low Density

AbstractIn order to provide experimental material for a future test of the extended law of corresponding states formulated by Kestin, Ro, and Wakeham, we report here measurements of the viscosity of several binary and ternary mixtures of polyatomic gases with monatomic and polyatomic gases. All measurements were performed at atmospheric pressure from 25°C to 200, 600, or 700°C, as the case may be. Measurements were performed with the aid of an oscillating disk instrument, and the accuracy ranged from ±0.1% at 25°C to ±0.3% at 700°C. The systems covered, included CO2with He, Ne, Ar, N2CH4with He, Ne, Ar, N2, CO2, and N2 Ar  CO2as well as CH4N2CO2.

Multimode Vibrational Relaxation in Polyatomic Molecules

The acoustic behavior of polyatomic gas mixtures associated with multimode vibrational relaxation has been calculated. Rapid resonant energy exchange reactions have been assumed which maintain a Boltzmann distribution in each mode during the relaxation process. In this case, energy and temperature relaxation equations have been derived for multiple quanta and multiple mode v-v processes without the invalid assumptions made in previous work. The frequency-dependent and complex heat capacity is expressed in terms of the eigenproperties of the energy relaxation matrix.

Kinetic equations for vibrational relaxation in a mixture of polyatomic gases

Kinetic equations are derived for the relaxation of the vibrational energy in a mixture of polyatomic gases, which are ones with molecules simulated by harmonic oscillators. The most general case is envisaged, where the energy relaxation occurs not only via vibrational-translational transitions but also via multiquantum vibrational exchange involving an arbitrary number of vibrational modes. The analysis also incorporates the possible degeneracy of each mode when the molecules colliding are the same. An expression is derived that extends previous results [1–6] and that relates the vibrational temperatures in the case of quasiequilibrium. Equations are derived for the vibrational relaxation for the CO2-N2 case.

Thermal Diffusion of Polyatomic Molecules

The transport properties of a multicomponent mixture of polyatomic gases in field-free space and in a constant, static magnetic or electric field are discussed. The kinetic equations are developed in detail for binary mixtures of monatomic—diatomic and diatomic—diatomic gases, and these equations are solved using a rigid ellipsoid collision model. Calculated thermal-diffusion factors are compared with experiment for several different isotopic mixtures of carbon monoxide.

The Slip Problems for a Simple Gas

Abstract Simple and accurate expressions for the velocity slip coefficient, the slip in the thermal creep, and the temperature jump coefficient are obtained by applying a variational technique to the linearized Boltzmann equation for a simple gas. Completely general forms of the boundary conditions are used, and the final results are presented in a form such that the results for any particular intermolecular force law or the gas-surface interaction law can easily be calculated. Further, it is shown that, with little extra effort, the present results can be easily extended to include the case of a polyatomic gas. It is felt that the present work, together with a recent paper in which the author has considered the solutions of the linearized Boltzmann equation for a monatomic multicomponent gas mixture, provide the desired basis for the consideration of the various slip problems associated with the polyatomic gas mixtures.

Thermal conductivity of polyatomic gaseous mixtures at elevated temperatures

A recent expression of Saksena and Sharma for the thermal conductivity of polyatomic gas mixtures has been presented in a well known form after Wassiljewa. The utility of the modified form has been tested by calculating the thermal conductivity of dry air, considered as a binary mixture, and comparing the values with experimental results.

Slip and Creep in Polyatomic Gas Mixtures

Explicit expressions are obtained for viscous slip, thermal creep, and diffusive slip in polyatomic gas mixtures through the use of the “dusty-gas” model. The most significant result is that the thermal creep depends only on the translational parts of the thermal conductivity and thermal diffusion coefficients. The multicomponent generalization is obtained, but is complicated for diffusive slip.

Relaxation effects and the thermal conductivity of polyatomic gases and gas mixtures

The recent thermal conductivity data of several homonuclear diatomic molecules and a number of binary gas mixtures have been compared with the recent theories of thermal conductivity which take into consideration inelastic effects. For the pure gases the results show the uncertainty in the prediction of the temperature dependence of rotational relaxation times from thermal conductivity data. For binary mixtures the experimental data show the inability of the theory of Monchick, Pereira and Mason (1965) to represent the cross-relaxation effect on thermal conductivity.

Thermal diffusion in polyatomic gas mixtures : methane+methyl chloride system

Thermal diffusion factor for the system methane + methyl chloride has been measured as a function of temperature and composition. Attempts have been made to interpret the data by taking into consideration inelastic collisions in terms of recent theories of thermal diffusion in polyatomic gas mixtures. The experimental data indicate the influence of inelastic collisions on thermal diffusion which, however, can be interpreted only qualitatively.

Thermal Conductivities of Methyl Chloride–Sulfur Dioxide Mixtures

The thermal conductivities of binary mixtures of polar gases, methyl chloride, and sulfur dioxide have been measured over the temperature range 0°–200°C for various compositions by the hot-wire method. The results have been utilized to test the recent theories of heat conductivity of polyatomic gas mixtures. It has been found that the experimental data are in good agreement with those calculated from the Hirschfelder–Eucken formula, provided the pure component thermal conductivities are assumed to be given by the corresponding experimental values.

Thermal conductivity of nitric oxide, carbon monoxide and their binary mixtures

Thermal conductivity of the gases nitric oxide, carbon monoxide and their binary mixtures has been measured over the temperature range from 0 to 200°C by the hot-wire method. An attempt has been made to interpret the data in terms of the recent theories of thermal conductivity of polyatomic gases and gas mixtures.

Heat conduction through polyatomic gas mixtures

The theory of heat conduction through polyatomic gas mixtures given by Saxena, Saksena, Gambhir and Gandhi has been extended for those mixtures where each component may have more than one internal degree of freedom. It is concluded that for mixtures consisting of complex molecules, the deviations from the above theory will be quite pronounced.

Thermal Conductivity of Argon-Carbondioxide and Nitrogen-Carbondioxide Gas Mixtures

The thermal conductivity of the binary gas mixtures A–CO 2 and N 2 –CO 2 has been measured over temperature range 0° to 200°C by the hot-wire method. An attempt has been made to interpret the data in terms of the recent theories of heat conductivity of polyatomic gas mixtures.

Operation of Thermal-Diffusion Column with Mixtures of Gases Having Equal Molecular Weights (CO2–N2O)

Steady-state separation factors of 1:1 carbon dioxide—nitrous oxide mixture at mean temperatures 363°, 401.5°, and 435.5°K and at pressures ranging from 0.30 to 0.95 atm have been measured by operating a coaxial thermal-diffusion column. It has been found that the variation of separation factor with pressure agrees qualitatively with Furry—Jones' theory for isotopic mixtures. A detailed comparison of the experimental results with the theory has been made on the Maxwellian and Lennard-Jones (12:6) models and values for the thermal-diffusion factor for this polyatomic gas mixture have been estimated.

Thermal conductivity of hydrogen-nitrogen and hydrogen-carbon-dioxide gas mixtures

The thermal conductivity of H2-N2 and H2-CO2 mixtures has been measured from -15 to 200°C by using the thick-wire variant of the hot-wire method. The experimental values have been compared with those calculated from the Hirschfelder-Eucken formula. Although fairly satisfactory agreement between theory and experiment is obtained it appears that for a precise interpretation of the thermal conductivity of polyatomic gas mixtures a better representation of the cross-relaxation phenomena is necessary.

Thermal conductivity of polyatomic gas mixtures and Wassiljewa form

An effort is made to put the recently derived expression of multicomponent thermal conductivity of polyatomic gases by Saxena, Saksena, Gambhir and Gandhi in the familiar well-known Wassiljewa form. It is shown that this representation for the thermal conductivity coefficient is possible only when the pure thermal conductivity is replaced by a newly defined effective thermal conductivity,λeff. The two are interconnected and this relationship is critically examined.

Relations between thermal conductivity and diffusion coefficients of pure and mixed polyatomic gases

Theoretical expressions for the thermal conductivity of pure polyatomic gases and mixtures of polyatomic gases are given in a form which involves only measurable quantities. Four such relations for pure gases have been investigated by analysing available experimental data for H2, N2, O2, CH4 and CO2. Three relations applicable to mixtures are discussed. The formula based on Hirschfelder's theory has been tested in considerable detail for fifty-nine mixtures of thirteen different gas pairs with good overall success. The two other relations have also been discussed. Nevertheless, the work described here reveals that the relation obtained on the basis of Hirschfelder's theory is adequate for interpreting the existing binary thermal conductivity data, and more complicated theories do not show any appreciable improvement at least for these systems.

Thermal conductivity of the gas mixtures: Ar-D 2, Kr-D 2 and Ar-Kr-D 2

Employing the thick-wire variant of the hot-wire cell, thermal conductivity has been measured for the gas mixtures of Ar-D 2, Kr-D 2 and Ar-Kr-D 2 as a function of composition at temperatures 35, 50, 70 and 90°C. These results are compared and interpreted on the theory of Hirschfelder, and its simplified form as given by Mason and Saxena. Two more theories of thermal conduction for mixtures of polyatomic gases recently developed have also been considered. Some interesting and useful conclusions emerge from this overall study.