Viscosity of polar gas mixtures: Wilke's method

Summary The simple expression of Wilke for viscosity which has proved very successful for mixtures of nonpolar gases has been examined here for mixtures involving polar gases also. The success achieved here is comparable to that obtained for nonpolar gases. A modification of the original procedure of Wilke has been suggested and tested successfully. It will be particularly useful where pure viscosity data may be lacking.     

Viscosity of moderately compeessed gases and their binary mixtures

The temperature dependence of the first correction in the density to the coefficient of viscosity of pure gases is obtained on the basis of an effective potential function of intramolecular interaction. The universality of this dependence and the possibility of its use to calculate the coefficient of viscosity of moderately compressed gases and their binary mixtures are shown.     

Wall jumps in temperature,partial pressures and populations of multicomponent mixtures of nonequilibrium polyatomic gases

The Maxwell-Loyalka method is used to derive formulas for the jumps in the macroparameters of a multicomponent nonequilibrium gas mixture. It is assumed that within the kinetic (Knudsen) wall layer one group of internal states of the molecules is close to equilibrium at the translational temperature, while another group and homogeneous chemical reactions are excited fairly slowly, so that they may be considered to be frozen and the corresponding inelastic collision integrals in the kinetic equations can be neglected. However, at the wall different groups of internal states of the molecules may be excited and chemical reactions may take place. The final calculation formulas are obtained under a series of simplifying assumptions in accordance with the recommendations made in [1, 2].Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 133–141, March–April, 1993.The author is grateful to N. K. Makashev for important comments.     

Film condensation of multicomponent mixtures

The classic Nusselt model is generalized for the condensation process of a multicomponent vapor mixture. The condensed vapors may be miscible in their liquid state or contain noncondensable gases.The reduction in the condensation rate owing to the accumulation of a noncondensable gas or the more volatile components near the condensate interface is demonstrated for three component systems of methanol—water—air and acetone—methanol—water. Also the effects of interfacial suction and forced convection are included.The analytical solution incorporates Diffusion Law for a multicomponent system and both exact and approximate integral method solutions are applied. The accuracy of the integral method turns out to be remarkably good.     

Field fluctuations in multicomponent mixtures

Fluctuations of electrostatic and elastostatic fields in a random phase mixture may be characterized by mean values and square means of the fields in each component. Exact relations between the square means and the analytical properties of the effective moduli are established for isotropic mixtures. Moreover, a modified effective medium procedure for calculating the field fluctuations in mixtures with aggregate topology is proposed. Explicit results are given for mixtures of isotropic components and spherical grain shapes. Particularly strong fluctuations occur in strongly heterogeneous media near the percolation threshold.     

The higher order Chapman-Cowling bracket integrals for the viscosity coefficient of multicomponent gas mixtures

Summary The rigorous kinetic theory bracket integrals for the Chapman-Cowling third order approximation to the viscosity coefficient of multicomponent gas mixtures are reported. These expressions will be found useful in interpreting the highly accurate viscosity data on multicomponent gas mixtures now possible. Specially for mixtures involving molecules quite different in nature the contribution is comparable with experimental accuracy.     

Measurements of the thermal conductivity of gases and gas mixtures,methods and results

Two methods for measuring the thermal conductivity have been employed:

1. a cylindrical cell type of apparatus for absolute measurements, with an accuracy of 0.5%.
2. a thermistor katharometer bridge for differential measurements, allowing an accuracy of 0.1%. The thermistor bridge is described in some detail and its performance is analysed.

Results are presented for a number of pure gases and binary mixtures. A special study was made of mixtures with water vapour or heavy water vapour as a component. Measurements were performed at room temperature and 333 K. In general our results compare well with those of other investigators, although differences are noted that surpass the degree of accuracy we believe to hold for our values. For a number of the binary mixtures investigated no results have -to our knowledge-been reported previously. The results for six of the binary mixtures containing water as a component are represented by a Wassiljewa-type formula. No agreement was obtained with values calculated from four different theories based on this formula.     

Effective diffusion of multicomponent mixtures in multidimensional flows

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 113–120, July–August, 1991.     

Two-dimensional lattice gases for regular binary mixtures

This paper reports on the development of two-dimensional lattice gas models for regular binary mixtures. In particular, results are reproduced concerning equilibrium solutions and an expression for the diffusion coefficient. In our model, a volume force is incorporated, and the system of macroscopic evolution equations resembles the Boussinesq approximation in convection theory. As an example, a lattice gas Rayleigh-Bénard system is considered. We conclude with a few remarks on implementation and optimisation of the program using a SIMD parallel computer.     

New phenomenological model of multicomponent gas diffusion

A new phenomenological model is proposed for diffusion of multicomponent gas mixtures. Obvious general structural relations between the mass diffusion fluxes and the gradients of gas mixture components are obtained within the framework of the model in the case of the multicomponent diffusion coefficients expressed in terms of the “intrinsic” diffusion coefficients of individualmixture components. The molecular mean free path model can be used to estimate the latter.     

Couette flow of a multicomponent ionized gas

We consider equilibrium flow of a multicomponent ionized gas between two catalytic plates of infinite length, one of which moves parallel to the other with constant velocity. The results of [1] are generalized for ionized gaseous mixtures which are in local thermodynamic equilibrium. Formulas are presented for calculating the thermal flux and the effective thermal conductivity for ambipolar diffusion.Then a special ionization case is discussed.Notation A_i chemical symbol of the i-th component - W_i projection of the molar diffusive flux vector of the i-th component on the y-axis - x_i molar concentration - H_i enthalpy - m_i molecular weight - Q_s heat of the s-th reaction - K_ps(T) equilibrium constant of the s-th reaction - W_i mass formation rate of the i-th component per unit volume - Z_i charge number - e unit charge (electron charge) - E electric field intensity - distance between the plates - N number of components - v _sl stoichiometric coefficients - density - T temperature - p pressure - u projection of average velocity on y-axis - viscosity - thermal conductivity - D_ij binary diffusion coefficient - R universal gas constant - k Boltzmann constant In conclusion, the author wishes to thank G. A. Tirskii for proposing the study and for suggestions made in the course of the investigation.     

Numerical simulation of flow of multicomponent mixtures in porous media

A study is made of the isothermal flow of multicomponent mixtures in a porous medium, accompanied by phase transitions, interphase mass exchange, and change in the physicochemical properties of the phases [1–3], It is assumed that at each point of the flow region, phase equilibrium is established instantaneously and the flow velocities of the separate phases conform to Darcy's law. Approximate solutions of problems of displacing oil by high-pressure gas were obtained in [1]. By generalizing the theory developed in [4], a study is made in [5] of the structure of the exact solutions of the problems of the flow of three-component systems which describe the displacement of oil by different reactants (gases, solvents, micellar solutions). The numerical solutions of the problems of multicomponent system flow are considered in [2, 3, 6, 7]. This paper presents a numerical method which is distinguished from the well-known ones [2, 3, 6, 7] by the following characteristics. The flow equations are approximated by a completely conservative finite-difference scheme of the implicit pressure-explicit saturation type, the calculation being carried out using Newton's method of iteraction with spect to both the pressure and the composition of the mixture. The minimum derivative principle [8] is used in the approximation of the divergence terms of the equations. The phase equilibrium is calculated using the equation of state.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 101–110, July–August, 1985.     

Thermodynamics of binary mixtures of molecular and noble gases

A theory based on rational thermodynamics and statistical mechanics for a binary mixture of a noble gas and a molecular gas with vibrating molecules is developed. The problem concerning the propagation of plane harmonic waves of small amplitudes is investigated in the limit of low frequencies. Constitutive equations for a linear irreversible thermodynamic theory and the Onsager relations are also analyzed.     

Dielectric properties of heterogeneous mixtures with a polar constituent

Summary After defining the boundaries for the dielectric constant of a heterogeneous mixture, the behaviour of such a mixture is studied as a function of the frequency, when one of its components is polar. Deviations from a semicircle are to be expected for the function _m =f( _m ) even when the dielectric properties of the polar constituent can be described with a semicircular Cole-Cole-arc. The relaxation time of the mixture is shorter than that of the polar constituent.     

Component desorption effect on the material catalyticity in high-temperature multicomponent gases

The distinctive features of the formation of the catalyticity of materials with respect to atom recombination on the material surface are investigated for mixtures of different high-temperature gases under conditions of hypersonic atmospheric flight or bench setups. It is shown that in general the catalyticity constants (heterogenous recombination probabilities) of individual components determined experimentally in dissociated flows of “pure” gases are improperly used for calculating the heat fluxes to material surfaces in multicomponent gas flows, owing to differences in the occupation of the surface by atoms in pure gases and mixtures. This effect must be taken into account in interpreting the experimental data which so far have been the only source of information on material catalyticity in gas mixtures. Otherwise, the results of calculations of the heat transfer to hypersonic flight vehicles could turn out to be invalid. Examples of the possible effect of ignoring this factor on the calculated heat fluxes are presented.