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.     

Viscosity of multicomponent gas mixtures of polar gases

Summary The rigorous binary viscosity expression _mix as transformed to the form originally suggested by Sutherland is studied for mixtures involving polar gases. Any attempt to simplify the _ij of the Sutherland viscosity expression turns out to be only approximately successful. A relation for _ij / _ji is however derived, and the procedure suggested for computing _mix on this basis appears to be very successful. The _ij to a large extent are temperature and composition independent and it has been shown that this fact can be utilised with success for predicting _mix values at high temperatures.     

Effective diffusion of multicomponent mixtures in multidimensional flows

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

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.     

Diffusion in multicomponent gaseous mixtures in a model of local thermodynamic equilibrium

Diffusion of chemical elements into an ionized multicomponent gaseous mixture is considered in a model of local thermodynamic equilibrium. A linear dependence of the mass flows of chemical elements and the heat flow on the temperature gradient, mass fractions of the chemical elements, and the electric field is obtained. An example is given of a calculation of the effective diffusion coefficients for a hydrogen-helium mixture.     

Estimation of air traces in steam-air mixtures subjected to dropwise condensation

Low air-concentrations of various flowing steam-air mixtures have been determined by a sampling loop process. The process depends upon the measurements of the vacuum pressure of the remaining air in the sampling loop after immersing it in an ice-water bath. From the insignificant differences of the estimated air-concentrations for the various experimental runs it can be concluded that the sampling loop process is of satisfactory performance in estimating air traces in flowing steam-air mixtures.

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Abschätzung von Luftspuren in Dampf-Luft-Gemischen bei Tropfenkondensation

Zusammenfassung Es wurde der Luftgehalt bei niedrigen Luftkonzentrationen verschiedener strömender Dampf-Luft-Gemische mit Hilfe einer Auffangmethode bestimmt. Die Methode beruht auf Messungen des Druckes der Luft, die nach Auskondensation des Dampfes in einem Eis-Wasserbad verbleibt. Aus den geringen Unterschieden zu den berechneten Luftkonzentrationen verschiedener Experimente kann geschlossen werden, daß diese Auffangmethode zufriedenstellend bei strömenden Dampf-Luft-Gemischen niedriger Luftkonzentration arbeitet.

     

Prediction of forced convective condensation of non-azeotropic refrigerant mixtures inside enhanced surface tubing

In this paper, an experimental study on the heat transfer characteristics of two phase flow condensation of pure refrigerants such as R-12 and R-22 as well as non-azeotropic refrigerant mixtures R-22/R-114 and R-22/R-152a on horizontal enhanced surface tubing is presented.The enhanced surface tubing data showed a significant enhancement of the heat transfer compared to an equivalent smooth tube depending on the mixture components and their concentrations.     

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.     

Flow of chemically nonequilibrium gas mixtures with spontaneous condensation at low mach numbers

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 54–60, May–June, 1989.     

Effect of temperature gradient on Marangoni condensation heat transfer for ethanol–water mixtures

This paper experimentally studied the effect of macroscopic temperature gradient on Marangoni condensation of ethanol–water vapor mixtures under a wide range of concentrations. For each concentration, the experiment was performed at different velocities and pressures. An oblique copper block was employed to create surface temperature gradient. The results indicated that local heat flux was varied along transversal condensation surface, which was caused by surface temperature gradient. This difference in heat flux might be attributed to the variation of condensate thickness on condensation surface. In addition, a mean heat transfer coefficient was derived along transversal condensation surface. For low ethanol concentration (0.5%, 1%), the coefficient kept a high value over a relative wide range of vapor-to-surface temperature difference (<10 K) and could be augmented as much as 15% as compared with literature under similar experimental condition. Moreover, the mean heat transfer coefficient generally increased with increasing velocity or pressure for all concentrations of the ethanol–water mixtures.