Equilibrium and Kinetic Properties of Methane Hydrate

During methane dissolution in water in a closed space, the pressure varies exponentially with time until the formation of methane hydrate. A model of this process is proposed that fits experimental data well. The methane concentration at the onset of hydrate formation is calculated as a function of temperature and pressure.     

Combined equation of state for liquids and gases, which includes the classical and scaling parts

A new equation of state is suggested, which describes the P-ρ-T data for ⁴He and SF₆ in the ranges of reduced densities ?1 < (ρ?ρ _c )/ρ _c < 1 and of reduced temperatures ?0.3 < (T-T _c )/T _c < 0.3 (ρ _c and T _c are the critical values). This equation includes the regular equation of state approximating the P-ρ-T data outside of the critical region and the nonparametric scaling equation of state adequately describing the P-ρ-T data in the vicinity of the critical points, which are combined by the crossover function. The classical function of damping of fluctuations of density and temperature when moving away from the critical point is suggested as the crossover function. Two equations of state are used for the regular part of combined equation, namely, the new cubic equation of state suggested by us and the equation of state of Kaplun and Meshalkin. The nonparametric scaling equation of state with three system-dependent constants is used as the scaling part of the combined equation. The conditions (?P/?v) _T = 0 and (?² P/?v ² ) _T = 0 are valid for the combined equation at the critical point; binodal and spinodal are present, as is the case in classical equations of state. The approximation of the most exact data on ⁴He and SF₆ using the new equation reveals that the latter equation correctly describes the P-ρ-T data with mean-square error with respect to pressure of ±0.5%.     

Device for measurement of heat capacity of small specimens in the range 10–20°K

The construction of a calorimeter for rapid measurement of heat capacity by the cooling method is described.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 6, pp. 1068–1973, December, 1979.     

Modified Leung-Griffiths equation for describing the thermodynamic properties of a CO2-Ne solution near the critical point of CO2 vaporization

A scaling equation of state is proposed, allowing for the asymmetry of the actual liquids and their nonasymptotic behavior with greater distance from the critical point. Experimental data for CO₂-Ne solutions near the critical point of CO₂ vaporization are approximated with this equation.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 1, pp. 71–76, January, 1986.     

Nonstationary Absorption of Methane by a Quiescent Aqueous Phase

Nonequilibrium dissolution of methane in unstirred water was investigated. The experiments were carried out in the ranges of temperatures, pressures, and concentrations corresponding to the existence of methane hydrate in an equilibrium state. The experimental data were satisfactorily described by a model taking into account the methane transfer both through the gas–liquid interface layer and in the liquid phase. Calculations using the model and the experimental data showed that the methane diffusivity in water is lower than in the interface layer. This can be associated with the formation of methane hydrate in the aqueous phase, since methane hydrate molecules are larger than methane molecules.     

Mutual diffusion and mobility in a CO2-40Ar-36Ar mixture near the critical point of vaporization of CO2

Experiments have revealed that the relaxation of the chemical composition is strongly retarded, while the equalization of the isotopic composition has no singularities near the critical line of vaporization of the mixture.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 5, pp. 806–809, November, 1985.     

Relaxation of concentration inhomogeneities in nonideal solutions

Numerical solutions of the nonlinear diffusion equation are obtained for non-ideal solutions satisfying an equation of state of the Van der Waals-Landau average field type. The results are compared with experiment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 1, pp. 55–65, January 1988.