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.     

Studies of the thermophysical properties of substances and materials at the Novosibirsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences, 2002–2012

This review contains the results of theoretical and experimental studies performed by the thermo-physicists of the Novosibirsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences over the last ten years. The problems of constructing the wide-range equations of state that take into account the singular behavior of thermodynamic functions in the critical region are considered, and new experimental data on the thermodynamic and transport properties of refrigerants and low-melting alloys, including alloys used as heat-transfer agents in the nuclear energy industry, are reviewed. A complete bibliography of the published papers, first of all, from the journal High Temperatures is given.     

Thermocycling strengthening in chromium and an alloy of it in thermal cycles

Institute of Problems of Material Science, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 3, pp. 65–70, March, 1989.     

Calculation of thermodynamic properties of SF<Subscript>6</Subscript> including the critical region. Thermal functions and speed of sound

Specific heats C _v and C _p, entropy S, enthalpy H, and speed of sound W have been calculated using a new thermal equation of state with a small number of variable constants, which includes regular and scale contributions with a new transition function. The calculation results correspond to the accuracy level of the modern reference equations of state with a large number of determined parameters in the regular behavioral region of SF₆ properties; in the critical region, these results make it possible to supplement the existing reference data with the related tables, taking into account the scaling-theory advances. The experimental and tabular data on C _v, C _p, S, H, and W have not been used to determine the constants of the calculation equations (except for isochoric specific heat, C _v, in the ideal-gas state). These data have been applied only for comparison of the calculated values with the experimental and tabular values. To calculate the behavior of thermal properties in the critical region, universal critical indices α, β, and γ have been used according to the threedimensional Ising model. The mean error in describing thermal properties of SF₆ does not exceed the error of the existing experimental data. The calculated values coincide with the modern reference data in the regular region in the entire range of gas and liquid states. The discrepancies in the critical region are due to the application of the scale equation of state (in contrast to the regular equations used previously in this region for composing reference tables).     

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%.     

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.     

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.