A model of incomplete phase transitions of gas hydrates in a porous medium

The kinetics of incomplete phase transitions of gas hydrates in a porous medium is considered. In such transformations, the solid hydrate and its decomposition products coexist in extended regions. The conservation laws that take into account mass, momentum, and energy transfer between the components of the medium are formulated. The concept of phase transition dissipation is introduced. A general form of the constitutive relations, which is necessary and sufficient for the entropy inequality to be satisfied in any processes involving a change of state of the medium, is found. A potential of the skeleton that takes into account the surface energy, the latent energy of the phase transition and the temperature dependence is proposed. A thermodynamically consistent kinetic equation is formulated. The conditions under which the phase transition of a hydrate begins and is completed are found. The problem of isothermal dissociation of a hydrate when the pressure on part of the boundary of the body is reduced is examined. The influence of several parameters of the model on the seepage of the decomposition products is investigated.