Phase transitions in solid-liquid-gas systems with applications to alkali metal generators

Motivated by physical applications we consider a mathematical model describing the evaporation process in solid-liquid-gas systems with two moving boundaries of the phase transition. An alkali metal generator with a working substance in the form of an intermetallic compound and the evaporation of a volatile component into a vacuum is considered. Explicit analytical solutions of the problem under consideration are constructed in three different geometries of the process. We demonstrate that the evaporation boundary moves much more slowly than the dissolution boundary and the liquid layer thickness increases with time. The role of the evaporation coefficient on the evaporation stream and the nonlinear dynamics of the process is studied. An approach developed in the present study can be used for solutions of mathematical models describing similar Stefan-type processes met in other areas of applied physics.