Hydrodynamics and kinetics of condensed matter evaporation

Abstract

The vaporisation of condensed matter is studied theoretically in a wide temperature range. When the temperature is well below the critical point of a substance, the evaporation can be described in terms of a simple model assuming that (i) a sharp boundary separates the condensed and gaseous phase; (ii) the atoms emitted from the phase boundary have nonequilibrium velocity distribution; (iii) the equilibrium is attained within the Knudsen layer, the thickness of which is of the order of the mean free path of atoms. When the temperature of the condensed phase is comparable to or higher than the critical temperature the sharp boundary is transformed to the macroscopic interphase layer. The dynamics of both condensed and gaseous phases are described in this case by the equations of hydrodynamics supplemented by a wide-range semi-empirical equation of state. The vaporisation of strongly superheated metal is analysed.