Irreversible condensation conditions near the cryosurface

The circumstances attending irreversible condensation through the mechanism of heterophase fluctuations within the boundary layer, are discussed theoretically within the scope of approximation called 'monophase boundary-layer approximation' (MBL). Both the classical theory of nucleation and the theory of the monophase binary boundary layer are used in predicting the spontaneous phase change within the binary gas, free convective, laminar boundary layer. As opposed to what is called the 'critical supersaturation model' (CSM), in the MBL approximation the fields of temperature and condensing component concentration are not determined a priori but rather so as to satisfy both the system of partial differential equations of the boundary layer and the corresponding boundary conditions, on the one hand, and the additional thermodynamic condition collocated on the boundary of the fog sublayer, in accordance with the theory of heterophase fluctuations, on the other. The findings of this analysis are illustrated by the example of the binary mixture of air and water vapour in contact with the vertical isothermal surface at cryogenic temperature. Theoretical predictions are compared with experimental data.