Kinetics of phase transition is studied for the more general case when the size of the system is assumed time dependent. In the three dimensional case typical examples in this respect could be connected with the solution of cosmological problems. In the two dimensional case could be the spreading and crystallization of undercooled water on oil or the experiments concerning phase transition in monolayers in a Lengmuir balance. The time dependence of the degree of overall transformation α(t) is formulated in a generalized form corresponding to above assumption. Explicit solutions are given for a constant rate of expanding (or shrinking) and for a constant acceleration of the size change of the system under the assumption that both nucleation rate I and linear growth rate G are constants. It is demonstrated that the process of phase transition proceeds much faster in a shrinking systems and is impeded in expanding ones. The reason for this effect is that parts of the new phase, formed in the initial parts of the system, are transferred into the diminishing volume (or surface). Thus the concentration of the new phase is mechanically increased.

Keywords: kinetics, phase transition

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