OP-II-3

PP-I-9DYNAMICS OF FIRST-ORDER PHASE TRANSITIONSBykov V.I. 1 , Tsybenova S.B. 21 Mendeleev University of Chemical Technology, Moscow, Russia, vibykov@mail.ru2 Moscow Humanitarian Pedagogical Institute, Moscow, Russia, tsybenova@mail.ruIt is well known that first-order phase transitions are frequently associated withnoticeable heat effects. For example, melting is characterized as an exothermalprocess, whereas liquid–solid transformation can occur with heat evolution. In thesimplest case, the rates of these transitions can be described as a function oftemperature in a standard way using the classical Arrhenius relationship. Thenonlinearity and sluggishness of thermal processes in the small vicinity of phasetransitions can give rise to typical nonlinear and non-steady-state effects, namely, themultiplicity of steady states and oscillations [1−7].Here, we propose the simplest dynamic model of a phase transition and performits parametric analysis. Conditions have been recognized for the existence of threeand five steady states; the ranges of the parameters where auto-oscillations exist in adynamic system have been found; and characteristic parametric and phase portraitsof the mathematical model have been designed. The process dynamics in the vicinityof a phase-transition point has been shown to be rather complex. The processesobserved here include the hysteresis of temperature dependences, undampedconcentration and temperature oscillations, and considerable dynamic bursts duringthe establishment of a steady state.For phase transitions of the type(1)in a system where there is heat exchange with the environment, a dimensionlessspatially homogeneous model in accordance with [4] can be represented as(2)where(3)(4)x 1 and y are dimensionless concentration and temperature, respectively;dimensionless parameters Da i , γ i , and β i according to Frank-Kamenetskii,235