Mathematical simulation of phase change fluid - solid.

The paper presents a problem of simulation of phase equilibrium curve fluid - solid for binaryand multicomponent mixtures. Researching of equilibrium is important for all processes where aninteraction between solid and liquid stages exists.The minimization of a free energy of the Gibbs on parameter of salvation ƒ is applied tobuild-up of mathematical model, gated in as the relation of number of moleculas of a builder A tonumber of moleculas of a builder B in molecular compound generated solution. The model usingminimization on parameter of salvation, can be referred to predictive model, which are based onstate equation. Introduced method of model operation of phase equilibrium a solid body - fluidfor binary systems allows to obtain the expression for temperature as function mole rate of componentmixture:T(z1) = [ƒH10z1 + ƒH20(1-z1)]/{ ƒH10z1 / T 10 + ƒH20(1-z1)/ T20 -R[ z1 ln z1 +(1-z1) ln (1-z1)]},where ƒHi0 - enthalpy melting of pure component i by temperature Ti0; zi - effective mole part ofcomponents in binary systems: z1 = x1/(x1+ ƒx2), z2 = x2/(x1 /ƒ + x2); ƒ - parameter of solvation;i = 1,2.Thermodynamic coordination of model is tested by Heringtons and Redlih-Kisters methods:11 20lg( / ) 0, 1  γ γ dz =where ƒi - activity coefficient of component, i = 1,2. From thermodynamic coordination of modelthe coefficient of association k = k1/k2 is defined, which is equal the ratio of molecules number incluster of component А to number of molecules in cluster of component B in liquid states. Thisallows one to build curves of liquidus lines, which are close to experimentally measured values.That model also can be used to describe the fluid - steam and solid-solid equilibrium withformation of compound in solid phase. This method used for computation of phase equilibrium intriple and multicomponent real systems, accompanied by solvation of molecules in solution andassociation pure components. The advantage of the method of phase equilibrium consists in smallnumber of parameters for computation, for example a temperature and enthalpy melting of purecomponents for ideal systems.

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