he currently used methods for determining the thermodynamic equilibrium of the two phase mixed substances is to judge the equality of the coefficient of each component in two phases, and by this analysis each component mole fraction can be got at the equilibrium state. Introduced diffusion equation to describe various gas and liquid components from exposure to the stabilization process, established a mathematical model to describe the two-phase non-equilibrium diffusion process, meantime introduced a new algorithm to solve the mathematical model. Using this methods a real gas-liquid two-phase system was analyzed. The results compared with the experimental data proved the feasibility of the method, thus the non-equilibrium phase transition analysis of the issue provided a new analysis method.

Using volume translation method to improve the calculation of the accuracy of liquid density for the SRK state equation ,so has no influence on the gas -liquid balance. On the basis of SRK state equation and volume translation method and PR state equation, more accurate calculation results of the density of saturated liquid were obtained. And the results were compared with the measured data of different methods.The results show that the calculation results of saturated liquid density using volume translation method are more accurate than using the SRK state equation or PR state equation and improved the scope of the application of SRK state equation.