A multicomponent real-fluid fully compressible four-equation model for two-phase flow with phase change

A fully compressible four-equation model for multicomponent two-phase flow coupled with a real-fluid phase equilibrium-solver is suggested. It is composed of two mass, one momentum, and one energy balance equations under the mechanical and thermal equilibrium assumptions. The multicomponent characteristics in both liquid and gas phases are considered. The thermodynamic properties are computed using a composite equation of state (EoS), in which each phase follows its own Peng-Robinson (PR) EoS in its range of convexity, and the two-phase mixtures are connected with a set of algebraic equilibrium constraints. The drawback of complex speed of the sound region for the two-phase mixture is avoided using this composite EoS. The phase change is computed using a phase equilibrium-solver, in which the phase stability is examined by the Tangent Plane Distance approach; an isoenergetic-isochoric flash including an isothermal-isobaric flash is applied to determine the phase change. This four-equation model has been i...