Multiphase isenthalpic and isentropic flash algorithms

Abstract Algorithms for calculation of multiphase equilibria at given pressure and enthalpy or entropy using a single Equation of State as the thermodynamic model are described. The algorithms are extensions of earlier work on specified pressure and temperature and likewise uses stability analysis for generation of initial estimates and minimization procedures for calculating phase splits corresponding to a fixed number of phases. The extension of the isothermal flash algorithm to specifications of enthalpy and entropy results in a more complex procedure which essentially maintains the efficiency of the algorithm for the isothermal case. Special precautions required for specification of enthalpy and entropy are described.