Rapid multi‐component phase‐split calculations using volume functions and reduction methods

Abstract We present a new family of fast and robust methods for the calculation vapor–liquid equilibrium at isobaric‐isothermal (PT‐flash), isochoric‐isothermal (VT‐flash), isenthalpic‐isobaric (HP‐flash), isoenergetic‐isochoric (UV‐flash) conditions. The framework is provided by formulating phase‐equilibrium conditions multi‐component mixtures in an effectively reduced space based on molar specific value recently introduced volume function derived from Helmholtz free energy. proposed algorithmic implementation can fully exploit optimum quadratic convergence Newton method with analytical Jacobian matrix. This article provides all required exact analytic expressions general cubic equation state. Computational results demonstrate effectivity efficiency methods. Compared to conventional methods, reduced‐space iteration leads considerable speed‐up as well improved robustness better behavior near spinodal coexistence curves mixtures, where preconditioning reduction most effective.