A numerical method has been derived to model dynamically varying vapor-liquid phase equilibrium for non-ideal binary systems by augmenting the existing constitutive equations of computational fluid dynamics (CFD). Mass transfer during condensation and vaporization is modeled via equivalently varying source and sink terms; this mass transfer is governed by chemical potential at the liquid-vapor interface. Mass transfer resulting from the chemical potential field is determined by solving the Maxwell-Stefan and energy equations for a time variable pressure, momentum and temperature distribution. Condensation and evaporation are simulated within a multiphase Eulerian framework in such a manner that the components undergoing phase change map the non-ideal phase equilibrium diagram locally at steady state. Equilibrium is assumed at the phase boundary during transient mass transfer prior to reaching global steady conditions. (c) 2006 Elsevier Ltd. All rights reserved.