GENERALIZED ENTHALPY METHOD FOR MULTICOMPONENT PHASE-CHANGE

Phase change problems with coupled transport of heat and species occur in solidification and other fields of materials processing. This arti cle describes a new formulation for numerical modeling of coupled phas e transformation. The technique is an extension of the conventional he at diffusion enthalpy method and uses the control volume approach. Num erical time-steps are separated into a transport section which updates extensive molar quantities from flux expressions and balance equation s, and a thermodynamic section which computes intensive quantities fro m state functions through local entropy maximization. Heat and species transport are handled in a symmetrical manner with flux expressions f rom irreversible thermodynamics. The scheme is general enough to cover an unrestricted number of species and phases in various systems and i s appropriate for three-dimensional modeling. Applications of the algo rithm are illustrated by computations on isomorphous, eutectic, and pe ritectic binary systems; a simplified dendritic growth problem with co upled heat and species transport is also presented.