DAEPACK: An open modeling environment for legacy models

Modeling and simulation have played extremely important roles in the chemical process industries for roughly 4 decades now. Several paradigms have been developed in this time to assist the modeler in performing the desired calculations rapidly and correctly. The two main approaches, modular and equation-oriented, have seen widespread use in recent years; however, the limited flexibility and control the user has within these environments, particularly when the user is trying to incorporate legacy models (typically in the form of FORTRAN subroutines) into a flowsheet, has motivated the search for improved methodologies. This paper describes how symbolic techniques can be applied to general FORTRAN code to perform automatically many tedious, time-consuming, and error-prone tasks required when using state-of-the-art algorithms for numerical computation. This new approach can be used to assist the modeler when performing FORTRAN-based simulation, to incorporate properly external FORTRAN subroutines within an equation-oriented environment, or as an enabling technology for CAPE-OPEN components.