A thermodynamic approach to modeling and stability analysis of multiphase systems

Thermodynamic systems design, analysis, and operation stand as fundamental elements in process systems engineering. In this thesis, we investigate how to characterize multiphase thermodynamic systems using physics-based methodologies. Multiphase systems are frequently assumed to operate as quasistationary processes. Quasistationary systems are restricted to evolve inside an abstract space known as the equilibrium manifold. We suggest the possibility of multiphase processes to operate far from the thermodynamic equilibrium manifold. Through the scope of (classical) irreversible thermodynamics, we address the modeling and analysis aspects of multiphase systems far from equilibrium. Using compartmental modeling techniques, we represent multiphase systems as the interconnection of simpler subsystems each of which has well defined (and not necessarily homogeneous) physical properties. Conservation laws on mass, energy, and momentum define the state of multiphase processes as the solution to differential-algebraic equation systems. As the main result for this thesis, we show that multiphase processes can evolve far from thermodynamic equilibrium as long as the state of the system is contained in what we call a domain of physical feasibility. The existence of the domain of feasibility follows as a direct consequence of the second law of thermodynamics applied to the study of multiphase systems.(FSA - Sciences de l'ingénieur) -- UCL, 201