Synthesis of energy-optimal HEN structures with specified flexibility index through simultaneous MILP formulation

Abstract

The synthesis of minimum-utility Heat-Exchanger Network (HEN) structures satisfying a given flexibility-index target is accomplished through a one-stage, non-iterative, superstructure-based-simultaneous-MILP formulation. The formulation assumes that the feasible region defined by the reduced inequality constraints is convex in uncertain parameters, so that the solution lies at any of the vertices of the polyhedral region of uncertainty. With this formulation, the standard definition of the HEN-synthesis problem is extended such that it now includes a flexibility-index specification for the potential HEN structure.