Minimum Total Annualized Cost for a Heat Exchange Network using the IDEAS Framework Jorge Pena-Lopez and Vasilios Manousiouthakis * , Chemical and Biomolecular Engineering Department, Hydrogen Engineering Research Consortium, University of California, Los Angeles, CA 90095, USA jpenalopez@ucla.edu , vasilios@ucla.edu * to whom correspondence should be addressed A classic problem that has occupied the area of process engineering for over four decades is the synthesis of heat exchanger networks (HEN). Several approaches have been employed to address this problem. They can be generally categorized into sequential synthesis 1-4 1 , 2 , 3 , 4 or simultaneous synthesis methods 5-9 5,6,7,8,9and are often based on evolutionary or optimization principles. Neither of these method categories are able to guarantee global optimality; the former because they are based on ad-hoc rules and the latter because they are based on nonlinear programming techniques that can only guarantee local optimality. The Infinite DimEnsionAl State-space (IDEAS) method is a novel conceptual framework for the synthesis of general process networks. With this approach, all possible process networks are considered and the resulting mathematical formulation gives rise to infinite dimensional optimization problems with feasible regions defined by linear constraints thus guaranteeing global optimality of the obtained solution 10 . In this work we discuss the application of the MultiFamily IDEAS based computer software developed at UCLA to a problem first proposed by Lee, Masso and Rudd 1 : 4sp1. This is a classical case study for HEN synthesis and one of the milestone tests for HEN synthesis