SYNTHESIS AND RETROFIT DESIGN OF OPERABLE HEAT-EXCHANGER NETWORKS .2. DYNAMICS AND CONTROL-STRUCTURE CONSIDERATIONS
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Dynamic controllability of heat exchanger networks is considered in this paper within a synthesis/retrofit framework to improve the operability of HENs (flexibility and controllability). Based on a hyperstructure network representation, where all structural and operational alternatives are included, a variable delay matrix and a variable gain matrix are introduced, to explore potential control structures simultaneously with network structures. Simple controllability criteria (diagonal dominance of the gain matrix, dynamic decoupling, time effective control) are postulated employing graph theory concepts and included within the synthesis/retrofit model. A modified generalized Benders decomposition is applied to solve the resulting mixed integer nonlinear programming synthesis/retrofit model and to derive a cost optimal network and a favorable control scheme. 1994, American Chemical Society. All rights reserved.