Cost-Effective Bypass Design of Highly Controllable Heat-Exchanger Networks

( ) Design of a cost-effecti®e and highly controllable heat-exchanger network HEN has drawn a great deal of attention for years. One of the key issues in such a design is how to effecti®ely minimize undesirable disturbance propagation in a network with minimum cost increment. Design options in this regard include the deri®ation of a superior network structure and the selection of bypasses associated with heat exchangers. A unique system modeling approach is de®eloped to predict disturbance propagation and to reject disturbances using bypasses. A no®el mathematical representation scheme for a HEN is introduced to facilitate system analysis and design. A relati®e gain-array approach is extended to the analysis of nonsquared systems. In addition, an iterati®e design procedure is introduced to determine optimal bypass locations and nominal fractions for complete disturbance rejection, while economic penalty reaches the minimum. The efficacy of the model-based approach is demonstrated by designing three HENs where bypasses are optimally placed, and the control schemes are simultaneously de®eloped.