A hybrid methodology for detailed heat exchanger design in the optimal synthesis of heat exchanger networks

Abstract

Abstract This paper presents a hybrid method for the synthesis and optimization of heat exchanger networks, which includes detailed design of heat exchangers. This task is achieved by combining the pinch design method with mathematical programming techniques, together with an optimal design algorithm of shell and tube heat exchangers based on the rigorous Bell-Delaware method. As result, the stream pressure drops are treated as optimization variables. Thus, the capital cost of the pumping devices and the electricity cost to run these equipments are considered in this problem together with the costs for heat exchanger area and utility consumption. The problem is decomposed as a binary tree, where each node is categorized as either capital-dominant or energydominant problem. Subsequent decomposition of each node is determined by this dominance. The final design is obtained recursively applying a design algorithm from child nodes to their parent node. The match-selection procedure is a hybrid method that exhibits some of the features of both evolutionary and mathematical programming methods. The method starts allocating matches using an IP assignment model. This step is then followed by an evolutionary procedure in which the remaining selections of the design are treated as new problems. The process is repeated until no savings can be discovered. The method avoids the solution of complex MINLP models, and consequently it is possible to solve large problems. Furthermore, it readily copes with typical constraints, such as forbidden matches and imposed matches. Therefore, safety and layout considerations are easily incorporated into the design.