Sustainable two-step MINLP heat exchanger network synthesis with practical detailed design

Abstract

Due to sustainable development that focuses on energy conservation, decreasing emissions and environmental effect, the research of heat exchanger network synthesis (HENS) is still necessary and challenging. Most academic studies in the subject of HENS aim on reducing total annual cost (TAC) through optimal topology design without the detailed design costs of each heat exchanger in the network, resulting in conceptual HEN designs. Hence, the detailed design of shell and tube heat exchangers is recalculated for TAC and corrected area costs, including the pumping costs from overall pressure drop of heat exchangers. For a shell and tube heat exchanger, its detailed design variables comprise of pressure drop, heat transfer coefficient, fluid velocity, etc. The stage-wise superstructure (SWS) model (Yee et al., 1990) for HENS is modified in two steps: the first step is to produce conceptual HEN using mixed-integer non-linear programming (MINLP), and the second one is to do the detailed design for individual heat exchanger. Therefore, the major objective is to synthesize the optimal practical HEN with the minimum TAC, the results reveal that two-step designs can significantly decrease more TAC compared to published case studies.