Synthesis of multi-period heat exchanger networks based on features of sub-period durations

In this work, a representative sub-period method is proposed for synthesis of multi-period heat exchanger networks (HENs). For the multi-period HENs with a large number and significantly different durations of sub-periods, the sub-period with the longest duration is taken as the representative sub-period. The cost-effective HEN structure in this representative sub-period can be obtained by solving the single-period HEN synthesis problems, and the operational parameters are then optimized to meet the requirements of other non-representative sub-periods on the fixed HEN structure achieved by the former step. In particular, for synthesis of multi-period of HENs with similar durations of sub-periods, a simplified model method is also proposed. In this method, the multi-period HENs are finalized by introducing the commonly shared heat exchangers in the multi-period HENs model. Both of the proposed methods avoid directly solving the multi-period HEN model, and hence the computational loads are reduced. An industrial case study for the synthesis of multi-period HENs is carried out to illustrate the procedure of the proposed methods. The effectiveness and advantages of the proposed methods are demonstrated by the comparison with the results obtained by the methods in literature. The effects of period duration on the cost-effectiveness of the multi-period HENs are discussed and highlighted.