Methodological Framework for Synthesis of Multiperiod Heat Exchanger Networks with Minimum Total Annual Cost Using an Optimization Model and Area Reassignment Technique

Heat exchanger network synthesis is one of the most important fields in the chemical processes. They are used to exchange heat among hot and cold streams. In this way, a great amount of heat can be recovered leading to a reduced utilities consumption, hence, improving the plant economics. Using heat exchangers increases the capital costs, therefore, a trade-off between the utility costs and capital costs should be considered. The optimal design of a multiperiod heat exchanger network is to configure a heat recovery system that achieves the temperature targets of the different periods at the minimum total annual costs. This paper presents a framework for designing multiperiod HENs, so that the trade-off between energy costs and capital costs can be simultaneously optimized. The proposed technique depends on a two-stage strategy, in the first stage, a model is built then solved using mathematical programming for the specified design periods to obtain a feasible configuration that achieves the heating targets with minimum total annual cost possible. In the second stage, further reduction in the total annual cost is obtained by using a technique that reassigns the heat exchangers areas over the different periods so that no excessive heat transfer areas are overdesigned.