Application of stream merging techniques in heat exchanger network design

An objective of the proposed design task is to minimize the number of exchanger units in a reference network by merging and splitting process streams without energy penalty and without violating the given constraint of Δ$TAU_min. Since stream merging/ splitting implies a modification of the stream data, a new pinch point may be created and a minimum energy consumption may increase. Thus, a quantitative criterion was derived to determine the feasibility of modifying stream data without increasing the utility usage. Also, the interpretation of graph analogy to an exchanger network needs to be generalized so that the opportunities for eliminating units in the ference structure can be discovered easily. Application of stream merging techniques are summarized in the evolutionary procedures presented in the second part of this paper. The proposed design strategy consists of two phases, i.e. whole-stream merging and part-stream merging. First, before the creation of the reference structure, the possibility of mixing streams entirely is examined by applying the feasibility criterion. Based on the resulting stream data, the reference structure can be constructed by using any available design methid, e.g. Linnhoff and Hindmarsh. Then, the part-stream merging techniques are used to redistribute heat loads among exchangers so that one or more units can be eliminated from this reference network.