A METHOD FOR AUTOMATED HEAT-EXCHANGER NETWORK SYNTHESIS USING BLOCK DECOMPOSITION AND NONLINEAR OPTIMIZATION

The 'block' concept has been applied successfully to heat exchanger ne twork (HEN) design problems(1,2). The methodology first produces simpl e initial designs by employing simple heuristic rules; subsequently th ese initial designs are optimised using NLP techniques. In this paper, an extension of the block concept to mathematical programming is disc ussed. The block concept is based on physical insights from the compos ite curves. The HEN synthesis problem is decomposed into a number of b locks determined such that streams in each block have similar characte ristics. When applied to mathematical programming, the block concept l eads to the block-based superstructure which is similar to the superst ructure suggested by Linnhoff and his co-workers and Yee and Grossmann (3). The difference is that this work is based on blocks (large enthal py intervals) which are derived from physical insights(1). As a conseq uence, the overall superstructure for a problem is much simplified and thus the dimensions of the mathematical models are greatly reduced. M oreover, since the block-based superstructure is based on the composit e curves, good initial solutions can be derived which also assist the subsequent optimization process. Combining the block concept with non- linear programming techniques therefore allows automatic generation of optimal or near-optimal networks.