Energy and capital targets for constrained heat exchanger networks

A new procedure for estimating area and capital cost targets of constrained heat exchanger networks is presented. The method allows for match constrai ned networks and exchangers with more than one tube pass. The procedure is based on modelling the problem as a non-linear formulation where the forbid den exchanger matches are included as constraints and the temperature diffe rence correction due to multipass exchangers is included in the model. The difficulty of converging to a solution due to the additional non-linear con straints imposed by the multipass exchangers required the use of a two-leve l approach: at the inner level, the area targets for simple pass exchangers are obtained, and at the outer level the temperature difference required f or multipass exchangers are computed and fed back to the inner level. The p rocedure is repeated until an appropriate tolerance between two iterations was achieved. A comparison between the estimated exchanger areas and costs estimated by the new procedure and the area and costs obtained from the fin al heat exchanger design shows a very good agreement.