Optimization of split fractions and cleaning schedule management in heat exchanger networks

Fouling is a non-negligible problem to heat exchange operation, because it will cause sustained reduction to the overall heat transfer coefficient due to the growth of deposit over heat transfer surface of heat exchange equipments. Implementing regular (routine) cleaning is a recommendable means to remove fouling. As heat load distribution of parallel branches is related to split fractions, this paper presents an approach to arrange the cleaning schedule with having split fractions optimized concurrently. To avoid the numerous integer decision variables produced in time discretization method, the maximum allowable fouling resistance of a heat exchanger is taken as the optimization variable in this study. Then the proposed method is formulated into a Mixed Integer Nonlinear Programming (MINLP) model, to aim for the minimum operating cost of an existing HEN. At last of the study, an example from literature is studied, and the effectiveness of the method has been demonstrated by the proper results.