Fouling over the heat transfer surface of equipments always causes reduction to the overall heat transfer coefficient. Regular cleanings become an important means of saving energy. In the existing researches about the optimal cleaning schedule in heat exchanger networks

too many binary variables were involved

which raised the difficulties to solve the problem. This paper took the maximum allowable fouling resistance of the heat unit as the optimization variable

instead of the binary variables to represent requirement of cleaning the heat exchangers. The proposed method converted the mixed integer nonlinear programming (MINLP) problem into a nonlinear programming (NLP) problem

effectively reducing the size of the problem and the difficulty to solve the problem. With consideration of both design and operation problems of the heat exchanger network

genetic/simulated annealing algorithm (GA/SA) was adopted to optimize areas and cleaning schedule of the heat exchangers simultaneously. An example was studied to illustrate the effectiveness of the method.