Algorithm development for dynamic optimization of heat exchanger network cleaning using continuous time formulation approach

Heat exchanger is important and employed in most stages of industrial processing. The main problem of heat exchanger is fouling on the heat transfer surfaces. The fouling causes the retardation of heat transfer efficiency with time. This is the reason for the loss in energy and the increment of operation cost. Therefore, the cleaning of fouled units is important in order to restore their hydrothermal performance. In this work, the simulations of heat exchanger in a case of single unit and also in network heat exchanger are performed based on linear and asymptotic fouling models. The effect of variation with time of fouling rate, overall heat transfer coefficient, temperatures of hot and cold streams, and heat transfer rate are studied. Besides this, we developed a new technique to formulate the optimization problem of optimal cleaning time schedule of heat exchanger cleaning using continuous time approach. In this approach, the number of cleaning operation is predicted priorly, and the time period between each cleaning operation is then determined. The objective function of this problem is the minimizing of overall operating cost. The results obtained from this technique are better than the results obtained using the discrete time approach.