Minimum-Cost Operation in Heat-Exchanger Networks

This report revises the use of the maximum energy recovery criterion as objective function for real-time optimisation of heat-exchanger networks. Though in general this criterion leads to minimum total heat exchanged in the service units, it is not sufficient to achieve the actual minimum operation cost. This analysis discusses the characteristics of the network structure for which the last statement is applicable, and proposes an alternative performance index to address more directly the final economic objective for which these heat-recovery systems are created. An application example demonstrates the significant differences in operating conditions that may result from using one or the other criterion, something of outmost importance when defining online optimisation for these systems.