Heat-exchanger network analysis. 2. Steady-state operability evaluation

In cases where the optimum design of heat-exchanger network alternatives have about the same processing costs, the selection of the network for the final design may be based on process operability or other considerations. Most heat-exchanger networks are not operable at the optimum steady-state design conditions; i.e., normally they can tolerate disturbances that decrease the loads but not those that increase loads and there are not an adequate number of manipulative variables to be able to satisfy the process constraints and to optimize all of the significant operating variables.