Control structure selection for optimal operation of a heat exchanger network

We consider the control structure design for a heat exchanger network (HEN), where a stream is split into parallel lines which are heated individually before they are merged together again. The objective is to find a control structure which maximizes the final temperature. We consider two scenarios, where (Scenario 1) the flow rates and the heat transfer coefficients are considered as disturbances, and (Scenario 2) where the hot stream temperatures are treated as additional disturbances. In both scenarios it is found that controlling linear measurement combinations gives very good performance, and that including flow measurements in the combinations gives little advantage over using only combinations of temperature measurements.