Direct optimal control of valve openings in heat exchanger networks and experimental validations

Heat exchanger networks (HENS) optimizations benefit the energy conservation, with many set point strategies controlling the operations indirectly by the help of detail control techniques. Based on the newly proposed thermal resistance-based optimization method and the flow resistance analysis, we obtain the physical models of heat exchangers, pumps and pipelines with adjustable valves. Combining these models, we introduce a direct optimal control strategy for adjustable valves in HENs to obtain the optimal valve openings directly. On this basis, we take a HEN with two heat exchangers as an example to validate the proposed control strategy. Groups of experiments and the results illustrate the optimal valve openings obtained from the proposed strategy lead a lower power consumption of all the pumps than that of any other alternative experiment, which indicates the potentials to reduce power consumption by the optimal control of valves. Finally, further experiments with optimal valve openings under different required heat transfer rates demonstrate the universality of the newly proposed control strategy. (C) 2015 Elsevier Ltd. All rights reserved.