Reliable simultaneous operation strategy in heat exchanger networks under variable heat loads

The variation of heat loads challenges the operation strategy of heat exchanger networks (HENs). Previous individual valve control strategies enlarge the flow resistance, while the individual variable speed pump (VSP) control strategies might cause dangerous working conditions. This paper develops an optimal simultaneous operation strategy of both VSPs and valves in HENs under variable heat loads, which can avoid the extreme VSP operating frequencies and improve the performance of HEN on energy conservation. Optimization experiments with three different control strategies are operated on a practical multi-loop HEN to validate the effectiveness of new operation strategy. The results show that the new simultaneous operation strategy can achieve energy conservation on the premise of safe operation, about 90% power consumption reduction to individual valve control strategy at the heat load 800 W. What's more, besides boundary conditions, control strategies also influence the optimal operating parameters, which shows the limitation of traditional operation strategy with prescribed set-point temperatures.