Energy efficient chilled water system with dual-temperature modulating valves

Chilled water circulation systems with fan coil units commonly suffer from low delta-T syndrome, increasing the pump power consumption. This problem cannot be solved merely by hydraulic balance or pump variable speed control. The control strategy of water valve of fan coil units must be improved. Analyses the features of traditional control strategy, including continuous control and on-off control. Presents a new control strategy, which combines the advantages of continuous control and on-off control. Based on this strategy, the dual-temperature modulating valve is developed. This valve chooses its control mode according to the return water temperature. It can maintain room air temperature at set point and keep room air relative humidity within proper range, meanwhile increase water temperature differential and save pump power. The dual-temperature modulating valve uses cascade control loop to increase its capacity of resisting disturbance. Performs simulation tests on the dynamic simulation platform of chilled water system to test the control effect and energy-saving potential of the dual-temperature modulating valve.