For the chilled water system, the outlet water temperature depends on the set value of the evaporator, while the return water temperature depends on the heat received by the evaporator. The designed maximum temperature difference between the outlet water temperature of the chilled water and the return water temperature of the chilled water in the central air conditioning system is 5℃ (for example: The outlet water is 7℃, the return water is 12℃). Now the evaporator outlet water pipe and the return water pipe are equipped with the temperature detection of the transmitter, PID temperature regulator and frequency converter to form a closed-loop control system, through the frozen water temperature difference (such as: △T=5℃) control, can make the frozen water pump speed changes in accordance with the change of thermal load. 4.2
For the chilled water system, because the temperature of the cryogenic chilled water depends on the working condition of the cooling tower, we only need to control the temperature of the high-temperature chilled water (condenser water) to control the temperature difference. The temperature difference transmitter, PID regulator and frequency converter are used to form a closed-loop control system. The water temperature of the condenser is controlled at T2 (e.g 37℃), so that the speed of the cooling water pump changes according to the change of the thermal load