Analysis on operation control of chilled water transmission and distribution in district cooling systems

 Based on the process of the chilled water transmission and distribution of the district cooling system (DCS), analyses the specification of the distribution pump of the DCS plant and the flow control valve of the energy transfer station (ETS) and the determination of the operation parameters, as well as their influence on the operation control of the chilled water transmission and distribution system. The determination of the number, head, design flow, and frequency conversion characteristics of the distribution pumps needs to meet the energy saving operation of the DCS at a load rate of 0 to 100%. Taking Shenzhen Qianhai No.10 plant as an example, it corresponds to a load range of 0 to 77 000 kW. Actual operating experience shows that the DCS runs most of the time under a small load rate, the head and flow of the existing distribution pump are designed to be too large, it can be equipped with a motor that can be frequency-converted to a lower speed, or a small-head and small-flow frequency conversion water pump, optimizing the operation of small load rate conditions. The current combination process of static balance valve, self-operated regulator and butterfly flow control valve of the typical domestic ETS cannot accurately control the cooling requirement of multiple ETSs, nor can flexibly meet the hydraulic characteristics of continuous access by new users in DCS. The use of control valves with a high turndown ratio such as V-notch ball valves to replace the existing traditional technology of butterfly valves as the control valve can achieve accurate control of chilled water flow rate under various user access conditions and different load rates in all ETSs in the chilled water transmission and distribution systems.