Hydraulic analysis of typical user substations of district cooling systems

The typical process configurations of the user substations of district cooling systems are classified, and the design and operating conditions of each process are studied with hydraulic analysis. The results show that the processes 3 to 6 have a smaller minimum allowable pressure difference between the supply and return pipes of the substation when the flow load rate is small, which have a greater energy-saving advantage than the processes 1 and 2. While the process 6 adopts one valve by one valve operation strategy, it can withstand a large pressure difference and variation of the pipe network, the regulating accuracy is high, and it has a wide range of application. Under the condition that the pump head allows, the static balance valve can be eliminated for the process 1. The processes 3 and 4 have a larger actual regulation ratio than that of the processes 1 and 2, and the valve regulation strategy of the process 4 has a better regulation accuracy. Due to the use of high regulation ratio control valves, the processes 5 and 6 can overcome the influence of the variation of pressure difference of the pipe network on the change of actual regulation ratio. The theoretical analysis method proposed in this paper provides a theoretical basis for the process selection and optimization design of the user substation, and can also be used as the theoretical basis for the operation optimization of the pipe network.