Study On Energy Efficiency Of The District Cooling Multistage Pump System

The evaluation method of the energy consumption of the variable flow transmission and distribution system is systematically studied in this dissertation, based on which the energy efficiency of the district cooling multistage pump system is analyzed. In connection with the engineering problem, technical measures for tracking the high efficiency zone of variable speed pumps in variable flow transmission and distribution systems are brought forward. The main content of this dissertation is divided into six chapters, and is as follows:The second chapter is to study the evaluation method of energy consumption of the transmission and distribution system of the district cooling system. Based on the classification of the energy consumption of the transmission and distribution system, the transmission and distribution efficiency is defined, which is to evaluate the energy consumption performance of the transmission and distribution pipe network. For the pipe network whose topology and parameters have been identified, the transmission and distribution efficiency can objectively evaluate its energy consumption, which can provide specific guidance for reducing energy consumption. The transmission and distribution efficiency can provide an independent criterion for the optimization of the system form and operation method of the transmission and distribution system. The transmission and distribution efficiency can quantify the maximum energy saving value, which provides an objective for the control system design. The efficiency of the variable speed pump in the variable flow transmission and distribution system is studied and technical measures for tracking the high efficiency zone of variable speed pumps are brought forward.In chapter three, the dynamic mathematical model of the transmission and distribution system is studied. The dynamic mathematical model is classified into the design condition and the operation condition. By solving the operation condition dynamic mathematical model, the impedance of all users and the operating condition of all pumps can be calculated, which can provide theoretical calculation methods for the energy consumption of transmission and distribution system and the transmission and distribution efficiency which are defined in chapter two.Chapter four focuses attention on the pipe network impedance identification method of the district cooling transmission and distribution system. Based on the combination of the site identification and the system identification, the complex identification method is brought forward. The mathematical model of the complex identification method is established and the numerical calculation method is studied. Numerical experiments on the sample project shows that the pipe network impedance which is obtained by the complex identification method has the satisfactory accuracy when it is used for operation condition analysis of the transmission and distribution system. The study of this chapter can clear the obstacle for the practical application of the dynamic mathematical model which is established in chapter three.Generic design methods of the variable flow district cooling transmission and distribution system are studied and summarized in chapter five, which is to quantify the functions of different transmission and distribution programs and provide a unified premise for different programs comparison.In chapter six, simulation methods of operation conditions of the district cooling multistage pump system are studied by using the dynamic mathematical model of the pipe network which is established in chapter three. The simplified method of the operation condition simulation of the bypass user multistage pump system is proposed.Chapter seven is about case study. With an engineering example the energy efficiency evaluation method of the district cooling multistage pump system is investigated by using the transmission and distribution efficiency evaluation method which is proposed in this dissertation. The significance of the application of the multistage pump is analyzed.The results of this dissertation can provide sufficient theoretical and computational basis for the selection of the system form and control method of the district cooling multistage pump system, which can save a lot of scientific research funds. The research of this dissertation can provide references to the energy saving researches of all the other HVAC transmission and distribution systems.