Research On Coupling Hydraulic And Thermal Calculation Method For District Heating System Based On Loop Expansion

There are new many systems with the changes in heating technology development. All new systems have general characteristics, less energy consumption and convenient control.In this paper, starting from a large number of literatures on heating, described heating the cause of the status quo at home and abroad. Because of the low energy consumption, the traditional heating system is replaced by the distributed heating system. Through the comparison of several existing forms of heating system, a new type of heating system is introduced. It calls district heating system based on the loop expansion. The system has both the characteristics of the distributed heating system and the direct-attached heating system. And the main contents and its research significance are proposed.Based on the structural characteristics and the hydraulic diagram of district heating system based on the loop expansion, it obtained that this system has irreplaceable advantages: Based on the structural characteristics of the loop expansion of the central heating system and hydraulic diagram obtained in the heating has irreplaceable advantages:with water mixing characteristic of the hydraulic divider, the user side pipe network and the outdoor pipe network are separated, and the impact to outdoor pipe network is avoid; the water supply parameters can be improved and the diameter of the pipe network can be reduced; while the system still use straight form, it has high heating efficiency than the indirect connection system; the pump of the system are distributed, so its transmission energy consumption is relatively lower.Through the analysis of regulating ways to the existing heating systems, suitable regulating way which is called constant temperature difference is determined, so that the system is able to adapt to the changes of the load during the actual operation. With the knowledge of graph theory, the pipe network is simplified to the model which can be recognized by computer. Then through the analysis of the model, numerical solution of the heating pipe network hydraulic and heating calculation is obtained. Using C language program to solve hydraulic Calculation of the model, a simple model can be calculated.The series of multi-user computing model is created. Through the analysis of the system, it is proved that the series progression of the system is3, i.e. we can connect a radiator user and a fool radiant heating user on the prior radiator user back water pip.Through the analysis of the supply and return water temperature in the existing heating system, it is obtained that we can know the specific frictional resistance referring to the two conditions:95/70℃and110/70℃. However, for the district heating system based on the loop expansion, the supply and return water temperature is not constant, but mutative. If we refer the specific frictional resistance to the two conditions, it will lead to calculation errors. This paper uses the data processing function in Excel, combined with the principles and formulas of "heating project", the dynamic hydraulic calculation tables of both indoor and outdoor heating pipe network are worked out, the table can vary according to temperature and derive the specific frictional resistance. In addition, the form data is accurate, and convenient, so that the district heating system based on the loop expansion have reference basis.