Research On Energy Consumption For District Heating System Based On Loop Expansion

With the implementation of heating charge, how to solve the problem of dynamic hydraulic balance of the distribution system, improve the distribution efficiency, and realize variable flow operation, has become so urgent.This paper first reviews the development process of the central heating distribution system at home and abroad, and then describes the characteristics and the theoretical basis of closed-cycle hot water heating, comparing several main forms of distribution system in domestic. Because distributed system has good energy saving effect, so it has got the attention of more and more people in the industry, the central heating system based on the loop expansion is proposed, this system is based on a distributed hierarchical cycle principle, it not only has the advantages of distributed systems, and its heat transfer efficiency is high, the most important thing is that can realize the variable flow operation of the pipe network, and its energy saving effect is remarkable.Then, the author compares two kinds of distribution efficiency indicators, electricity transport heat efficiency ratio and water circulation distribution system efficiency. The electricity transport heat efficiency ratio is used to check the water pump selection in design conditions, and the water circulation distribution system efficiency is used to calculate the distribution efficiency during the entire operation process, which can better reflect the real situation of distribution efficiency. Theoretically analyses the main reason of low efficiency of traditional heating distribution, congenital pipe network hydraulic imbalance, low efficiency of water pumps and pipe network can’t realize variable flow operation. Subsequently, the author puts forward the way to improve the distribution efficiency of the pipe network, we should use the central heating system based on the loop expansion, thereby we can solve the problem of dynamic hydraulic balance of the distribution system, improve the efficiency of water pumps, realize variable flow operation, so as to improve distribution efficiency of the pipe network.Then, the author analyzes the distribution of energy consumption of several forms of distribution system, which are the traditional heating system, distributed heating system, the heating system based on the loop expansion that is running under constant flow and variable flow. The results showed that the heating system based on the loop expansion not only can save energy consumption of the valve, due to the effect of mixed water of the hydraulic divider, you can achieve the different mixed water ratio of the primary and secondary pipe network, greatly reducing the flow of the primary pipe network, and can achieve variable flow operation. The author has calculated the central heating system based on the loop expansion can have about80%energy saving than traditional direct-connect system (based on meteorological parameters of Tianjin), its energy-saving effect is remarkable.Subsequently, the author introduces the method of heating regulation that includes the regulation of several commonly used traditional methods and new adjustment method, namely the quality and quantity adjustment in different stages, which is a more optimal method that is different from traditional mode of regulation. Then the author proposes the suitable regulation method and control strategy of the central heating system based on the loop expansion, the primary pipe network uses the method of the quality and quantity adjustment in different stages and the secondary pipe network uses the method of the quality and quantity adjustment in same stage, which not only can adapt to the requirement of household heat metering, and can achieve the goal of energy saving.Finally, the authors took the project in Tianjin as an example, and participated in the design of the heating pipe network and introduced the central heating system based on the loop expansion from several aspects, which includes the system principle, design calculation, and the actual effect of reconstruction. The results showed that the heat source and pipe network, each thermal station, pipe networks and between each user are independent of each other, good stability, good adjustment, and realizes the variable flow operation. Distributed by pump arrangement, with the aid of mixed water hydraulic divider, the system can realize variable flow operation system in the whole operation process, reducing the flow of pipe network traffic, reducing the power consumption of the water pump.