Study On Reconstruction And Expansion Of Existing District Heating System

With the development of urbanization in China,the demand for heating increases gradually.However,the new district heating system is not only difficult to install pipelines,but also have huge investment.Therefore,the effective way is reconstruct and expand the existing district heating system.In the paper,the methods of primary heating network and two stage heating network are studied and a suitable reconstruction way of existing heating network is obtained.In order to improve the primary heating network this paper focuses on the related problems of using distributed water pump technology in the loop heating system.First of all,the economy of the heating system is analyzed,and a universal economic model is established.Theoretical analysis of annular heating pipe network pipe pressure distribution,using the average frictional resistance instead of each pipe friction resistance.According to the universal economic model,the economic model is suitable for distributed water pump system pipe network,and derive economic frictional resistance formula.Secondly,the characteristics of distributed water pump system are studied,and the location and quantity relation of zero pressure point in the system is mainly concerned.According to the model and the engineering case,and the economic frictional resistance formula,the new heating system engineering is analyzed,and the economy of the economic frictional resistance is verified.To obtain the method of choosing appropriate pipe diameter in reconstruction project,a existing ring system project is utilized.Finally,the design of the new pipe network and the expansion process of the existing pipe network are concluded.Based on the design process of existing pipe network expansion,a reconstruction method of distributed water pump system in ring pipe network of actual project is introduced in this paper.A retrofit project of a heating system in Harbin is introduced.For the heating network of the two stage heating network reconstruction method,the main research is series single pipe heating system.First,the series single pipe system is introduced,and its definition,system form and network form suitable for the system are given.Secondly,the limiting condition of the series single pipe reconstruction system is studied,and the maximum calculation method can be obtained.The design method of the system is analyzed theoretically,including the hydraulic calculation of the pipe network and the selection of power equipment.And summarizes the characteristics of this system which is different from traditional reconstruction system.Finally,combining the economic model of the heating system,the economy of the traditional transformation mode and the series pipe system transformation mode is compared.Considering the influence of new heat load area and new users' connection position on the economic efficiency of the system transformation,the characteristics of this reform method are obtained.In this paper,the design of the existing heating system transformation mode is studied,which provides a certain theoretical basis and decision-making basis for practical projects.