Research On Hydraulic Conditions Of Central Heating Distributed Transmission And Distribution

With the continuous progress of our society and the acceleration of the process of urbanization,urban heating area is getting larger and larger,and urban central heating system is also developing constantly.The head of the heat source circulating pump of the traditional central heating transmission and distribution system needs to overcome the most unfavorable loop resistance of the pipe network,and near-end users need to adjust the rich pressure head with valves.Distributed transmission and distribution systems are widely used because they save energy consumption for valve regulation.However,the centralized heating distributed transmission and distribution system belongs to the parallel operation of multiple circulating pumps,and the system adjustment is complicated.The current research lacks detailed analysis of hydraulic conditions of the central heating distributed transmission and distribution system.This paper takes the primary network of the centralized heating distributed transmission and distribution system as the research object,and studies the hydraulic conditions of the centralized heating distributed transmission and distribution system through the method of combining theoretical analysis and experiment.First,a comparative analysis of the traditional central heating system transmission and distribution system and the central heating distributed transmission and distribution system is carried out,and the differences between the two heating systems in the operation form,adjustment mode and water pressure diagram are summarized.This paper summarizes the advantages of distributed transmission and distribution system for central heating,designs the experimental platform of distributed transmission and distribution system for central heating,and introduces the main components and experimental scheme of the experimental platform.This paper analyzes the types and causes of hydraulic imbalance in the heating pipe network,sorts out the hydraulic stability analysis methods of the traditional central heating transmission and distribution system,and proposes a hydraulic stability analysis method suitable for the central heating distributed transmission and distribution system.Combined with the change of performance curve after parallel operation of water pumps,the fluid mechanics formula was used to analyze the change of flow rate of other branches after the experimental bench adjusted the flow rate of one branch.Experiments were conducted to study the changes of the flow of one branch and the reasons for the changes of the flow of other branches after the change of the flow of one branch.Experiments were conducted on the stability of the branch and the stability of the system,and the factors affecting the stability of the branch and the stability of the system were analyzed,so as to provide reference for the operation regulation of the distributed transmission and distribution system of central heating.It is found that when the flow of a branch in the central heating distributed transmission and distribution system decreases,the total flow of the system will decrease and the flow of other branches will increase.The flow of the main pipe between the regulating branch and the equalizing pipe will decrease and the flow of the main pipe between the regulation branch and the end of the system will increase.The reason for the change of the flow of other branches after changing the flow of one branch is: after the flow of the branch changes,the system supply and return water main flow changes and the pressure drop changes,which causes the change of the pressure difference between the other branches and the change of the operating point of the branch water pump.Thus the branch flow is changed.The stability of the branch is mainly affected by the following factors: the steeper the pump performance curve,the better the stability;the branch closer to the equalizing pipe has better stability;the larger the diameter of the branch,the less likely it is to be affected by other branches.The system stability of the central heating distributed transmission and distribution system is mainly affected by the impedance distribution of the pipe network.The smaller the main pipe impedance,the better the stability of the system.The distributed transmission and distribution system of central heating should be designed so that the friction resistance of the main pipe of supply and return water should be as small as possible,which can effectively improve the stability of the system.In a centralized heating distributed transmission and distribution system,similar laws cannot be used to adjust the flow of branch water pumps.