Determination And Application Research Of Partial Working Condition Of Mixed Regulation Of Heating System

With the improvement of people's living standards,people's awareness of environmental protection has become more and more intense,and the centralized heating business has been able to develop rapidly.However,the centralized heating system still has problems such as immature operation control technology and low level of automation,resulting in increased energy consumption of the centralized heating system and low energy utilization.In order to improve the energy efficiency of the district heating system and achieve energy conservation and consumption reduction,this paper first proposes the concept of basic flow,and combines the knowledge of graph theory and Kirchhoff's law to establish a model of the heat supply network for hydronic networks.The accessibility analysis method is used to determine the basic flow of the heating pipe network.Secondly,based on the similarity theory,the experimental system of heating pipe network was designed and built.The experimental system simulates a single heat source branch pipe network system consisting of two frequency conversion circulating pumps(one for one use)and four users.During the experiment,different conditions were simulated by changing the opening of the valve on the user 1-4.The experimental research shows that:(1)When the pipe network is not adjusted at the beginning,the comparison between the hydraulic simulation results and the experimental results shows that the pressure and flow changes of the pipe network are basically consistent under the same frequency.When the frequency of circulating water pump is 50 HZ,the maximum error of user's pressure differential is 1.81%,while the maximum flow error is 0.88%.And by analyzing the flow of the most unfavorable users and the pressure difference changes,when the circulating pump frequency is 26.5HZ,the circulating flow of the pipe network is the basic flow of the system.This verifies the correctness of the basic flow of the pipe network determined by the availability analysis method.(2)By closing the test of any user except the most unfavorable user,t it is also found that at the same frequency,the simulated values of the pressure and flow of the pipe network are consistent with the trends of the experimental values.And the user who is close to the most unfavorable user at the close distance is obtained.When the circulation flow of the pipe network reaches the basic flow,the frequency of the circulating water pump is smaller.And draw close to the most disadvantaged users closer to the user,the network cycle flow reaches the basic flow,the smaller the circulating pump frequency.(3)By designing a set of orthogonal experiments,it is concluded that the frequency of the circulating pump when the flow of the pipe network is based on the flow is mainly determined by the resistance of the most unfavorable users.Moreover,when the resistance of the user changes within a certain range,the frequency of the circulating water pump needed for the network flow to reach the basic flow has little change,and the variation range is 26-27.5HZ.In order to meet the needs of users,the frequency of the circulating pump in the pipe network during operation should not be lower than this interval.Finally,by analyzing the running cost of the heating system,the mathematical model between the operating parameter vector and the operating cost of the heating system is established,and the constraints for satisfying the heat demand and related regulations are analyzed,and the method for solving the model using the nonlinear programming theory is briefly introduced.The establishment of this model provides theoretical guidance for the mixed regulation of heating system.Among them,the limitation of the basic flow rate ensures that the heating system will not suffer from hydraulic imbalance during the process of mixed regulation.