Simulated And Experimental Study And Platform Development Of Multi-heat Source And Ring-shaped Heating Networks

With the continuous development of China's urbanization process,the size of resident buildings and the area of central heating are increasing.Based on high economic efficiency,safe and reliable,and good operation flexibility,multi-heat source and ring-shaped heating networks have attracted more and more attention in old network transformation and new network construction.However,the topological structures of multi-heat source and ring-shaped networks are more complex,and the number of pipes and heat users are relatively large,it is still difficult to systematically and accurately grasp the hydraulic characteristics of its operating conditions,particularly the specific number and location of hydraulic intersection points,which directly affect the actual heating range and effect of each heat source.Therefore,for the multi-heat source and ring-shaped heating network,based on the determination of the number and location of hydraulic intersection points,the systematical analysis of hydraulic and thermal characteristics of heating networks has great significance and application prospect to achieve its hydraulic and thermal balance.First of all,this paper focuses on the simplification of different types of public pipelines by the virtual partition of the hydraulic intersection users in hydraulic multi-heat source and ring-shaped networks,based on the fluid network analysis method,the basic theory of graph theory,the Kirchhoff's law,pipeline characteristic equation and the ring energy equation,while taking the a multi-heat source and ring-shaped experimental network as an example.Aiming at whether there are users on common pipes,as well as hydraulic intersection users,this paper proposes corresponding hydraulic modeling method,including the disconnection and omission of the common pipes,setting up virtual users or virtual heat source at two end points.Then,this paper systematically puts forward the hydraulic modeling method and steps of the multi-heat source and ring-shaped heating network with universal applicability based on the experimental network,to establish a single heat source and double rings,double heat sources and double rings and three heat sources and three rings by using MATLAB software respectively.Secondly,based on the above three different hydraulic simulation models and the corresponding experimental network,this paper makes simulated and experimental study for different conditions,including one variable condition of the single heat source and double rings,the ideal condition and two variable conditions of the double heat sources and double rings,and the ideal condition of the three heat sources and three rings.At the same time,this paper focuses on the analysis of the number and position of hydraulic intersection users,as well as the respective changes of user's pressure drops and flow rates,and the error analysis is carried out in the consideration of the errors caused by the measuring instruments.The results show that the maximum absolute value of relative errors between user's simulated and experimental pressure drops are 0.42%,2.83%,2.40%,3.17% and 0.98% in the 5 conditions,while the maximum absolute value of relative errors of user's flow rates are 1.96%,2.07%,3.60%,2.18% and 1%,which verifies the validity and accuracy of the simulation model,and proves the rationality and applicability of the proposed modeling method in this paper.Then,in order to systematically and efficiently analyze the hydraulic condition of the multi-heat source and ring-shaped heating experimental network,Matlab GUI is used to establish a systematic and simple hydraulic simulation platform of the multi-heat source and ring-shaped heating experimental network,and the corresponding executable file is obtained.The platform can be friendly and easy to use to simulate and study the ideal conditions and variable conditions of the hydraulic simulation models of three heating modes of the multi-heat source and ring-shaped heating experimental network,and the simulation data can be compared with the corresponding experimental data,so that it can promote the more efficient analysis and research on the hydraulic conditions of multi-heat source and ring-shaped heating network.Finally,to further study the influence of pipe heat loss on the thermal balance,energy saving and consumption reducing of central heating systems,the thermal simulation model of a single heat source and tree-like primary network is built by the method of fluid network analysis on the basis of considering pipe heat loss.Then,based on the quality and energy conservation of the pipe network,the temperature and volume of supply water are respectively adjusted to meet the heat need of the farthest user in the network,and five thermal conditions of the simulation model for the pipe network are analyzed and compared.The simulation results show that heat loss of the simulated network,caused by pipe network heat loss,increases at least 6.42×104GJ in one heating period(120 days),and under the premise of satisfying the heat demand of the farthest user,the heat consumption of thermal balance can save at least 1.79×10~2GJ more than that of hydraulic balance.