Research On The Method Of Reserve Design Of Transportation Capacity Of Single Heat Source And Single Ring Heating Network

With the continuous advancement of China’s infrastructure construction,district heating in northern urban areas has been greatly developed,and it has become one of the lifeline projects to ensure people’s lives and industrial production.Ensuring the reliability of the heating system has become a more pressing social issue.The ring-shaped pipe network is more widely used in new pipe networks and transformation of existing pipe networks due to its topological structure advantages of high connectivity reliability.However,the parameters of the current loop pipe network are still designed by traditional hydraulic calculation methods.The pipeline capacity presents the characteristics of branched pipelines.The diameter of the pipeline gradually decreases from the heat source to the hydraulic confluence point in the design working condition,and the minimum diameter pipeline appears next to the hydraulic confluence point.In the event of a failure,pipeline flow is redistributed,and some small-capacity pipelines have hydraulic bottlenecks,which cannot fully utilize the advantages of the high reliability of the ringshaped pipeline network structure,and instead becomes a weak link in the heating system.To improve the reliability of the ring-shaped heating network and ensure the heating quality under fault conditions,how to realize the reservation design of the transportation capacity is a problem that we need to solve urgently.In this paper,we use the pipeline faults in the heating network as the basis of analysis.Under the assumption of constant supply and return water temperature,with the goal of realizing limited heating requirements under fault conditions,a fully controllable single heat source and single loop heating pipe network transmission capacity reservation design method is established.It includes two parts: pipeline capacity(pipe diameter distribution)and cyclic power(head parameter).First,establish an ideal single heat source and single loop heating pipe network structure model,by changing the functional parameters(user design flow unevenness coefficient,pipe length unevenness coefficient)and reliability parameters(quota flow coefficient,failure characteristics),explore the design rule of the transportation capacity reserve in the initial design of the single heat source and single loop heating pipe network.In addition,in order to solve the problem that the combination of initial design pipeline capacity and cyclic power is difficult to meet the transportation requirements of the worst fault conditions,this paper introduces the cyclic power reserve correction factor and the pipeline capacity reserve correction factor.By studying the relationship between this two reserve correction coefficients,explore the method for determining the combination ratio of the single heat source and single loop heating pipe network transportation capacity reserve.Finally,a heat supply pipe network in a county in Heilongjiang Province is taken as an actual case to verify the validity of the calculation formulas for pipeline capacity reserve and circulating power reserve proposed in this paper.Finally,a heating network in a county in Heilongjiang Province is taken as an actual case to verify the validity of the pipeline capacity reserve and circulating power reserve calculation formula proposed in this paper.Research shows that for the three pipeline capacity design methods proposed in this paper,namely,the pipeline capacity design method based on the design condition pipeline flow,the multi-condition pipeline maximum flow and the multi-condition pipeline flow expectation.Among them,the pipeline capacity reservation design method based on pipeline flow expectation under multiple working conditions can greatly reduce the flow resistance of the main line under fault conditions with only a small amount of pipeline reservation,and has a higher reliability improvement advantage.In the calculation of the case heating network,when the heating network characteristic is less than 33,the pipeline capacity reservation design method based on the maximum flow rate of the multicondition pipeline is more suitable for the heating network with a low failure characteristic.After studying the factors affecting the pipeline capacity reserve amount,it is found that the greater the design flow rate of the near-end user of the heat source,the longer the distal end length of the heat source,and the smaller the reserve requirement when designing the pipeline capacity reserve for the pipeline network;the pipeline capacity reserve and quota the flow coefficient is positively correlated.The larger the failure characteristic in the pipe network,the more even the designed pipe diameter distribution.In addition,the research on the reserve performance of cyclic power shows that the smaller the length of the remote pipe of the heat source,the more obvious the improvement effect of the system flow coefficient under the most unfavorable fault conditions.For the heating network that has been designed for pipeline capacity reservation,when the number of characteristics of the pipeline network is less than 7,the smaller the user design flow near the heat source end,the more effective the use of cyclic power backup and pipeline capacity reservation to improve the transportation capacity under fault conditions Obviously;on the contrary,when the number of characteristics of the heating network is greater than 7,the user design flow rate near the heat source end should be increased to amplify the effect of the reservation on the transportation capacity of the fault condition.