Research On Rational Connecting Method Of Urban District Heating System

With the economic development of the whole society and improvement ofpeople’s life quality, China’s urbanization heating enterprise is gonging after the scaleof further expanation, while also more and more attention is paying on security ofheating quality and increasing energy efficiency, but today in some cities there is aproblem, the city is divided into a plurality of district heating systems,which supplyheat separately. Many of individual heating systems only have single heat sourse andbranched pipe network, there is no link in the internal system and betwen severaldifferent systems, even though there are some simple contact lines, but they can notachieve adequate heat for thermal users when it comes to pooled operation or runningon accident emergency situation.Sometimes it can not meet the requirements ofthermal users sometimes because the new operating pressure and temperature of heatmedium can not make the entire system operate properly.In response to these problems, the contact principles of urban district heatingsystems are proposed in this paper, there are three contact methods between districtheating system based on the series and parallel relationship of heat sources, includingcontaction pipe connection, parallel connection, series connection, which consists oftraditional connection in series, double pipe with the same way connection, one-wayloop main line hot water heating network.Hydraulic calculations for the designconditions, economic analysis and the maximum heating coefficient of differentcontactions are studied comparatively.First, validate if the pressure capacity of pipeline can bear the primary stress innetwork according to the stress taxonomy, calculate thermal elongation of the pipebased on the stability analysis (elastic-plastic analysis), verify if the compensate lengthof the thermal compensator can fit the operating condition,in which the pressure andtemperature may change. Secondly, analyze the requirements for insulation materialsin case of the heat medium’s temperature increase, the pipe heat loss is calculatedaccording to the basic principles of heat transfer, check if the heat loss is in theacceptable range. By analyzing the characteristics of the pipe network resistancecalculate the flow rate through the connecting pipe aiming at adjustable users and non- adjustable users, which lay the foundation for determining the flow coefficience.Through the hydraulic calculations of the design conditions to determine thecirculating pump flow and head in accordance with standard requirements, check if thepump head meets fault condition after a operating hydraulic calculation. Researchthrough the heat exchanger in the heat transfer coefficient inside the station designconditions to calculate the fault conditions of heat transfer, thermal network checkingwhether the primary heat transport to the thermal stations can be converted intothermal heat users loads.Choose annual costs as the objective function in the economic analysis, Throughthe economic calculations for different ways to contact the district heating system todetermine the reasonable contact methods under normal operating conditions.Caculatethe cost in contact line connection,in which the contact pipes have different positionsand diameters.Definit the fault heating coefficience and adequate failure outdoor tempreture.Choose maximum fault heating coefficience as the objective function for the existingpipe network in different contact pipe locations and diameter, in the case of theexisting pipeline network conditions and cycle power to determine the various methodsto achieve maximum fault heating coefficience.Caculate the fault heating coefficience in a city heating system after connectingand analyze the connectivity reliability of the thermal user.