Study On The Balance Adjustment Strategy And Dynamic Thermal Characteristics Of Secondary Pipe Network

With the scale of central heating system expand constantly,the operation and adjustment of the pipe network becomes particularly important.In this paper,the simulation thermal model was established,based on the research of the secondary pipe network of Chengde area,the characteristics of the pipe network system and the operation data.The flow characteristics of law of several common valves were studied in the experiment.The balance adjustment strategy of secondary pipe network was obtained based on valve regulation technology,as well as the dynamic characteristics in the law of the system thermal conditions.The main work of the paper was as follow.Firstly,the situation of operation and adjustment of district heating system was investigated and analyzed,and the problems existing in the actual operation of residential district pipe network were defined.Besides,by building a common valve performance test experimental bench,the working flow characteristics of different valves were studied in the experiment,and the relationship between valve opening and flow coefficient and loss coefficient was obtained,which provided a theoretical basis for the establishment of the subsequent heating system simulation model.Secondly,simulation model of hydraulic-thermal coupling condition calculation was established,based on the theoretical analysis and secondary pipe network in a certain district.The variation law of the hydraulic-thermal conditions of the system were simulated,by adjusting the main valve,the front unit valve and the low temperature valve respectively.The corresponding adjustment strategies under different working conditions of the valve were given to realize energy-saving operation system on the premise of the heat mass of low temperature users.Finally,the dynamic thermal simulation model of the typical secondary pipe network was established,based on the theoretical analysis of dynamic thermal process of the buildings.The change of heat source water temperature and outdoor temperature on the influence of users indoor temperature was studied by simulation.The results showed that the temperature of heat users increased by about 0.4 ℃ when the heat source temperature was increased by 1 ℃,and the delay time of heat users was about 130min-170 min.And the variation law of indoor temperature and its lag time under different lifting ranges of supply water temperature was simulated.At the same time,when the outdoor temperature dropped from-5 ℃ to-8 ℃,the temperature of heat users dropped by 1.8 ℃,the temperature lag time of the heat users were about 180min-230 min.In addition,it was found that the different deceleration and different decreasing values of the outdoor temperature will have an effect on the lag time of the change of indoor temperature.And when the outdoor temperature decreased from-5 ℃ to-10 ℃ for 30 min,60min and 120 min,the change of indoor temperature of one typical user was given.The research results of this paper have a certain theoretical guiding effect on the regulation of the actual heating system.