Study On The Regulation Characteristics Of District Heating System With Building Level Substation

District heating system(DHS)with building level substations(BLS)has many advantages over DHS with traditional large-scale substations.For example,the operating parameters(such as supply water temperature and circulation flow of secondary network)can be regulated effectively and flexibly and the balance between supply and demand can be achieved.However,most of the current operating modes still based on operators’ experience,over-heating isssues cause a large amount of energy waste.Explore the scientific and reasonable operating modes of DHS and reducing the current energy consumption are very urgent tasks at the moment.Main research contents of the thesis are as follows:First of all,we conducted some field surveys on a real DHS with BLS in Chengde.Collected data show that over-heating and less-heating were quite common at different times of the day,the overall performance of district heating was unsatisfactory.Based on the theoretical analysis of the operation and regulation of the district heating system with BLS and the heating parameters in Chengde,the paper gives the theoretical regulation formulas of four regulation modes,puts forward an operation and regulation strategy to control the temperature and flow of the secondary pipe network supply water in different periods,and deduces the operation and variation law of the temperature and flow of the secondary pipe network supply water and return under the regulation mode,and gives the opening of the electric control valve with the theoretical analysis The law of outdoor temperature change.Secondly,the on-site real-time regulation and control of the district heating system of a building level substation in Chengde city is carried out.For a typical day,the outdoor temperature is divided into control periods according to 5 ℃ temperature difference.The results of field operation control data show that compared with the current operation mode,the room temperature of building users increases by 0.24-0.41 ℃,and the maximum room temperature of users also eases.The power consumption of circulating pump is reduced by4.25%,and the total heat supply is reduced by 5.64%.A dynamic simulation model is established for the district heating system of a building level substation in Chengde,and the effectiveness of the simulation model is verified with the actual operation data.Under the regulation mode of outdoor air temperature divided by different temperature difference,the change rule of room temperature and flow rate of allbuilding users is studied.It is found that when the outdoor temperature is divided by 3 ℃temperature difference,the indoor temperature fluctuation range of users on different floors is between 0.35-0.5 ℃,and the flow change is between 0.356-0.396 m3 / h.with the increase of outdoor temperature difference,the fluctuation range and flow of users’ room temperature increase.Finally,the dynamic thermal characteristics of the district heating system were studied when the supply water temperature and outdoor temperature change.It is found that when the supply water temperature was increased by 1 ℃,the time needed for the room temperature of each user to reach the new steady state is 168-220 min;when the outdoor temperature drops from-8 ℃ to-10 ℃,the time needed for the room temperature of each user to reach the new steady state is 200-230 min.With the increase of outdoor temperature drop,the time required for the user to reach the new steady state is also increased.The research results of this paper can provide some reference for the operation and regulation of district heating system with building level substation.