Research On The Condition Of Secondary Sides Of District Heating Systems In China And Measures Of Energy Saving

The purpose of this study is to answer three questions about the potential energysaving of the secondary side of district heating system in China,“where”,“how much”and “what to do”.In this study, the current situation of the secondary system of district heating isconcluded by analysis of data and testing on typical systems. The overmuch heatcaused by the overhigh temperature of supplying water(24%) and the imbalance of thesecondary system are key points to save the heat consumption of the secondarysystems. The imbalance of the secondary system contains the imbalance amongbuildings (about10%) and inside of buildings (10%). The reducing of the resistanceof secondary systems and the optimizing of the working condition of pumps are keypoints to save the electricity consumption of the secondary systems. To reduce theresistance of secondary system, the most important is to reduce the resistance ofcomponents and pipes inside of substations. To optimize the working condition ofpumps, the most important is to choose pumps of lower water head, and make pumpswork in the same speed.Some cases of technologies to save the energy consumption of the secondarysystems, concluding the heat controllers of weather compensation, the water mixingpumps in the entrance of buildings and the ways to reduce the resistance of systemand optimize the working condition of pumps are introduced and the effect of themare showed through testing. The problems to be faced when using these technologiesare concluded. The heat controllers of weather compensation can do well in saving theheat consumption, but will cause the changing of the heat supplied by the primarysystem in a day. The water mixing pumps will save the energy consumption of floorheating users, but the popularization of it will face some auxiliary projects. Themeasures to reduce the resistance of the system includes cleaning heat exchangers andfilters immediately, expanding the diameter of pipe of overhigh flow velocity andadding a pump in the branch of the highest pressure drop. The choosing of pumps oflower water head and making pumps work in the same speed are proved to beeffective by testing.