Study Of An Innovative Ejector Heat Pump-Boosted District Heating System

District heating with combined heat and power, who has been spread and applied energetically throughout the world, is one ofthe effective methods to improve the total energy utilization efficiency of a city. It has become the main way for space heating in China and has the trend of further development, especially the indirect district heating system. With the increase of heating area and the improvement of national standard for district heating, the problem of heating shortage is becoming more and more serious. However, it is confined greatly from several aspects to solve this problem, and there are always some drawbacks for researchers’ solutions. This paper aims to propose a noveldistrict heating substation to solve the existing heating shortage problem with avoiding the weaknesses of traditional solutions.The premises of the heating substation improvement program include:keeping the supply water parameters of the original primary heating network unchanged (temperature and flow rate), keeping the original primary heating network stucture unchanged, keeping the building structure and internal layout of the original heating substation unchanged, adding no extra circulation of heat source. Based on the original district heating system, the novel heating substation is tried not to change the original system, expect adding an ejector heat pump.The main contents include:(1) Though analyzing the characteristics of the heating substation and the working nature of some kinds of heat pump, a novel and reasonable heating substation improvement program based on ejector heat pump is proposed.(2) Analyzing the working principle and characteristics of the ejector heat pump in the novel heating substation (including the driving heat source, recycling heat source and equipment analysis etc.), analyzing the working characteristics of the primary heating network and the secondary heating network (including working process and heat exchange process etc.), building a thermodynamic model among all ofthe components and circulation circuits and an exergy analysis model for the system.(3) Experimental study is taken to verify the performance of the novel heating substation. Detailed analysis ofthe design method is made to the ejector, which is the core part of the ejector heat pump system. And a comprehensive comparative study of several refrigerants is made (including environmental friendliness. operation pressure, pipe diameter and entrainment ratio etc.),R141b is selected as the working fluid. Taking decreasing the return water temperature of the primary heating network and keeping the supply water temperature of the secondary heating network unchanged as targets, the influence of many parameters to the new system’s performance is studied, such as mass flow ratio between the primary and secondary heating network, supply water temperature of the primary heating network, return water temperature of the secondary heating network, evaporating temperature of the ejector heat pump etc. The results show that the new heating substation can decrease the return water temperature of the primary heating network and increase the heating capacity of the original primary heating network under the testing range.(4) An engineering case with this method is analyzed for an existing heating substation. And the actual operating performance of the novel heating substation is analyzed based on the commissioning records.