Researches on the performance of steam injector for district-heating system

The steam injector is a device without moving parts, in which steam is used as an energy source to pump cold water from a pressure much lower than the steam pressure to a pressure higher than the steam pressure. With the characteristics of no moving parts, no external energy supply, high heat transfer coefficient and excellent safety reliability, the steam injector can be used in thermal power plant, chemical plant, refrigeration, paper industry, food industry and nuclear engineering, especially in the district-heating system to replace electric pumps and heaters for saving electric energy and improving thermo-economics. In this paper, a steam injector for district-heating system was designed and the calculation model of lifting-pressure performance was set up. The thermal system and operation performance of steam injector were shown. The steam injector operated at a rating outlet water flow rate of about 150t/h and inlet water temperature ranging from 15 to 65degreesC, with steam pressure of 0.4MPa, and the discharge pressure ranging from 0.5 to 0.9MPa. Correspondingly, the mathematical model of heat economy and technical economy was developed with the equivalent heat drop theory. It is verified by the test systems that the analysis method of the heat economy and technical economy is correct, and the steam injector is stable, reliable and profitable, can save electric energy 27.41kWh per hour. The energy utilization and economic benefit of thermal power plant can be improved using steam injector.