Experimental Research On The Injection Low-pressure Heater With Tapered Mixing Space

It is an important task of energy saving and emission reduction to reduce exergy loss of low pressure heater in low pressure recuperative system and to enhance operating efficiency and integral hot economic in thermal power generator, which is also the hot issue of energy saving and emission research in power plant. Injection heater has some advantages such as: higher coefficient of heat transfer, lacking of dropping system, simple construction and fewer monitoring data etc. If injection heater is used to replace surface low pressure heater in the low pressure recuperative system of thermal power generator, it must decrease exergy loss of generator, simplify the construction of low pressure recuperative system, improve hot economic and operating security of system and has significant engineering practical value. However, the research on injection heater used in low pressure recuperative system of thermal power generator just involves in the field of hot economic. Therefore, based on actual operating situation of low pressure recuperative system in thermal power generator, designing injection low pressure heater, conducting characteristic experiment and exploring the flow and resistance & heat characteristics further impel and enrich the research on injection heater used in low pressure recuperative system of thermal power generator and perfect the feasibility theoretical analysis of application of injection heater technology.On the basis of analyzing considerable surveys of study about injection heater at home & abroad and addressing actual operating conditions in low pressure recuperative system of thermal power generator, a new injection heater, of which construction combines common water-steam injection heater with steam-water injection heater, with tapered mixture space is established in this paper. Furthermore, a one-dimensional mathematical model of injection heater is set up with. Size calculation of construction is conducted under experimental conditions. Injection characteristic, flow resistance characteristic and heat characteristic of low pressure injection heater with tapered mixture space are studied deeply through experiments. Meanwhile, the low pressure injection heater is used in low pressure recuperative system of actual thermal power generator to replace surface low pressure heater, of which hot economic analysis is conducted with equivalent enthalpy reduction method by similarity rule.The results indicate that the low pressure injection heater with tapered mixture space has combination of the advantages of common water-steam injection heater and steam-water injection heater, it also has preferable self-regulating under different experimental conditions. The low pressure injection heater with tapered mixture space creates sub-atmospheric pressure at its jet-exit and the pressure declines with increase of condensate flow at the inlet, which suggests that this heater has better pumping capacity, can reduce the crisis of condensed water into steam lines and replace the surface heater in low pressure recuperative system of actual thermal power generator compatibly. Jet-exit pressure is a critical factor of characteristic of low pressure injection heater with tapered mixture space, but the influence of steam pressure on heater characteristic is not obvious. The jet-exit pressure is influenced by inlet pressure and flow of condensed water, while that of steam pressure can be ignored. The outlet pressure of heater increases with the inlet condensate flow and pressure, which yet results the fall of outlet temperature. The heater efficiency is maximal when inlet condensate flow is 0.6m3/h and pressure is 0.35 Mpa. With similarity rules, low pressure injection heater with tapered mixture space is used in low pressure recuperative system of actual 200MW power generator of which results indicate the heater can replace the penult stage surface low pressure heater and raise hot economic of system by 0.07%. Moreover, all surface low pressure heaters are replaced by the heater with tapered mixture space, the hot economic of system can be enhanced by 0.22%.The characteristics of low pressure injection heater with tapered mixture space are stated systematically. The conclusions in this paper can boost the research on the injection heater that can be used in low pressure recuperative system of thermal power generator, enrich the relevant theoretical research achievements, offers an important theory basis to the feasibility of the application that low pressure injection heater is used in low pressure recuperative system of thermal power generator, and has unique technical application prospect in the field of energy saving of thermal generator.