Numerical Study Of Performance Of Tapered Mixing Chamber Ejection Heater Under Variable Items For135MW Thermal Power Plant

At present, there are a lot of problems for surface heater in thermal power unit suchas, the low thermal efficiency, the high temperature difference, the complex systemetc..Many scholars believe that these problems can be solved by using the ejectionheater instead of the surface heater. The heat transfer and energy saving effect ofejection heater is more efficiency. Low pressure heater operating characters undervariable load have been challenged because of the thermal power unit load constantlychange. A ejection heater with optimal structure and adapting to the power applicationwas designed, and it may have an important academic meaning and engineering value.According to the actual running conditions of low pressure heater of135MW unit,the model of ejection heater with tapered mixing chamber is established, and the size ofthe injection heater structure is determined. Comparing the simulation and experimentalresults, the reliability of condensation model is verified. According to the operationcharacteristics of135MW unit under variable load, the ejecting and heatingperformance of ejection heater with the different diameter of water nozzle, mixingchamber length, throat mouth section ratio and water mixing chamber entrance nozzlerelative displacement is analyzed under varying load. Safety and effectiveness of theejection heater instead of the low-pressure heater was studied.The results show that the condensation model previously proposed is reliable.According to the simulation results, ejection heater performance is stable under varyingload. When the nozzle to throat area ratio is greater than or equal to7.84, the heaterperformance can meet the requirements of the unit under variable conditions. When themixing chamber length is500mm, the water outlet nozzle mixing chamber entrancerelative position displacement is-0.5mm, the heater had the best performance. When theejection heater structure needs to be optimized, the following factors are consideredsuccessively: the mixing chamber length, nozzle to throat area ratio and the diameter ofwater nozzle.The safety and efficacy of the heater when the ejection heater instead thelow-pressure heater were also analyzed. Negative pressure area pressure is lower thanthe extraction steam pressure when ejector operates in common load. At the same time,there is no threat of working fluid back into the steam turbine. The working ability ofthe ejection heater can meet the need of the original unit and has been improved to acertain extent. Application of ejector heater can improve the energy utilization of extraction steam and improve the heater outlet temperature. Its application is safe andeffective.