Numerical Simulation Research For Eddying Tube Of Revolving Water Film Deaerator

Revolving water film deaerator is a new thermal deaerator.Three kinds of heat transfer and mass transfer approach,which are jet flow,rotary membrane and hanging bubble boiling,are combined together by revolving water film deaerator.Because of its numerous advantages,such as high water-spraying density,high temperature improving,large oxygen-containing concentration difference between the water inlet and outlet,small steam discharge amount and whole slide pressure,it is widely used in petrochemical and power systems.Operation and test results show that compared with other type deaerator,the revolving water film deaerator have significantly improved in deaerating effect,stability and load adaptability.It is the trend of thermal deaerators.The eddying tube,which is not only the key component of revolving water film deaerator but also the main position of strengthening the heat transfer and mass transfer,can remove the water-supply oxygen content by 90%to 95%.The size and length of eddying tube,the diameter,direction,number of holes and the differential pressure between feedwater and deaerating heads decide the water film skirt length,thickness and rotating speed.Optimization design of the eddying tube structure,combined with reasonable arrangement of the diameter,inclination and arrangement mode of jet-hole,can make both of the water-film forming within the eddying tube and the water-film skirt forming at the tube outlet at their best,so as to not only strengthen the heat transfer and mass transfer between steam and water-film but also improve revolving water film deaerator efficiency.At present researches on the eddying tube structure is much insufficient,mainly at the stage of experiment and study.Empirical estimating method is often used in the design and produce of the eddying tube and few numerical simulations of eddying tube have been conducted.In this paper,a series of numerical simulations of the flow field characteristics within and outside of the eddying tube are conducted by using the finite element software ANSYS13.0-FLUENT.Simulated results consisted well with other investigator's experimental data,which verified the correctness and reliability.The simulation processed by further changing the entry conditions and structural parameters.It provided a dependable basis for the structure optimization of eddying tube.Simulation results show that:(1)The tangential velocity declined gradually with the water moving down along the eddying tube wall.The tangential velocity presents increasing trend of radial distance by the geometric center of the eddying tube and quickly decreased at the boundary layer area near the eddying tube wall.The axial velocity was more and more large with the water moving down along the eddying tube wall and the increase was relatively slow at the bottom of eddying tube.(2)At the water inlet cross section z=70mm,water mainly distributes within 0-9mm distance from the inner wall of eddying tube.The water-film,which mainly distributes within 0-3mm distance from the inner wall,gets thinner and thinner with the water flowing down.(3)The higher the inlet speed of water,the higher the tangential velocity of the export section and water film half conical angle.The changing of the inlet speed had little influence on the water film thickness.(4)The bigger the diameter and effective length of eddying tube,the smaller the tangential velocity of the export section and water film half conical angle.The changing of the bigger the diameter and effective length of eddying tube had little influence on the water film thickness.(5)On the five conditions of inlet speed inlet speed v = 3.72 m/s,v =5.13 m/s,v = 6.28 m/s,v = 7.52 m/s,v = 8.75 m/s,the bigger the angle of jet holes,the higher the tangential velocity of the export section and water film half conical angle.The changing of the angle of jet holes had little influence on the water film thickness.(6)Water flowed upward from jet holes forming backflow,when the vertical spacing of jet holes was 0 millimetre that constant altitude arrangement.Backflow was not obvious,when the vertical spacing of jet holes was not 0 millimetre that spiral arrangement.The tangential velocity of the export section and water film half conical angle was increaseed gradually,when the vertical spacing of jet holes was increaseed.The changing of the vertical spacing of jet holes had little influence on the water film thickness.