Numerical Simulation Research For QSH Steam-water Mixing Heater

QSH steam-water mixing heater is a new type of device,which can mix steam and water directly and then heat water.It has been widely applied in the field of heating,chemical industry,petroleum,electricity,because of its characteristics of high thermal efficiency,low noise,simple structure,low operation cost,etc.In the QSH steam-water mixing heater,there exists complex gas-liquid two-phase flowing,interaction of multiple jets,free surface and shear layer,transfer of momentum,heat and mass.At present,the design of QSH steam-water mixing heater has not fully mature feasible calculation formula and it mainly depends on the designer's experience and trial and error.This limits the rationality of the design of QSH steam-water mixing heater.In virtue of FLUENT software,simulation of QSH steam-water mixing heater is carried out.Through analysis of the simulation result,many relations between QSH steam-water mixing heater and structural parameters and operating parameters were mastered.Based on the above,a new swirl type QSH steam-water mixing heater was proposed.The improvement of QSH steam-water mixing heater on vibration was performed.The numerical results were compared with the experimental result and gave an excellent agreement.So the experimental method was right.Conclusions were as follows:(1)In the gradual shrink,cold water conducted the depressurization and deceleration process closing to diabatic entropic process.Cold water speed reached a maximum in the venture.Vapor jeted inthe cold water through the heating holes,released a large number of latent heat,transfered heart with cold water,and then rised the temperature of cold water.This can appear local uneven mixed and form elliptic steam plume while vapor jeted in the cold water.(2)The smaller the venture diameter,the smaller the mass flow of the cold water,the greater the resistant loss,the smaller the speed of the cold water in the venture,the little the temperature rise of the cold water.The shorter the venture length,the higher the speed at the exit,the higher the temperature,the smaller the jet angle of the heating holes,the greater the momentum transfers to cold water,the higher the speed of the water at the exit,the higher the mass flow of the vapor,the higher the temperature rise of the wate.The length of the steam plume increased with jet angle decreased.when the jet angle was small,the steam plume overlap and the performance of the steam-water mixing heater were affected.(3)The higher the pressure of vapor,the higher the speed and the temperature of the water at the exit,the longer the length of the steam plume.Dimensionless penetration length of steam plume the relationship between dimensionless penetration length of steam plume and vapor inlet pressure approximated linear.(4)The bigger the offset of the-vapor entrance,the better the swirl formation of vapor,the better the mixed degree between cold water and vapor,the smaller the temperature difference.At present,the research of the QSH steam-water mixing heater is limited.The result of this study have provided basis for the design and optimization of QSH steam-water mixing heater.Meanwhile,this study on the change of the properties and heat exchange efficiency is also very important.In addition,the author has achieved some useful exploration in model establishment and simplification of such complicated model,grid division,calculation model choice,etc.