Heat Transfer Enhancement Mechanism And Fouling Development Outside Vibrating Pipe

Vibrating enhance heat transfer was attentioned in 70's last century,companied with the develop and progress of technologies,the title are mentioning more and more.The research in heat transfer mechanism of vibrating surface would be a theory to direct the practice.The fouling can block heat transfer progress and can not be neglect.It is necessary to research the fouling development on the vibrating surface.The synergism theory is a basic tool to research heat and mass transfer, and it should be expanded,inspected and utilized.Effect of the main fluid to boundary layer and heat transfer was discussed using Lagrange method.In turbulent flow,velocity and angle decide the depth that the particle enters the boundary layer,and then influence the heat transfer of that and surface.The heat transfer of boundary layer can be realized by the main flow velocity and the angle with the surface normal line(SNL).Average synergism angle(ASA)and the integral synergism angle(ISA)are defined in article.The ASA can be used while value the arithmetic average cosine that the between the velocity and SNL,and the ISA can be used while value the weighting average cosine that between the velocity and SNL,in which velocity as the weighting.The synergism match coefficient K is a ratio between the cosine ISA and cosine ASA,and it decide the matching of velocity and its angles between velocity and SNL.While K＞1 the synergism matching performance(SMP)is well, and on the contrary is bad.Dimensionless angles consine(DAC)and dimensionless velocity(DV)are defined in this article.And the matching performance of the fluid flow can be showed in the DAC-DV distribution figure.The K dividing line(KDL)is useful in measure the matching performance of the point.If a point inside the KDL its K＞1, while outside the KDL its K＜1.the matching line cut apart the first quadrant in four zones,and named A,B,C,D zone.While the point position in A and B zone it will contribute to K,and if it position in C and D zone it will decrease K. Field synergism angle(FSA),average velocity(AV)outside the vibrating cylinder(OVC)are researched.The distribution of FSA are regular patterned.Field synergism performance(FSP)outside the vibrating pipe was valued.The research indicate that the synergism performance is obviously regularity on every time phase.The synergism performance is well on the location phase 0°and 180°and decrease at both sides.While the time phase close to the balance,the location phase that have well ESP is larger.Flow velocity on LP 0°is lower than which on LP 90°nearby the TP 0°.the flow velocity increase gradually everywhere from TP 0°to 90°.The flow velocity well-distributed while TP between 40°to 60°;And the flow velocity on LP 90°lower than which on LP 0°,which result in the ASA larger than ISA,and the SMP is better.While the ISA larger than the ASA,the SMP is worse and come back to the performance at TP 180°as same as TP 0°.Time ISA and time average velocity determine the heat transfer coefficient variation on the pipe.The SNL velocity is unobvious linear to heat transfer coefficient for the temperature gradient is not well-distributed and the influence of boundary layer.Location ISA and the location average velocity determine the heat transfer coefficient variation along time.And the heat transfer coefficient changes not large for the thermal inertia in the boundary layer.Whole field synergism performance(FSP)are calculated and the ASA between 47°-66°,the FSP of heat transfer surface is well.ISA smaller than ASA indicate that the whole SMP is well.All which shows that the vibration can enhance the SMP and FSP,on the other side,vibration decrease the thickness of the boundary layer.Influence of frequency to high flow nearby the pipe are amylase,the increase of frequency will decrease the integral time,and the high flow nearby the pipe will decrease for being depressed.High flow nearby the pipe is not benefit to the FSP,and an improved measurement is proposed and be inspected by the numerical simulation.The simulation shows that the rib on the pipe can improved the heat transfer coefficient to a certain degree.And the altitude of the rib and eddy is the whole altitude which takes effect.Heat transfer enhancement performance was experimented,the heat tran-sfer coefficient increase according with the increase of frequency,and the heat transfer coefficient increase suddenly after the breaking point.The breaking point's frequency will decrease along with the increase of amplitude of vibra-tion.The equation of heat transfer coefficient and the depended parameters are correlative,and a high frequency low amplitude will donate larger to heat transfer than a low frequency high amplitude frequency if vibrating Re_v number are equal, and this alike the conclusions of the numerical simulation.Fouling development of the stationary pipe and vibrating pipe was exa-mined,and the experimental demonstrated that vibration decrease the fouling resistance obviously at the same heat flux density.The asymptote fouling resi-stance is function of the Re_v number,for which the exponent are negative.And the experimental not give a clearly relation between constant time and vibration parameters.Fouling shape was analysis from the influence of shear stress,difference of fouling structure,the uniform of hardness,which bring about a concavo convex surface of the vibration surface.And the models for fouling remove are discussed, vibration bring about the mass transfer enhancement,which cause the dissolve increase;vibration bring about the shear stress became a dynamic load,which cause the fouling remove easily while the load is smaller than the static load; vibration bring about the additive mass force,for which the acceleration will take effect in fouling remove.Steady thermal resistance method was analysis and a new method for mea-sure the fouling resistance and constant time was proposed.The fouling cons-tant time is inverse ratio to the logarithm of fouling development velocity of two measures.And the asymptotic value of fouling resistance can be exp-ressed by the first fouling develop velocity and the second measure of the fouling resistance.The method give consult to fouling measurement and forecast.