Heat Transfer Enhancement By Passive Vibration Of Helical Elastic Bundle With Elliptical Section

Some heat transfer devices enhance heat transfer by making the elastic element vibrate.However,the traditional plane elastic tube bundle heat exchanger mass and covers a large area,the connection between the tube many joints,easy to leak,the risk is strong,the required material is more,increased the material flow resistance,reduce the coverage area,heat transfer performance is also affected by the bad,resulting in enhanced heat transfer effect is not obvious.Therefore,in order to obtain better heat transfer effect,some researchers have proposed the helical elastic tube bundle heat exchanger.This kind of heat exchanger combines the advantages and disadvantages of traditional tube heat exchanger,has the characteristics of lightweight,miniaturization,compact,more flexible,controllable,and can obviously improve the heat transfer effect of heat exchanger.In this paper,the structure of the elastic bundle heat exchanger is adjusted.According to the basic principle of heat transfer enhanced by fluid-induced vibration,a calculation model of fluid-solid-thermal coupling is established.ANSYS is used to carry out numerical simulation calculation and specific analysis of the parameters affecting the vibration and heat transfer of heat exchanger.Analysis of vibration results shows that When the fluid flows in the flow field,there are a lot of backflow and eddy currents,resulting in different vibration response distribution of the tube bundle.With the increase of coil number,the vibration frequency of tube bundle decreases,but the vibration amplitude increases greatly.And with the increase of the inlet velocity,the vibration amplitude of the tube bundle is reduced,but the vibration frequency is not affected.The larger the difference between the long and short diameters of the elliptic tube bundle,the larger the vibration displacement of the tube bundle.Therefore,only improving the strength of vibration can not improve the performance of the heat exchanger,in the process of transforming the spiral elastic tube bundle heat exchanger,at the same time for the tube bundle assembly of appropriate location and adjust the cross section of the tube bundle shape.The direction of tube bundle arrangement has little effect on the vibration amplitude and frequency of external tube bundle.For the inner tube bundle,the vibration amplitude under the reverse arrangement is higher than that under the downward arrangement,but the direction of the tube bundle arrangement has little influence on the vibration amplitude and frequency of the outer tube bundle.For the inner tube bundle,the vibration amplitude under the reverse arrangement is higher than that under the downward arrangement,but the direction of the tube bundle arrangement has little effect on the vibration frequency of the inner tube bundle.The arrangement direction of the inner tube bundle has little effect on the vibration frequency.The location of the baffle has no great effect on the total vibration displacement of the bundle,but the vibration displacement of the bundle near the baffle is larger.As a whole,the location of the baffle has little effect on the vibration frequency of the helical elastic bundle.The analysis of the heat transfer results showed that the vibration of the tube bundle had an effect on the heat transfer effect,and the increase of the inlet velocity was also conducive to improving the heat transfer coefficient of the tube bundle.However,with the increase of flow velocity,the increase of heat transfer coefficient of tube bundle becomes slow.Among them,under the same precondition,the elliptic shape of four kinds of tube bundle cross section shapes(quadrilateral,hexagon,ellipse,circle)has the best heat transfer effect.When the inlet flow rate is 0.7m/s,the difference between the heat transfer coefficient of elliptical shape and other shape bundles is the most,and compared with quadrangle,hexagon,circle,respectively increased by 20.3%,17.0%,9.9%,but quadrangle heat transfer enhancement effect is the best.The further study of the elliptic tube bundle found that the ovality of 2/1 was the most beneficial to the heat transfer of the tube bundle.Among the three spiral coil numbers(3,5,7),the heat transfer effect of the tube bundle with 5 spiral coils was the best.On the basis of this ovality and tube bundle heat exchanger,the heat transfer coefficient of the inner layer is only 2.63% higher than that of the original structure.However,the heat transfer performance of the inner layer is not improved by adding a layer of tube bundle in the direction of the inner layer.The heat transfer coefficient of tube bundle can be greatly improved by adding baffle in proper position.Figure [53] Table [11] Reference [93]...