Study On The Pulsating Flow Generating Device In Elastic Tube Bundle Heat Exchanger

Nowadays, in face of the increasing serious energy shortage, energy-saving seems extremely important and needs to be solved insistently. Therefore, the technology of heat transfer enhancement receives extensive interest and concern. The technology of heat transfer enhancement via flow-induced vibration is an innovative and original way in the area of passive and complex heat transfer enhancement. When the shell-side fluid flow passes by, the self-excited vibration of planar elastic tube bundle occurs, which plays positive factor in the tube heat transfer enhancement and fouling inhibition, thus the complex heat transfer enhancement is obtained, and it have been successfully applied in production processes. The vibrations of heat exchange components inside a heat exchanger impose significant impacts on heat exchange coefficient as well as its lifetime. Taking this into account, the analysis by the combination of numerical simulation and experimental study of a branched pulsating flow generating device was developed based on the research of elastic tube bundle’s appropriate vibration induction and its effective vibration control, hopes to provide a new method for effective vibration control of heat transfer elements, and to improve the uniformity of vibration and heat transfer performance of elastic tube bundles in heat exchanger. The contents of research are as follows:The finite element model of planar elastic tube bundle was created based on the studies of heat exchange components’ natural vibration characteristics. Then the bundle’s natural frequency and vibration mode were calculated through Ansys mode analysis (structure dynamics analysis module), and it provides a basis to decide the dimensions of pulsating element. In the meanwhile, natural characteristics of the bundle were also analyzed through mode experiment, the result of which corresponds with the simulation. The influences of all the planar bundle’s structure parameters on its natural characteristics were investigated as well.A two-dimensional finite element model of straight tube with various pulsating elements was created for the branched part of the pulsating flow generating device. Then simulation calculation was conducted via Fluent in order to analyze the influence of cross-sectional shape on the pulsating parameters of the generated pulsating flow, the results show that the strength and stability of pulsating flow generated by triangular prism pulsating element is better than other pulsating elements, and the cross-section dimensions of triangular prism was obtained; Moreover, the influences of the factors such as bundle length, entry velocity on pulsating flow parameters at the outlet were also analyzed; In addition, different existing forms of vortex in various structure dimensions were discussed.A3D finite element model of pulsating flow generating device’s branched part as well as its overall structure was created on the basis of2D simulation calculation. Through Fluent simulation calculation, the influences of entry velocity and some other factors on the parameters of generated pulsating flow were analyzed; and the fluid state in the pulsating flow generating device which has a hole at the end of straight part was analyzed, the simulation results of this device proved that pulsating flow with same frequency and amplitude can be obtained at the branch outlets, and the structure with a hole at the end of straight tube part is more conducive to produce vortex shedding in branched part.A pulsating flow induced elastic tube bundle vibration testing platform was established; and what’s more, the frequency changes of the planar elastic tube bundle under different entry velocities caused by the impact of the generated pulsating flow were tested with experiments, the result of which corresponds with the simulation.