Simulation And Experimental Research On Mechanical Expanding Of Interstage Fin-Tube Heat Exchanger

Mechanical expanding is a forming process using bullet moving in the tube to make the heat exchanger swell and realize the connection between heat exchanger and fins. Mechanical expanding is widely used in heat exchanger manufacture due to its simple technology, easy to large-scale automated production, high connection strength of tube-fin. Because of the limitation of expanding stroke, mechanical expanding is mainly used in the production of small heat exchanger. The application of mechanical expanding in large heat exchanger production has always been a difficulty and a hot spot in this field. Mechanical expanding process of large heat exchanger is studied in this thesis by both numerical simulation and experiment.This thesis will analyze the tube expanding process with analytical solution based on the theory of elastic-plastic mechanics. And the analytical solution of the residual contact pressure between fin and tube will also be deduced.Finite element model of mechanical expanding of large scale heat exchanger was established. From the simulation results, expanding force, the change of tube parameter, the law of the fin lodging was analyzed. The effect of the existence of support plane on the deformation of fin was also studied. The deformation of support planes was studied. The influence of expanding of adjacent tube on the middle tube was studied by simulation. The effect of bullet geometry on expanding forming was also analyzed. Through the above analysis, the bullet and expanding process were optimized.The critical pressure of rod was calculated by both analytical method and numerical simulation method. And the analytic calculation formula was corrected. The situations of push rod failure were put forward by comparing the expanding force to the critical pressure. Improvement opinion was proposed.Expanding experiment was conducted. And the expanding force, the change of tube inner diameter, thickness and length were measured. Compared with the simulation results, the accuracy of the simulation model was verified.