Study On Tube-sheet Expanded Performance And Equivalent Method Of Porous Tube-sheet For Heat Exchanger

In petroleum and petrochemical process of production, shell-and-tube heat exchanger is most commonly used equipment and one of the most malfunctioned equipments. Especially, there are still problems in the connection between tube-sheet and tubes, and in the equivalent solid plate like porous tube-sheet. According to elastic-plastic finite element analysis method, this paper established a 3-D nonlinear finite element model. Considering the impact of working medium on the contact zone between tube-sheet and tubes, the numerical simulation method of residue contact pressure was built based on expanding and unloading process. The result showed that the maximum residue contact pressure gradually decreases with tube-pass pressure increases, first stays unchanged and then rapidly drops with shell-pass pressure increases to a certain threshold limited value; along the axial direction, the residue contact pressure zone changes a little with tube-pass pressure, but changes a lot with shell-pass pressure and the zone gradually shrinks when shell-pass pressure surpasses the threshold value; as for pull-off force, it gradually increases with the raise of tube-pass pressure. It also experiences a process of slightly decreases with the raise of shell-pass pressure and then rapidly drops as soon as the pressure surpasses the threshold; when the expanded pressure has 160MPa~200MPa, the threshold shell-pass pressure increases from 5MPa to 25MPa; when shell-pass pressure has 5MPa below, the strong expanded process is recommend. Considering the supporting of tubes and porous tube-sheet, the 3-D finite element model for the heat exchanger porous tube-sheet was established, and the numerical simulation method of the expanded and welding between tube-sheet and tubes was studied. The 3-D finite element model for the heat exchanger equivalent solid tube plate was established. Comparing the two equivalent methods of connecting between tubes and tube-sheet concludes that error between the deformation of solid tube plate using multipoint constraint method and porous tube-sheet is from 3.4% to 20.5%, better than method of sharing node. Through the numerical simulation result comparison between porous tube-sheet model and equivalent solid plate model, the deformable relative error of inlet and outlet tube-sheet is from 0 to 20.5%, and the stress difference is from 1.69 to 3.26 times. By using the stress concentration coefficien and multipoint constraint method to simulate the connection between tube-sheet and tubes, an improved method of equivalence of porous tube-sheet to solid plate, which applies to finite element analysis is established.