Finite Element Analysis Of High Pressure U-Tube Heat Exchanger

Shell and tube heat exchangers are widely used in petrochemical industries and electric power. Tube sheet is the most import part, which is used to connect shell, tube, bundle and channel and bear pressure, temperature load and other loads. For a large tube sheet, performing stress analysis is especially useful for saving the material while keeping sufficient strength of the tube sheet.In this paper, we study the U-tube heat exchanger which is first developed and used in 1000 MW ultra supercritical unit. By using the general finite element analysis software ANSYS10.0, a solid model of heater, including tube sheet, shell and tubes is established. On this basis, the analysis of the five typical high transient conditions plus the tube sheet and shell temperature distribution and thermal stress field distribution. Based on the stress analysis standard JB4732-1995, the stress analysis are done for 7 steady or transient operating cases which may occur during the start-up, steady operating and shut-down.The result of stress analysis shows that the position of maximum thermal stress is always located at the transition arc tube plate and connected to the shell in various transient conditions. This is due to the geometry of the structure where the mutation occurred, causing localized stress concentrations. The temperature difference caused by the high stress areas are mainly concentrated in the surface of the shell and the tube bore little other regional stress intensity, which was further confirmed by the so-called "skin thermal effect" phenomenon.The result of strength analysis shows that the most dangerous case of the tube sheet is not the steady case, but the transient case that the shell-side fluid is firstly shut down, but tube side pressure load and thermal load still retain.The result of fatigue analysis shows that we can get the high instantaneous metamorphosis in different conditions and combinations of conditions to allow the number of cycles.