Thermal stress analysis on the thick tubesheet with square layout of tubes

In this paper, finite element analyses were carried out on thermal stresses at the tubesheet of floating-head or U-tube heat exchangers with square layout of tubes based on parametric finite element models of the tubesheet established with ANSYS parametric design language (APDL). It is found that for thick tubesheet with large temperature difference between two the sides, the maximum thermal stress can be comparable with the mechanical stress induced by pressures and should not be neglected in some circumstances. When hot fluid flows on the tube-side, both the shell-side and tube-side surfaces of the tubesheet are in tensile stress state while the region in the middle of the tubesheet is in compressive. Conversely, if the cold fluid flows on the tube-side, compressive thermal stresses are produced at the two tubesheet surfaces, which is helpful to prevent the tubesheet from cracking. By changing design parameters in APDL commands, parametric analysis was completed and the results show that the thermal stresses at the surface center of the tubesheet are sensitive to the thickness and the perforated region size of the tubesheet. Based on sufficient numerical results, a regressed formula for evaluating the thermal stress at the surface center of the tubesheet with squarely arranged tubes was obtained, this can facilitate the strength design of the tubesheet in floating-head or U-tube heat exchangers when considering the thermal stress.