ANSYS-Based Fea Of The Kettle-Type Reboiler With Fixed Tubesheet And Slant Conical Shell

With the aid of software ANSYS, the 3D FEA (Finite Element Analysis) model of kettle-type reboiler with fixed-tubesheet and slant conical shell is constructed. Several types of element such as Solid45, Beam188, Link10, Conta175 and Targe170 are adopted to build the model, in which MPC (Multipoint Constraints) algorithm is used to connect the Solid45 and Beam188 elements, and CE (Constraints Equations) are used to connect the coarse and fine element of Solid45. With the help of APDL (ANSYS Parametric Design Language), the parametrical FEA model is finished.In the FEA model, the tubesheet is simplified into solid plate with effective elastic constants. By the analysis of tubesheet and tube sub-model in the hot and cool side, the equivalent temperatures of the tubesheet are obtained, and meanwhile the equivalent temperature of the tube at hot and cool side are also obtained. The tube is simulated with Beam188, and the Possion's effect is replaced by the equivalent temperature of the tube.Stress analysis and stress intensity evaluation are performed for the seven load cases according to the start-up, the shut-down and the normal-work conditions as well as for two hydraulic tests cases. The cases of temperature load and shell pressure coupled with temperature are the two dangerous load cases, in which the maximal stress intensity are located at two zones, namely, one at the conjunction of the tubesheet and tube channel,the other in the small side transition section of the slant conical shell. Thermal stress takes the major part of the total stress, and is the crucial factor to the reliability of the equipment. In addition, the self-weight of the equipment and the hydraulic pressure can be ignored because of its little contribution to the total stress intensity.By the eigenvalue buckling analysis method, the stability analysis is conducted for the structure. The buckling occurs at the big-side of the slant conical shell with the biggest slant angle. Both the meridional and the circumferencial stresses are big and compressive, which lead to the buckling of the slant conical shell. The tube-bundle, saddle, the length of the shell and the reinforcing ring are discussed for their influences on the buckling load. It shows that the tube-bundle has little effect on the buckling load, so the tube-bundle can be ignored when in the buckling analysis of the structure. However, the saddle and the reinforcing ring can improve the the buckling load of the structure.