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Using SIMSOLID for complex heat exchanger

Heat exchanges can be complex structures. With Heat exchangers, we see different loads on nearly every part resulting from different pressure loads on tube side and shell side, temperature loads due to thermal expansion and nozzle loads from the attached pipes. In addition, external loads like wind or earthquake loads might affect the apparatus.

Up to now, the stress and stability in these exchangers were calculated by formula using different codes like ASME or if the task is more complicated by FEM. The disadvantage of FEM in this case is, that we need a very fine mesh on the tube sheet to solve the problems on this highly perforated part. On the other hand, the tube sheet might get very large in diameter, which causes a very high number of elements, and subsequently a very long calculation time.

Take for example the following heat exchanger. This complex assembly consists of 566 separate parts including 112 nuts and bolts.

Figure 1 - Model with stressesFigure 1 - Model with stresses Figure 2 - Transparent view of heat exchanger showing internal pipe detailsFigure 2 - Transparent view of heat exchanger showing internal pipe details Figure 3 - Detailed view of internal pipes with external shell hiddenFigure 3 - Detailed view of internal pipes with external shell hidden

SIMSOLID allows not only to calculated the tube sheet displacements and stresses using a fraction of time spent for meshing the FEM calculation, but also allows to overlay the loads resulting from the additional effects. Moreover, we are now for the first time able to optimize these material consuming tube sheets, due to the quick answers. Typical run times for this project is under 10 minutes.

Figure 4 - v. Mises stress during critical start-up conditions with floating head cover hiddenFigure 4 - v. Mises stress during critical start-up conditions with floating head cover hidden Figure 5 - Detail view of v. Mises stress during critical conditionFigure 5 - Detail view of v. Mises stress during critical condition Figure 6 - Critical areas with a safety factor near or less than 1.5Figure 6 - Critical areas with a safety factor near or less than 1.5

We find SIMSOLID to be a very valuable tool analyzing complex structures. We look forward to using in more and more in our business. That is why we have become a consulting partner of SIMSOLID.