Hello Azman
Section UHX of ASME VIII, Division 1 is quite complicated. There are many equations, and many load cases to be considered. Therefore there is no convenient 'rule of thumb' to determine whether or not bellows are to be encorporated into the design. It is really a matter of trial and error and perhaps a little experience. Designing a heat exchanger takes patience. Perhaps several designs should be tried until an economical design is achieved.
Your question about growth:
Growth is determined by mainly two factors: The temperature and the coefficient of thermal expansion. In the case of a fixed tubesheet configuration, the shell is a different temperature from the temperature of the tubes, so the growth of one is fighting with the growth of the other. The calculations to determine the final growth are complicated.
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Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM