Q9-3 Modeling Intermediate Tube Supports in Xist

K. J. Farrell

Xist® 5.0 (release planned for 2006) will include an option for specifying intermediate tube supports to reduce the vibration response of vulnerable tubes in the end zones of shell-and-tube heat exchangers. The reduced response is proportional to the ratio of the span lengths raised to a power. The new feature will decrease the number of vibration warnings in Xist. However, an example demonstrates that the simplified Xist screening can indicate the need for intermediate supports when the more accurate finite element program Xvib® will not. In such cases, the time saved on the design effort using this new Xist option and avoiding an Xvib analysis more than offsets the cost of the intermediate tube support. Moreover, the stiffer entry/exit spans will likely accommodate a future flow rate increase without additional modification.