In box-type high-temperature flue gas heat exchangers, how is expansion addressed?
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The flue gas temperature is over 700 degrees, the heat exchange tubes are over 1 meter long, and there are multiple processes involved； How to solve the expansion problems on the shell side and tube side
I checked various sources myself, but found no information on the use of expansion joints in box-type heat exchangers; expansion joints are used in shell-and-tube heat exchangers instead. Is this problem not present in box-type heat exchangers? Is there anyone who knows this and can give some guidance?
Use elbows; just don’t weld the tube sheet to the tubes directly.
Tubes use increased curvature to increase the expansion amount, while the shell side generally does not require expansion calculation.
Multiple processes are involved; each process features multiple rows of tubes arranged in a triangular pattern. Using elbows would make it difficult to arrange the tubes properly, so it is considered that the ends of the heat exchange tubes should be welded to the tube sheet
There are a large number of tubes, with multiple processes and rows of tubes; using elbows might make it difficult to arrange them properly. Therefore, it was decided to weld the ends of the heat exchange tubes directly to the tube sheet. The flue gas temperature is quite high, and there is a risk of welding failure
Yes, when the number of tubes per row is greater than 3, U-tubes are indeed not very useful. With tube sheets (tube banks), there is an expansion issue. Please share your valuable insights.
Expansion joints are added at the connection between the tube sheet and the shell to eliminate expansion stress.
This type of heat exchange should be implemented using coiled water pipes; otherwise, smoke pipes can also be used.
It can be designed in the form of a movable tube sheet, with the fixed end welded to the shell, while the movable end tube box maintains an expansion gap from the shell; it seems that preheaters in steel plants are all built this way, with them being inserted into the flue