4 replies to this topic

Hello,
We have come across sizing of steam/water heat exchanger with large variation in water flow rate. For water in tube option, this results in messages related to bundle entry/exit vibrations. When we select Bundle inlet/outlet supports, the vibrations are subsided. In the results, the distance of such supports from the tubesheet are displayed. however, it is not very clear as to what the nature of these supports is. It does not get reflected in any of the HTRI schematics/drawings either, unless I have missed it. Could someone advise on the mechanical details of these supports? Thanks in advance.

[mvp]

Some information from help files in HTRI
1. Inlet vibration support

Specifies the presence of a tube support device in the bundle entrance area. The tube support is assumed to support only the first few tube rows under the inlet nozzle and not all rows in the inlet baffle spacing.

2. Support plates
Support plates have both windows cut but support all tubes because there are none in the windows; these plates do not interfere with thermal and hydraulic performance of the heat exchanger. However, eliminating tubes from the windows usually requires a larger diameter shell to provide sufficient heat transfer surface; a good design calls for a small baffle cut to minimize the number of tubes lost.

And there are other help information on this topic.
Alternately, you can Email HTRI, and they'd Clarify

MVP

Thank you MVP for reply. I am looking for the actual design details of the 'tube support device in the bundle entrance area' as you have mentioned in item 1 in your reply. HTRI output provides no sizing details of this in any of their sketches. Will be great if you or any one else helps in this.
Thanks in advance and best regards.

Thank you MVP for reply. I am looking for the actual design details of the 'tube support device in the bundle entrance area' as you have mentioned in item 1 in your reply. HTRI output provides no sizing details of this in any of their sketches. Will be great if you or any one else helps in this.
Thanks in advance and best regards.

Come on guys. Please share your expertise. Thanking you.

[daryon]

Thank you MVP for reply. I am looking for the actual design details of the 'tube support device in the bundle entrance area' as you have mentioned in item 1 in your reply. HTRI output provides no sizing details of this in any of their sketches. Will be great if you or any one else helps in this.
Thanks in advance and best regards.

Come on guys. Please share your expertise. Thanking you.

I think you are expecting slighty too much from HTRI, it is after all a thermal design tool, not meant for full mechanical design of a shell and tube heat exchanger. A reputable exchanger fabricator will have their own mechanical design for tube supports. I think all you would need to do is advise the exchanger supplier of the vibration warnings from HTRI, specify the tube support spacing and that HTRI is recomending a support at the entrance nozzle.

Just check that the unsupported tube span in this entrance region is small. " Unsupported tube spans adjacent to the tubesheet are frequently longer than those in the baffled region of the exchanger, and result in low natural frequencies" (ref. TEMA Standard). I supsect you entrance is at one end of the shell near the tubesheet? HTRI is recomending a tube support in this region, but I don't see a tube support plate which is at the bundle entrance being any different from a support plate elsewhere along the bundle, apart from the fact it may not support all of the tubes in the bundle - probably just the top section of tubes near the inlet nozzle. They are just metal plates of a calculated thickness with holes for tubes. It is still held in place with tie rods and spacers, and must be firmly fixed.