I'd think that spiral design heat exchangers could handle expansion quite well. When Steve mentions "coning" that may be a hint. Think limit stops and pressure sealing maybe.
My limited experience is with cryogenics (ambient to -320F, and come to think of it those are pretty extreme conditions) and I've never thought about it before. Good original question.
More thinking may be required here.
Paul
> Hi Mike
>
> I am a but out of date with tube in tube units so you are probably
> better seeing what Alfa Laval offer. From memory, they consisted of
tube
> in tube U sections with the outer tube coned onto the inner tube just
> before each end flange. They could then be bolted together (inner
pipe)
> and the outer pipes connected by jumper pipes. This largely avoids
> differential stressing.
> Not familiar with spiral tube units but presumably they are like
spiral
> plates - big coil in a bucket with close clearances to promote
> counterflow.
> Years ago I used to make stainless S&T heat exchangers for the meat
> industry - used to condense rendering plant steam (100 C) and produce
> potable hot water (85 C). Others had problems with stress corrosion
> cracking using 316L so we went to 3RE60/SAF2205/2RK65/904L. The steam
> went through the tubes and the water over them. 75% baffles were
spaced
> at about half the shell diameter to approach counterflow conditions
and
> provide tube support. The tubes were welded into a thin (6mm)
tubesheet.
> The tubesheets (1.6mm) were welded to the shell, and the shell had a
> single large corrugation (fabricated from two "washers" and a band
with
> corners radiussed) at midspan. The corrugation was sized to
accommodate
> a 100 deg C temperature differential between tube and shell without
> overstressing.
> Cant recall any failures.
> For liquid food work, mostly plate exchangers are used here now as
the
> thermal performance (bang per buck) is heaps better.
>
> Cheers
>
> Steve
>
> -----Original Message-----
> From: Michael Waugh [mailto:mike@waudesign.com]
> Sent: Friday, July 02, 2004 1:18 PM
> To: PipingDesign@yahoogroups.com
> Subject: RE: [PipingDesign] Shell and tube Heat exchangers
>
>
>
> Hi Steve:
>
> Thanks. I am familiar with "spiral tube units", are these the same?
> With those, I would agree that expansion would be much less of an
> issue. Dare I ask how these are built?
>
> I want to build a straight shooter, with 3/4" SS316L, polished. Mine
is
> basic or much like a normal HE, but some changes.
>
> I used to work for a large beverage outfit here in Florida, and they
> had fairly large units, about 6" Dia for each tube. We would
experience
> cracks right at the welded end and we used a florescent green dye to
> detect them. It's that joint of the tube and the plate weld that has
> been bugging me. I have been looking at different designs for some
> ideas.
>
> Appreciate your comments.
>
> Mike Waugh
>
>
> -----Original Message-----
> From: Steve McKenzie <mechproj@xtra.co.nz>
> Sent: Jul 1, 2004 6:31 PM
> To: PipingDesign@yahoogroups.com
> Subject: RE: [PipingDesign] Shell and tube Heat exchangers
>
> Hi Mike
> some dairy installations use tube-in tube exchangers for ease of
> cleaning. By using a serpentine pattern, expansion can be easily
> accommodated. Before designing you may want to see whats currently
> available so you can either "borrow" the best ideas or just buy what
you
> need. APV and Alfa Laval make some good stuff in the dairy industry.
>
> Cheers
>
> Steve
>
> -----Original Message-----
> From: mikebw_99 [mailto:mike@waudesign.com]
> Sent: Friday, July 02, 2004 3:02 AM
> To: PipingDesign@yahoogroups.com
> Subject: [PipingDesign] Shell and tube Heat exchangers
>
>
> Greetings
>
> Anybody with information on design of heat exchangers? I am starting
> out on a design, I am seeking some technical information, literature
> or any other guidance on how to correctly determine the innner shell
> tube lengths for a sanitary shell and tube heat exchanger(tubes to be
> built into a bundle). I would like to better understand thermal
> expansion effects and properties, stress related effects on welded
> ends, in order to prevent bending of the tubes. These tubes would be
> welded into end plates and specifying the welds to stop leaks is a
> concern.
Received on Fri Jul 02 06:59:00 2004
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