reducing turbulent flow around an elbow
reducing turbulent flow around an elbow
(OP)
I am currently looking at the gas flow into the top of a large vertical cylinder. There is an elbow in the pipe directly before the inlet. Because of the turbulent flow produced as the gas goes around the bend, uneven buildup is accumulating in the cylinder. Does anyone have any suggestions for companies that produce devices to decrease the effect of the turbulence while the gas in in the pipe?
Any help would be appreciated. Thank you.
Any help would be appreciated. Thank you.





RE: reducing turbulent flow around an elbow
The usual problem caused by bends is UNEVEN gas flow DISTRIBUTION. For this you can buy gas straightening devices (turning vanes).
However, you spoke of buildup - presumably solids carried in the gas stream. Turning vanes may just be another place for solids to build up.
To minimize solids buildup on turning vane, consider installing staggered vertical blades only.
RE: reducing turbulent flow around an elbow
RE: reducing turbulent flow around an elbow
We had a similar problem two years ago. CFD Engineers (Computational Fluid Dynamics) promised to make a model so we could judge how to place large plates (vanes) to equalize the flow homogenuously across the complete cross sectional area. Not so easy, but it gave some good info
(and of course nice and colorful CFD pictures with the predicted velocity profiles).
In the end we balanced the tower by trial and error. We did a lot of measurements with a "propellor air speed meter". With this small device you can measure gas speeds and direction at any position in the pipe.
Best solution still is to ensure you have a straight (decomposer) inlet of a least 10 times the pipe diameter.
Regards,
CARF
RE: reducing turbulent flow around an elbow
RE: reducing turbulent flow around an elbow
RE: reducing turbulent flow around an elbow
And consider the use of a long radius ell, if space permits.
RE: reducing turbulent flow around an elbow
m777182
RE: reducing turbulent flow around an elbow
RE: reducing turbulent flow around an elbow
I have never seen an elbow like this. Do you have the name of a vendor or a link?
Thanks
StoneCold
RE: reducing turbulent flow around an elbow
RE: reducing turbulent flow around an elbow
I am curious to hear why a mechanical engineer would not be inclined to use your solution of an elliptical cross-section at the center of the elbow.
RE: reducing turbulent flow around an elbow
http://www.chengfluid.com/crv_info.htm
RE: reducing turbulent flow around an elbow
Do you have any links to test data, or plots of the loss coefficient for the elliptical section elbow you describe? I can think of a couple of ways to fabricate such an elbow, and this is one mechanical engineer who'd love to use it if it works...
Ben T.
RE: reducing turbulent flow around an elbow
The elliptical section elbow might be possible for low pressure duct work, but there are concerns for moderate to high pressure service along with thermal expansion. There might not be much difference for smaller elbows (<12 inch?) but for larger size elliptical sections I could imagine the ellipse deforminig with pressure toward a circular cross section. The Bourdon effect would cause the angle of the elbow to open up. The flexibility and stresses could be higher - a designer would need to qualify the component for ASME B31 since it is not a referenced standard elbow.
To m177128
Does the elliptical section have to maintain the same perimeter, or does the perimeter increase to maintain the same cross section area? To be effective does the ellipse need to be at least a 2:1 aspect ratio?
Duct work designs have turning vanes to change flow direction and smooth out turbulence. Internal flow vanes like the Cheng flow conditioner would probably be easier to implement in an existing system. If everything had to fit inside an existing elbow, a flat plate in the plane of the elbow would provide some benefit, but not as much benefit as would a curved plate following the centerline radius of the elbow. I could visualize an internal half size / half pipe elbow fit inside existing elbow on centerline radius.
RE: reducing turbulent flow around an elbow
http://www.vortab.com/pdfs/VOREL%20Elbow.pdf
or the company's main site
http://www.vortab.com/Index.htm
RE: reducing turbulent flow around an elbow
a good source is a book by Bruno Eck, Technische Stroemungslehre, Band 2 (p55), Springer 1981, ISBN 3-540-03488-9. I think there is a translation into English too.I have copies of data tables, but cannot find them at the moment. I do not know for vendors.
m777182
RE: reducing turbulent flow around an elbow
less the original question be lost sight of:
the problem is solids build up not turbulence as such
RE: reducing turbulent flow around an elbow
RE: reducing turbulent flow around an elbow