Minor Losses in Ducts with Laminar Flow

[backjourne]

Hello everyone,

I am seeking thoughts and opinions on modeling minor losses in systems where flow is laminar using loss coefficients (or any other methods). The only discussion of this I’ve seen to date was in Internal Flow Systems by Miller. It seemed to suggest that the loss coefficient would be inversely proportional to Re for Re < Re,crit. However, it also suggested that if flow is tripped turbulent in the pipe feature, this would not be a valid approach.

I am looking at this issue for rather generic features (e.g., pipe inlets, outlets, bends, etc.) so I don’t have a component manufacturer to get advice from.

Thanks in advance for any suggestions.

 

[katmar]

The most comprehensive discussion I know of covering minor losses in the laminar regime is in the book "Chemical Engineering Fluid Mechanics" by Ron Darby.

Darby also published his work in an article in Chemical Engineering magazine, April 2001, pgs 127-130. His method is generally known as the "3-K Method" because it is an extension of the original "2-K Method" published by Hooper.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Mech85]

Hi Backjourne,

Obtain a copy of the following technical paper - Edwards, M.F., Jadallah, M.S.M. and Smith, R., Head Losses in Pipe Fittings at Low Reynolds Numbers. Chemical Engineering Research & Design, Vol. 63, pp. 43-50. (1985)

Also there is a small table of frictional losses for laminar flow through fittings and valves in Perry Chemical Engineer's Handbook. In the seventh edition, refer to Table 6.5 on Page 6.18

Hope this helps