Pipe elbows less than 90 degrees.
Pipe elbows less than 90 degrees.
(OP)
Hello,
I have a Crane's handbook here. I am looking for pressure drops across pipe elbows that are not 90 degrees in bend. Basically I am looking for a correlation between angle in bend and pressure drop. Page A-29 has something like that but only for Standard Elbows at 90 and 45 degrees.
Thanks!
I have a Crane's handbook here. I am looking for pressure drops across pipe elbows that are not 90 degrees in bend. Basically I am looking for a correlation between angle in bend and pressure drop. Page A-29 has something like that but only for Standard Elbows at 90 and 45 degrees.
Thanks!





RE: Pipe elbows less than 90 degrees.
And yet, if that was true, then how would one reconcile or treat the term "n" in that expression? That's what escapes me...
Maybe a simpler approach is this:
I have data that suggests that the "L/D" ratio for a standard 90-degree elbow is 14, and the "L/D" ratio for a standard 45-degree elbow is 8. At some point, after factoring in the appropriate centreline arclengths, extrapolation of the bend angle to zero would produce an "L/D" ratio for straight pipe of a length equal to the arclength of the fitting under consideration, and presumably, a line or curve through those data points would produce a correlation for equivalent lengths of bends of any angle between 90 and 0.
You could do the same for other ratios of bend radius to diameter with the knowledge that k = f*L/D.
Regards,
SNORGY.
RE: Pipe elbows less than 90 degrees.
Thank you for the prompt reply.
If we are looking at the same figure, second one from the bottom on the left of A-29. It reads that n= number of 90 degree bends. So I assume I cant use it for anything less than 90.
I will study what you wrote about extrapolating arclength. But I don't see how it will capture momentum loss due to direction change?
Thanks again.
RE: Pipe elbows less than 90 degrees.
RE: Pipe elbows less than 90 degrees.
The system has 2 bends that are shallow that I can consider straight (less than 15 degrees). The rest of the system is coils.
Some of the bends are deep or close to 90 degrees (about 80 degrees). So in actuality, if I assume the aforementioned bends are either straight or 90 degrees, I should be ok.
If I have some correlation for non standard bends, I can compare 15 degree bends with straight pipe to know for sure what the difference is.
RE: Pipe elbows less than 90 degrees.
http://www
Pages 126/127 address different angle bends.
RE: Pipe elbows less than 90 degrees.
where n=number of 90° bends and K = resistance coefficient for one 90° bend per table?
You can set n to zero and calculate a K value from the table based on the r/d value.
With n at 0, the formula becomes KB= K-(0.25π*fT*r/d +0.5K)
Patricia Lougheed
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RE: Pipe elbows less than 90 degrees.
The above book should cover most of the info you are asking. From your response, your main resistance might be the "curved segment" (coil). As such, Idelchik might be a good reference.
RE: Pipe elbows less than 90 degrees.
I wasn't sure that that would be legitimate. Then I got sidetracked before I reviewed it in greater detail. But yes, that is the equation in question.
Regards,
SNORGY.
RE: Pipe elbows less than 90 degrees.
RE: Pipe elbows less than 90 degrees.
Correcting a piping system pressure drop calculation for elbows other than 90 degrees is not worth it....
Your calculation is only within 5-10% accuracy at best...
RE: Pipe elbows less than 90 degrees.