Flow Losses Associated with 90 Degree Sharp Bend

Equivalent to about 90 diameters of straight pipe according to Perry, "The Chemical Engineer's Handbook", any edition.

How sharp is "sharp"? Short-radius elbow, or 90° (2 x 45°) mitered joint?

It would be primarily a pressure loss, anyway, which would affect flow somewhat as a consequence.

To do this, you find the Length Equivalent (Le), which is like saying the losses from the bend (or valve, fitting, or any other obstructive device) would be equivalent to not having the obstruction, but a certain amount of length added to the piping.

Le = (Le/D) * D

where (Le/D) is a given number for an obstructive device, and D is the diameter of the pipe.

For a Standard 90 degree elbow, the (Le/D) = 30 (Taken from Table 10.4 in 'Applied Fluid Mechanics' by Mott).

You would then use the new equivalent length of the system for your calculations to find the losses. If there are more elbows or fittings in the system, then you simply calculate their respective Le values separately, then add them together. Also, you should not be looking for "Flow losses", but instead pressure, or head loss.

For a 90° sharp (mitred) bend 1.5*V²/(2*g)

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