Where can I find the Loss Coefficient (k) for bends below 90 degrees? 1

[mtroche]

Where can I find the Loss Coefficient (k) for bends below 90 degrees? Is there any table or chart to get this value?

 

[luisdaniel]

The K value is also dependent on the pipe diameter. The L/D value for a 45-degree bend is 16 for a short radius, and 9.9 for a long radius bend. For mitre bends (i.e. no radius) the following are the L/D:

angle L/D
15 4
30 8
45 15
60 25
75 40
90 60

 

[Thrusterman]

Hi mtroche,
hope this helps, it's in SI units:
TM
---------------------------------------------
Loss factor for pipe fittings and bends:

dp = 0.5 * k * roh * v^2

dp [MPa] differential pressure
k [ ] coefficient factor
roh [kg/m^3] density
v [m/s] velocity

where the loss coefficient is depending on the ratio between radius and diameter:
R [m] radius
D [m] diameter

R/D k (90deg)
-----------------------
smooth rough
1 ▐ 0.21 0.51
2 ▐ 0.14 0.30
4 ▐ 0.11 0.23
6 ▐ 0.09 0.18
10 ▐ 0.11 0.20

for any angle other than 90 deg:

k (phi) = x * k (90 deg)

phi x
------------
30 ▐ 0.4
60 ▐ 0.7
120 ▐ 1.25
150 ▐ 1.5
180 ▐ 1.7

[these numbers are from the "Dubbel", Springer-Verlag (17 edition, page B50)]