Duct fitting pressure drop coefficients for
elbow with smooth radius

From ASHRAE (1989), with permission

The pressure drop coefficient is given by C = Kq · C90

 

A5-6b.gif (7673 bytes)

Coefficients for 90° elbows

Angle correction factors Kq

r/D

C90

q

Kq

0.5

0.71

0

0

0.75

0.33

20

0.31

1.0

0.22

30

0.45

1.5

0.15

45

0.60

2.0

0.13

60

0.78

2.5

0.12

75

0.90

 

90

1.00

110

1.13

130

1.20

150

1.28

180

1.40