Duct fitting pressure drop coefficients for
mitered, rectangular elbow

From ASHRAE (1989), with permission

The pressure drop coefficient is given by C = KRE · C'

A5-6d.gif (9998 bytes)

Angle correction factors Kq

Re x 10-4

1

2

3

4

6

8

10

³ 14

KRE

1.40

1.26

1.19

1.14

1.09

1.06

1.04

1.0

Values for C'

  H/W
0.25 0.5 0.75 1.0 1.5 2.0 3.0 4.0 5.0 6.0 8.0
q, deg 20 0.08 0.08 0.08 0.07 0.07 0.07 0.06 0.06 0.05 0.05 0.05
30 0.18 0.17 0.17 0.16 0.15 0.15 0.23 0.13 0.12 0.12 0.11
45 0.38 0.37 0.36 0.34 0.33 0.31 0.28 0.27 0.26 0.25 0.24
60 0.60 0.59 0.57 0.55 0.52 0.49 0.46 0.43 0.41 0.39 0.38
75 0.89 0.87 0.84 0.81 0.77 0.73 0.67 0.63 0.61 0.58 0.57
90 1.3 1.3 1.2 1.2 1.1 1.1 0.98 0.92 0.89 0.85 0.83