Duct fitting pressure drop coefficients for
mitered, rectangular elbow with single-thickness vanes

From ASHRAE (1989), with permission

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

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Design no.

Dimensions,
inches

C

r

s

L

1*

2.0

1.5

0.75

0.12

2

4.5

2.25

0

0.15

3

4.5

3.25

1.60

0.18

*When extension of trailing edge is not provided for this vane, losses are approximately unchanged for single elbows, but increase considerably for elbows in series.