Duct fitting pressure drop coefficients for
round butterfly damper

From ASHRAE (1989), with permission

A5-6j.gif (11024 bytes)

Values of C0

q, deg

0

10

20

30

40

50

60

70

75

80

85

D / D0

0.5

0.19

0.27

0.37

0.49

0.61

0.74

0.86

0.96

0.99

1.0

1.0

0.6

0.19

0.32

0.48

0.69

0.94

1.2

1.5

1.7

1.8

1.9

1.9

0.7

0.19

0.37

0.64

1.0

1.5

2.1

2.8

3.5

3.7

3.9

4.1

0.8

0.19

0.45

0.87

1.6

2.6

4.1

6.1

8.4

9.4

10

10

0.9

0.19

0.54

1.2

2.5

5.0

9.6

17

30

38

45

50

1.0

0.19

0.67

1.8

4.4

11

32

113

-

-

-

-