Mitsubishi Electric Lossnay series Technical Manual page 49

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CHAPTER 4 Characteristics
2.2 Calculating of Duct Pressure Loss
(1) How to Calculate Curved Sections in Ductwork
Duct
Outline Diagram Conditions
No.
Area
90°
1 Smooth
Elbow
Rectangular
2 Radius
Elbow
Rectangular
Vaned
3
Radius
Elbow
90°
4 Miter
Elbow
Rectangular
5 Square
Elbow
Rectangular
Vaned
6
Square
Elbow
Rectangular
Vaned
7
Square
Junction
Rectangular
Vaned
8
Radius
Junction
45°
9 Smooth
Elbow
10 Expansion
11 Contraction
U-40
Table 6. Pressure Losses in Each Duct Area
Length of
C
Equivalent
Value
Round
Pipe
R/D = 0.5 0.73 43D
= 0.75 0.38 23D
= 1.0 0.26 15D
= 1.5 0.17 10D
= 2.0 0.15 9D
W/D R/D
0.5 1.30 79D
0.75 0.47 29D
0.5
1.0 0.28 17D
1.5 0.18 11D
0.5 0.95 57D
0.75 0.33 20D
1-3
1.0 0.20 12D
1.5 0.13 8D
No. of
R/D
vanes
0.5 0.70 42D
0.75 0.16 10D
1
1.0 0.13 8D
1.5 0.12 7D
0.5 0.45 27D
0.75 0.12 7D
2
1.0 0.10 6D
1.5 0.15 9D
0.87 53D
1.25 76D
0.35 21D
Same loss as circular duct.
Velocity is based on inlet.
With or without
vanes, 1/2 times value
rectangular or for similar 90°
round
a = 5°
0.17 10D
10°
0.28 17D
20°
30° 0.45 27D
40°
0.59 36D
Loss is for
0.73 43D
hV - hV
1 2
a = 30°
0.02 1D
45°
60° 0.04 2D
Loss is for
0.07 4D
V
2
Duct
No. Outline Diagram Conditions
Area
12 Transformer
14° or less
Short
13
Entrance
Short
14
Exit
Bell-shaped
15
Entrance
Bell-shaped
16
Exit
Re-entering
17
inlet
Sharp edge,
18
round orifice
Pipe inlet
(with
19
circular
hood)
Pipe inlet
(with
20
rectangular
hood)
Short
21
contraction
Short
22
expansion
Suction
inlet
23 (punched
narrow
plate)
Length of
C
Equivalent
Value
Round
Pipe
0.15 9D
0.50 30D
1.0 60D
0.03 2D
1.0 60D
0.85 51D
V1/V2 = 0 2.8 170D
0.25 2.4 140D
0.50 1.9 110D
0.75 1.5 90D
1 1.0 60D
Loss is for
V2
20° 0.02
40° 0.03
β 60° 0.05
90° 0.11
120° 0.20
20° 0.03
40° 0.08
β 50° 0.12
90° 0.19
120° 0.27
V /V = 0 0.5 30D
1 2
0.25 0.45 27D
0.50 0.32 19D
0.75 0.18 11D
Loss is for
V
2
1.0 60D
V /V = 0
1 2
0.64 39D
0.20
0.36 22D
0.40
0.16 9D
0.60
0.04 2D
0.80
Loss is for
V
1
0.2 35
0.4 7.6
0.6 3.0
0.8 1.2