Daikin VAM Series Engineering Data page 182

Appendix
17.5.3 Local Pressure Loss for Duct
1) Local Pressure Loss
In the bend part of the duct and diagonal change, there is loss in quality that is different from the straight pipe such as the vortex. The
following formula expresses for pressure loss other than these straight pipes.
2
v
P = ζ · γ = ζ · Pv
2
ζ : Local pressure loss
γ : Specific weight of air ································ (1.2 kg/m
V : Air velocity ······················································· (m/s)
*Excluding merging flow, there is air velocity for the local upper flow.
Pv : Dynamic pressure ············································· (Pa)
2) Calculation of Local Pressure Loss for Duct
Example) in the case of a duct bend as shown in the lower figure
R
Condition = 1.5
d
ζ
From Table-A = 0.15
2
v
Pv =
2
Pv = 15 (Pa)
P = ζ (Local pressure loss) × Pv (Dynamic pressure)
= 0.15 × 15 ≈ 2.25 Pa
The right column in Table A is the value expressing for when this local pressure loss is converted to duct diameter. However, because
the value expressed here belongs to "friction resistance coefficient γ = 0.018 of time, "please use the following formula for other cases.
re : Partial resistance for equivalent length of straight pipe ··· (m)
ζ
re = d d : Straight pipe diameter ····················································· (m)
λ
ζ : Local pressure loss
Table-A
180
v = 5.0 (m/s)
25
γ =
× 1.2
2
No. Name Shape diagram
Circular
d
1 diagonal round
bend
d
Circular diagonal
2
square bend
Rectangular
W
3 diagonal round
bend
H
Rectangular
W
4 diagonal square
bend
H
Pipe entrance
5 (circular feed
θ
attached)
Pipe entrance
6 (rectangular
θ
feed attached)
3
)
V
d
R
Condition
H/W R/dR/W
0.5
0.75
– 1.0
R
1.5
2.0
– –
0.5
0.75
0.25
1.0
1.5
0.5
0.75
0.5
1.0
1.5
0.5
R
0.75
1.0
1.0
1.5
0.5
0.75
4.0
1.0
1.5
0.5
0.75
–
1.0
1.5
Vo
20˚
40˚
θ
60˚
90˚
Round shape
Vo
20˚
40˚
θ
60˚
90˚
EDMMT712101
Circular diagonal round bend
Local pressure
ζ
loss
0.71
0.33
0.22
0.15
0.13
1.20
1.30
0.57
0.27
0.22
1.30
0.52
0.25
0.20
1.20
0.44
0.21
0.17
0.92
0.40
0.19
0.15
1.30
1.20
1.20
1.10
0.02
0.03
0.05
0.11
0.13
0.08
0.12
0.19
VAM-HVE/HVLT Series