Daikin VAM-FA8VE Technical Data Manual page 267

• HRV • VKM-GA(M)V1
Conversion from rectangular to round duct
Long side
<How to use the chart>
Example) A rectangular duct of 40×200 is equivalent to a round duct of 90 in diameter.
200
11.3.3 Pressure Loss Due to Local Features
1. Local feature loss coefficient (local feature resistance coefficient)
Bends, and sections where the sectional area is suddenly changed, have, unlike straight sections,
particular types of pressure losses due to eddy current and other factors. The pressure loss of these
non-straight parts is given by the following equation.
Where
2. Calculation of pressure loss due to local features
(Example) Bend as shown in the figure
[Conditions]
• HRV • Heat Reclaim Ventilation
Short side
I) Find the intersection of the short side 40 and long side 200 : Point A.
II) Draw the line B passing through Point A until it intersects with the slant
A
line C : Point D.
B This is the equivalent diameter. In this case, the diameter is 90.
D
C
40
Short side
2
V
ΔP (Pa) = ζ · γ = ζ · Pv
2g
ζ : Local loss coefficient
v : Air velocity...................................[m/s]
* This is the velocity measured at the upstream side of the feature except junctions.
Pv : Dynamic pressure.....................[Pa]
R
= 1.5 v = 5.0 [m/s]
d
ζ = 24
V 2 25
γ
Pv = = × 1.2
2g 2
Pv = 1.53 [Pa]
ΔP = ζ (Local loss coefficient) × Pv (Dynamic pressure)
= 0.24 × 1.5326 = 0.37 Pa
2
11
R bend, round duct
265