Daikin VAM-FA8VE Technical Data Manual page 265

• HRV • VKM-GA(M)V1
11.3.1 Procedure for Calculating Pressure Drops and Finally Determining the Type of Ventilators
11.3.2 Pressure Loss Calculation for Straight Duct
For round ducts
1. The resistance of a duct can be calculated using the following equation.
Pressure drop ΔP due to the frictional resistance of a straight duct can be calculated using the following
equation.
Resistance of duct Δ P (Pa) = λ ×
λ : Duct friction coefficient (0.01~0.25)
γ : Air specific gravity (kg/m
L : Duct length (m)
d : Duct diameter (m)
V : Duct air velocity (m/sec)
V =
Q : Air flow (m
Where, λ = 0.01 (very smooth pipe), and γ = 1.2
P = 0.01 ×
Friction coefficient of major duct types
Duct material
Aluminum flexible duct
Vinyl chloride pipe
Galvanized steel pipe
• HRV • Heat Reclaim Ventilation
Calculation of required air flow
Ducting design (duct diameter, type, routing, length and bends)
Calculate the
pressure losses of
the straight sections
using "the friction
resistance diagram".
Calculate the
pressure losses of
the local features
using "the relevant
local feature loss
coefficients".
Calculate the overall
losses throughout the
entire duct system.
Add 10 ~ 20% safety margins to the calculated pressure
losses to determine the required static pressure.
Referring to "the static pressure vs. air flow characteristics
curves" of various types of ventilating fans, select a type
that can satisfy the abovementioned pressure requirement.
γ
2
3 ) = 1.20 kg/m
Q 4
×
2
d 3,600π
3 /h)
{ }
1.2 L Q 4
× × ×
2 d d 2
3,600π
0.03~0.04
0.01~0.02
0.016~0.025
Using the equivalent
straight piping length
conversion table,
calculate "the equivalent
straight pipe length" of
the entire duct system.
Plot "the loss-resistance
curve" on "the static
pressure vs. air flow
characteristics curve
chart" to find the
intersection of these two
curves.
L
× × V 2 × 9.80665
d
3
2
× 9.80665
λ
2
11
263