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CHAPTER 4
Characteristics
1. How to Read the Characteristic Curves
1.1 Obtaining characteristics from static pressure loss
(1) Static pressure loss from straight pipe duct length (at required air volume)
(2) Static pressure loss at curved section (at required air volume)
(3) Static pressure loss of related parts (at required air volume)
2. Calculating the Static Pressure Loss
2.1 How to read the air volume - static pressure curve
It is important to know the amount of static pressure loss applied
onto the Lossnay when using parts such as ducts for the air
distribution. If the static pressure increases, the air volume will
decrease. The air volume - static pressure curve (Q-H curve)
shows this percentage. A static pressure of 19.6 Pa is applied on
to point A, and the air volume is 500 m
curve shows how the static pressure is applied when a duct is
connected to the Lossnay. Thus, the L = 9.97 m duct resistivity
curve in the diagram is the curve that shows how the static
pressure is applied when a 10 m duct is connected. The
intersecting point A with the Lossnay Q-H curve is the operation
point.
Duct resistivity curve
The duct resistivity curve shows how much static pressure a duct will apply on the Lossnay, as explained above.
In general, the interrelation between the duct and static pressure is as follows:
Duct
When duct is long
If length is the same but the air volume
increases
If the duct diameter is narrow
If the duct inner surface is rough
(such as a spiral)
40
Total static pressure loss
6 Static pressure loss at
application point
2 Total static
pressure loss
1 Required air
3
/h. The duct resistivity
Static pressure
Increases
Increases
Increases
Increases
Estimated static pressure loss curve
obtained from 1 and 2
3
4 Intersection with air volume static
pressure characteristic curve
5 Air volume at application point
volume
Air volume
19.6 Pa
A
Air volume
500 m
3
/h
Air volume
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