Introduction
Example
Assuming Heat Value within Equipment=1kw
Temperature Rise within Equipment=8°C
Q= 6.25 m3 / min
System impedance of Equipment
In accordance with the Internal construction of the equipment to be cooled, the resistance will appear when passing air through the equipment.
This will cause reduction of stationary pressure during the ventilation and is called the system impedance.
Consequently, it becomes necessary for us to give stationary pressure value higher than the impedance for performing ventilation to the equipment.
System impedance can be given using the following formula:
ΔP=Reduced pressure (mm-H2O)
Q=Air Volume (m3 / min)
ΔP=KQn K5 Constant
n=Index to be determined by air flow
n=1: laminar flow
n=2: turbulent flow (normally n=2)
The constant K here cannot be determined unless measure it
Physically equipment by equipment.
Selection of the Fan
The selection of fan is done in accordance with following steps:
a) Estimate the heat value (hw) of the heat source.
b) Determine the allowable temperature rise value ΔT.
c) Assume the approximate ventilation volume in accordance with Formula (1).
d) Assumption of system impedance based on the ventilation of internal equipment or past data.
e) Decide on the fan by referring to the Characteristic curve in Figure 2 from your catalog.
f) Determine the adaptability of the fan by physically installing it is the equipment and measure the air temperature rise value ΔT or draft volume Q. If draft volume Q is insufficient, it is caused by the high system impedance, so it advisable to replace it with a highter quality fan.
Measurement and measures against the Noises
Measurement of Noises
Measure it at 1.0 meters from the maching plane (at the central line of the air inlet) according to JIS-B8330 (A characteristics)
Measures against Noise
Although our fan motors are designed with special consideration of noises, sometime, it still can be affected by the user's machine design to a large extent, so your attention is drawn to the following points:
a. Keep some distance between the object to be cooled and the inlet of the fan (Figure a-1)
b. When fittings are used, pay attention not to cross each other with a spring (Figure b-1)
c. When more than two fans are used, please keep them apart (Figure c-1)
d. When finger guide is used, please keep it separated from the fan (we have kept some for this purpose).
