| Fan air flow performance curves
is obtained by using the Double-Chamber method
based on AMCA standard. The difference between
the pressures before and after the nozzle
(differential pressure Pn) is measured to
obtain the air flow at the nozzle. Static
pressure Ps is also measured and recorded.
The auxiliary blower cancels out the aerodynamic
resistance. Air flow rate is calculated by
following equation |
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Q = 60 A x V |
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where
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Q: air flow rate(M3/min) |
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A: nozzle sectional area (M2) |
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V: average flow velocity through nozzle
(M/sec) |
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V=
[2 g Pn / r] |
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where
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g: gravitational acceleration, 9.8m/s2 |
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Pn: differential pressure (mm H2O) |
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Ps: static pressure |
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r: specific gravity of air, 1.2 kg/M3
at 20oC, 1atm |
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| Maximum air flow: when opening
the nozzle and absorbing the air using the
auxiliary blower to make the static pressure
(Ps) equal to zero, the differential pressure
between chamber A and B, Pn, will be at its
maximum value. Plug this Pn value to the above
equation will result in the maximum air flow
rate. |
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| Maximum static pressure: if the
nozzle is closed the pressure in the chamber
A will be at it's maximum value. The differential
pressure, Ps, between the ambient air pressure
and the pressure in the chamber can now be
considered the maximum static pressure. |
