Page 13 - FANS. Aerodynamic _Selection Meethod__Combine_part2

b) in the cross section of the discharge pipe

 full (total) - 174

 static (static) - minus 17
 dynamic (dynamic) - 191

c) total pressure for the aerodynamic characteristics of the fan (in current
terminology)

 full (total) Рt - 176
 static (static) Ps - minus 15 (2 - 17 = -15)
 dynamic (dynamic) Pv - 191

The dynamic pressure Pv of the fan is greater than its total pressure Pt.

B. HIGH PRESSURE FAN

The difference between the larger dynamic Pv and the smaller total
pressure Pt will increase even more if we compare the fans starting with
No. 5 (impeller D = 500mm and higher), since a high-pressure fan with a
smaller impeller diameter (D ‹500mm), at the same speed that low- and
medium-pressure fans will have, will show the total pressure Pt as a

medium-pressure fan, which will not be correct for comparison.

Outputs for an off-line fan

1. Artificial separation of the total pressure of the fan into static Ps and
dynamic Pv completely deviates.

2. The aerodynamic characteristics of the centrifugal fan should show
only the total pressure Pt developed by the fan, which can be
distributed to: the part spent on overcoming the resistance of the
ventilation network Pnw and the part spent on overcoming the
resistance of the static atmosphere Рatv.
3. The total pressure on the suction inlet of the fan is present, although
it has a small amount.
4. On the discharge pipe of the fan, the total pressure is less than the

dynamic pressure, since static pressure below atmospheric.
5. The total (∑ - summarnoe) total pressure of the fan for the
aerodynamic characteristics of the centrifugal fan is lower than the
dynamic pressure at the discharge pipe of the fan.