Page 17 - FANS. Aerodynamic _Selection Meethod__Combine_part2

Zhdanov. Part III. The author of the text and the developer: engineer
Zhdanov V.P. Minsk, Belarus.

TWO-NETWORK AERODYNAMIC METHOD

FAN SELECTION

Part III.

Note: See theoretical rationale for Ing. Zhdanova V.P.

Selection procedure (for example, centrifugal fan)

1. Calculate the drop in total pressure in the air ducts and in the built-in
ventilation equipment, i.e. in the ventilation network (without taking
into account the dynamic pressure at the outlet of the ventilation
network). Denote the calculated point, for example, as t.9 with
parameters P = 500Pa and L = 2000 m³ / h (see Fig.4).
2. The graph (image proportional, linear) of the aerodynamic

characteristics of the fan (in the example of low pressure) shows the
atmospheric resistance curve Patv (see theoretical justification). See
also “Recommendations for aerodynamic testing of a centrifugal fan
and description of the stand”.
3. The fan impeller will rearrange the calculated point of the ventilation
network (v. 9) to the fan’s aerodynamic curve (t.10), and then transfer
it to t.11, which will be the real “operating point of the fan” for the

designed (constructed) ventilation unit - with new parameters, for
example, P = 600Pa and L = 1800 m³ / h. With these parameters, the
total pressure increased by 20%, and the air consumption (capacity)
decreased by 10%.
4. When comparing the total pressure drop (value 12-11) in the
ventilation network and air flow L = 1800 m³ / h, obtained on the

graph of the aerodynamic characteristics of the fan (see Fig.4) with
actually measured parameters, we get their coincidence (or minor
deviations related with technical factors in the measurements and the
physical condition of the transported air - if it differs from standard
air).
5. With the planned drop in total pressure (value 14-9) and air flow L =
2000 m³ / h, the actual drop (value 12-11) of the total pressure in the