Page 6 - FANS. Aerodynamic _Selection Meethod__Combine_part2

regulation by additional installation of the speed controller of the AC
motor (frequency converter);

 the method of “static pressure” was formed due to the fact that in
some cases there was a difficulty of “binding” to the total pressure of
the fan. It should be recalled that the static pressure - both for the fan
and for the air ducts - is not working.

Accordingly, these methods lead in most cases to an overstatement of
energy consumption (overestimation of the installed power of the electric
motor).

The American, European and Russian specialists did not achieve positive

results in the accuracy of the selection of a centrifugal fan (“fan operating
point”). Unfortunately, even in the web-version of the well-known journal
HPAC Engineering there are practically no comments on the articles on this
topic (“fan operating point”, energy saving). Perhaps it is difficult to move
away from the 'old school'.

The articles also talk about the excessive consumption of electricity by

ventilation systems, air conditioning systems (including pumps) for one
(conditional) building - approximately 60%.

Positive in European and American practice is the display of the
aerodynamic characteristics of the fan on a linear scale (in the Russian,
mainly - on a logarithmic scale) - which allows you to graphically determine
the exact 'operating point of the fan'.

The proposed method will resolve three more important issues:

1. The designer can compare his calculations based on more reliable
actual readings of total pressure and performance - and see his
mistakes.
2. Laboratories can adjust the coefficients of local resistances of the
ventilation network (including in the zones of the inlet and discharge
pipes of the fan).

3. Laboratories can transfer this method to other types of fans.

The author assumes that this method of selection of a centrifugal fan will be
introduced by leading ventilation companies, and thus there will be a
departure from the “old school”.

Therefore, for the first time in world practice, the additional Рatv curve is
applied to the aerodynamic characteristics of the fan, so that the ventilation
specialists can see the advantages in determining the exact “operating point
of the fan” and evaluating the accuracy of the ventilation network

calculation.