Page 23 - FANS. Aerodynamic _Selection Meethod__Combine_part2

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

PRESSURE DISTRIBUTION SCHEDULE

ON FAN TUBES, IN

AIR DUCTS AND ATMOSPHERE

Part V.

The new theoretical justification corresponds to the graph shown in Fig.5.
The graph shows: total pressure Рt (including Рt ngn. And Pt suction),

pressure drop in the ventilation network Рnw (including Рnw ngn and Pnw
suction), pressure drop in Рtv atmosphere (in including Ратv nag. and Рatv
suction.), as well as static pressure Рs nag. and Ps suction. and dynamic
pressure Pd nag. and Pd suction .

For this graph (Fig.5), the static pressure (depicted by the dotted line) is for

reference only, since it is not a working pressure, due to:

1. static pressure does not work because in the direction of its action
there is no movement;
2. in the intake duct, it supports energy generation in a moving air flow;
3. for an injection duct, static pressure cannot be displayed
unambiguously, since after the fan nozzle it can be below

atmospheric pressure in magnitude - in many cases.

Note.

1. It is also erroneous in the German textbook (translated into Russian) by
Anette Becker “Lűftungsanlagen” that static pressure is working.

2. It is impossible to operate (world practice) with the static pressure of the

Ps fan due to the fact that it may have a small amount, since to obtain it,
you need to add the total pressure Pt suction. (performs work) on the
suction inlet of the fan and the static pressure Ps nag. (does not work) at
the discharge pipe, which can be “negative” (conditionally, with a minus
sign), i.e. below atmospheric pressure (see Fig.5).