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Pressure drop in rectangular or squared ventilation channels.

Ventilation channel with rectangular or squared section

Calculates the pressure drop or the dynamic pressure drop of a channel part suction or blowing air (ventilation channel) with rectangular section.
For circuits composed by different parts with different sections is necessary calculate separately and sum the results of each part.

Data input
Pipe characteristic.

Selection channel material

Notes on the material

Absolute roughness of the inner wall

Wait roughness value.


Side of the channel . . . W


Width-height ratio of the channel.

Side of the channel . . . H


Gas velocity in the channel.

Required flow rate


Normal values for civil and silent applications..
Conditioning public places, home and office, space heating in general, air recirculation system, fume exhaust.
Normal values for industrial applications.
Heating or cooling system, circulating ovens at a low temperature, air recirculation system for environments, fume extraction and harmful gases.
Normal values for special applications.
Suction shavings, pneumatic conveying of solids (eg plastic granules), pieces cooling after molding, power cyclones separators powders, implants for compressed air and other gases.
Gas characteristics.

Selection of the gas to be carried

Gas density

Wait load gas parameter.


Circuit components.
Straight rectangular or squared tube.

Channel lenght


Rectangular or squared 90 degrees curve

Angle deviation


Rectangular or squared curve of 90 degrees with started flow.

90 degrees curve


Ratio R/D

R (mm)

Wait calculate
Gas velocity in the tube m/s
Relative roughness of the inner wall r/d
Reynolds number
Friction coefficient (Colebrook)
Result of dynamic pressure drop mm H2O
Equivalent section diameter mm
Equivalent hydraulic diameter mm
Section of the channel m2


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The apps about pressure drop.

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(round pipe).
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