Pressure drop in rectangular or squared ventilation channels.

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

mm

Side of the channel . . . W

mm

Side of the channel . . . H

mm

Gas velocity in the channel.

Required flow rate

m3/h

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

kg/m3

Circuit components.

Channel lenght

m

Angle deviation

n.

90 degrees curve

n.

Ratio R/D

R (mm)

 Results 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

Notes.

• Curves with R/D ratio greater than the maximum available can be ignored (add the development of the curve on the lenght of the pipe).
• The gas velocity in the yellow zone are used for pneumatic transfer of various chips or pellets, not usable for the suction or ventilation plants.
• Increasing the curve radius decrease the pressure drop due to the change of the direction of the gas, but increase the lenght of the tube with apparent greater pressure drop, for a correct valuation insert the real lenght in the straight pipe by substrating the part occupied by the curves.
• The equivalent hydraulic diameter is which offer the same performance on the channel.

Instructions
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