Ductsize                                     Air temperature   20°C   50% RH

Volume flow  

Ductwork:

Circular    diameter mm   

Flat oval mm (width) x mm (height)

  
Rectangular  mm (width) x mm (height)

Velocity  m/s  (typical 2 to 10 m/s)

    

Material    Roughness  k  mm              See CIBSE C guide table 4.1  

                                                 

Results:  

Pressure drop per unit length   Pa / m   (typical 1 Pa/m for low vel) Effective diameter   mm 
Velocity Pressure Pa Reynolds Number  
Equivalent length le  m  (length for pressure drop of 1 velocity pressure)