2.6.1. Duct Friction or Pipe Resistance

Duct friction resistances are calculated according to:

 p_K=\frac{\Lambda}{d}\cdot L\cdot p_d  

  \Lambda : Pipe friction coefficient 
 

 L: Length of the pipeline

For non-circular cross sections, use the equivalent diameter  d_h (hydraulic diameter) for  d:

 D_h=\frac{2bh}{b+h}

However,  D_h must not be used to determine the flow velocity  v or the dynamic pressure  p_d. Values for  \frac{\Lambda}{\differentialD}  can be taken from the general literature on fluid mechanics or obtained from the manufacturer.