Bends, branches, contraction, expansion etc. associated with ducting system results in pressure drop of the system. The pressure drop in the system varies in magnitude and depends upon the velocity head and type of bend, contraction and expansion.
The factor associated for the determination of the pressure drop is called “K” factor. This K factor is multiplied to the velocity pressure to determine the pressure drop.
Velocity pressure is calculated by the formula
Velocity Head is calculated by the formula
Example:
The velocity of air in a pile line is 25m/s, the length of the pipe is 10m and it has a circular bend of 30o in the line. Density of the air is 0.92 gm/cc
K factor for circular bend at 30o = 0.218
Pressure drops across the bend alone = 29.3 x 0.218 = 6.39 mm WG
Total pressure drops = 29.3 +6.39 = 35.7 mm WG
