Pipe friction head loss
Pipe friction head is the amount of energy loss due to friction of the fluid moving through pipes and fittings. It takes a force to move the fluid against friction, in the same way that a force is required to lift a weight.
For straight pipes:
pv = Pressure loss
l
= Pipe roughness
d = Diameter of the pipe
L = Length of the pipe
r
= Density of liquid
v = Velocity of flow
More Information:
Link:
http://www.lutz-pumpen.com/desktopdefault.aspx/tabid-238/306_read-303/