Pipe Friction Pressure Drop
Pipe Friction Pressure Drop
The pressure a pump must overcome along a pipe comes from wall friction, expressed by Darcy–Weisbach.
The pressure drop is Δp = f·(L/D)·(ρ·v²/2). where f is the friction factor, L the length, D the diameter, ρ the density and v the velocity.
Inputs
f := 0.02=0.02
L := 100 m=100 m
D := 100 mm=100 mm
rho := 1000 kg/m^3=1000 kg/m^3
v := 2.5 m/s=2.5 m/s
Apply the Darcy–Weisbach pressure-drop form.
dP := f·(L/D)·(rho·v^2/2)=62500 Pa
Results
The drop rises with the square of velocity, so oversizing pipe a little sharply cuts pumping cost. Divide by ρg to express it as head.
Assumptions & limitations
- Fully developed, steady flow.
- Constant diameter.
- Minor (fitting) losses excluded.