Pipe flow and pressure drop
Enter the flow rate and pipe inner diameter to see the velocity, flow regime and pressure loss over a given length.
Result
- Reynolds number
- 70,467 (turbulent)
- Darcy friction factor f
- 0.02269
- Loss along the pipe
- 45.34 kPa = 0.4534 bar
- Minor losses
- 0 Pa = 0 bar
- Drop per 100 m
- 0.4534 bar
- Head loss
- 4.632 m
- Dynamic pressure
- 998.9 Pa
v = Q / (π·D²/4)
Re = ρ·v·D / μ
Δp = (f·L/D + ΣK) · ρ·v²/2
1/√f = −2·log₁₀(ε/(3.7·D) + 2.51/(Re·√f))
Pressure drop in a pipe
Pressure loss along a straight run is given by Darcy–Weisbach: Δp = f · (L/D) · ρ·v²/2. The friction factor f depends on the Reynolds number and the relative roughness ε/D. For laminar flow (Re < 2300) f = 64/Re; for turbulent flow the tool solves the Colebrook–White equation.
Elbows, valves and tees add minor losses ΣK · ρ·v²/2. Enter the sum of their K values from the manufacturer’s data.
What velocities to use
For water, typically 0.5–1.5 m/s on pump suction and 1–3 m/s in discharge lines. A higher velocity means a smaller pipe but more loss, noise and risk of water hammer.
Common questions
Does it work for gases?
Yes, as long as the pressure drop is small compared with the absolute pressure (under about 10%). For larger drops the gas density changes along the pipe and you need to calculate in sections.
Where do I find the viscosity of another liquid?
In its data sheet or in tables. Kinematic viscosity in mm²/s (cSt) times density in g/cm³ gives dynamic viscosity in mPa·s.