Result
Preliminary calculation: This tool is for quick sizing and information. In real projects, load calculation, selection and commissioning require engineering calculations and a site survey. Results are approximate values.
Formula
d = √( 4 × Q / (π × v) ), Q [m³/s]Q [m³/h] ≈ kW / (1.163 × ΔT)For the same flow rate, the pipe gets smaller as velocity increases, but pressure loss rises roughly in proportion to the square of velocity. That is why main lines are sized for lower velocities and branches and terminals for higher velocities.
- Use the pump power tool to find the pump head
- Chiller flow rate calculator for flow rate
- Don't forget expansion in a closed circuit: expansion tank
Frequently asked questions
What should the pipe velocity be in m/s?
A range of about 0.5–2 m/s is commonly used in water lines inside buildings. A lower velocity is chosen for main lines and a higher one for short branches; the exact value depends on the project and the material.
What does DN mean?
Nominal diameter; it is the nominal size of the pipe. The actual inner diameter varies with the pipe material and wall thickness.
What happens if the velocity is too high?
Noise, vibration, pressure loss and wear increase; pump energy rises.