Pipe DN Recommendation

System Type

System type automatically sets velocity limits (and, for Heating/Cooling, a verified friction-rate target). Fire systems require high velocity, heating/cooling are sized primarily on friction loss.

Flow Input Method

Switch to "Calculate from Heat Load" to size the pipe from kW + ΔT instead of typing m³/h directly. Only available when System Type is Heating/Cooling.

Flow Rate (m³/h)

Total flow rate through the pipe

Heat Load (kW)

Heating or cooling capacity carried by this pipe

Temperature Difference (°C)

ΔT for heating/cooling systems (typically 20°C for heating, 5-6°C for chilled water — e.g. 80/60°C heating or 6/12°C chilled water)

Fluid Temperature (°C)

Used only for density in the heat-load-to-flow conversion. Heating: 70-80°C, Chilled water: 6-12°C

Pipe Material

Pipe material affects inner diameter and roughness

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Smart Diameter Selection

This calculator recommends the optimal pipe diameter based on your system type and flow requirements. Each system has specific velocity limits: <ul> <li>HVAC: 0.5-1.5 m/s (noise control)</li> <li>Fire: 2.0-6.0 m/s (emergency response)</li> <li>Water: 0.6-2.0 m/s (balanced)</li> <li>Compressed Air: 6-12 m/s (high velocity OK)</li> </ul>

Key Points:

System-specific velocity limits
Automatic standard pipe selection
Alternative options provided
Head loss calculation included

Calculation Steps:

Enter all required parameters
Click "Update Calculation"
Review results and analysis

Formula Variables:

D Diameter (mm)

Q Flow Rate (m³/h)

V Velocity (m/s)

Re Reynolds (-)

f Friction Factor (-)