Heating

Pressure drop

Head

0,22m

Pressure

21,0mbar

Velocity

0,44m/s

Pressure drop calculates friction and local losses of a heating run. Pipe friction follows Darcy–Weisbach, and fittings enter as the sum of zeta values. Pressure loss and pump head for selecting the pump come from that.

Pump head

0,22

m

with 15%

0,25

m

Friction
19,1mbar
Fittings
1,9mbar
Total
21,0mbar
R
127Pa/m

k = 0,0015 mm

Pipe

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How it's calculated

The pressure drop of a heating run is pipe friction plus local losses. Friction follows Darcy–Weisbach with Colebrook-White, and the fittings are the sum of the ζ values times the dynamic pressure. Pump head is that pressure divided by density and gravity. A 15% allowance is shown only as a note for selecting the pump, not inside the physics. ζ may be zero, an empty field may not.

Worked example

Copper DN 20, 400 l/h, 60 °C, 12 m, sum of ζ = 2.5: 11.8 mbar, which is 0.12 m of pump head.

FAQ

Is this the manometric head of the pump?
Only for this one run. The network, the index circuit and the plant resistance are missing.
Where does ζ come from?
From guide values for bends, valves and branches. The tool only adds them up; it does not know the components.
Why does the loss rise so fast with velocity?
Dynamic pressure grows with the square of velocity, and friction does much the same. One size smaller can raise the loss sharply.
May the length be zero?
No. Without a positive length there is no run. Fittings alone are not entered here as a length of zero.