Calculating pressure loss

To select the right pump and achieve proper balance in the system, it is necessary to calculate the pressure loss throughout the system.

To select the right pump and achieve proper balance in the system, it is necessary to calculate the pressure loss throughout the system.

The loss of pressure in a heating system is related to:

  • the heat production: boilers, heat exchangers, solar collectors, generators etc.
  • the distribution: pipes, fittings, valves, pumps
  • heat consumption: radiators, calorifiers, heating surfaces, fan coils, floor heating coils, domestic hot water production.

The pressure loss calculation for the pipe system can be done by adding the sum of the pressure losses in the pipe sections and in single resistive elements (valves and fittings):

ΔPtot = ΔPpipe + ΔPindividual [Pa]
ΔPpipe = Σ(½ x ρ x v² x ζp)
ΔPindividual = Σ(ζr x ½ x ρ x v²)

ρ = media density
v = flow velocity of medium in pipe
ζp = friction coefficients for straight pipe sections
ζr = friction coefficients for single resistors

Pressure losses through other system components including radiators, heating surfaces, boilers, etc are provided by the individual suppliers.

Once the total pressure loss of the system is calculated, the data is used to create the system characteristics curve. It shows the correlation between volume flow and pressure loss in the entire system.

Pump selection and sizing is done by comparing the system characteristics with pump performance curves to determine the expected operating point.





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