functionpressureDrop_volumeFlowRate

Function that returns the pressure drop ratio due to a change in medium properties for a given volume flow rate ratio

Extends from Modelica.Icons.Function (Icon for functions).

Information

Function that converts a volume flow rate ratio to a pressure drop ratio due to a change in medium properties.

The flow coefficient is n=1 for laminar and n=1.688 for turbulent flow. Note that typical textbook equations use n=2. The value n=1.688 is based on a friction coefficient for a Reynolds number of Re=2,300...10,000, in which case the friction coefficient can be approximated as f1 = 0.2767 Re-0.312 with a maximum error or 0.8% (Melinder, 2010), and hence the pressure drop is proportional to v1.688, where v is the flow velocity.

The function assumes that the flow geometry and the flow regime (laminar or turbulent) do not change when the medium changes.

References

Melinder, Åke (2010a). Handbook on Indirect Refrigeration and Heat Pump Systems. Kullavik, Sverige: Svenska Kyltekniska Föreningen. https://varmtochkallt.se/wp-content/uploads/Projekt/Effsys2/P02/ke-Melinder-engelsk-handbok.pdf

Inputs

TypeNameDefaultDescription
Realratio_V_flowRatio of volume flow rates
RealnFlow coefficient n, n=1 for laminar, n=2 for fully turbulent

Outputs

TypeNameDefaultDescription
Realratio_dpRatio of pressures

Revisions

  • May 11, 2026, by Michael Wetter:
    First implementation.