modelPowerLawResistance

Flow resistance that uses the power law

Extends from IBPSA.Fluid.Interfaces.PartialTwoPortInterface, IBPSA.Airflow.Multizone.BaseClasses.ErrorControl.

Information

This model describes the mass flow rate and pressure difference relation of an orifice in the form 

    V_flow = k * dp^m,

where k is a variable and m a parameter. For turbulent flow, set m=1/2 and for laminar flow, set m=1.

The model is used as a base for the interzonal air flow models.

Parameters

TypeNameDefaultDescription
RealmFlow exponent, m=0.5 for turbulent, m=1 for laminar
Advanced
BooleanuseDefaultPropertiestrueSet to false to use density and viscosity based on actual medium state, rather than using default values
Modelica.SIunits.PressureDifferencedp_turbulent0.1Pressure difference where laminar and turbulent flow relation coincide. Recommended = 0.1
BooleanhomotopyInitializationtrue= true, use homotopy method

Components

TypeNameDefaultDescription
Modelica.SIunits.VolumeFlowRateV_flowVolume flow rate through the component
Modelica.SIunits.VelocityvAverage velocity
Modelica.SIunits.DensityrhoFluid density at port_a

Revisions

  • June 24, 2018, by Michael Wetter:
    Removed parameter A because IBPSA.Airflow.Multizone.EffectiveAirLeakageArea uses the effective leakage area L rather than A.
    Removed calculation v=V_flow/A as parameter A has been removed.
    Removed parameter lWet as this is only used to compute the Reynolds number, and the Reynolds number is not used by this model. Also removed the variable Re for the Reynolds number.
    This change is non-backward compatible.
    This is for IBPSA, #932.
  • May 1, 2018, by Filip Jorissen:
    Set final allowFlowReversal=true. See #877.
  • January 22, 2016, by Michael Wetter:
    Corrected type declaration of pressure difference. This is for #404.
  • November 19, 2015, by Michael Wetter:
    Removed assignment of parameter showDesignFlowDirection in extends statement. This is for #349.
  • January 21, 2015 by Michael Wetter:
    Changed type of mExc as Modelica.SIunits.Mass sets min=0, but mExc can be negative.
  • October 8, 2013 by Michael Wetter:
    Changed the parameter useConstantDensity to useDefaultProperties and also applied the parameter to the computation of the dynamic viscosity. The conversion script can be used to update this parameter.
    Change model to not use the instance sta_a, as this may be conditionally removed and hence it is not proper Modelica syntax to use it outside of a connect statement.
  • March 27, 2013 by Michael Wetter:
    Added assignment of initial value for mExc to avoid error when checking model in pedantic mode with Dymola 2014.
  • December 14, 2012 by Michael Wetter:
    Renamed protected parameters for consistency with the naming conventions.
  • December 6, 2011 by Michael Wetter:
    Removed fixed=false attribute of protected parameter k.
  • July 20, 2010 by Michael Wetter:
    Migrated model to Modelica 3.1 and integrated it into the Buildings library.
  • February 4, 2005 by Michael Wetter:
    Released first version.