modelMixingBox

Outside air mixing box with interlocked air dampers

Extends from IBPSA.Fluid.Actuators.BaseClasses.ActuatorSignal.

Information

Model of an outside air mixing box with air dampers. Set y=0 to close the outside air and exhast air dampers.

If dp_nominalIncludesDamper=true, then the parameter dp_nominal is equal to the pressure drop of the damper plus the fixed flow resistance at the nominal flow rate. If dp_nominalIncludesDamper=false, then dp_nominal does not include the flow resistance of the air damper.

Parameters

TypeNameDefaultDescription
Booleanuse_deltaMtrueSet to true to use deltaM for turbulent transition, else ReC is used
RealdeltaM0.3Fraction of nominal mass flow rate where transition to turbulent occurs
Modelica.SIunits.Velocityv_nominal1Nominal face velocity
BooleanroundDuctfalseSet to true for round duct, false for square cross section
RealReC4000Reynolds number where transition to turbulent starts
Assumptions
BooleanallowFlowReversaltrue= false to simplify equations, assuming, but not enforcing, no flow reversal
Nominal condition
Booleandp_nominalIncludesDamperfalseset to true if dp_nominal includes the pressure loss of the open damper
Modelica.SIunits.MassFlowRatemOut_flow_nominalMass flow rate outside air damper
Modelica.SIunits.PressureDifferencedpOut_nominalPressure drop outside air leg
Modelica.SIunits.MassFlowRatemRec_flow_nominalMass flow rate recirculation air damper
Modelica.SIunits.PressureDifferencedpRec_nominalPressure drop recirculation air leg
Modelica.SIunits.MassFlowRatemExh_flow_nominalMass flow rate exhaust air damper
Modelica.SIunits.PressureDifferencedpExh_nominalPressure drop exhaust air leg
Advanced
Booleanfrom_dptrue= true, use m_flow = f(dp) else dp = f(m_flow)
Booleanlinearizedfalse= true, use linear relation between m_flow and dp for any flow rate
Booleanuse_constant_densitytrueSet to true to use constant density for flow friction
Damper coefficients
Reala-1.51Coefficient a for damper characteristics
Realb0.105*90Coefficient b for damper characteristics
RealyL15/90Lower value for damper curve
RealyU55/90Upper value for damper curve
Realk01E6Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Realk10.45Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Components

TypeNameDefaultDescription
VAVBoxExponentialdamOA
VAVBoxExponentialdamExhExhaust air damper
VAVBoxExponentialdamRecRecirculation air damper
Modelica.Fluid.Interfaces.FluidPort_aport_OutFluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_bport_ExhFluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_aport_RetFluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_bport_SupFluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Blocks.Sources.ConstantuniUnity signal
Modelica.Blocks.Math.AddaddAdder

Contents

NameDescription
MediumMedium in the component

Revisions

  • March 24, 2017, by Michael Wetter:
    Renamed filteredInput to use_inputFilter.
    This is for #665.
  • March 22, 2017, by Michael Wetter:
    Removed the assignments of AOut, AExh and ARec as these are done in the damper instance using a final assignment of the parameter. This allows scaling the model with m_flow_nominal, which is generally known in the flow leg, and v_nominal, for which a default value can be specified.
    This is for #544.
  • January 22, 2016, by Michael Wetter:
    Corrected type declaration of pressure difference. This is for #404.
  • December 14, 2012 by Michael Wetter:
    Renamed protected parameters for consistency with the naming conventions.
  • February 14, 2012 by Michael Wetter:
    Added filter to approximate the travel time of the actuator.
  • February 3, 2012, by Michael Wetter:
    Removed assignment of m_flow_small as it is no longer used in its base class.
  • February 23, 2010 by Michael Wetter:
    First implementation.