modelCooling

Active beam unit for cooling
Diagram of CoolingOpen the diagram
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Information

Model of an active beam, based on the EnergyPlus beam model AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam.

This model operates only in cooling mode. For a model that operates in both heating and cooling mode, use Buildings.Fluid.HeatExchangers.ActiveBeams.CoolingAndHeating.

For a description of the equations, see the User's Guide.

Performance data are available from Buildings.Fluid.HeatExchangers.ActiveBeams.Data.

References

  • June 17, 2026, by Michael Wetter:
    Updated implementation to allow a flow coefficient n that is different from 2. This allows use of the model for not fully turbulent flow.
    This is for Buildings, #4620.
  • DOE(2015) EnergyPlus documentation v8.4.0 - Engineering Reference.

Parameters

TypeNameDefaultDescription
BooleanhomotopyInitializationtrue= true, use homotopy method
IntegernBeams1Number of beams in parallel
Nominal condition
Data.GenericperCooPerformance data for cooling
Assumptions
BooleanallowFlowReversalWattrue= true to allow flow reversal in water circuit, false restricts to design direction (port_a -> port_b)
BooleanallowFlowReversalAirtrue= true to allow flow reversal in air circuit, false restricts to design direction (port_a -> port_b)
Dynamics › Nominal condition
Modelica.Units.SI.Timetau30Time constant at nominal flow (if energyDynamics <> SteadyState)
Flow resistance
Booleanfrom_dpWatfalse= true, use m_flow = f(dp) else dp = f(m_flow)
RealnWat2Flow exponent for water-side, nWat=1 for laminar, nWat=2 for turbulent
RealnAir2Flow exponent for air-side, nWat=1 for laminar, nWat=2 for turbulent
BooleanlinearizeFlowResistanceWatfalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaMWat0.1Fraction of nominal flow rate where flow transitions to laminar
Dynamics › Conservation equations
Modelica.Fluid.Types.DynamicsenergyDynamicsModelica.Fluid.Types.Dynamics.DynamicFreeInitialType of energy balance: dynamic (3 initialization options) or steady state
Initialization › Cooling
MediumWat.AbsolutePressurepWatCoo_startMediumWat.p_defaultStart value of pressure
MediumWat.TemperatureTWatCoo_startMediumWat.T_defaultStart value of temperature
Advanced
MediumWat.MassFlowRatemWat_flow_small1E-4*abs(perCoo.mWat_flow_nominal)Small mass flow rate for regularization of zero flow
MediumAir.MassFlowRatemAir_flow_small1E-4*abs(perCoo.mAir_flow_nominal)Small mass flow rate for regularization of zero flow
Advanced › Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed

Connectors

TypeNameDefaultDescription
Modelica.Fluid.Interfaces.FluidPort_awatCoo_aFluid connector watCoo_a (positive design flow direction is from watCoo_a to watCoo_b)
Modelica.Fluid.Interfaces.FluidPort_bwatCoo_bFluid connector watCoo_b (positive design flow direction is from watCoo_a to watCoo_b)
Modelica.Fluid.Interfaces.FluidPort_aair_aFluid connector air_a (positive design flow direction is from air_a to air_b)
Modelica.Fluid.Interfaces.FluidPort_bair_bFluid connector air_b (positive design flow direction is from air_a to air_b)
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_aheaPorHeat port, to be connected to room air

Components

TypeNameDefaultDescription
MediumWat.ThermodynamicStatestaWatCoo_aMediumWat.setState_phX(watCoo_a.p, noEvent(actualStream(watCoo_a.h_outflow)), noEvent(actualStream(watCoo_a.Xi_outflow)))Medium properties in port watCoo_a
MediumWat.ThermodynamicStatestaWatCoo_bMediumWat.setState_phX(watCoo_b.p, noEvent(actualStream(watCoo_b.h_outflow)), noEvent(actualStream(watCoo_b.Xi_outflow)))Medium properties in port watCoo_b
MediumAir.ThermodynamicStatestaAir_aMediumAir.setState_phX(air_a.p, noEvent(actualStream(air_a.h_outflow)), noEvent(actualStream(air_a.Xi_outflow)))Medium properties in port air_a
MediumAir.ThermodynamicStatestaAir_bMediumAir.setState_phX(air_b.p, noEvent(actualStream(air_b.h_outflow)), noEvent(actualStream(air_b.Xi_outflow)))Medium properties in port air_b
Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlowheaToRooHeat tranferred to the room (in addition to heat from supply air)
Modelica.Units.SI.PressureDifferencedpWatCoowatCoo_a.p - watCoo_b.pPressure difference watCoo_a minus watCoo_b
Modelica.Units.SI.PressureDifferencedpAirair_a.p - air_b.pPressure difference air_a minus air_b
FixedResistances.PressureDropresFlow resistance on air-side

Contents

NameDescription
MediumWatMedium 1 in the component
MediumAirMedium 2 in the component

Revisions

  • March 3, 2022, by Michael Wetter:
    Removed massDynamics.
    This is for issue 1542.
  • March 30, 2021, by Michael Wetter:
    Added annotation HideResult=true.
    This is for IBPSA, #1459.
  • April 14, 2020, by Michael Wetter:
    Changed homotopyInitialization to a constant.
    This is for IBPSA, #1341.
  • January 18, 2019, by Jianjun Hu:
    Limited the media choice. See #1050.
  • November 3, 2016, by Michael Wetter:
    Set final alpha=0 for prescribed heat flow rate.
  • September 17, 2016, by Michael Wetter:
    Corrected wrong annotation to avoid an error in the pedantic model check in Dymola 2017 FD01 beta2.
    This is for issue 557.
  • June 14, 2016, by Michael Wetter:
    Revised implementation.
  • May 20, 2016, by Alessandro Maccarini:
    First implementation.