modelCoilRegister

Register for a heat exchanger

Extends from Buildings.Fluid.Interfaces.FourPortFlowResistanceParameters (Parameters for flow resistance for models with four ports).

Information

Register of a heat exchanger with dynamics on the fluids and the solid. The register represents one array of pipes that are perpendicular to the air stream. The hA value for both fluids is an input. The driving force for the heat transfer is the temperature difference between the fluid volumes and the solid in each heat exchanger element.

Parameters

TypeNameDefaultDescription
IntegernPipPar2Number of parallel pipes in each register
IntegernPipSeg3Number of pipe segments per register used for discretization
IntegernElenPipPar*nPipSegNumber of heat exchanger elements
Flow resistance › Medium 1
BooleancomputeFlowResistance1 (from FourPortFlowResistanceParameters)true=true, compute flow resistance. Set to false to assume no friction
Booleanfrom_dp1 (from FourPortFlowResistanceParameters)false= true, use m_flow = f(dp) else dp = f(m_flow)
Realn1 (from FourPortFlowResistanceParameters)2Flow exponent for side 1, n=1 for laminar, n=2 for turbulent
BooleanlinearizeFlowResistance1 (from FourPortFlowResistanceParameters)false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM1 (from FourPortFlowResistanceParameters)0.1Fraction of nominal flow rate where flow transitions to laminar
Nominal condition
Modelica.Units.SI.PressureDifferencedp1_nominal (from FourPortFlowResistanceParameters)Pressure difference
Modelica.Units.SI.PressureDifferencedp2_nominal (from FourPortFlowResistanceParameters)Pressure difference
Modelica.Units.SI.ThermalConductanceUA_nominalThermal conductance at nominal flow, used to compute time constant
Modelica.Units.SI.MassFlowRatem1_flow_nominalMass flow rate medim 1
Modelica.Units.SI.MassFlowRatem2_flow_nominalMass flow rate medium 2
Modelica.Units.SI.Timetau120Time constant at nominal flow for medium 1
Modelica.Units.SI.Timetau21Time constant at nominal flow for medium 2
Modelica.Units.SI.Timetau_m60Time constant of metal at nominal UA value
Flow resistance › Medium 2
BooleancomputeFlowResistance2 (from FourPortFlowResistanceParameters)true=true, compute flow resistance. Set to false to assume no friction
Booleanfrom_dp2 (from FourPortFlowResistanceParameters)false= true, use m_flow = f(dp) else dp = f(m_flow)
Realn2 (from FourPortFlowResistanceParameters)2Flow exponent for side 2, n=1 for laminar, n=2 for turbulent
BooleanlinearizeFlowResistance2 (from FourPortFlowResistanceParameters)false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM2 (from FourPortFlowResistanceParameters)0.1Fraction of nominal flow rate where flow transitions to laminar
Advanced
Booleaninitialize_p1not Medium1.singleStateSet to true to initialize the pressure of volume 1
Booleaninitialize_p2not Medium2.singleStateSet to true to initialize the pressure of volume 2
Assumptions
BooleanallowFlowReversal1true= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
BooleanallowFlowReversal2true= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics › Conservation equations
Modelica.Fluid.Types.DynamicsenergyDynamicsModelica.Fluid.Types.Dynamics.DynamicFreeInitialDefault formulation of energy balances

Connectors

TypeNameDefaultDescription
Modelica.Fluid.Interfaces.FluidPort_aport_a1Fluid connector a for medium 1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_bport_b1Fluid connector b for medium 1 (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_aport_a2Fluid connector a for medium 2 (positive design flow direction is from port_a2 to port_b2)
Modelica.Fluid.Interfaces.FluidPort_bport_b2Fluid connector b for medium 2 (positive design flow direction is from port_a to port_b)
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a[nPipPar,nPipSeg]heaPor1Heat port for heat exchange with the control volume 1
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a[nPipPar,nPipSeg]heaPor2Heat port for heat exchange with the control volume 2
Modelica.Blocks.Interfaces.RealInputGc_2Signal representing the convective thermal conductance medium 2 in [W/K]
Modelica.Blocks.Interfaces.RealInputGc_1Signal representing the convective thermal conductance medium 1 in [W/K]

Components

TypeNameDefaultDescription
Buildings.Fluid.HeatExchangers.BaseClasses.HexElementSensible[nPipPar,nPipSeg]ele
Modelica.Units.SI.HeatFlowRateQ1_flowHeat transferred from solid into medium 1
Modelica.Units.SI.HeatFlowRateQ2_flowHeat transferred from solid into medium 2

Contents

NameDescription
Medium1Medium 1 in the component
Medium2Medium 2 in the component

Revisions

  • October 19, 2017, by Michael Wetter:
    Changed initialization of pressure from a constant to a parameter.
    This is for Buildings, issue 1013.
  • February 5, 2015, by Michael Wetter:
    Changed initalize_p from a parameter to a constant. This is only required in finite volume models of heat exchangers (to avoid consistent but redundant initial conditions) and hence it should be set as a constant.
  • December 22, 2014 by Michael Wetter:
    Removed Modelica.Fluid.System to address issue #311.
  • August 10, 2014, by Michael Wetter:
    Reformulated the multiple iterators in the sum function as this language construct is not supported in OpenModelica.
  • July 3, 2014, by Michael Wetter:
    Added parameters initialize_p1 and initialize_p2. This is required to enable the coil models to initialize the pressure in the first volume, but not in the downstream volumes. Otherwise, the initial equations will be overdetermined, but consistent. This change was done to avoid a long information message that appears when translating models.
  • June 26, 2014, by Michael Wetter:
    Removed parameters energyDynamics1 and energyDynamics2, and used instead of these two parameters the new parameter energyDynamics. Removed parameters steadyState_1 and steadyState_2. This was done as this complexity is not required.
  • August 12, 2008 by Michael Wetter:
    Introduced option to compute each medium using a steady state model or a dynamic model.
  • March 25, 2008, by Michael Wetter:
    First implementation.