Buildings.Fluid.HeatExchangers

Package with heat exchanger models

Information


This package contains models for heat exchangers with and without humidity condensation.




Package Content




NameDescription


Buildings.Fluid.HeatExchangers.CoolingTowers CoolingTowers
Package with cooling tower models


Buildings.Fluid.HeatExchangers.Radiators Radiators
Package with radiators models for hydronic space heating systems


Buildings.Fluid.HeatExchangers.ConstantEffectiveness ConstantEffectiveness
Heat exchanger with constant effectiveness


Buildings.Fluid.HeatExchangers.DryEffectivenessNTU DryEffectivenessNTU
Heat exchanger with effectiveness - NTU relation and not moisture condensation


Buildings.Fluid.HeatExchangers.DryCoilCounterFlow DryCoilCounterFlow
Counterflow coil with discretization along the flow paths and humidity condensation


Buildings.Fluid.HeatExchangers.WetCoilCounterFlow WetCoilCounterFlow
Counterflow coil with discretization along the flow paths and humidity condensation


Buildings.Fluid.HeatExchangers.DryCoilDiscretized DryCoilDiscretized
Coil with discretization along the flow paths and no humidity condensation


Buildings.Fluid.HeatExchangers.WetCoilDiscretized WetCoilDiscretized
Coil with discretization along the flow paths and humidity condensation


Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed HeaterCoolerPrescribed
Heater or cooler with prescribed heat flow rate


Buildings.Fluid.HeatExchangers.Examples Examples
Collection of models that illustrate model use and test models


Buildings.Fluid.HeatExchangers.BaseClasses BaseClasses
Package with base classes for heat exchanger models








Buildings.Fluid.HeatExchangers.ConstantEffectiveness
Buildings.Fluid.HeatExchangers.ConstantEffectiveness

Heat exchanger with constant effectiveness

Buildings.Fluid.HeatExchangers.ConstantEffectiveness

Information





Model for a heat exchanger with constant effectiveness.




This model transfers heat in the amount of 

  Q = Q_max * eps,


where eps is a constant effectiveness and 
Q_max is the maximum heat that can be transferred.




In the region mK_flow_small > abs(mK_flow) > mK_flow_small/2, for K = 1 or
2, the effectivness eps is transitioned from 
its user-specified value to 0. This improves the numerical robustness near
zero flow.




For a heat and moisture exchanger, use

Buildings.Fluid.MassExchangers.ConstantEffectiveness
instead of this model.




Extends from Buildings.Fluid.HeatExchangers.BaseClasses.PartialEffectiveness (Partial model to implement heat exchangers based on effectiveness model).

Parameters




TypeNameDefaultDescription


replaceable package Medium1PartialMediumMedium 1 in the component


replaceable package Medium2PartialMediumMedium 2 in the component


Realeps0.8Heat exchanger effectiveness


Nominal condition


MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]


MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp1_nominal Pressure [Pa]


Pressuredp2_nominal Pressure [Pa]


Initialization


MassFlowRatem1_flow.start0Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]


Pressuredp1.start0Pressure difference between port_a1 and port_b1 [Pa]


MassFlowRatem2_flow.start0Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]


Pressuredp2.start0Pressure difference between port_a2 and port_b2 [Pa]


Assumptions


BooleanallowFlowReversal1system.allowFlowReversal= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)


BooleanallowFlowReversal2system.allowFlowReversal= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)


Initialization


SpecificEnthalpyh_outflow_a1_startMedium1.h_defaultStart value for enthalpy flowing out of port a1 [J/kg]


SpecificEnthalpyh_outflow_b1_startMedium1.h_defaultStart value for enthalpy flowing out of port b1 [J/kg]


SpecificEnthalpyh_outflow_a2_startMedium2.h_defaultStart value for enthalpy flowing out of port a2 [J/kg]


SpecificEnthalpyh_outflow_b2_startMedium2.h_defaultStart value for enthalpy flowing out of port b2 [J/kg]


Advanced


MassFlowRatem1_flow_small1E-4*m1_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


MassFlowRatem2_flow_small1E-4*m2_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Flow resistance


Medium 1


Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar


Medium 2


Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar




Connectors




TypeNameDescription


FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)


FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)




Modelica definition


model ConstantEffectiveness 
  "Heat exchanger with constant effectiveness"
  extends Buildings.Fluid.HeatExchangers.BaseClasses.PartialEffectiveness(
    sensibleOnly1 = true,
    sensibleOnly2 = true);
  parameter Real eps(min=0, max=1) = 0.8 "Heat exchanger effectiveness";
equation 
  // transfered heat
  Q1_flow = eps * QMax_flow;
  // no heat loss to ambient
  0 = Q1_flow + Q2_flow;
  // no mass exchange
  mXi1_flow = zeros(Medium1.nXi);
  mXi2_flow = zeros(Medium2.nXi);
end ConstantEffectiveness;







Buildings.Fluid.HeatExchangers.DryEffectivenessNTU
Buildings.Fluid.HeatExchangers.DryEffectivenessNTU

Heat exchanger with effectiveness - NTU relation and not moisture condensation

Buildings.Fluid.HeatExchangers.DryEffectivenessNTU

Information





Model of a heat exchanger without humidity condensation. 
This model transfers heat in the amount of 

  Q_flow = QMax_flow * eps(NTU, Z, flowRegime),


where
QMax_flow is the maximum heat that can be transferred,
eps is the heat transfer effectiveness,
NTU is the Number of Transfer Units,
Z is the ratio of minimum to maximum capacity flow rate and
flowRegime is the heat exchanger flow regime.
such as
parallel flow, cross flow or counter flow.




The flow regimes depend on the heat exchanger configuration. All configurations
defined in

Buildings.Fluid.Types.HeatExchangerConfiguration
are supported.




For a heat exchanger with humidity condensation, use

Buildings.Fluid.HeatExchangers.WetEffectivenessNTU,
instead of this model.


For a heat and moisture exchanger, use

Buildings.Fluid.MassExchangers.ConstantEffectiveness
instead of this model.




Extends from Buildings.Fluid.HeatExchangers.BaseClasses.PartialEffectiveness (Partial model to implement heat exchangers based on effectiveness model).

Parameters




TypeNameDefaultDescription


replaceable package Medium1PartialMediumMedium 1 in the component


replaceable package Medium2PartialMediumMedium 2 in the component


HeatExchangerConfigurationconfiguration Heat exchanger configuration


Realr_nominal2/3Ratio between air-side and water-side convective heat transfer (hA-value) at nominal condition


Nominal condition


MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]


MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp1_nominal Pressure [Pa]


Pressuredp2_nominal Pressure [Pa]


HeatFlowRateQ_flow_nominal Nominal heat transfer [W]


TemperatureT_a1_nominal Nominal temperature at port a1 [K]


TemperatureT_a2_nominal Nominal temperature at port a2 [K]


Initialization


MassFlowRatem1_flow.start0Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]


Pressuredp1.start0Pressure difference between port_a1 and port_b1 [Pa]


MassFlowRatem2_flow.start0Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]


Pressuredp2.start0Pressure difference between port_a2 and port_b2 [Pa]


Assumptions


BooleanallowFlowReversal1system.allowFlowReversal= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)


BooleanallowFlowReversal2system.allowFlowReversal= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)


Initialization


SpecificEnthalpyh_outflow_a1_startMedium1.h_defaultStart value for enthalpy flowing out of port a1 [J/kg]


SpecificEnthalpyh_outflow_b1_startMedium1.h_defaultStart value for enthalpy flowing out of port b1 [J/kg]


SpecificEnthalpyh_outflow_a2_startMedium2.h_defaultStart value for enthalpy flowing out of port a2 [J/kg]


SpecificEnthalpyh_outflow_b2_startMedium2.h_defaultStart value for enthalpy flowing out of port b2 [J/kg]


Advanced


MassFlowRatem1_flow_small1E-4*m1_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


MassFlowRatem2_flow_small1E-4*m2_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Flow resistance


Medium 1


Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar


Medium 2


Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar




Connectors




TypeNameDescription


FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)


FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)




Modelica definition


model DryEffectivenessNTU 
  "Heat exchanger with effectiveness - NTU relation and not moisture condensation"
  extends Buildings.Fluid.HeatExchangers.BaseClasses.PartialEffectiveness(
    sensibleOnly1 = true,
    sensibleOnly2 = true);
  import con = Buildings.Fluid.Types.HeatExchangerConfiguration;
  import flo = Buildings.Fluid.Types.HeatExchangerFlowRegime;

  parameter Modelica.SIunits.HeatFlowRate Q_flow_nominal 
    "Nominal heat transfer";
  parameter Modelica.SIunits.Temperature T_a1_nominal 
    "Nominal temperature at port a1";
  parameter Modelica.SIunits.Temperature T_a2_nominal 
    "Nominal temperature at port a2";
  parameter con configuration "Heat exchanger configuration";

  parameter Real r_nominal(min=0, max=1)=2/3 
    "Ratio between air-side and water-side convective heat transfer (hA-value) at nominal condition";
  Buildings.Fluid.HeatExchangers.BaseClasses.HADryCoil hA(
    final r_nominal = r_nominal,
    final UA_nominal = UA_nominal,
    final m_flow_nominal_w = m1_flow_nominal,
    final m_flow_nominal_a = m2_flow_nominal,
    waterSideTemperatureDependent = false,
    airSideTemperatureDependent = false) 
    "Model for convective heat transfer coefficient";
  Modelica.SIunits.ThermalConductance UA "UA value";

  Real eps(min=0, max=1) "Heat exchanger effectiveness";
  Real Z(min=0, max=1) "Ratio of capacity flow rate (CMin/CMax)";
// NTU has been removed as NTU goes to infinity as CMin goes to zero.
// This quantity is not good for modeling.
//  Real NTU(min=0) "Number of transfer units";

  final parameter Modelica.SIunits.ThermalConductance UA_nominal(fixed=false) 
    "Nominal UA value";
  final parameter Real NTU_nominal(min=0, fixed=false) 
    "Nominal number of transfer units";
  final parameter Real eps_nominal(fixed=false) 
    "Nominal heat transfer effectiveness";

protected 
  parameter Modelica.SIunits.SpecificHeatCapacity cp1_nominal(fixed=false) 
    "Specific heat capacity of medium 1 at nominal condition";
  parameter Modelica.SIunits.SpecificHeatCapacity cp2_nominal(fixed=false) 
    "Specific heat capacity of medium 2 at nominal condition";

  parameter Modelica.SIunits.ThermalConductance C1_flow_nominal(fixed=false) 
    "Nominal capacity flow rate of Medium 1";
  parameter Modelica.SIunits.ThermalConductance C2_flow_nominal(fixed=false) 
    "Nominal capacity flow rate of Medium 2";
  parameter Modelica.SIunits.ThermalConductance CMin_flow_nominal(fixed=false) 
    "Minimal capacity flow rate at nominal condition";
  parameter Modelica.SIunits.ThermalConductance CMax_flow_nominal(fixed=false) 
    "Maximum capacity flow rate at nominal condition";
  parameter Real Z_nominal(min=0, max=1, fixed=false) 
    "Ratio of capacity flow rate at nominal condition";
  parameter Modelica.SIunits.Temperature T_b1_nominal(fixed=false) 
    "Nominal temperature at port b1";
  parameter Modelica.SIunits.Temperature T_b2_nominal(fixed=false) 
    "Nominal temperature at port b2";
  parameter flo flowRegime_nominal(fixed=false) 
    "Heat exchanger flow regime at nominal flow rates";

  flo flowRegime(fixed=false, start=flowRegime_nominal) 
    "Heat exchanger flow regime";
initial equation 
  assert(m1_flow_nominal > 0, "m1_flow_nominal must be positive, m1_flow_nominal = " + realString(m1_flow_nominal));
  assert(m2_flow_nominal > 0, "m2_flow_nominal must be positive, m2_flow_nominal = " + realString(m2_flow_nominal));
  cp1_nominal = Medium1.specificHeatCapacityCp(
      Medium1.setState_pTX(Medium1.p_default, T_a1_nominal, Medium1.X_default));
  cp2_nominal = Medium2.specificHeatCapacityCp(
      Medium2.setState_pTX(Medium2.p_default, T_a2_nominal, Medium2.X_default));
  // heat transfered from fluid 1 to 2 at nominal condition
  Q_flow_nominal =   m1_flow_nominal * cp1_nominal * (T_a1_nominal-T_b1_nominal);
  Q_flow_nominal =  -m2_flow_nominal * cp2_nominal * (T_a2_nominal-T_b2_nominal);
  C1_flow_nominal = m1_flow_nominal * cp1_nominal;
  C2_flow_nominal = m2_flow_nominal * cp2_nominal;
  CMin_flow_nominal = min(C1_flow_nominal, C2_flow_nominal);
  CMax_flow_nominal = max(C1_flow_nominal, C2_flow_nominal);
  Z_nominal    = CMin_flow_nominal/CMax_flow_nominal;
  eps_nominal = abs(Q_flow_nominal / ((T_a1_nominal-T_a2_nominal)*CMin_flow_nominal));
  assert(eps_nominal > 0 and eps_nominal < 1, "eps_nominal out of bounds, eps_nominal = " + realString(eps_nominal) +
    "\n  To achieve the required heat transfer rate at epsilon=0.8, set |T_a1_nominal-T_a2_nominal| = " +
    realString(abs(Q_flow_nominal/0.8*CMin_flow_nominal)) +
    "\n  or increase flow rates. The current parameters result in " +
    "\n  CMin_flow_nominal = " + realString(CMin_flow_nominal) +
    "\n  CMax_flow_nominal = " + realString(CMax_flow_nominal));

  // Assign the flow regime for the given heat exchanger configuration and capacity flow rates
  if ( configuration == con.CrossFlowStream1MixedStream2Unmixed) then
    flowRegime_nominal = if ( C1_flow_nominal < C2_flow_nominal) then 
        flo.CrossFlowCMinMixedCMaxUnmixed else 
        flo.CrossFlowCMinUnmixedCMaxMixed;
  elseif ( configuration == con.CrossFlowStream1UnmixedStream2Mixed) then
    flowRegime_nominal = if ( C1_flow_nominal < C2_flow_nominal) then 
        flo.CrossFlowCMinUnmixedCMaxMixed else 
        flo.CrossFlowCMinMixedCMaxUnmixed;
  elseif (configuration == con.ParallelFlow) then
      flowRegime_nominal = flo.ParallelFlow;
  elseif (configuration == con.CounterFlow) then
      flowRegime_nominal = flo.CounterFlow;
  elseif (configuration == con.CrossFlowUnmixed) then
      flowRegime_nominal = flo.CrossFlowUnmixed;
  else
    flowRegime_nominal = 0;
    assert(configuration > 0 and configuration < 6, "Invalid heat exchanger configuration.");
  end if;

  // The equation sorter of Dymola 7.3 does not guarantee that the above assert is tested prior to the
  // function call on the next line. Thus, we add the test on eps_nominal to avoid an error in ntu_epsilonZ
  // for invalid input arguments
  NTU_nominal  = if (eps_nominal > 0 and eps_nominal < 1) then 
         Buildings.Fluid.HeatExchangers.BaseClasses.ntu_epsilonZ(eps=eps_nominal, Z=Z_nominal, flowRegime=flowRegime_nominal) else 
         0;
  UA_nominal = NTU_nominal * CMin_flow_nominal;

equation 
  // Assign the flow regime for the given heat exchanger configuration and capacity flow rates
  if ( configuration == con.ParallelFlow) then
    flowRegime = if ( C1_flow * C2_flow >= 0) then 
       flo.ParallelFlow else flo.CounterFlow;
  elseif ( configuration == con.CounterFlow) then
    flowRegime = if ( C1_flow * C2_flow >= 0) then 
       flo.CounterFlow else flo.ParallelFlow;
  elseif ( configuration == con.CrossFlowUnmixed) then
      flowRegime = flo.CrossFlowUnmixed;
  elseif ( configuration == con.CrossFlowStream1MixedStream2Unmixed) then
    flowRegime = if ( C1_flow < C2_flow) then 
        flo.CrossFlowCMinMixedCMaxUnmixed else 
        flo.CrossFlowCMinUnmixedCMaxMixed;
  else // have ( configuration == con.CrossFlowStream1UnmixedStream2Mixed)
    flowRegime = if ( C1_flow < C2_flow) then 
        flo.CrossFlowCMinUnmixedCMaxMixed else 
        flo.CrossFlowCMinMixedCMaxUnmixed;
  end if;
  // Convective heat transfer coefficient
  hA.m1_flow = m1_flow;
  hA.m2_flow = m2_flow;
  hA.T_1 = T_in1;
  hA.T_2 = T_in2;
  UA = 1/(1/hA.hA_1+1/hA.hA_2);
  // effectiveness
  (eps, Z) = Buildings.Fluid.HeatExchangers.BaseClasses.epsilon_C(UA=UA,
       C1_flow=C1_flow, C2_flow=C2_flow, flowRegime=flowRegime,
       CMin_flow_nominal=CMin_flow_nominal, CMax_flow_nominal=CMax_flow_nominal, delta=delta);
  // transfered heat. QMax_flow is maximum heat transfered into medium
  Q1_flow = eps * QMax_flow;
  // no heat loss to ambient
  0 = Q1_flow + Q2_flow;
  // no mass exchange
  mXi1_flow = zeros(Medium1.nXi);
  mXi2_flow = zeros(Medium2.nXi);
end DryEffectivenessNTU;







Buildings.Fluid.HeatExchangers.DryCoilCounterFlow
Buildings.Fluid.HeatExchangers.DryCoilCounterFlow

Counterflow coil with discretization along the flow paths and humidity condensation

Buildings.Fluid.HeatExchangers.DryCoilCounterFlow

Information





Model of a discretized coil without water vapor condensation.
The coil consists of two flow paths which are, at the design flow direction,
in opposite direction to model a counterflow heat exchanger.
The flow paths are discretized into nEle elements. 
Each element is modeled by an instance of

Buildings.Fluid.HeatExchangers.BaseClasses.HexElement.
Each element has a state variable for the metal. Depending
on the value of the boolean parameters steadyState_1 and
steadyState_2, the fluid states are modeled dynamically or in steady
state.




The convective heat transfer coefficients can, for each fluid individually, be 
computed as a function of the flow rate and/or the temperature,
or assigned to a constant. This computation is done using an instance of

Buildings.Fluid.HeatExchangers.BaseClasses.HADryCoil.




To model humidity condensation, use the model 

Buildings.Fluid.HeatExchangers.WetCoilCounterFlow instead of this model, as
this model computes only sensible heat transfer.




Extends from Fluid.Interfaces.PartialStaticFourPortInterface (Partial model transporting fluid between two ports without storing mass or energy), Buildings.Fluid.Interfaces.FourPortFlowResistanceParameters (Parameters for flow resistance for models with four ports).

Parameters




TypeNameDefaultDescription


replaceable package Medium1PartialMediumMedium 1 in the component


replaceable package Medium2PartialMediumMedium 2 in the component


Nominal condition


MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]


MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp1_nominal Pressure [Pa]


Pressuredp2_nominal Pressure [Pa]


ThermalConductanceUA_nominal Thermal conductance at nominal flow, used to compute heat capacity [W/K]


Realr_nominal2/3Ratio between air-side and water-side convective heat transfer coefficient


Timetau120Time constant at nominal flow for medium 1 [s]


Timetau21Time constant at nominal flow for medium 2 [s]


Timetau_m20Time constant of metal at nominal UA value [s]


Initialization


MassFlowRatem1_flow.start0Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]


Pressuredp1.start0Pressure difference between port_a1 and port_b1 [Pa]


MassFlowRatem2_flow.start0Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]


Pressuredp2.start0Pressure difference between port_a2 and port_b2 [Pa]


Geometry


IntegernEle4Number of pipe segments used for discretization


Assumptions


BooleanallowFlowReversal1system.allowFlowReversal= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)


BooleanallowFlowReversal2system.allowFlowReversal= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)


Dynamics


DynamicsenergyDynamics1Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 1


DynamicsenergyDynamics2Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 2


Initialization


SpecificEnthalpyh_outflow_a1_startMedium1.h_defaultStart value for enthalpy flowing out of port a1 [J/kg]


SpecificEnthalpyh_outflow_b1_startMedium1.h_defaultStart value for enthalpy flowing out of port b1 [J/kg]


SpecificEnthalpyh_outflow_a2_startMedium2.h_defaultStart value for enthalpy flowing out of port a2 [J/kg]


SpecificEnthalpyh_outflow_b2_startMedium2.h_defaultStart value for enthalpy flowing out of port b2 [J/kg]


Advanced


MassFlowRatem1_flow_small1E-4*m1_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


MassFlowRatem2_flow_small1E-4*m2_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Booleanshow_Ttrue= true, if actual temperature at port is computed (may lead to events)


Flow resistance


Medium 1


BooleancomputeFlowResistance1false=true, compute flow resistance. Set to false to assume no friction


Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar


Medium 2


BooleancomputeFlowResistance2false=true, compute flow resistance. Set to false to assume no friction


Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar


Heat transfer


BooleanwaterSideFlowDependenttrueSet to false to make water-side hA independent of mass flow rate


BooleanairSideFlowDependenttrueSet to false to make air-side hA independent of mass flow rate


BooleanwaterSideTemperatureDependentfalseSet to false to make water-side hA independent of temperature


BooleanairSideTemperatureDependentfalseSet to false to make air-side hA independent of temperature




Connectors




TypeNameDescription


FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)


FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)




Modelica definition


model DryCoilCounterFlow 
  "Counterflow coil with discretization along the flow paths and humidity condensation"
  extends Fluid.Interfaces.PartialStaticFourPortInterface(show_T = true);
  extends Buildings.Fluid.Interfaces.FourPortFlowResistanceParameters(
    final computeFlowResistance1=false,
    final computeFlowResistance2=false,
    from_dp1 = false,
    from_dp2 = false);

  parameter Modelica.SIunits.ThermalConductance UA_nominal(min=0) 
    "Thermal conductance at nominal flow, used to compute heat capacity";
  parameter Real r_nominal=2/3 
    "Ratio between air-side and water-side convective heat transfer coefficient";
  parameter Integer nEle(min=1) = 4 
    "Number of pipe segments used for discretization";

  parameter Modelica.Fluid.Types.Dynamics energyDynamics1=
    Modelica.Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for volume 1";
  parameter Modelica.Fluid.Types.Dynamics energyDynamics2=
    Modelica.Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for volume 2";

  parameter Modelica.SIunits.Time tau1=20 
    "Time constant at nominal flow for medium 1";
  parameter Modelica.SIunits.Time tau2=1 
    "Time constant at nominal flow for medium 2";
  parameter Modelica.SIunits.Time tau_m=20 
    "Time constant of metal at nominal UA value";

  parameter Boolean waterSideFlowDependent = true 
    "Set to false to make water-side hA independent of mass flow rate";
  parameter Boolean airSideFlowDependent = true 
    "Set to false to make air-side hA independent of mass flow rate";
  parameter Boolean waterSideTemperatureDependent = false 
    "Set to false to make water-side hA independent of temperature";
  parameter Boolean airSideTemperatureDependent = false 
    "Set to false to make air-side hA independent of temperature";

  Modelica.SIunits.HeatFlowRate Q1_flow 
    "Heat transfered from solid into medium 1";
  Modelica.SIunits.HeatFlowRate Q2_flow 
    "Heat transfered from solid into medium 2";

  Modelica.SIunits.Temperature T1[nEle] "Water temperature";
  Modelica.SIunits.Temperature T2[nEle] "Air temperature";
  Modelica.SIunits.Temperature T_m[nEle] "Metal temperature";

  BaseClasses.HADryCoil hA(
    final UA_nominal=UA_nominal,
    final m_flow_nominal_a=m2_flow_nominal,
    final m_flow_nominal_w=m1_flow_nominal,
    final waterSideTemperatureDependent=waterSideTemperatureDependent,
    final waterSideFlowDependent=waterSideFlowDependent,
    final airSideTemperatureDependent=airSideTemperatureDependent,
    final airSideFlowDependent=airSideFlowDependent,
    r_nominal=r_nominal) "Model for convective heat transfer coefficient";
protected 
  constant Boolean allowCondensation = false 
    "Set to false to compute sensible heat transfer only";
  Buildings.Fluid.Sensors.TemperatureTwoPort temSen_1(
                                              redeclare package Medium =
        Medium1) "Temperature sensor";
  Buildings.Fluid.Sensors.MassFlowRate masFloSen_1(redeclare package Medium =
        Medium1) "Mass flow rate sensor";
  Buildings.Fluid.Sensors.TemperatureTwoPort temSen_2(
                                              redeclare package Medium =
        Medium2) "Temperature sensor";
  Buildings.Fluid.Sensors.MassFlowRate masFloSen_2(redeclare package Medium =
        Medium2) "Mass flow rate sensor";
  Modelica.Blocks.Math.Gain gai_1(k=1/nEle) 
    "Gain medium-side 1 to take discretization into account";
  Modelica.Blocks.Math.Gain gai_2(k=1/nEle) 
    "Gain medium-side 2 to take discretization into account";

  BaseClasses.HexElement ele[nEle](
    redeclare each package Medium1 = Medium1,
    redeclare each package Medium2 = Medium2,
    each allowFlowReversal1=allowFlowReversal1,
    each allowFlowReversal2=allowFlowReversal2,
    each tau1=tau1/nEle,
    each m1_flow_nominal=m1_flow_nominal,
    each tau2=tau2,
    each m2_flow_nominal=m2_flow_nominal,
    each tau_m=tau_m/nEle,
    each UA_nominal=UA_nominal/nEle,
    each energyDynamics1=energyDynamics1,
    each energyDynamics2=energyDynamics2,
    each allowCondensation=allowCondensation,
    each deltaM1=deltaM1,
    each deltaM2=deltaM2,
    each from_dp1=from_dp1,
    each from_dp2=from_dp2,
    dp1_nominal={if i == 1 then dp1_nominal else 0 for i in 1:nEle},
    dp2_nominal={if i == nEle then 0 else dp2_nominal for i in 1:nEle}) 
    "Heat exchanger element";
  Modelica.Blocks.Routing.Replicator rep1(nout=nEle) "Signal replicator";
  Modelica.Blocks.Routing.Replicator rep2(nout=nEle) "Signal replicator";

initial equation 
  assert(UA_nominal>0,     "Parameter UA_nominal is negative. Check heat exchanger parameters.");
equation 
  Q1_flow = sum(ele[i].Q1_flow for i in 1:nEle);
  Q2_flow = sum(ele[i].Q2_flow for i in 1:nEle);
  T1[:] = ele[:].vol1.medium.T;
  T2[:] = ele[:].vol2.medium.T;
  T_m[:] = ele[:].mas.T;
  connect(masFloSen_1.m_flow, hA.m1_flow);
  connect(port_a2, masFloSen_2.port_a);
  connect(masFloSen_2.port_b, temSen_2.port_a);
  connect(temSen_2.T, hA.T_2);
  connect(masFloSen_2.m_flow, hA.m2_flow);
  connect(hA.hA_1, gai_1.u);
  connect(hA.hA_2, gai_2.u);
  connect(port_a1, masFloSen_1.port_a);
  connect(masFloSen_1.port_b, temSen_1.port_a);
  connect(temSen_1.T, hA.T_1);
  connect(temSen_1.port_b, ele[1].port_a1);

  connect(ele[nEle].port_b1, port_b1);
  connect(temSen_2.port_b, ele[nEle].port_a2);
  connect(ele[1].port_b2, port_b2);
  for i in 1:nEle-1 loop
   connect(ele[i].port_b1, ele[i+1].port_a1);
  connect(ele[i].port_a2, ele[i+1].port_b2);
  end for;

  connect(gai_1.y, rep1.u);
  connect(rep1.y, ele.Gc_1);
  connect(gai_2.y, rep2.u);
  connect(rep2.y, ele.Gc_2);
end DryCoilCounterFlow;







Buildings.Fluid.HeatExchangers.WetCoilCounterFlow
Buildings.Fluid.HeatExchangers.WetCoilCounterFlow

Counterflow coil with discretization along the flow paths and humidity condensation

Buildings.Fluid.HeatExchangers.WetCoilCounterFlow

Information





Model of a discretized coil with water vapor condensation.
The coil consists of two flow paths which are, at the design flow direction,
in opposite direction to model a counterflow heat exchanger.
The flow paths are discretized into nEle elements. 
Each element is modeled by an instance of

Buildings.Fluid.HeatExchangers.BaseClasses.HexElement.
Each element has a state variable for the metal. Depending
on the value of the boolean parameters steadyState_1 and
steadyState_2, the fluid states are modeled dynamically or in steady
state.




The convective heat transfer coefficients can, for each fluid individually, be 
computed as a function of the flow rate and/or the temperature,
or assigned to a constant. This computation is done using an instance of

Buildings.Fluid.HeatExchangers.BaseClasses.HADryCoil.




In this model, the water (or liquid) flow path
needs to be connected to port_a1 and port_b1, and
the air flow path needs to be connected to the other two ports.




The mass transfer from the fluid 2 to the metal is computed using a similarity law between
heat and mass transfer, as implemented by the model

Buildings.Fluid.HeatExchangers.BaseClasses.MassExchange. 




This model can only be used with medium models that
implement the function enthalpyOfLiquid and that contain
an integer variable Water whose value is the element number where
the water vapor is stored in the species concentration vector. Examples for
such media are

Buildings.Media.PerfectGases.MoistAir and

Modelica.Media.Air.MoistAir.




To model this coil for conditions without humidity condensation, use the model 

Buildings.Fluid.HeatExchangers.DryCoilCounterFlow instead of this model.




Extends from Buildings.Fluid.HeatExchangers.DryCoilCounterFlow (Counterflow coil with discretization along the flow paths and humidity condensation).

Parameters




TypeNameDefaultDescription


replaceable package Medium1PartialMediumMedium 1 in the component


replaceable package Medium2PartialMediumMedium 2 in the component


Nominal condition


MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]


MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp1_nominal Pressure [Pa]


Pressuredp2_nominal Pressure [Pa]


ThermalConductanceUA_nominal Thermal conductance at nominal flow, used to compute heat capacity [W/K]


Realr_nominal2/3Ratio between air-side and water-side convective heat transfer coefficient


Timetau120Time constant at nominal flow for medium 1 [s]


Timetau21Time constant at nominal flow for medium 2 [s]


Timetau_m20Time constant of metal at nominal UA value [s]


Initialization


MassFlowRatem1_flow.start0Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]


Pressuredp1.start0Pressure difference between port_a1 and port_b1 [Pa]


MassFlowRatem2_flow.start0Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]


Pressuredp2.start0Pressure difference between port_a2 and port_b2 [Pa]


Geometry


IntegernEle4Number of pipe segments used for discretization


Assumptions


BooleanallowFlowReversal1system.allowFlowReversal= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)


BooleanallowFlowReversal2system.allowFlowReversal= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)


Dynamics


DynamicsenergyDynamics1Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 1


DynamicsenergyDynamics2Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 2


Initialization


SpecificEnthalpyh_outflow_a1_startMedium1.h_defaultStart value for enthalpy flowing out of port a1 [J/kg]


SpecificEnthalpyh_outflow_b1_startMedium1.h_defaultStart value for enthalpy flowing out of port b1 [J/kg]


SpecificEnthalpyh_outflow_a2_startMedium2.h_defaultStart value for enthalpy flowing out of port a2 [J/kg]


SpecificEnthalpyh_outflow_b2_startMedium2.h_defaultStart value for enthalpy flowing out of port b2 [J/kg]


Advanced


MassFlowRatem1_flow_small1E-4*m1_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


MassFlowRatem2_flow_small1E-4*m2_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Booleanshow_Ttrue= true, if actual temperature at port is computed (may lead to events)


Flow resistance


Medium 1


Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar


Medium 2


Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar


Heat transfer


BooleanwaterSideFlowDependenttrueSet to false to make water-side hA independent of mass flow rate


BooleanairSideFlowDependenttrueSet to false to make air-side hA independent of mass flow rate


BooleanwaterSideTemperatureDependentfalseSet to false to make water-side hA independent of temperature


BooleanairSideTemperatureDependentfalseSet to false to make air-side hA independent of temperature




Connectors




TypeNameDescription


FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)


FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)




Modelica definition


model WetCoilCounterFlow 
  "Counterflow coil with discretization along the flow paths and humidity condensation"
  extends Buildings.Fluid.HeatExchangers.DryCoilCounterFlow(
    final allowCondensation = true,
    ele(redeclare each Buildings.Fluid.MixingVolumes.MixingVolumeMoistAir vol2(
          final use_HeatTransfer = true)));

  Modelica.SIunits.HeatFlowRate QSen2_flow 
    "Sensible heat input into air stream (negative if air is cooled)";
  Modelica.SIunits.HeatFlowRate QLat2_flow 
    "Latent heat input into air (negative if air is dehumidified)";
  Real SHR(
    min=0,
    max=1,
    unit="1") "Sensible to total heat ratio";

  Modelica.SIunits.MassFlowRate mWat_flow "Water flow rate";

equation 
  mWat_flow = sum(ele[i].vol2.mWat_flow for i in 1:nEle);
  QLat2_flow = sum(Medium2.enthalpyOfCondensingGas(ele[i].vol2.medium.T)*ele[i].vol2.mWat_flow for i in 1:nEle);
  Q2_flow = QSen2_flow + QLat2_flow;
  Q2_flow*SHR = QSen2_flow;
end WetCoilCounterFlow;







Buildings.Fluid.HeatExchangers.DryCoilDiscretized
Buildings.Fluid.HeatExchangers.DryCoilDiscretized

Coil with discretization along the flow paths and no humidity condensation

Buildings.Fluid.HeatExchangers.DryCoilDiscretized

Information





Model of a discretized coil with no water vapor condensation.
The coil consists of nReg registers
that are perpendicular to the air flow path. Each register consists of nPipPar
parallel pipes, and each pipe can be divided into nPipSeg pipe segments along
the pipe length. Thus, the smallest element of the coil consists of a pipe 
segment. Each pipe segment is modeled by an instance of

Buildings.Fluid.HeatExchangers.BaseClasses.HexElement.
Each element has a state variable for the metal. Depending
on the value of the boolean parameters steadyState_1 and
steadyState_2, the fluid states are modeled dynamically or in steady
state.
If the parameter steadyStateDuctConnection is set the false, then
a mixing volume of length dl is added to the duct connection. This can
help reducing the dimension of the nonlinear system of equations.




The convective heat transfer coefficients can, for each fluid individually, be 
computed as a function of the flow rate and/or the temperature,
or assigned to a constant. This computation is done using an instance of

Buildings.Fluid.HeatExchangers.BaseClasses.HADryCoil.




In this model, the water (or liquid) flow path
needs to be connected to port_a1 and port_b1, and
the air flow path need to be connected to the other two ports.




To model humidity condensation, use the model 

Buildings.Fluid.HeatExchangers.WetCoilDiscretized instead of this model, as
this model computes only sensible heat transfer.




Extends from Fluid.Interfaces.PartialStaticFourPortInterface (Partial model transporting fluid between two ports without storing mass or energy), Buildings.Fluid.Interfaces.FourPortFlowResistanceParameters (Parameters for flow resistance for models with four ports).

Parameters




TypeNameDefaultDescription


replaceable package Medium1PartialMediumMedium 1 in the component


replaceable package Medium2PartialMediumMedium 2 in the component


Nominal condition


MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]


MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp1_nominal Pressure [Pa]


Pressuredp2_nominal Pressure [Pa]


ThermalConductanceUA_nominal Thermal conductance at nominal flow, used to compute heat capacity [W/K]


Timetau120Time constant at nominal flow for medium 1 [s]


Timetau21Time constant at nominal flow for medium 2 [s]


Timetau_m20Time constant of metal at nominal UA value [s]


Initialization


MassFlowRatem1_flow.start0Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]


Pressuredp1.start0Pressure difference between port_a1 and port_b1 [Pa]


MassFlowRatem2_flow.start0Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]


Pressuredp2.start0Pressure difference between port_a2 and port_b2 [Pa]


MassFlowRatemStart_flow_a1m1_flow_nominalGuess value for mass flow rate at port_a1 [kg/s]


MassFlowRatemStart_flow_a2m2_flow_nominalGuess value for mass flow rate at port_a2 [kg/s]


Geometry


IntegernReg2Number of registers


IntegernPipPar3Number of parallel pipes in each register


IntegernPipSeg4Number of pipe segments per register used for discretization


Lengthdh10.025Hydraulic diameter for a single pipe [m]


Lengthdh21Hydraulic diameter for duct [m]


Assumptions


BooleanallowFlowReversal1system.allowFlowReversal= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)


BooleanallowFlowReversal2system.allowFlowReversal= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)


Dynamics


DynamicsenergyDynamics1Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 1


DynamicsenergyDynamics2Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 2


DynamicsductConnectionDynamicsModelica.Fluid.Types.Dynamic...Default formulation of energy balances for duct connection


Lengthdl0.3Length of mixing volume for duct connection [m]


Initialization


SpecificEnthalpyh_outflow_a1_startMedium1.h_defaultStart value for enthalpy flowing out of port a1 [J/kg]


SpecificEnthalpyh_outflow_b1_startMedium1.h_defaultStart value for enthalpy flowing out of port b1 [J/kg]


SpecificEnthalpyh_outflow_a2_startMedium2.h_defaultStart value for enthalpy flowing out of port a2 [J/kg]


SpecificEnthalpyh_outflow_b2_startMedium2.h_defaultStart value for enthalpy flowing out of port b2 [J/kg]


Advanced


MassFlowRatem1_flow_small1E-4*m1_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


MassFlowRatem2_flow_small1E-4*m2_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Booleanuse_dh1falseSet to true to specify hydraulic diameter for pipe pressure drop


Booleanuse_dh2falseSet to true to specify hydraulic diameter for duct pressure drop)


RealReC_14000Reynolds number where transition to turbulent starts inside pipes


RealReC_24000Reynolds number where transition to turbulent starts inside ducts


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Booleanshow_Tfalse= true, if actual temperature at port is computed (may lead to events)


Flow resistance


Medium 1


BooleancomputeFlowResistance1true=true, compute flow resistance. Set to false to assume no friction


Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar


Medium 2


BooleancomputeFlowResistance2true=true, compute flow resistance. Set to false to assume no friction


Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar


Heat transfer


BooleanwaterSideFlowDependentfalseSet to false to make water-side hA independent of mass flow rate


BooleanairSideFlowDependentfalseSet to false to make air-side hA independent of mass flow rate


BooleanwaterSideTemperatureDependentfalseSet to false to make water-side hA independent of temperature




Connectors




TypeNameDescription


FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)


FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)




Modelica definition


model DryCoilDiscretized 
  "Coil with discretization along the flow paths and no humidity condensation"
  extends Fluid.Interfaces.PartialStaticFourPortInterface;
  extends Buildings.Fluid.Interfaces.FourPortFlowResistanceParameters(
    final computeFlowResistance1=true,
    final computeFlowResistance2=true,
    from_dp1 = false,
    from_dp2 = false);

  parameter Modelica.SIunits.ThermalConductance UA_nominal(min=0) 
    "Thermal conductance at nominal flow, used to compute heat capacity";
  parameter Integer nReg(min=2)=2 "Number of registers";
  parameter Integer nPipPar(min=1) = 3 
    "Number of parallel pipes in each register";
  parameter Integer nPipSeg(min=1) = 4 
    "Number of pipe segments per register used for discretization";
  parameter Boolean use_dh1 = false 
    "Set to true to specify hydraulic diameter for pipe pressure drop";
  parameter Boolean use_dh2 = false 
    "Set to true to specify hydraulic diameter for duct pressure drop)";

  parameter Modelica.Fluid.Types.Dynamics energyDynamics1=
    Modelica.Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for volume 1";
  parameter Modelica.Fluid.Types.Dynamics energyDynamics2=
    Modelica.Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for volume 2";

  Buildings.Fluid.HeatExchangers.BaseClasses.CoilRegister hexReg[nReg](
    redeclare each package Medium1 = Medium1,
    redeclare each package Medium2 = Medium2,
    each final allowFlowReversal1=allowFlowReversal1,
    each final allowFlowReversal2=allowFlowReversal2,
    each final nPipPar=nPipPar,
    each final nPipSeg=nPipSeg,
    each final m1_flow_nominal=m1_flow_nominal/nPipPar,
    each final m2_flow_nominal=m1_flow_nominal/nPipPar/nPipSeg,
    each tau1=tau1,
    each tau2=tau2,
    each tau_m=tau_m,
    each final energyDynamics1=energyDynamics1,
    each final energyDynamics2=energyDynamics2,
    each allowCondensation=allowCondensation,
    each from_dp1=from_dp1,
    each linearizeFlowResistance1=linearizeFlowResistance1,
    each deltaM1=deltaM1,
    each from_dp2=from_dp2,
    each linearizeFlowResistance2=linearizeFlowResistance2,
    each deltaM2=deltaM2,
    each dp1_nominal=0,
    each dp2_nominal=0,
    each final UA_nominal=UA_nominal/nReg) "Heat exchanger register";
  Buildings.Fluid.HeatExchangers.BaseClasses.PipeManifoldFixedResistance
    pipMan_a(
    redeclare package Medium = Medium1,
    final nPipPar=nPipPar,
    final m_flow_nominal=m1_flow_nominal,
    final dp_nominal=dp1_nominal,
    final dh=dh1,
    final ReC=ReC_1,
    final mStart_flow_a=mStart_flow_a1,
    final linearized=linearizeFlowResistance1,
    final use_dh=use_dh1,
    final deltaM=deltaM1,
    final from_dp=from_dp1,
    final allowFlowReversal=allowFlowReversal1) "Pipe manifold at port a";
  Buildings.Fluid.HeatExchangers.BaseClasses.PipeManifoldNoResistance pipMan_b(
    redeclare package Medium = Medium1,
    final nPipPar=nPipPar,
    final mStart_flow_a=-mStart_flow_a1,
    final allowFlowReversal=allowFlowReversal1) "Pipe manifold at port b";
  Buildings.Fluid.HeatExchangers.BaseClasses.DuctManifoldNoResistance ducMan_b(
    redeclare package Medium = Medium2,
    final nPipPar=nPipPar,
    final nPipSeg=nPipSeg,
    final mStart_flow_a=-mStart_flow_a2,
    final allowFlowReversal=allowFlowReversal2) "Duct manifold at port b";
  Buildings.Fluid.HeatExchangers.BaseClasses.DuctManifoldFixedResistance
    ducMan_a(
    redeclare package Medium = Medium2,
    final nPipPar = nPipPar,
    final nPipSeg = nPipSeg,
    final m_flow_nominal=m2_flow_nominal,
    final dp_nominal=dp2_nominal,
    final dh=dh2,
    final ReC=ReC_2,
    final dl=dl,
    final mStart_flow_a=mStart_flow_a2,
    final linearized=linearizeFlowResistance2,
    final use_dh=use_dh2,
    final deltaM=deltaM2,
    final from_dp=from_dp2,
    final allowFlowReversal=allowFlowReversal2,
    final energyDynamics=ductConnectionDynamics) "Duct manifold at port a";
public 
  parameter Modelica.SIunits.Length dh1=0.025 
    "Hydraulic diameter for a single pipe";
  parameter Real ReC_1=4000 
    "Reynolds number where transition to turbulent starts inside pipes";
  parameter Real ReC_2=4000 
    "Reynolds number where transition to turbulent starts inside ducts";
  parameter Modelica.SIunits.MassFlowRate m1_flow_nominal 
    "Mass flow rate at port_a1 for all pipes";
  parameter Modelica.SIunits.Length dh2=1 "Hydraulic diameter for duct";
  Modelica.SIunits.HeatFlowRate Q1_flow 
    "Heat transfered from solid into medium 1";
  Modelica.SIunits.HeatFlowRate Q2_flow 
    "Heat transfered from solid into medium 2";
  parameter Modelica.SIunits.Time tau1=20 
    "Time constant at nominal flow for medium 1";
  parameter Modelica.SIunits.Time tau2=1 
    "Time constant at nominal flow for medium 2";
  parameter Modelica.SIunits.Time tau_m=20 
    "Time constant of metal at nominal UA value";

protected 
  BaseClasses.CoilHeader hea1[nReg/2](
      redeclare each final package Medium = Medium1,
      each final nPipPar = nPipPar,
      each final mStart_flow_a=mStart_flow_a1,
      each allowFlowReversal=allowFlowReversal1) if 
      nReg > 1 "Pipe header to redirect flow into next register";
  BaseClasses.CoilHeader hea2[nReg/2-1](
      redeclare each final package Medium = Medium1,
      each final nPipPar = nPipPar,
      each final mStart_flow_a=mStart_flow_a1,
      each allowFlowReversal=allowFlowReversal1) if 
      nReg > 2 "Pipe header to redirect flow into next register";
  Modelica.Blocks.Math.Gain gai_1(k=1/nReg) 
    "Gain medium-side 1 to take discretization into account";
  Modelica.Blocks.Math.Gain gai_2(k=1/nReg) 
    "Gain medium-side 2 to take discretization into account";
public 
  parameter Boolean waterSideFlowDependent = false 
    "Set to false to make water-side hA independent of mass flow rate";
  parameter Boolean airSideFlowDependent = false 
    "Set to false to make air-side hA independent of mass flow rate";
  parameter Boolean waterSideTemperatureDependent = false 
    "Set to false to make water-side hA independent of temperature";
  constant Boolean airSideTemperatureDependent = false 
    "Set to false to make air-side hA independent of temperature";
  BaseClasses.HADryCoil hA(
    final UA_nominal=UA_nominal,
    final m_flow_nominal_a=m2_flow_nominal,
    final m_flow_nominal_w=m1_flow_nominal,
    final waterSideTemperatureDependent=waterSideTemperatureDependent,
    final waterSideFlowDependent=waterSideFlowDependent,
    final airSideTemperatureDependent=airSideTemperatureDependent,
    final airSideFlowDependent=airSideFlowDependent) 
    "Model for convective heat transfer coefficient";
protected 
  constant Boolean allowCondensation = false 
    "Set to false to compute sensible heat transfer only";

protected 
  Buildings.Fluid.Sensors.TemperatureTwoPort temSen_1(
                                              redeclare package Medium =
        Medium1) "Temperature sensor";
  Buildings.Fluid.Sensors.MassFlowRate masFloSen_1(redeclare package Medium =
        Medium1) "Mass flow rate sensor";
  Buildings.Fluid.Sensors.TemperatureTwoPort temSen_2(
                                              redeclare package Medium =
        Medium2) "Temperature sensor";
  Buildings.Fluid.Sensors.MassFlowRate masFloSen_2(redeclare package Medium =
        Medium2) "Mass flow rate sensor";
public 
  parameter Modelica.Fluid.Types.Dynamics ductConnectionDynamics=
    Modelica.Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for duct connection";
  parameter Modelica.SIunits.Length dl=0.3 
    "Length of mixing volume for duct connection";
  parameter Modelica.SIunits.MassFlowRate mStart_flow_a1=m1_flow_nominal 
    "Guess value for mass flow rate at port_a1";
  parameter Modelica.SIunits.MassFlowRate mStart_flow_a2=m2_flow_nominal 
    "Guess value for mass flow rate at port_a2";
initial equation 
  assert(UA_nominal>0,     "Parameter UA_nominal is negative. Check heat exchanger parameters.");
equation 
  Q1_flow = sum(hexReg[i].Q1_flow for i in 1:nReg);
  Q2_flow = sum(hexReg[i].Q2_flow for i in 1:nReg);

  // air stream connections
  for i in 2:nReg loop
    connect(hexReg[i].port_a2, hexReg[i-1].port_b2);
  end for;
  connect(ducMan_a.port_b, hexReg[1].port_a2);
  connect(hexReg[nReg].port_b2, ducMan_b.port_b);
  connect(pipMan_a.port_b, hexReg[1].port_a1);
  connect(hexReg[nReg].port_b1, pipMan_b.port_b);
  connect(pipMan_b.port_a, port_b1);
  connect(ducMan_b.port_a, port_b2);
  for i in 1:2:nReg loop

  // header after first hex register
    connect(hexReg[i].port_b1, hea1[(i+1)/2].port_a);
    connect(hea1[(i+1)/2].port_b, hexReg[i+1].port_b1);
  end for;
  // header after 2nd hex register
  for i in 2:2:(nReg-1) loop
    connect(hexReg[i].port_a1, hea2[i/2].port_a);
    connect(hea2[i/2].port_b, hexReg[i+1].port_a1);
  end for;
  connect(masFloSen_1.m_flow, hA.m1_flow);
  connect(port_a2, masFloSen_2.port_a);
  connect(masFloSen_2.port_b, temSen_2.port_a);
  connect(temSen_2.port_b, ducMan_a.port_a);
  connect(temSen_2.T, hA.T_2);
  connect(masFloSen_2.m_flow, hA.m2_flow);
  connect(hA.hA_1, gai_1.u);
  connect(hA.hA_2, gai_2.u);
  for i in 1:nReg loop
    connect(gai_1.y, hexReg[i].Gc_1);
    connect(gai_2.y, hexReg[i].Gc_2);
  end for;
  connect(port_a1, masFloSen_1.port_a);
  connect(masFloSen_1.port_b, temSen_1.port_a);
  connect(temSen_1.port_b, pipMan_a.port_a);
  connect(temSen_1.T, hA.T_1);
end DryCoilDiscretized;







Buildings.Fluid.HeatExchangers.WetCoilDiscretized
Buildings.Fluid.HeatExchangers.WetCoilDiscretized

Coil with discretization along the flow paths and humidity condensation

Buildings.Fluid.HeatExchangers.WetCoilDiscretized

Information





Model of a discretized coil with humidity condensation.
This model is identical to 

Buildings.Fluid.HeatExchangers.DryCoilDiscretized
but in addition, the mass transfer from fluid 2 to the metal is computed.
The mass transfer is computed using a similarity law between
heat and mass transfer, as implemented by the model

Buildings.Fluid.HeatExchangers.BaseClasses.MassExchange. 
See this model for details.




This model can only be used with medium models that
implement the function enthalpyOfLiquid and that contain
an integer variable Water whose value is the element number where
the water vapor is stored in the species concentration vector. Examples for
such media are

Buildings.Media.PerfectGases.MoistAir and

Modelica.Media.Air.MoistAir.




Extends from DryCoilDiscretized (Coil with discretization along the flow paths and no humidity condensation).

Parameters




TypeNameDefaultDescription


replaceable package Medium1PartialMediumMedium 1 in the component


replaceable package Medium2PartialMediumMedium 2 in the component


Nominal condition


MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]


MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp1_nominal Pressure [Pa]


Pressuredp2_nominal Pressure [Pa]


ThermalConductanceUA_nominal Thermal conductance at nominal flow, used to compute heat capacity [W/K]


Timetau120Time constant at nominal flow for medium 1 [s]


Timetau21Time constant at nominal flow for medium 2 [s]


Timetau_m20Time constant of metal at nominal UA value [s]


Initialization


MassFlowRatem1_flow.start0Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]


Pressuredp1.start0Pressure difference between port_a1 and port_b1 [Pa]


MassFlowRatem2_flow.start0Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]


Pressuredp2.start0Pressure difference between port_a2 and port_b2 [Pa]


MassFlowRatemStart_flow_a1m1_flow_nominalGuess value for mass flow rate at port_a1 [kg/s]


MassFlowRatemStart_flow_a2m2_flow_nominalGuess value for mass flow rate at port_a2 [kg/s]


Geometry


IntegernReg2Number of registers


IntegernPipPar3Number of parallel pipes in each register


IntegernPipSeg4Number of pipe segments per register used for discretization


Lengthdh10.025Hydraulic diameter for a single pipe [m]


Lengthdh21Hydraulic diameter for duct [m]


Assumptions


BooleanallowFlowReversal1system.allowFlowReversal= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)


BooleanallowFlowReversal2system.allowFlowReversal= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)


Dynamics


DynamicsenergyDynamics1Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 1


DynamicsenergyDynamics2Modelica.Fluid.Types.Dynamic...Default formulation of energy balances for volume 2


DynamicsductConnectionDynamicsModelica.Fluid.Types.Dynamic...Default formulation of energy balances for duct connection


Lengthdl0.3Length of mixing volume for duct connection [m]


Initialization


SpecificEnthalpyh_outflow_a1_startMedium1.h_defaultStart value for enthalpy flowing out of port a1 [J/kg]


SpecificEnthalpyh_outflow_b1_startMedium1.h_defaultStart value for enthalpy flowing out of port b1 [J/kg]


SpecificEnthalpyh_outflow_a2_startMedium2.h_defaultStart value for enthalpy flowing out of port a2 [J/kg]


SpecificEnthalpyh_outflow_b2_startMedium2.h_defaultStart value for enthalpy flowing out of port b2 [J/kg]


Advanced


MassFlowRatem1_flow_small1E-4*m1_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


MassFlowRatem2_flow_small1E-4*m2_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Booleanuse_dh1falseSet to true to specify hydraulic diameter for pipe pressure drop


Booleanuse_dh2falseSet to true to specify hydraulic diameter for duct pressure drop)


RealReC_14000Reynolds number where transition to turbulent starts inside pipes


RealReC_24000Reynolds number where transition to turbulent starts inside ducts


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Booleanshow_Tfalse= true, if actual temperature at port is computed (may lead to events)


Flow resistance


Medium 1


Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar


Medium 2


Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar


Heat transfer


BooleanwaterSideFlowDependentfalseSet to false to make water-side hA independent of mass flow rate


BooleanairSideFlowDependentfalseSet to false to make air-side hA independent of mass flow rate


BooleanwaterSideTemperatureDependentfalseSet to false to make water-side hA independent of temperature




Connectors




TypeNameDescription


FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)


FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)


FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)




Modelica definition


model WetCoilDiscretized 
  "Coil with discretization along the flow paths and humidity condensation"
  // When replacing the volume, the Medium is constrained so that the enthalpyOfLiquid
  // function is known. Otherwise, checkModel(...) will fail
  extends DryCoilDiscretized(final allowCondensation=true,
  each hexReg(ele(redeclare each Buildings.Fluid.MixingVolumes.MixingVolumeMoistAir
          vol2(
          final use_HeatTransfer = true,
          medium(T(stateSelect=StateSelect.never))))));

end WetCoilDiscretized;







Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed
Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed

Heater or cooler with prescribed heat flow rate

Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed

Information





Model for an ideal heater or cooler with prescribed heat flow rate to the medium.




This model adds heat in the amount of Q_flow = u Q_flow_nominal to the medium.
The input signal u and the nominal heat flow rate Q_flow_nominal 
can be positive or negative.




Note that for non-zero Q_flow,
if the mass flow rate tends to zero, the temperature difference over this 
component tends to infinity.
Hence, using a proper control for u is essential when using this component.




Extends from Buildings.Fluid.Interfaces.PartialStaticTwoPortHeatMassTransfer (Partial model transporting fluid between two ports without storing mass or energy).

Parameters




TypeNameDefaultDescription


replaceable package MediumPartialMediumMedium in the component


HeatFlowRateQ_flow_nominal Heat flow rate at u=1, positive for heating [W]


Nominal condition


MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]


Pressuredp_nominal Pressure [Pa]


Initialization


MassFlowRatem_flow.start0Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]


Pressuredp.start0Pressure difference between port_a and port_b [Pa]


Assumptions


BooleanallowFlowReversalsystem.allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)


Advanced


MassFlowRatem_flow_small1E-4*m_flow_nominalSmall mass flow rate for regularization of zero flow [kg/s]


Diagnostics


Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed


Booleanshow_Tfalse= true, if actual temperature at port is computed (may lead to events)


Flow resistance


Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)


BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate


RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar




Connectors




TypeNameDescription


FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)


FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)


input RealInputuControl input




Modelica definition


model HeaterCoolerPrescribed 
  "Heater or cooler with prescribed heat flow rate"
  extends Buildings.Fluid.Interfaces.PartialStaticTwoPortHeatMassTransfer(
    sensibleOnly=true);

  parameter Modelica.SIunits.HeatFlowRate Q_flow_nominal 
    "Heat flow rate at u=1, positive for heating";
  Modelica.Blocks.Interfaces.RealInput u "Control input";
equation 
  Q_flow = Q_flow_nominal * u;
  mXi_flow = zeros(Medium.nXi); // no mass added or removed (sensible heat only)
end HeaterCoolerPrescribed;





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