Buildings.Fluid.HeatExchangers

Information

Package Content

Name	Description
CoolingTowers	Package with cooling tower models
Radiators	Package with radiators models for hydronic space heating systems
ConstantEffectiveness	Heat exchanger with constant effectiveness
DryEffectivenessNTU	Heat exchanger with effectiveness - NTU relation and no moisture condensation
DryCoilCounterFlow	Counterflow coil with discretization along the flow paths and without humidity condensation
WetCoilCounterFlow	Counterflow coil with discretization along the flow paths and humidity condensation
DryCoilDiscretized	Coil with discretization along the flow paths and no humidity condensation
WetCoilDiscretized	Coil with discretization along the flow paths and humidity condensation
HeaterCoolerPrescribed	Heater or cooler with prescribed heat flow rate
Examples	Collection of models that illustrate model use and test models
BaseClasses	Package with base classes for heat exchanger models

Buildings.Fluid.HeatExchangers.ConstantEffectiveness

Information

Model for a heat exchanger with constant effectiveness.

This model transfers heat in the amount of

Q = Q_max ε,

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

Type	Name	Default	Description
replaceable package Medium1		PartialMedium	Medium 1 in the component
replaceable package Medium2		PartialMedium	Medium 2 in the component
Real	eps		Heat exchanger effectiveness [1]
Nominal condition
MassFlowRate	m1_flow_nominal		Nominal mass flow rate [kg/s]
MassFlowRate	m2_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp1_nominal		Pressure [Pa]
Pressure	dp2_nominal		Pressure [Pa]
Initialization
MassFlowRate	m1_flow.start	0	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]
Pressure	dp1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m2_flow.start	0	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]
Pressure	dp2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
Assumptions
Boolean	allowFlowReversal1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Initialization
SpecificEnthalpy	h_outflow_a1_start	Medium1.h_default	Start value for enthalpy flowing out of port a1 [J/kg]
SpecificEnthalpy	h_outflow_b1_start	Medium1.h_default	Start value for enthalpy flowing out of port b1 [J/kg]
SpecificEnthalpy	h_outflow_a2_start	Medium2.h_default	Start value for enthalpy flowing out of port a2 [J/kg]
SpecificEnthalpy	h_outflow_b2_start	Medium2.h_default	Start value for enthalpy flowing out of port b2 [J/kg]
Advanced
MassFlowRate	m1_flow_small	1E-4*m1_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m2_flow_small	1E-4*m2_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Flow resistance
Medium 1
Boolean	from_dp1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1	0.1	Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Boolean	from_dp2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2	0.1	Fraction of nominal flow rate where flow transitions to laminar

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid 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(start=0.8, min=0, max=1, unit="1") 
    "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

Information

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

Q = Q_max ε
&epsilon = f(NTU, Z, flowRegime),

The flow regimes depend on the heat exchanger configuration. All configurations defined in Buildings.Fluid.Types.HeatExchangerConfiguration are supported.

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

Type	Name	Default	Description
replaceable package Medium1		PartialMedium	Medium 1 in the component
replaceable package Medium2		PartialMedium	Medium 2 in the component
HeatExchangerConfiguration	configuration		Heat exchanger configuration
Real	r_nominal	2/3	Ratio between air-side and water-side convective heat transfer (hA-value) at nominal condition
Nominal condition
MassFlowRate	m1_flow_nominal		Nominal mass flow rate [kg/s]
MassFlowRate	m2_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp1_nominal		Pressure [Pa]
Pressure	dp2_nominal		Pressure [Pa]
HeatFlowRate	Q_flow_nominal		Nominal heat transfer [W]
Temperature	T_a1_nominal		Nominal temperature at port a1 [K]
Temperature	T_a2_nominal		Nominal temperature at port a2 [K]
Initialization
MassFlowRate	m1_flow.start	0	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]
Pressure	dp1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m2_flow.start	0	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]
Pressure	dp2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
Assumptions
Boolean	allowFlowReversal1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Initialization
SpecificEnthalpy	h_outflow_a1_start	Medium1.h_default	Start value for enthalpy flowing out of port a1 [J/kg]
SpecificEnthalpy	h_outflow_b1_start	Medium1.h_default	Start value for enthalpy flowing out of port b1 [J/kg]
SpecificEnthalpy	h_outflow_a2_start	Medium2.h_default	Start value for enthalpy flowing out of port a2 [J/kg]
SpecificEnthalpy	h_outflow_b2_start	Medium2.h_default	Start value for enthalpy flowing out of port b2 [J/kg]
Advanced
MassFlowRate	m1_flow_small	1E-4*m1_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m2_flow_small	1E-4*m2_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Flow resistance
Medium 1
Boolean	from_dp1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1	0.1	Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Boolean	from_dp2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2	0.1	Fraction of nominal flow rate where flow transitions to laminar

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)

Modelica definition

model DryEffectivenessNTU 
  "Heat exchanger with effectiveness - NTU relation and no 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

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

Type	Name	Default	Description
replaceable package Medium1		PartialMedium	Medium 1 in the component
replaceable package Medium2		PartialMedium	Medium 2 in the component
Nominal condition
MassFlowRate	m1_flow_nominal		Nominal mass flow rate [kg/s]
MassFlowRate	m2_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp1_nominal		Pressure [Pa]
Pressure	dp2_nominal		Pressure [Pa]
ThermalConductance	UA_nominal		Thermal conductance at nominal flow, used to compute heat capacity [W/K]
Real	r_nominal	2/3	Ratio between air-side and water-side convective heat transfer coefficient
Time	tau1	20	Time constant at nominal flow for medium 1 [s]
Time	tau2	1	Time constant at nominal flow for medium 2 [s]
Time	tau_m	20	Time constant of metal at nominal UA value [s]
Initialization
MassFlowRate	m1_flow.start	0	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]
Pressure	dp1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m2_flow.start	0	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]
Pressure	dp2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
Geometry
Integer	nEle	4	Number of pipe segments used for discretization
Assumptions
Boolean	allowFlowReversal1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics1	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 1
Dynamics	energyDynamics2	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 2
Initialization
SpecificEnthalpy	h_outflow_a1_start	Medium1.h_default	Start value for enthalpy flowing out of port a1 [J/kg]
SpecificEnthalpy	h_outflow_b1_start	Medium1.h_default	Start value for enthalpy flowing out of port b1 [J/kg]
SpecificEnthalpy	h_outflow_a2_start	Medium2.h_default	Start value for enthalpy flowing out of port a2 [J/kg]
SpecificEnthalpy	h_outflow_b2_start	Medium2.h_default	Start value for enthalpy flowing out of port b2 [J/kg]
Advanced
MassFlowRate	m1_flow_small	1E-4*m1_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m2_flow_small	1E-4*m2_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	true	= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Medium 1
Boolean	computeFlowResistance1	false	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1	0.1	Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Boolean	computeFlowResistance2	false	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2	0.1	Fraction of nominal flow rate where flow transitions to laminar
Heat transfer
Boolean	waterSideFlowDependent	true	Set to false to make water-side hA independent of mass flow rate
Boolean	airSideFlowDependent	true	Set to false to make air-side hA independent of mass flow rate
Boolean	waterSideTemperatureDependent	false	Set to false to make water-side hA independent of temperature
Boolean	airSideTemperatureDependent	false	Set to false to make air-side hA independent of temperature

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid 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 without 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,
    allowFlowReversal=allowFlowReversal1,
    m_flow_nominal=m1_flow_nominal) "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,
    final allowFlowReversal=allowFlowReversal2,
    m_flow_nominal=m2_flow_nominal) "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

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 without humidity condensation).

Parameters

Type	Name	Default	Description
replaceable package Medium1		PartialMedium	Medium 1 in the component
replaceable package Medium2		PartialMedium	Medium 2 in the component
Nominal condition
MassFlowRate	m1_flow_nominal		Nominal mass flow rate [kg/s]
MassFlowRate	m2_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp1_nominal		Pressure [Pa]
Pressure	dp2_nominal		Pressure [Pa]
ThermalConductance	UA_nominal		Thermal conductance at nominal flow, used to compute heat capacity [W/K]
Real	r_nominal	2/3	Ratio between air-side and water-side convective heat transfer coefficient
Time	tau1	20	Time constant at nominal flow for medium 1 [s]
Time	tau2	1	Time constant at nominal flow for medium 2 [s]
Time	tau_m	20	Time constant of metal at nominal UA value [s]
Initialization
MassFlowRate	m1_flow.start	0	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]
Pressure	dp1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m2_flow.start	0	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]
Pressure	dp2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
Geometry
Integer	nEle	4	Number of pipe segments used for discretization
Assumptions
Boolean	allowFlowReversal1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics1	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 1
Dynamics	energyDynamics2	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 2
Initialization
SpecificEnthalpy	h_outflow_a1_start	Medium1.h_default	Start value for enthalpy flowing out of port a1 [J/kg]
SpecificEnthalpy	h_outflow_b1_start	Medium1.h_default	Start value for enthalpy flowing out of port b1 [J/kg]
SpecificEnthalpy	h_outflow_a2_start	Medium2.h_default	Start value for enthalpy flowing out of port a2 [J/kg]
SpecificEnthalpy	h_outflow_b2_start	Medium2.h_default	Start value for enthalpy flowing out of port b2 [J/kg]
Advanced
MassFlowRate	m1_flow_small	1E-4*m1_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m2_flow_small	1E-4*m2_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	true	= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Medium 1
Boolean	from_dp1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1	0.1	Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Boolean	from_dp2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2	0.1	Fraction of nominal flow rate where flow transitions to laminar
Heat transfer
Boolean	waterSideFlowDependent	true	Set to false to make water-side hA independent of mass flow rate
Boolean	airSideFlowDependent	true	Set to false to make air-side hA independent of mass flow rate
Boolean	waterSideTemperatureDependent	false	Set to false to make water-side hA independent of temperature
Boolean	airSideTemperatureDependent	false	Set to false to make air-side hA independent of temperature

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid 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));

  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

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

Type	Name	Default	Description
replaceable package Medium1		PartialMedium	Medium 1 in the component
replaceable package Medium2		PartialMedium	Medium 2 in the component
Nominal condition
MassFlowRate	m1_flow_nominal		Nominal mass flow rate [kg/s]
MassFlowRate	m2_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp1_nominal		Pressure [Pa]
Pressure	dp2_nominal		Pressure [Pa]
ThermalConductance	UA_nominal		Thermal conductance at nominal flow, used to compute heat capacity [W/K]
Time	tau1	20	Time constant at nominal flow for medium 1 [s]
Time	tau2	1	Time constant at nominal flow for medium 2 [s]
Time	tau_m	20	Time constant of metal at nominal UA value [s]
Initialization
MassFlowRate	m1_flow.start	0	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]
Pressure	dp1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m2_flow.start	0	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]
Pressure	dp2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
MassFlowRate	mStart_flow_a1	m1_flow_nominal	Guess value for mass flow rate at port_a1 [kg/s]
MassFlowRate	mStart_flow_a2	m2_flow_nominal	Guess value for mass flow rate at port_a2 [kg/s]
Geometry
Integer	nReg	2	Number of registers
Integer	nPipPar	3	Number of parallel pipes in each register
Integer	nPipSeg	4	Number of pipe segments per register used for discretization
Length	dh1	0.025	Hydraulic diameter for a single pipe [m]
Length	dh2	1	Hydraulic diameter for duct [m]
Assumptions
Boolean	allowFlowReversal1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics1	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 1
Dynamics	energyDynamics2	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 2
Dynamics	ductConnectionDynamics	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for duct connection
Length	dl	0.3	Length of mixing volume for duct connection [m]
Initialization
SpecificEnthalpy	h_outflow_a1_start	Medium1.h_default	Start value for enthalpy flowing out of port a1 [J/kg]
SpecificEnthalpy	h_outflow_b1_start	Medium1.h_default	Start value for enthalpy flowing out of port b1 [J/kg]
SpecificEnthalpy	h_outflow_a2_start	Medium2.h_default	Start value for enthalpy flowing out of port a2 [J/kg]
SpecificEnthalpy	h_outflow_b2_start	Medium2.h_default	Start value for enthalpy flowing out of port b2 [J/kg]
Advanced
MassFlowRate	m1_flow_small	1E-4*m1_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m2_flow_small	1E-4*m2_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	use_dh1	false	Set to true to specify hydraulic diameter for pipe pressure drop
Boolean	use_dh2	false	Set to true to specify hydraulic diameter for duct pressure drop)
Real	ReC_1	4000	Reynolds number where transition to turbulent starts inside pipes
Real	ReC_2	4000	Reynolds number where transition to turbulent starts inside ducts
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	false	= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Medium 1
Boolean	computeFlowResistance1	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1	0.1	Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Boolean	computeFlowResistance2	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2	0.1	Fraction of nominal flow rate where flow transitions to laminar
Heat transfer
Boolean	waterSideFlowDependent	false	Set to false to make water-side hA independent of mass flow rate
Boolean	airSideFlowDependent	false	Set to false to make air-side hA independent of mass flow rate
Boolean	waterSideTemperatureDependent	false	Set to false to make water-side hA independent of temperature

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid 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,
    final allowFlowReversal=allowFlowReversal1,
    m_flow_nominal=m1_flow_nominal) "Temperature sensor";
  Buildings.Fluid.Sensors.MassFlowRate masFloSen_1(redeclare package Medium =
        Medium1, final allowFlowReversal=allowFlowReversal1) 
    "Mass flow rate sensor";
  Buildings.Fluid.Sensors.TemperatureTwoPort temSen_2(
                                              redeclare package Medium =
        Medium2,
    m_flow_nominal=m2_flow_nominal,
    final allowFlowReversal=allowFlowReversal2) "Temperature sensor";
  Buildings.Fluid.Sensors.MassFlowRate masFloSen_2(redeclare package Medium =
        Medium2, final allowFlowReversal=allowFlowReversal2) 
    "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

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

Type	Name	Default	Description
replaceable package Medium1		PartialMedium	Medium 1 in the component
replaceable package Medium2		PartialMedium	Medium 2 in the component
Nominal condition
MassFlowRate	m1_flow_nominal		Nominal mass flow rate [kg/s]
MassFlowRate	m2_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp1_nominal		Pressure [Pa]
Pressure	dp2_nominal		Pressure [Pa]
ThermalConductance	UA_nominal		Thermal conductance at nominal flow, used to compute heat capacity [W/K]
Time	tau1	20	Time constant at nominal flow for medium 1 [s]
Time	tau2	1	Time constant at nominal flow for medium 2 [s]
Time	tau_m	20	Time constant of metal at nominal UA value [s]
Initialization
MassFlowRate	m1_flow.start	0	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s]
Pressure	dp1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m2_flow.start	0	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s]
Pressure	dp2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
MassFlowRate	mStart_flow_a1	m1_flow_nominal	Guess value for mass flow rate at port_a1 [kg/s]
MassFlowRate	mStart_flow_a2	m2_flow_nominal	Guess value for mass flow rate at port_a2 [kg/s]
Geometry
Integer	nReg	2	Number of registers
Integer	nPipPar	3	Number of parallel pipes in each register
Integer	nPipSeg	4	Number of pipe segments per register used for discretization
Length	dh1	0.025	Hydraulic diameter for a single pipe [m]
Length	dh2	1	Hydraulic diameter for duct [m]
Assumptions
Boolean	allowFlowReversal1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics1	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 1
Dynamics	energyDynamics2	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for volume 2
Dynamics	ductConnectionDynamics	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances for duct connection
Length	dl	0.3	Length of mixing volume for duct connection [m]
Initialization
SpecificEnthalpy	h_outflow_a1_start	Medium1.h_default	Start value for enthalpy flowing out of port a1 [J/kg]
SpecificEnthalpy	h_outflow_b1_start	Medium1.h_default	Start value for enthalpy flowing out of port b1 [J/kg]
SpecificEnthalpy	h_outflow_a2_start	Medium2.h_default	Start value for enthalpy flowing out of port a2 [J/kg]
SpecificEnthalpy	h_outflow_b2_start	Medium2.h_default	Start value for enthalpy flowing out of port b2 [J/kg]
Advanced
MassFlowRate	m1_flow_small	1E-4*m1_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m2_flow_small	1E-4*m2_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	use_dh1	false	Set to true to specify hydraulic diameter for pipe pressure drop
Boolean	use_dh2	false	Set to true to specify hydraulic diameter for duct pressure drop)
Real	ReC_1	4000	Reynolds number where transition to turbulent starts inside pipes
Real	ReC_2	4000	Reynolds number where transition to turbulent starts inside ducts
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	false	= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Medium 1
Boolean	from_dp1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1	0.1	Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Boolean	from_dp2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2	0.1	Fraction of nominal flow rate where flow transitions to laminar
Heat transfer
Boolean	waterSideFlowDependent	false	Set to false to make water-side hA independent of mass flow rate
Boolean	airSideFlowDependent	false	Set to false to make air-side hA independent of mass flow rate
Boolean	waterSideTemperatureDependent	false	Set to false to make water-side hA independent of temperature

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid 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 final Buildings.Fluid.MixingVolumes.MixingVolumeMoistAir
          vol2(
          medium(T(stateSelect=StateSelect.never))))),
    temSen_1(m_flow_nominal=m1_flow_nominal),
    temSen_2(m_flow_nominal=m2_flow_nominal));

end WetCoilDiscretized;

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

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
HeatFlowRate	Q_flow_nominal		Heat flow rate at u=1, positive for heating [W]
Nominal condition
MassFlowRate	m_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp_nominal		Pressure [Pa]
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressure	dp.start	0	Pressure difference between port_a and port_b [Pa]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*m_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	false	= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
input RealInput	u	Control 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;