Modelica.Fluid.Examples.HeatExchanger.BaseClasses

Information

Package Content

Name	Description
BasicHX	Simple heat exchanger model
WallConstProps	Pipe wall with capacitance, assuming 1D heat conduction and constant material properties

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX

Information

Simple model of a heat exchanger consisting of two pipes and one wall in between. For both fluids geometry parameters, such as heat transfer area and cross section as well as heat transfer and pressure drop correlations may be chosen. The flow scheme may be concurrent or counterflow, defined by the respective flow directions of the fluids entering the component. The design flow direction with positive m_flow variables is counterflow.

Parameters

Type	Name	Default	Description
Integer	nNodes	2	Spatial segmentation
Length	length		Length of flow path for both fluids [m]
Length	s_wall		Wall thickness [m]
Boolean	use_HeatTransfer	false	= true to use the HeatTransfer_1/_2 model
Fluid 1
Area	crossArea_1		Cross sectional area [m2]
Length	perimeter_1		Flow channel perimeter [m]
Area	area_h_1		Heat transfer area [m2]
Length	roughness_1	2.5e-5	Absolute roughness of pipe (default = smooth steel pipe) [m]
Fluid 2
Area	crossArea_2		Cross sectional area [m2]
Length	perimeter_2		Flow channel perimeter [m]
Area	area_h_2		Heat transfer area [m2]
Length	roughness_2	2.5e-5	Absolute roughness of pipe (default = smooth steel pipe) [m]
Solid material properties
Density	rho_wall		Density of wall material [kg/m3]
SpecificHeatCapacity	c_wall		Specific heat capacity of wall material [J/(kg.K)]
ThermalConductivity	k_wall		Thermal conductivity of wall material [W/(m.K)]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	allow flow reversal, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics	system.energyDynamics	Formulation of energy balance
Dynamics	massDynamics	system.massDynamics	Formulation of mass balance
Dynamics	momentumDynamics	system.momentumDynamics	Formulation of momentum balance, if pressureLoss options available
Initialization
Wall
Temperature	Twall_start		Start value of wall temperature [K]
Temperature	dT		Start value for pipe_1.T - pipe_2.T [K]
Boolean	use_T_start	true	Use T_start if true, otherwise h_start
Fluid 1
AbsolutePressure	p_a_start1	Medium_1.p_default	Start value of pressure [Pa]
AbsolutePressure	p_b_start1	Medium_1.p_default	Start value of pressure [Pa]
Temperature	T_start_1	if use_T_start then Medium_1...	Start value of temperature [K]
SpecificEnthalpy	h_start_1	if use_T_start then Medium_1...	Start value of specific enthalpy [J/kg]
MassFraction	X_start_1[Medium_1.nX]	Medium_1.X_default	Start value of mass fractions m_i/m [kg/kg]
MassFlowRate	m_flow_start_1	system.m_flow_start	Start value of mass flow rate [kg/s]
Fluid 2
AbsolutePressure	p_a_start2	Medium_2.p_default	Start value of pressure [Pa]
AbsolutePressure	p_b_start2	Medium_2.p_default	Start value of pressure [Pa]
Temperature	T_start_2	if use_T_start then Medium_2...	Start value of temperature [K]
SpecificEnthalpy	h_start_2	if use_T_start then Medium_2...	Start value of specific enthalpy [J/kg]
MassFraction	X_start_2[Medium_2.nX]	Medium_2.X_default	Start value of mass fractions m_i/m [kg/kg]
MassFlowRate	m_flow_start_2	system.m_flow_start	Start value of mass flow rate [kg/s]

Connectors

Type	Name	Description
FluidPort_b	port_b1
FluidPort_a	port_a1
FluidPort_b	port_b2
FluidPort_a	port_a2

Modelica definition

model BasicHX "Simple heat exchanger model"
  outer Modelica.Fluid.System system "System properties";
  //General
  parameter Integer nNodes(min=1) = 2 "Spatial segmentation";
  replaceable package Medium_1 = Modelica.Media.Water.StandardWater constrainedby 
    Modelica.Media.Interfaces.PartialMedium "Fluid 1";
  replaceable package Medium_2 = Modelica.Media.Water.StandardWater constrainedby 
    Modelica.Media.Interfaces.PartialMedium "Fluid 2";
  parameter SI.Area crossArea_1 "Cross sectional area";
  parameter SI.Area crossArea_2 "Cross sectional area";
  parameter SI.Length perimeter_1 "Flow channel perimeter";
  parameter SI.Length perimeter_2 "Flow channel perimeter";
  parameter SI.Length length(min=0) "Length of flow path for both fluids";
  parameter SI.Length s_wall(min=0) "Wall thickness";
  parameter Boolean use_HeatTransfer = false 
    "= true to use the HeatTransfer_1/_2 model";

  // Heat transfer
  replaceable model HeatTransfer_1 =
      Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.IdealFlowHeatTransfer
    constrainedby 
    Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.PartialFlowHeatTransfer 
    "Heat transfer model";

  replaceable model HeatTransfer_2 =
      Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.IdealFlowHeatTransfer
    constrainedby 
    Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.PartialFlowHeatTransfer 
    "Heat transfer model";

  parameter SI.Area area_h_1 "Heat transfer area";
  parameter SI.Area area_h_2 "Heat transfer area";
 //Wall
  parameter SI.Density rho_wall "Density of wall material";
  parameter SI.SpecificHeatCapacity c_wall 
    "Specific heat capacity of wall material";
  final parameter SI.Area area_h=(area_h_1 + area_h_2)/2 "Heat transfer area";
  final parameter SI.Mass m_wall=rho_wall*area_h*s_wall "Wall mass";
  parameter SI.ThermalConductivity k_wall 
    "Thermal conductivity of wall material";

  // Assumptions
  parameter Boolean allowFlowReversal = system.allowFlowReversal 
    "allow flow reversal, false restricts to design direction (port_a -> port_b)";
  parameter Types.Dynamics energyDynamics=system.energyDynamics 
    "Formulation of energy balance";
  parameter Types.Dynamics massDynamics=system.massDynamics 
    "Formulation of mass balance";
  parameter Types.Dynamics momentumDynamics=system.momentumDynamics 
    "Formulation of momentum balance, if pressureLoss options available";

  //Initialization pipe 1
  parameter SI.Temperature Twall_start "Start value of wall temperature";
  parameter SI.Temperature dT "Start value for pipe_1.T - pipe_2.T";
  parameter Boolean use_T_start=true "Use T_start if true, otherwise h_start";
  parameter Medium_1.AbsolutePressure p_a_start1=Medium_1.p_default 
    "Start value of pressure";
  parameter Medium_1.AbsolutePressure p_b_start1=Medium_1.p_default 
    "Start value of pressure";
  parameter Medium_1.Temperature T_start_1=if use_T_start then Medium_1.
      T_default else Medium_1.temperature_phX(
        (p_a_start1 + p_b_start1)/2,
        h_start_1,
        X_start_1) "Start value of temperature";
  parameter Medium_1.SpecificEnthalpy h_start_1=if use_T_start then Medium_1.specificEnthalpy_pTX(
        (p_a_start1 + p_b_start1)/2,
        T_start_1,
        X_start_1[1:Medium_1.nXi]) else Medium_1.h_default 
    "Start value of specific enthalpy";
  parameter Medium_1.MassFraction X_start_1[Medium_1.nX]=Medium_1.X_default 
    "Start value of mass fractions m_i/m";
  parameter Medium_1.MassFlowRate m_flow_start_1 = system.m_flow_start 
    "Start value of mass flow rate";
  //Initialization pipe 2

  parameter Medium_2.AbsolutePressure p_a_start2=Medium_2.p_default 
    "Start value of pressure";
  parameter Medium_2.AbsolutePressure p_b_start2=Medium_2.p_default 
    "Start value of pressure";
  parameter Medium_2.Temperature T_start_2=if use_T_start then Medium_2.
      T_default else Medium_2.temperature_phX(
        (p_a_start2 + p_b_start2)/2,
        h_start_2,
        X_start_2) "Start value of temperature";
  parameter Medium_2.SpecificEnthalpy h_start_2=if use_T_start then Medium_2.specificEnthalpy_pTX(
        (p_a_start2 + p_b_start2)/2,
        T_start_2,
        X_start_2[1:Medium_2.nXi]) else Medium_2.h_default 
    "Start value of specific enthalpy";
  parameter Medium_2.MassFraction X_start_2[Medium_2.nX]=Medium_2.X_default 
    "Start value of mass fractions m_i/m";
  parameter Medium_2.MassFlowRate m_flow_start_2 = system.m_flow_start 
    "Start value of mass flow rate";

  //Pressure drop and heat transfer
  replaceable model FlowModel_1 =
      Modelica.Fluid.Pipes.BaseClasses.FlowModels.DetailedPipeFlow
    constrainedby 
    Modelica.Fluid.Pipes.BaseClasses.FlowModels.PartialStaggeredFlowModel 
    "Characteristic of wall friction";
  replaceable model FlowModel_2 =
      Modelica.Fluid.Pipes.BaseClasses.FlowModels.DetailedPipeFlow
    constrainedby 
    Modelica.Fluid.Pipes.BaseClasses.FlowModels.PartialStaggeredFlowModel 
    "Characteristic of wall friction";
  parameter SI.Length roughness_1=2.5e-5 
    "Absolute roughness of pipe (default = smooth steel pipe)";
  parameter SI.Length roughness_2=2.5e-5 
    "Absolute roughness of pipe (default = smooth steel pipe)";

  //Display variables
  SI.HeatFlowRate Q_flow_1 "Total heat flow rate of pipe 1";
  SI.HeatFlowRate Q_flow_2 "Total heat flow rate of pipe 2";

  BaseClasses.WallConstProps wall(
    rho_wall=rho_wall,
    c_wall=c_wall,
    T_start=Twall_start,
    k_wall=k_wall,
    dT=dT,
    s=s_wall,
    energyDynamics=energyDynamics,
    n=nNodes,
    area_h=(crossArea_1 + crossArea_2)/2);

  Modelica.Fluid.Pipes.DynamicPipe pipe_1(
    redeclare final package Medium = Medium_1,
    final isCircular=false,
    final diameter=0,
    final nNodes=nNodes,
    final allowFlowReversal=allowFlowReversal,
    final energyDynamics=energyDynamics,
    final massDynamics=massDynamics,
    final momentumDynamics=momentumDynamics,
    final length=length,
    final use_HeatTransfer=use_HeatTransfer,
    redeclare final model HeatTransfer = HeatTransfer_1,
    final use_T_start=use_T_start,
    final T_start=T_start_1,
    final h_start=h_start_1,
    final X_start=X_start_1,
    final m_flow_start=m_flow_start_1,
    final perimeter=perimeter_1,
    final crossArea=crossArea_1,
    final roughness=roughness_1,
    redeclare final model FlowModel = FlowModel_1);

  Modelica.Fluid.Pipes.DynamicPipe pipe_2(
    redeclare final package Medium = Medium_2,
    final nNodes=nNodes,
    final allowFlowReversal=allowFlowReversal,
    final energyDynamics=energyDynamics,
    final massDynamics=massDynamics,
    final momentumDynamics=momentumDynamics,
    final length=length,
    final isCircular=false,
    final diameter=0,
    final use_HeatTransfer=use_HeatTransfer,
    redeclare final model HeatTransfer = HeatTransfer_2,
    final use_T_start=use_T_start,
    final T_start=T_start_2,
    final h_start=h_start_2,
    final X_start=X_start_2,
    final m_flow_start=m_flow_start_2,
    final perimeter=perimeter_2,
    final crossArea=crossArea_2,
    final p_a_start=p_a_start1,
    final p_b_start=p_b_start2,
    final roughness=roughness_2,
    redeclare final model FlowModel = FlowModel_2);

  Modelica.Fluid.Interfaces.FluidPort_b port_b1(redeclare final package Medium
      = Medium_1);
  Modelica.Fluid.Interfaces.FluidPort_a port_a1(redeclare final package Medium
      = Medium_1);
  Modelica.Fluid.Interfaces.FluidPort_b port_b2(redeclare final package Medium
      = Medium_2);
  Modelica.Fluid.Interfaces.FluidPort_a port_a2(redeclare final package Medium
      = Medium_2);

equation 
  Q_flow_1 = sum(pipe_1.heatTransfer.Q_flows);
  Q_flow_2 = sum(pipe_2.heatTransfer.Q_flows);
  connect(pipe_2.port_b, port_b2);
  connect(pipe_1.port_b, port_b1);
  connect(pipe_1.port_a, port_a1);
  connect(pipe_2.port_a, port_a2);
  connect(wall.heatPort_b, pipe_1.heatPorts);
  connect(pipe_2.heatPorts[nNodes:-1:1], wall.heatPort_a[1:nNodes]);
end BasicHX;

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.WallConstProps

Information

Parameters

Type	Name	Default	Description
Integer	n	1	Segmentation perpendicular to heat conduction
Length	s		Wall thickness [m]
Area	area_h		Heat transfer area [m2]
Density	rho_wall		Density of wall material [kg/m3]
SpecificHeatCapacity	c_wall		Specific heat capacity of wall material [J/(kg.K)]
ThermalConductivity	k_wall		Thermal conductivity of wall material [W/(m.K)]
Mass	m[n]	fill(rho_wall*area_h*s/n, n)	Distribution of wall mass [kg]
Temperature	T_start		Wall temperature start value [K]
Temperature	dT		Start value for port_b.T - port_a.T [K]
Assumptions
Dynamics
Dynamics	energyDynamics	system.energyDynamics	Formulation of energy balance

Connectors

Type	Name	Description
HeatPort_a	heatPort_a[n]	Thermal port
HeatPort_a	heatPort_b[n]	Thermal port

Modelica definition

model WallConstProps 
  "Pipe wall with capacitance, assuming 1D heat conduction and constant material properties"
  parameter Integer n(min=1)=1 "Segmentation perpendicular to heat conduction";
//Geometry
  parameter SI.Length s "Wall thickness";
  parameter SI.Area area_h "Heat transfer area";
//Material properties
  parameter SI.Density rho_wall "Density of wall material";
  parameter SI.SpecificHeatCapacity c_wall 
    "Specific heat capacity of wall material";
  parameter SI.ThermalConductivity k_wall 
    "Thermal conductivity of wall material";
  parameter SI.Mass[n] m=fill(rho_wall*area_h*s/n,n) 
    "Distribution of wall mass";
//Initialization
  outer Modelica.Fluid.System system;
  parameter Types.Dynamics energyDynamics=system.energyDynamics 
    "Formulation of energy balance";
  parameter SI.Temperature T_start "Wall temperature start value";
  parameter SI.Temperature dT "Start value for port_b.T - port_a.T";
//Temperatures
  SI.Temperature[n] Tb(each start=T_start+0.5*dT);
  SI.Temperature[n] Ta(each start=T_start-0.5*dT);
  SI.Temperature[n] T(start=ones(n)*T_start, stateSelect=StateSelect.prefer) 
    "Wall temperature";
  Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a[n] heatPort_a 
    "Thermal port";
  Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a[n] heatPort_b 
    "Thermal port";

initial equation 
  if energyDynamics == Types.Dynamics.SteadyState then
    der(T) = zeros(n);
  elseif energyDynamics == Types.Dynamics.FixedInitial then
    T = ones(n)*T_start;
  end if;
equation 
  for i in 1:n loop
   assert(m[i]>0, "Wall has negative dimensions");
   if energyDynamics == Types.Dynamics.SteadyState then
     0 = heatPort_a[i].Q_flow + heatPort_b[i].Q_flow;
   else
     c_wall*m[i]*der(T[i]) = heatPort_a[i].Q_flow + heatPort_b[i].Q_flow;
   end if;
   heatPort_a[i].Q_flow=k_wall/s*(Ta[i]-T[i])*area_h/n;
   heatPort_b[i].Q_flow=k_wall/s*(Tb[i]-T[i])*area_h/n;
  end for;
  Ta=heatPort_a.T;
  Tb=heatPort_b.T;
end WallConstProps;

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX.HeatTransfer_1

Parameters

Type	Name	Default	Description
Ambient
CoefficientOfHeatTransfer	k	0	Heat transfer coefficient to ambient [W/(m2.K)]
Temperature	T_ambient	system.T_ambient	Ambient temperature [K]
Internal Interface
replaceable package Medium		PartialMedium	Medium in the component
Integer	n	1	Number of heat transfer segments
Boolean	use_k	false	= true to use k value for thermal isolation
Geometry
Real	nParallel		number of identical parallel flow devices

Connectors

Type	Name	Description
HeatPorts_a	heatPorts[n]	Heat port to component boundary

Modelica definition

replaceable model HeatTransfer_1 =
    Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.IdealFlowHeatTransfer
  constrainedby 
  Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.PartialFlowHeatTransfer 
  "Heat transfer model";

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX.FlowModel_1

Parameters

Type	Name	Default	Description
AbsolutePressure	dp_nominal	1e3*dp_small	Nominal pressure loss (for nominal models) [Pa]
MassFlowRate	m_flow_nominal	1e2*m_flow_small	Mass flow rate for dp_nominal (for nominal models) [kg/s]
Boolean	from_dp	momentumDynamics >= Types.Dy...	= true, use m_flow = f(dp), otherwise dp = f(m_flow)
AbsolutePressure	dp_small	system.dp_small	Within regularization if |dp| < dp_small (may be wider for large discontinuities in static head) [Pa]
MassFlowRate	m_flow_small	system.m_flow_small	Within regularization if |m_flows| < m_flow_small (may be wider for large discontinuities in static head) [kg/s]
Advanced
Boolean	useUpstreamScheme	true	= false to average upstream and downstream properties across flow segments
Boolean	use_Ib_flows	momentumDynamics <> Types.Dy...	= true to consider differences in flow of momentum through boundaries
Diagnostics
Boolean	show_Res	false	= true, if Reynolds numbers are included for plotting
Internal Interface
replaceable package Medium		PartialMedium	Medium in the component
Integer	n	2	Number of discrete flow volumes
Geometry
Real	nParallel		number of identical parallel flow devices
Static head
Acceleration	g	system.g	Constant gravity acceleration [m/s2]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (states[1] -> states[n+1])
Dynamics	momentumDynamics	system.momentumDynamics	Formulation of momentum balance
Initialization
MassFlowRate	m_flow_start	system.m_flow_start	Start value of mass flow rates [kg/s]
AbsolutePressure	p_a_start		Start value for p[1] at design inflow [Pa]
AbsolutePressure	p_b_start		Start value for p[n+1] at design outflow [Pa]

Modelica definition

replaceable model FlowModel_1 =
    Modelica.Fluid.Pipes.BaseClasses.FlowModels.DetailedPipeFlow
  constrainedby 
  Modelica.Fluid.Pipes.BaseClasses.FlowModels.PartialStaggeredFlowModel 
  "Characteristic of wall friction";

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX.HeatTransfer_2

Parameters

Type	Name	Default	Description
Ambient
CoefficientOfHeatTransfer	k	0	Heat transfer coefficient to ambient [W/(m2.K)]
Temperature	T_ambient	system.T_ambient	Ambient temperature [K]
Internal Interface
replaceable package Medium		PartialMedium	Medium in the component
Integer	n	1	Number of heat transfer segments
Boolean	use_k	false	= true to use k value for thermal isolation
Geometry
Real	nParallel		number of identical parallel flow devices

Connectors

Type	Name	Description
HeatPorts_a	heatPorts[n]	Heat port to component boundary

Modelica definition

replaceable model HeatTransfer_2 =
    Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.IdealFlowHeatTransfer
  constrainedby 
  Modelica.Fluid.Pipes.BaseClasses.HeatTransfer.PartialFlowHeatTransfer 
  "Heat transfer model";

Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX.FlowModel_2

Parameters

Type	Name	Default	Description
AbsolutePressure	dp_nominal	1e3*dp_small	Nominal pressure loss (for nominal models) [Pa]
MassFlowRate	m_flow_nominal	1e2*m_flow_small	Mass flow rate for dp_nominal (for nominal models) [kg/s]
Boolean	from_dp	momentumDynamics >= Types.Dy...	= true, use m_flow = f(dp), otherwise dp = f(m_flow)
AbsolutePressure	dp_small	system.dp_small	Within regularization if |dp| < dp_small (may be wider for large discontinuities in static head) [Pa]
MassFlowRate	m_flow_small	system.m_flow_small	Within regularization if |m_flows| < m_flow_small (may be wider for large discontinuities in static head) [kg/s]
Advanced
Boolean	useUpstreamScheme	true	= false to average upstream and downstream properties across flow segments
Boolean	use_Ib_flows	momentumDynamics <> Types.Dy...	= true to consider differences in flow of momentum through boundaries
Diagnostics
Boolean	show_Res	false	= true, if Reynolds numbers are included for plotting
Internal Interface
replaceable package Medium		PartialMedium	Medium in the component
Integer	n	2	Number of discrete flow volumes
Geometry
Real	nParallel		number of identical parallel flow devices
Static head
Acceleration	g	system.g	Constant gravity acceleration [m/s2]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (states[1] -> states[n+1])
Dynamics	momentumDynamics	system.momentumDynamics	Formulation of momentum balance
Initialization
MassFlowRate	m_flow_start	system.m_flow_start	Start value of mass flow rates [kg/s]
AbsolutePressure	p_a_start		Start value for p[1] at design inflow [Pa]
AbsolutePressure	p_b_start		Start value for p[n+1] at design outflow [Pa]

Modelica definition

replaceable model FlowModel_2 =
    Modelica.Fluid.Pipes.BaseClasses.FlowModels.DetailedPipeFlow
  constrainedby 
  Modelica.Fluid.Pipes.BaseClasses.FlowModels.PartialStaggeredFlowModel 
  "Characteristic of wall friction";