Modelica.Media.Examples

Demonstrate usage of property models (currently: simple tests)

Information


Examples

Physical properties for fluids are needed in so many different variants that a library can only provide models for the most common situations. With the following examples we are going to demonstrate how to use the existing packages and functions in Modelica.Media to customize these models for advanced applications. The high level functions try to abstract as much as possible form the fact that different media are based on different variables, e.g. ideal gases need pressure and temperature, while many refrigerants are based on Helmholtz functions of density and temperature, and many water proeprties are based on pressure and specific enthalpy. Medium properties are needed in control volumes in the dynamic state equations and in many thermodynamic state locations that are independent of the dynamic states of a control volume, e.g. at a wall temperature, an isentropic reference state or at a phase boundary. The general structure of the library is such that:

A small library of generic volume, pipe, pump and ambient models is provided in Modelica.Media.Examples.Tests.Components to demonstrate how fluid components should be implemented that are using Modelica.Media models. This library is also used to test all media models in Modelica.Media.Examples.Tests.MediaTestModels.

Extends from Modelica.Icons.Library (Icon for library).

Package Content

NameDescription
Modelica.Media.Examples.SimpleLiquidWater SimpleLiquidWater Example for Water.SimpleLiquidWater medium model
Modelica.Media.Examples.IdealGasH2O IdealGasH2O IdealGas H20 medium model
Modelica.Media.Examples.WaterIF97 WaterIF97 WaterIF97 medium model
Modelica.Media.Examples.MixtureGases MixtureGases Test gas mixtures
Modelica.Media.Examples.MoistAir MoistAir Ideal gas flue gas model
Modelica.Media.Examples.TwoPhaseWater TwoPhaseWater extension of the StandardWater package
Modelica.Media.Examples.TestOnly TestOnly examples for testing purposes: move for final version
Modelica.Media.Examples.Tests Tests Library to test that all media models simulate and fulfill the expected structural properties
Modelica.Media.Examples.SolveOneNonlinearEquation SolveOneNonlinearEquation Demonstrate how to solve one non-linear algebraic equation in one unknown


Modelica.Media.Examples.SimpleLiquidWater Modelica.Media.Examples.SimpleLiquidWater

Example for Water.SimpleLiquidWater medium model

Information



Extends from Modelica.Icons.Example (Icon for an example model).

Parameters

TypeNameDefaultDescription
VolumeV1Volume [m3]
EnthalpyFlowRateH_flow_ext1.e6Constant enthalpy flow rate into the volume [W]

Modelica definition

model SimpleLiquidWater 
  "Example for Water.SimpleLiquidWater medium model"

  import SI = Modelica.SIunits;
  extends Modelica.Icons.Example;
  parameter SI.Volume V=1 "Volume";
  parameter SI.EnthalpyFlowRate H_flow_ext=1.e6 
    "Constant enthalpy flow rate into the volume";

  package Medium = Water.ConstantPropertyLiquidWater (SpecificEnthalpy(max=1e6)) 
    "Medium model";
  Medium.BaseProperties medium(
    T(start=300,fixed=true));

  Medium.BaseProperties medium2;
  Medium.ThermodynamicState state;
  Real m_flow_ext2;
  Real der_p;
  Real der_T;

  SI.Mass m(start = 1.0);
  SI.InternalEnergy U;

  // Use type declarations from the Medium
  Medium.MassFlowRate m_flow_ext;
  Medium.DynamicViscosity eta=Medium.dynamicViscosity(medium);
  Medium.SpecificHeatCapacity cv=Medium.specificHeatCapacityCv(medium);
equation 
  medium.p = 1.0e5;
  m = medium.d*V;
  U = m*medium.u;

  // Mass balance
  der(m) = m_flow_ext;

  // Energy balance
  der(U) = H_flow_ext;

  // Smooth state
  medium2.p = 1e5*time/10;
  medium2.T = 330;
  m_flow_ext2 = time - 30;
  state = Medium.setSmoothState(m_flow_ext2, medium.state, medium2.state, 10);
  der_p = der(state.p);
  der_T = der(state.T);
end SimpleLiquidWater;

Modelica.Media.Examples.IdealGasH2O Modelica.Media.Examples.IdealGasH2O

IdealGas H20 medium model

Information


An example for using ideal gas properties and how to compute isentropic enthalpy changes. The function that is implemented is approximate, but usually very good: the second medium record medium2 is given to compare the approximation.

Extends from Modelica.Icons.Example (Icon for an example model).

Modelica definition

model IdealGasH2O "IdealGas H20 medium model"
  extends Modelica.Icons.Example;
  package Medium = IdealGases.SingleGases.H2O "Medium model";
  Medium.ThermodynamicState state "thermodynamic state record";
  Medium.ThermodynamicState state2;
  Medium.SpecificHeatCapacity cp=Medium.specificHeatCapacityCp(state);
  Medium.SpecificHeatCapacity cv=Medium.specificHeatCapacityCv(state);
  Medium.IsentropicExponent k=Medium.isentropicExponent(state);
  Medium.SpecificEntropy s=Medium.specificEntropy(state);
  //  Medium.SpecificEntropy s2=Medium.specificEntropy(state2);
  Medium.VelocityOfSound a=Medium.velocityOfSound(state);
  Real beta = Medium.isobaricExpansionCoefficient(state);
  Real gamma = Medium.isothermalCompressibility(state);
  Medium.SpecificEnthalpy h_is = Medium.isentropicEnthalpyApproximation(2.0, state);

  Medium.ThermodynamicState smoothState;
  Real m_flow_ext;
  Real der_p;
  Real der_T;

equation 
  state.p = 100000.0;
  state.T = 200 + 1000*time;
  state2.p = 2.0e5;
  state2.T = 500.0;
  //  s2 = s;

  // Smooth state
  m_flow_ext = time - 0.5;
  smoothState = Medium.setSmoothState(m_flow_ext, state, state2, 0.1);
  der_p = der(smoothState.p);
  der_T = der(smoothState.T);

end IdealGasH2O;

Modelica.Media.Examples.WaterIF97 Modelica.Media.Examples.WaterIF97

WaterIF97 medium model

Information



Extends from Modelica.Icons.Example (Icon for an example model).

Parameters

TypeNameDefaultDescription
VolumeFlowRatedV0.0Fixed time derivative of volume [m3/s]
MassFlowRatem_flow_ext0Fixed mass flow rate into volume [kg/s]
EnthalpyFlowRateH_flow_ext10000Fixed enthalpy flow rate into volume [W]

Modelica definition

model WaterIF97 "WaterIF97 medium model"
  extends Modelica.Icons.Example;
  package Medium = Water.StandardWater "Medium model";
  Medium.BaseProperties medium(
    p(start=1.e5, stateSelect=StateSelect.prefer),
    h(start=1.0e5, stateSelect=StateSelect.prefer),
    T(start = 275.0),
    d(start = 999.0));
  Modelica.SIunits.Volume V(start = 0.1);
  parameter Modelica.SIunits.VolumeFlowRate dV = 0.0 
    "Fixed time derivative of volume";
  parameter Medium.MassFlowRate m_flow_ext=0 "Fixed mass flow rate into volume";
  parameter Medium.EnthalpyFlowRate H_flow_ext=10000 
    "Fixed enthalpy flow rate into volume";
  Modelica.SIunits.Mass m "Mass of volume";
  Modelica.SIunits.InternalEnergy U "Internal energy of volume";

  Medium.ThermodynamicState state2;
  Medium.ThermodynamicState state;
  Real m_flow_ext2;
  Real der_p;
  Real der_T;

equation 
  der(V) = dV;
  m = medium.d*V;
  U = m*medium.u;

  // Mass balance
  der(m) = m_flow_ext;

  // Energy balance
  der(U) = H_flow_ext;

  // smooth states
  m_flow_ext2 = time - 0.5;
  state2 = Medium.setState_pT(1e5*(1+time), 300+200*time);
  state = Medium.setSmoothState(m_flow_ext2, medium.state, state2, 0.05);
  der_p = der(state.p);
  der_T = der(state.T);
end WaterIF97;

Modelica.Media.Examples.MixtureGases Modelica.Media.Examples.MixtureGases

Test gas mixtures

Information



Extends from Modelica.Icons.Example (Icon for an example model).

Parameters

TypeNameDefaultDescription
VolumeV1Fixed size of volume 1 and volume 2 [m3]
MassFlowRatem_flow_ext0.01Fixed mass flow rate in to volume 1 and in to volume 2 [kg/s]
EnthalpyFlowRateH_flow_ext5000Fixed enthalpy flow rate in to volume and in to volume 2 [W]

Modelica definition

model MixtureGases "Test gas mixtures"
  extends Modelica.Icons.Example;

  parameter Modelica.SIunits.Volume V=1 "Fixed size of volume 1 and volume 2";
  parameter Modelica.SIunits.MassFlowRate m_flow_ext=0.01 
    "Fixed mass flow rate in to volume 1 and in to volume 2";
  parameter Modelica.SIunits.EnthalpyFlowRate H_flow_ext=5000 
    "Fixed enthalpy flow rate in to volume and in to volume 2";

  package Medium1 = Modelica.Media.IdealGases.MixtureGases.CombustionAir 
    "Medium model";
  Medium1.BaseProperties medium1(p(start=1.e5, stateSelect=StateSelect.prefer),
     T(start=300, stateSelect=StateSelect.prefer),
     X(start={0.8,0.2}));
  Real m1(quantity=Medium1.mediumName, start = 1.0);
  SI.InternalEnergy U1;
  Medium1.SpecificHeatCapacity cp1=Medium1.specificHeatCapacityCp(medium1.state);
  Medium1.DynamicViscosity eta1= Medium1.dynamicViscosity(medium1.state);
  Medium1.ThermalConductivity lambda1= Medium1.thermalConductivity(medium1.state);

  package Medium2 = Modelica.Media.IdealGases.MixtureGases.SimpleNaturalGas 
    "Medium model";
  Medium2.BaseProperties medium2(p(start=1.e5, stateSelect=StateSelect.prefer),
     T(start=300, stateSelect=StateSelect.prefer),
     X(start={0.1,0.1,0.1,0.2,0.2,0.3}));
  Real m2(quantity=Medium2.mediumName, start = 1.0);
  SI.InternalEnergy U2;
  Medium2.SpecificHeatCapacity cp2=Medium2.specificHeatCapacityCp(medium2.state);
  Medium2.DynamicViscosity eta2= Medium2.dynamicViscosity(medium2.state);
  Medium2.ThermalConductivity lambda2= Medium2.thermalConductivity(medium2.state);

  Medium2.ThermodynamicState state2 = Medium2.setState_pTX(1.005e5, 302, {0.3,0.2,0.2,0.1,0.1,0.1});
  Medium2.ThermodynamicState smoothState;
  Real m_flow_ext2;
  Real der_p;
  Real der_T;

equation 
  medium1.X = {0.8,0.2};
  m1 = medium1.d*V;
  U1 = m1*medium1.u;
  der(m1) = m_flow_ext;
  der(U1) = H_flow_ext;

  medium2.X ={0.1,0.1,0.1,0.2,0.2,0.3};
  m2 = medium2.d*V;
  U2 = m2*medium2.u;
  der(m2) = m_flow_ext;
  der(U2) = H_flow_ext;

  // Smooth state
  m_flow_ext2 = time - 0.5;
  smoothState = Medium2.setSmoothState(m_flow_ext2, medium2.state, state2, 0.2);
  der_p = der(smoothState.p);
  der_T = der(smoothState.T);
end MixtureGases;

Modelica.Media.Examples.MoistAir Modelica.Media.Examples.MoistAir

Ideal gas flue gas model

Information


An example for using ideal gas properties and how to compute isentropic enthalpy changes. The function that is implemented is approximate, but usually very good: the second medium record medium2 is given to compare the approximation.

Extends from Modelica.Icons.Example (Icon for an example model).

Parameters

TypeNameDefaultDescription
MolarMassMMx[2]{Medium.dryair.MM,Medium.ste...Vector of molar masses (consisting of dry air and of steam) [kg/mol]

Modelica definition

model MoistAir "Ideal gas flue gas  model"
    extends Modelica.Icons.Example;
    package Medium = Air.MoistAir "Medium model";
    Medium.BaseProperties medium(
       T(start = 274.0),
       X(start = {0.95,0.05}),
       p(start = 1.0e5));
  //  Medium.SpecificEntropy s=Medium.specificEntropy(medium);
  //  Medium.SpecificEnthalpy h_is = Medium.isentropicEnthalpyApproximation(medium, 2.0e5);
    parameter Medium.MolarMass[2] MMx = {Medium.dryair.MM,Medium.steam.MM} 
    "Vector of molar masses (consisting of dry air and of steam)";
    Medium.MolarMass MM = 1/((1-medium.X[1])/MMx[1]+medium.X[1]/MMx[2]) 
    "Molar mass of gas part of mixture";
  //  Real[4] dddX=Medium.density_derX(medium,MM);

  Medium.ThermodynamicState state1;
  Medium.ThermodynamicState state2;
  Medium.ThermodynamicState smoothState;
  Real m_flow_ext;
  Real der_p;
  Real der_T;
equation 
    der(medium.p) = 0.0;
    der(medium.T) = 90;
    medium.X[Medium.Air] = 0.95;
    //    medium.X[Medium.Water] = 0.05;
    // one simple assumption only for quick testing:
  //  medium.X_liquidWater = if medium.X_sat < medium.X[2] then medium.X[2] - medium.X_sat else 0.0;

   // Smooth state
   m_flow_ext = time - 0.5;
   state1.p = 1.e5*(1+time);
   state1.T = 300 + 10*time;
   state1.X = {time, 1-time};
   state2.p = 1.e5*(1+time/2);
   state2.T = 340 - 20*time;
   state2.X = {0.5*time, 1-0.5*time};
   smoothState = Medium.setSmoothState(m_flow_ext, state1, state2, 0.2);
   der_p = der(smoothState.p);
   der_T = der(smoothState.T);
end MoistAir;

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