Medium model with linear dependency of u, h from temperature. All other quantities, especially density, are constant.
Information
This medium model is identical to
Modelica.Media.Interfaces.PartialSimpleMedium, but it allows
to define a compressibility of the medium.
This helps breaking algebraic loops, but the system gets stiff.
The compressibility is defined by the constant kappa_const.
If kappa_const=0, then the density is constant. Otherwise,
the density is
rho(p) = rho(p0) * ( 1 + kappa_const * (p-p0))
Extends from Modelica.Media.Interfaces.PartialPureSubstance (base class for pure substances of one chemical substance).
Package Content
| Name | Description |
|---|
| cp_const | Constant specific heat capacity at constant pressure |
| cv_const | Constant specific heat capacity at constant volume |
| d_const | Constant density |
| eta_const | Constant dynamic viscosity |
| lambda_const | Constant thermal conductivity |
| a_const | Constant velocity of sound |
| T_min | Minimum temperature valid for medium model |
| T_max | Maximum temperature valid for medium model |
| T0=reference_T | Zero enthalpy temperature |
| MM_const | Molar mass |
| fluidConstants | fluid constants |
 ThermodynamicState
| Thermodynamic state |
| kappa_const=0 | Compressibility factor at constant temperature |
| p0=3E5 | Reference pressure for compressibility |
 BaseProperties
| Base properties |
 setState_pTX
| Return thermodynamic state from p, T, and X or Xi |
 setState_phX
| Return thermodynamic state from p, h, and X or Xi |
| setState_psX
| Return thermodynamic state from p, s, and X or Xi |
| setState_dTX
| Return thermodynamic state from d, T, and X or Xi |
| setSmoothState
| Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b |
| dynamicViscosity
| Return dynamic viscosity |
| thermalConductivity
| Return thermal conductivity |
| pressure
| Return pressure |
| temperature
| Return temperature |
| density
| Return density |
| specificEnthalpy
| Return specific enthalpy |
| specificHeatCapacityCp
| Return specific heat capacity at constant pressure |
| specificHeatCapacityCv
| Return specific heat capacity at constant volume |
| isentropicExponent
| Return isentropic exponent |
| velocityOfSound
| Return velocity of sound |
| specificEnthalpy_pTX
| Return specific enthalpy from p, T, and X or Xi |
| temperature_phX
| Return temperature from p, h, and X or Xi |
| density_phX
| Return density from p, h, and X or Xi |
| Inherited |
|---|
| setState_pT
| Return thermodynamic state from p and T |
| setState_ph
| Return thermodynamic state from p and h |
| setState_ps
| Return thermodynamic state from p and s |
| setState_dT
| Return thermodynamic state from d and T |
| density_ph
| Return density from p and h |
| temperature_ph
| Return temperature from p and h |
| pressure_dT
| Return pressure from d and T |
| specificEnthalpy_dT
| Return specific enthalpy from d and T |
| specificEnthalpy_ps
| Return specific enthalpy from p and s |
| temperature_ps
| Return temperature from p and s |
| density_ps
| Return density from p and s |
| specificEnthalpy_pT
| Return specific enthalpy from p and T |
| density_pT
| Return density from p and T |
| ThermoStates | Enumeration type for independent variables |
| mediumName="unusablePartialMedium" | Name of the medium |
| substanceNames={mediumName} | Names of the mixture substances. Set substanceNames={mediumName} if only one substance. |
| extraPropertiesNames=fill("", 0) | Names of the additional (extra) transported properties. Set extraPropertiesNames=fill("",0) if unused |
| singleState | = true, if u and d are not a function of pressure |
| reducedX=true | = true if medium contains the equation sum(X) = 1.0; set reducedX=true if only one substance (see docu for details) |
| fixedX=false | = true if medium contains the equation X = reference_X |
| reference_p=101325 | Reference pressure of Medium: default 1 atmosphere |
| reference_T=298.15 | Reference temperature of Medium: default 25 deg Celsius |
| reference_X=fill(1/nX, nX) | Default mass fractions of medium |
| p_default=101325 | Default value for pressure of medium (for initialization) |
| T_default=Modelica.SIunits.Conversions.from_degC(20) | Default value for temperature of medium (for initialization) |
| h_default=specificEnthalpy_pTX(p_default, T_default, X_default) | Default value for specific enthalpy of medium (for initialization) |
| X_default=reference_X | Default value for mass fractions of medium (for initialization) |
| nS=size(substanceNames, 1) | Number of substances |
| nX=nS | Number of mass fractions |
| nXi=if fixedX then 0 else if reducedX then nS - 1 else nS | Number of structurally independent mass fractions (see docu for details) |
| nC=size(extraPropertiesNames, 1) | Number of extra (outside of standard mass-balance) transported properties |
 FluidConstants
| critical, triple, molecular and other standard data of fluid |
| prandtlNumber
| Return the Prandtl number |
| specificInternalEnergy
| Return specific internal energy |
 specificEntropy
| Return specific entropy |
| specificGibbsEnergy
| Return specific Gibbs energy |
| specificHelmholtzEnergy
| Return specific Helmholtz energy |
| heatCapacity_cp
| alias for deprecated name |
| heatCapacity_cv
| alias for deprecated name |
| isentropicEnthalpy
| Return isentropic enthalpy |
| isobaricExpansionCoefficient
| Return overall the isobaric expansion coefficient beta |
| beta
| alias for isobaricExpansionCoefficient for user convenience |
| isothermalCompressibility
| Return overall the isothermal compressibility factor |
| kappa
| alias of isothermalCompressibility for user convenience |
| density_derp_h
| Return density derivative wrt pressure at const specific enthalpy |
| density_derh_p
| Return density derivative wrt specific enthalpy at constant pressure |
| density_derp_T
| Return density derivative wrt pressure at const temperature |
| density_derT_p
| Return density derivative wrt temperature at constant pressure |
| density_derX
| Return density derivative wrt mass fraction |
| molarMass
| Return the molar mass of the medium |
| density_pTX
| Return density from p, T, and X or Xi |
| temperature_psX
| Return temperature from p,s, and X or Xi |
| density_psX
| Return density from p, s, and X or Xi |
| specificEnthalpy_psX
| Return specific enthalpy from p, s, and X or Xi |
| AbsolutePressure
| Type for absolute pressure with medium specific attributes |
| Density
| Type for density with medium specific attributes |
| DynamicViscosity
| Type for dynamic viscosity with medium specific attributes |
| EnthalpyFlowRate
| Type for enthalpy flow rate with medium specific attributes |
| MassFlowRate
| Type for mass flow rate with medium specific attributes |
| MassFraction
| Type for mass fraction with medium specific attributes |
| MoleFraction
| Type for mole fraction with medium specific attributes |
| MolarMass
| Type for molar mass with medium specific attributes |
| MolarVolume
| Type for molar volume with medium specific attributes |
| IsentropicExponent
| Type for isentropic exponent with medium specific attributes |
| SpecificEnergy
| Type for specific energy with medium specific attributes |
| SpecificInternalEnergy
| Type for specific internal energy with medium specific attributes |
| SpecificEnthalpy
| Type for specific enthalpy with medium specific attributes |
| SpecificEntropy
| Type for specific entropy with medium specific attributes |
| SpecificHeatCapacity
| Type for specific heat capacity with medium specific attributes |
| SurfaceTension
| Type for surface tension with medium specific attributes |
| Temperature
| Type for temperature with medium specific attributes |
| ThermalConductivity
| Type for thermal conductivity with medium specific attributes |
| PrandtlNumber
| Type for Prandtl number with medium specific attributes |
| VelocityOfSound
| Type for velocity of sound with medium specific attributes |
| ExtraProperty
| Type for unspecified, mass-specific property transported by flow |
| CumulativeExtraProperty
| Type for conserved integral of unspecified, mass specific property |
| ExtraPropertyFlowRate
| Type for flow rate of unspecified, mass-specific property |
| IsobaricExpansionCoefficient
| Type for isobaric expansion coefficient with medium specific attributes |
| DipoleMoment
| Type for dipole moment with medium specific attributes |
| DerDensityByPressure
| Type for partial derivative of density with resect to pressure with medium specific attributes |
| DerDensityByEnthalpy
| Type for partial derivative of density with resect to enthalpy with medium specific attributes |
| DerEnthalpyByPressure
| Type for partial derivative of enthalpy with resect to pressure with medium specific attributes |
| DerDensityByTemperature
| Type for partial derivative of density with resect to temperature with medium specific attributes |
 Choices
| Types, constants to define menu choices |
Types and constants
constant SpecificHeatCapacity cp_const
"Constant specific heat capacity at constant pressure";
constant SpecificHeatCapacity cv_const
"Constant specific heat capacity at constant volume";
constant Density d_const "Constant density";
constant DynamicViscosity eta_const "Constant dynamic viscosity";
constant ThermalConductivity lambda_const "Constant thermal conductivity";
constant VelocityOfSound a_const "Constant velocity of sound";
constant Temperature T_min "Minimum temperature valid for medium model";
constant Temperature T_max "Maximum temperature valid for medium model";
constant Temperature T0=reference_T "Zero enthalpy temperature";
constant MolarMass MM_const "Molar mass";
constant FluidConstants[nS] fluidConstants "fluid constants";
constant Real kappa_const(unit="1/Pa") = 0
"Compressibility factor at constant temperature";
constant Modelica.SIunits.AbsolutePressure p0 = 3E5
"Reference pressure for compressibility";
Thermodynamic state
Information
Extends from (Minimal variable set that is available as input argument to every medium function).
Modelica definition
redeclare record extends ThermodynamicState "Thermodynamic state"
AbsolutePressure p "Absolute pressure of medium";
Temperature T "Temperature of medium";
end ThermodynamicState;
Base properties
Information
This is the most simple incompressible medium model, where
specific enthalpy h and specific internal energy u are only
a function of temperature T and all other provided medium
quantities are assumed to be constant.
Extends from .
Parameters
| Type | Name | Default | Description |
|---|
| Advanced |
| Boolean | preferredMediumStates | false | = true if StateSelect.prefer shall be used for the independent property variables of the medium |
Modelica definition
redeclare replaceable model extends BaseProperties(
T(stateSelect=if preferredMediumStates then StateSelect.prefer else
StateSelect.default),
p(stateSelect=if preferredMediumStates then StateSelect.prefer else
StateSelect.default)) "Base properties"
equation
assert(T >= T_min and T <= T_max, "
Temperature T (= " + String(T) + " K) is not
in the allowed range (" + String(T_min) + " K <= T <= " + String(T_max)
+ " K)
required from medium model \"" + mediumName + "\".
");
// h = cp_const*(T-T0);
h = specificEnthalpy_pTX(p,T,X);
u = cv_const*(T-T0);
// original equation d = d_const;
d = if (kappa_const > 1E-20) then d_const * (1+kappa_const*(p-p0)) else d_const;
// d = d_const * (1+kT*(T-T0)/T0); "this gives large coupled equations"
R = 0;
MM = MM_const;
state.T = T;
state.p = p;
end BaseProperties;
Return thermodynamic state from p, T, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
Modelica definition
redeclare function setState_pTX
"Return thermodynamic state from p, T, and X or Xi"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input Temperature T "Temperature";
input MassFraction X[:]=reference_X "Mass fractions";
output ThermodynamicState state "thermodynamic state record";
algorithm
state := ThermodynamicState(p=p,T=T);
end setState_pTX;
Return thermodynamic state from p, h, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
Modelica definition
redeclare function setState_phX
"Return thermodynamic state from p, h, and X or Xi"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input SpecificEnthalpy h "Specific enthalpy";
input MassFraction X[:]=reference_X "Mass fractions";
output ThermodynamicState state "thermodynamic state record";
algorithm
state := ThermodynamicState(p=p,T=T0+h/cp_const);
end setState_phX;
Return thermodynamic state from p, s, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
Modelica definition
redeclare replaceable function setState_psX
"Return thermodynamic state from p, s, and X or Xi"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input SpecificEntropy s "Specific entropy";
input MassFraction X[:]=reference_X "Mass fractions";
output ThermodynamicState state "thermodynamic state record";
algorithm
state := ThermodynamicState(p=p,T=Modelica.Math.exp(s/cp_const + Modelica.Math.log(T0)))
"here the incompressible limit is used, with cp as heat capacity";
end setState_psX;
Return thermodynamic state from d, T, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
Modelica definition
redeclare function setState_dTX
"Return thermodynamic state from d, T, and X or Xi"
extends Modelica.Icons.Function;
input Density d "density";
input Temperature T "Temperature";
input MassFraction X[:]=reference_X "Mass fractions";
output ThermodynamicState state "thermodynamic state record";
algorithm
assert(false,"pressure can not be computed from temperature and density for an incompressible fluid!");
end setState_dTX;
Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b
Information
Extends from (Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b).
Inputs
| Type | Name | Default | Description |
|---|
| Real | x | | m_flow or dp |
| ThermodynamicState | state_a | | Thermodynamic state if x > 0 |
| ThermodynamicState | state_b | | Thermodynamic state if x < 0 |
| Real | x_small | | Smooth transition in the region -x_small < x < x_small |
Outputs
| Type | Name | Description |
|---|
| ThermodynamicState | state | Smooth thermodynamic state for all x (continuous and differentiable) |
Modelica definition
redeclare function extends setSmoothState
"Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b"
algorithm
state := ThermodynamicState(p=Modelica.Media.Common.smoothStep(
x,
state_a.p,
state_b.p,
x_small), T=Modelica.Media.Common.smoothStep(
x,
state_a.T,
state_b.T,
x_small));
end setSmoothState;
Return dynamic viscosity
Information
Extends from (Return dynamic viscosity).
Inputs
Outputs
Modelica definition
redeclare function extends dynamicViscosity
"Return dynamic viscosity"
algorithm
eta := eta_const;
end dynamicViscosity;
Return thermal conductivity
Information
Extends from (Return thermal conductivity).
Inputs
Outputs
Modelica definition
redeclare function extends thermalConductivity
"Return thermal conductivity"
algorithm
lambda := lambda_const;
end thermalConductivity;
Return pressure
Information
Extends from (Return pressure).
Inputs
Outputs
Modelica definition
redeclare function extends pressure "Return pressure"
algorithm
p := state.p;
end pressure;
Return temperature
Information
Extends from (Return temperature).
Inputs
Outputs
Modelica definition
redeclare function extends temperature "Return temperature"
algorithm
T := state.T;
end temperature;
Return density
Information
Extends from (Return density).
Inputs
Outputs
| Type | Name | Description |
|---|
| Density | d | Density [kg/m3] |
Modelica definition
redeclare function extends density "Return density"
algorithm
d := d_const;
end density;
Return specific enthalpy
Information
Extends from (Return specific enthalpy).
Inputs
Outputs
Modelica definition
redeclare function extends specificEnthalpy
"Return specific enthalpy"
algorithm
h := cp_const*(state.T-T0);
end specificEnthalpy;
Return specific heat capacity at constant pressure
Information
Extends from (Return specific heat capacity at constant pressure).
Inputs
Outputs
Modelica definition
redeclare function extends specificHeatCapacityCp
"Return specific heat capacity at constant pressure"
algorithm
cp := cp_const;
end specificHeatCapacityCp;
Return specific heat capacity at constant volume
Information
Extends from (Return specific heat capacity at constant volume).
Inputs
Outputs
Modelica definition
redeclare function extends specificHeatCapacityCv
"Return specific heat capacity at constant volume"
algorithm
cv := cv_const;
end specificHeatCapacityCv;
Return isentropic exponent
Information
Extends from (Return isentropic exponent).
Inputs
Outputs
Modelica definition
redeclare function extends isentropicExponent
"Return isentropic exponent"
algorithm
gamma := cp_const/cv_const;
end isentropicExponent;
Return velocity of sound
Information
Extends from (Return velocity of sound).
Inputs
Outputs
Modelica definition
redeclare function extends velocityOfSound
"Return velocity of sound "
algorithm
a := a_const;
end velocityOfSound;
Return specific enthalpy from p, T, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
Modelica definition
redeclare function specificEnthalpy_pTX
"Return specific enthalpy from p, T, and X or Xi"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input Temperature T "Temperature";
input MassFraction X[nX] "Mass fractions";
output SpecificEnthalpy h "Specific enthalpy";
algorithm
h := cp_const*(T-T0);
end specificEnthalpy_pTX;
Return temperature from p, h, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
Modelica definition
redeclare function temperature_phX
"Return temperature from p, h, and X or Xi"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input SpecificEnthalpy h "Specific enthalpy";
input MassFraction X[nX] "Mass fractions";
output Temperature T "Temperature";
algorithm
T := T0 + h/cp_const;
end temperature_phX;
Return density from p, h, and X or Xi
Information
Extends from Modelica.Icons.Function (Icon for a function).
Inputs
Outputs
| Type | Name | Description |
|---|
| Density | d | density [kg/m3] |
Modelica definition
redeclare function density_phX
"Return density from p, h, and X or Xi"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input SpecificEnthalpy h "Specific enthalpy";
input MassFraction X[nX] "Mass fractions";
output Density d "density";
algorithm
d := density(setState_phX(p,h,X));
end density_phX;
HTML-documentation generated by Dymola Thu Jun 24 16:55:23 2010.
Buildings.Media.Interfaces.PartialSimpleMedium.ThermodynamicState
Buildings.Media.Interfaces.PartialSimpleMedium.BaseProperties
Buildings.Media.Interfaces.PartialSimpleMedium.setState_pTX