Buildings.Media.PerfectGases.MoistAir

Information

This is a medium model that is similar to Modelica.Media.Air.MoistAir but it has a constant specific heat capacity.

In particular, the medium is thermally perfect, i.e.,

• it is in thermodynamic equilibrium,
• it is chemically not reacting, and
• internal energy and enthalpy are functions of the temperature only.

References

Extends from Modelica.Media.Interfaces.PartialCondensingGases (Base class for mixtures of condensing and non-condensing gases).

Package Content

Name	Description
Water=1	Index of water (in substanceNames, massFractions X, etc.)
Air=2	Index of air (in substanceNames, massFractions X, etc.)
k_mair=steam.MM/dryair.MM	ratio of molar weights
dryair=Buildings.Media.PerfectGases.Common.SingleGasData.Air
steam=Buildings.Media.PerfectGases.Common.SingleGasData.H2O
TMin=200	Minimum temperature
TMax=400	Maximum temperature
BaseProperties
Xsaturation	Steam water mass fraction of saturation boundary in kg_water/kg_moistair
setState_pTX	Thermodynamic state as function of p, T and composition X
setState_phX	Thermodynamic state as function of p, h and composition X
setState_dTX	Thermodynamic state as function of d, T and composition X
gasConstant	Gas constant (computation neglects liquid fraction)
saturationPressureLiquid	Return saturation pressure of water as a function of temperature T in the range of 273.16 to 373.16 K
saturationPressureLiquid_der	Time derivative of saturationPressureLiquid
sublimationPressureIce	Saturation curve valid for 223.16 <= T <= 273.16. Outside of these limits a (less accurate) result is returned
saturationPressure	Saturation curve valid for 223.16 <= T <= 373.16 (and slightly outside with less accuracy)
pressure	Gas pressure
temperature	Gas temperature
density	Gas density
specificEntropy	Specific entropy (liquid part neglected, mixing entropy included)
enthalpyOfVaporization	Enthalpy of vaporization of water
HeatCapacityOfWater	Specific heat capacity of water (liquid only) which is constant
enthalpyOfLiquid	Enthalpy of liquid (per unit mass of liquid) which is linear in the temperature
der_enthalpyOfLiquid	Temperature derivative of enthalpy of liquid per unit mass of liquid
enthalpyOfCondensingGas	Enthalpy of steam per unit mass of steam
der_enthalpyOfCondensingGas	Derivative of enthalpy of steam per unit mass of steam
enthalpyOfNonCondensingGas	Enthalpy of non-condensing gas per unit mass of steam
der_enthalpyOfNonCondensingGas	Derivative of enthalpy of non-condensing gas per unit mass of steam
enthalpyOfGas	Enthalpy of gas mixture per unit mass of gas mixture
enthalpyOfDryAir	Enthalpy of dry air per unit mass of dry air
der_enthalpyOfDryAir	Derivative of enthalpy of dry air per unit mass of dry air
specificHeatCapacityCp	Specific heat capacity of gas mixture at constant pressure
specificHeatCapacityCv	Specific heat capacity of gas mixture at constant volume
dynamicViscosity	dynamic viscosity of dry air
thermalConductivity	Thermal conductivity of dry air as a polynomial in the temperature
h_pTX	Compute specific enthalpy from pressure, temperature and mass fraction
specificEnthalpy	Specific enthalpy
specificInternalEnergy	Specific internal energy
specificGibbsEnergy	Specific Gibbs energy
specificHelmholtzEnergy	Specific Helmholtz energy
T_phX	Compute temperature from specific enthalpy and mass fraction
Inherited
ThermodynamicState	thermodynamic state variables
FluidConstants	extended fluid constants
fluidConstants	constant data for the fluid
moleToMassFractions	Return mass fractions X from mole fractions
massToMoleFractions	Return mole fractions from mass fractions X
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
C_nominal=1.0e-6*ones(nC)	Default for the nominal values for the extra properties
setState_psX	Return thermodynamic state as function of p, s and composition X or Xi
setSmoothState	Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b
prandtlNumber	Return the Prandtl number
heatCapacity_cp	alias for deprecated name
heatCapacity_cv	alias for deprecated name
isentropicExponent	Return isentropic exponent
isentropicEnthalpy	Return isentropic enthalpy
velocityOfSound	Return velocity of sound
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 w.r.t. pressure at const specific enthalpy
density_derh_p	Return density derivative w.r.t. specific enthalpy at constant pressure
density_derp_T	Return density derivative w.r.t. pressure at const temperature
density_derT_p	Return density derivative w.r.t. temperature at constant pressure
density_derX	Return density derivative w.r.t. mass fraction
molarMass	Return the molar mass of the medium
specificEnthalpy_pTX	Return specific enthalpy from p, T, and X or Xi
specificEntropy_pTX	Return specific enthalpy from p, T, and X or Xi
density_pTX	Return density 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
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 Integer Water=1 
  "Index of water (in substanceNames, massFractions X, etc.)";

  constant Integer Air=2 
  "Index of air (in substanceNames, massFractions X, etc.)";

  constant Real k_mair =  steam.MM/dryair.MM "ratio of molar weights";

  constant Buildings.Media.PerfectGases.Common.DataRecord dryair=
        Buildings.Media.PerfectGases.Common.SingleGasData.Air;

  constant Buildings.Media.PerfectGases.Common.DataRecord steam=
        Buildings.Media.PerfectGases.Common.SingleGasData.H2O;

    constant Modelica.SIunits.Temperature TMin = 200 "Minimum temperature";

    constant Modelica.SIunits.Temperature TMax = 400 "Maximum temperature";

Buildings.Media.PerfectGases.MoistAir.BaseProperties

Information

Parameters

Type	Name	Default	Description
Boolean	standardOrderComponents	true	if true, and reducedX = true, the last element of X will be computed from the other ones
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),
  Xi(stateSelect=if preferredMediumStates then StateSelect.prefer else StateSelect.default))

  /* p, T, X = X[Water] are used as preferred states, since only then all
     other quantities can be computed in a recursive sequence. 
     If other variables are selected as states, static state selection
     is no longer possible and non-linear algebraic equations occur.
      */
  MassFraction x_water "mass of total water/mass of dry air";
  Real phi "relative humidity";

protected 
  constant SI.MolarMass[2] MMX = {steam.MM,dryair.MM} 
    "Molar masses of components";

  MassFraction X_liquid "Mass fraction of liquid water";
  MassFraction X_steam "Mass fraction of steam water";
  MassFraction X_air "Mass fraction of air";
  MassFraction X_sat 
    "Steam water mass fraction of saturation boundary in kg_water/kg_moistair";
  MassFraction x_sat 
    "Steam water mass content of saturation boundary in kg_water/kg_dryair";
  AbsolutePressure p_steam_sat "Partial saturation pressure of steam";

equation 
  assert(T >= TMin and T <= TMax, "
Temperature T is not in the allowed range "
                                          + String(TMin) + " <= (T ="
             + String(T) + " K) <= " + String(TMax) + " K
required from medium model \""   + mediumName + "\".");
  MM = 1/(Xi[Water]/MMX[Water]+(1.0-Xi[Water])/MMX[Air]);

  p_steam_sat = min(saturationPressure(T),0.999*p);
  X_sat = min(p_steam_sat * k_mair/max(100*Modelica.Constants.eps, p - p_steam_sat)*(1 - Xi[Water]), 1.0) 
    "Water content at saturation with respect to actual water content";
  X_liquid = max(Xi[Water] - X_sat, 0.0);
  X_steam  = Xi[Water]-X_liquid;
  X_air    = 1-Xi[Water];

  h = specificEnthalpy_pTX(p,T,Xi);
  R = dryair.R*(1 - X_steam/(1 - X_liquid)) + steam.R*X_steam/(1 - X_liquid);
  //
  u = h - R*T;
  d = p/(R*T);
  /* Note, u and d are computed under the assumption that the volume of the liquid
         water is neglible with respect to the volume of air and of steam
      */
  state.p = p;
  state.T = T;
  state.X = X;

  // this x_steam is water load / dry air!!!!!!!!!!!
  x_sat    = k_mair*p_steam_sat/max(100*Modelica.Constants.eps,p - p_steam_sat);
  x_water = Xi[Water]/max(X_air,100*Modelica.Constants.eps);
  phi = p/p_steam_sat*Xi[Water]/(Xi[Water] + k_mair*X_air);
end BaseProperties;

Buildings.Media.PerfectGases.MoistAir.Xsaturation

Inputs

Type	Name	Default	Description
ThermodynamicState	state		Thermodynamic state record

Outputs

Type	Name	Description
MassFraction	X_sat	Steam mass fraction of sat. boundary [kg/kg]

Modelica definition

function Xsaturation = Modelica.Media.Air.MoistAir.Xsaturation 
  "Steam water mass fraction of saturation boundary in kg_water/kg_moistair";

Buildings.Media.PerfectGases.MoistAir.setState_pTX

Information

Inputs

Type	Name	Default	Description
AbsolutePressure	p		Pressure [Pa]
Temperature	T		Temperature [K]
MassFraction	X[:]	reference_X	Mass fractions [kg/kg]

Outputs

Type	Name	Description
ThermodynamicState	state	Thermodynamic state

Modelica definition

redeclare function setState_pTX 
  "Thermodynamic state as function of p, T and composition X"
    extends Modelica.Media.Air.MoistAir.setState_pTX;
end setState_pTX;

Buildings.Media.PerfectGases.MoistAir.setState_phX

Information

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

Type	Name	Default	Description
AbsolutePressure	p		Pressure [Pa]
SpecificEnthalpy	h		Specific enthalpy [J/kg]
MassFraction	X[:]		Mass fractions [kg/kg]

Outputs

Type	Name	Description
ThermodynamicState	state

Modelica definition

redeclare function setState_phX 
  "Thermodynamic state as function of p, h and composition X"
extends Modelica.Icons.Function;
input AbsolutePressure p "Pressure";
input SpecificEnthalpy h "Specific enthalpy";
input MassFraction X[:] "Mass fractions";
output ThermodynamicState state;
algorithm 
state := if size(X,1) == nX then 
      ThermodynamicState(p=p,T=T_phX(p,h,X),X=X) else 
      ThermodynamicState(p=p,T=T_phX(p,h,X), X=cat(1,X,{1-sum(X)}));
end setState_phX;

Buildings.Media.PerfectGases.MoistAir.setState_dTX

Information

Inputs

Type	Name	Default	Description
Density	d		density [kg/m3]
Temperature	T		Temperature [K]
MassFraction	X[:]	reference_X	Mass fractions [kg/kg]

Outputs

Type	Name	Description
ThermodynamicState	state	Thermodynamic state

Modelica definition

redeclare function setState_dTX 
  "Thermodynamic state as function of d, T and composition X"
   extends Modelica.Media.Air.MoistAir.setState_dTX;
end setState_dTX;

Buildings.Media.PerfectGases.MoistAir.gasConstant

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state

Outputs

Type	Name	Description
SpecificHeatCapacity	R	mixture gas constant [J/(kg.K)]

Modelica definition

redeclare function gasConstant 
  "Gas constant (computation neglects liquid fraction)"
   extends Modelica.Media.Air.MoistAir.gasConstant;
end gasConstant;

Buildings.Media.PerfectGases.MoistAir.saturationPressureLiquid

Information

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

Type	Name	Default	Description
Temperature	Tsat		saturation temperature [K]

Outputs

Type	Name	Description
AbsolutePressure	psat	saturation pressure [Pa]

Modelica definition

function saturationPressureLiquid 
  "Return saturation pressure of water as a function of temperature T in the range of 273.16 to 373.16 K"
  annotation(derivative=saturationPressureLiquid_der);

  extends Modelica.Icons.Function;
  input SI.Temperature Tsat "saturation temperature";
  output SI.AbsolutePressure psat "saturation pressure";
algorithm 
  psat := 611.657*Modelica.Math.exp(17.2799 - 4102.99/(Tsat - 35.719));
end saturationPressureLiquid;

Buildings.Media.PerfectGases.MoistAir.saturationPressureLiquid_der

Information

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

Type	Name	Default	Description
Temperature	Tsat		Saturation temperature [K]
Real	dTsat		Saturation temperature derivative [K/s]

Outputs

Type	Name	Description
Real	psat_der	Saturation pressure [Pa/s]

Modelica definition

function saturationPressureLiquid_der 
  "Time derivative of saturationPressureLiquid"

  extends Modelica.Icons.Function;
  input SI.Temperature Tsat "Saturation temperature";
  input Real dTsat(unit="K/s") "Saturation temperature derivative";
  output Real psat_der(unit="Pa/s") "Saturation pressure";
algorithm 
  psat_der:=611.657*Modelica.Math.exp(17.2799 - 4102.99/(Tsat - 35.719))*4102.99*dTsat/(Tsat - 35.719)/(Tsat - 35.719);

end saturationPressureLiquid_der;

Buildings.Media.PerfectGases.MoistAir.sublimationPressureIce

Inputs

Type	Name	Default	Description
Temperature	Tsat		sublimation temperature [K]

Outputs

Type	Name	Description
AbsolutePressure	psat	sublimation pressure [Pa]

Modelica definition

function sublimationPressureIce =
    Modelica.Media.Air.MoistAir.sublimationPressureIce 
  "Saturation curve valid for 223.16 <= T <= 273.16. Outside of these limits a (less accurate) result is returned";

Buildings.Media.PerfectGases.MoistAir.saturationPressure

Information

Inputs

Type	Name	Default	Description
Temperature	Tsat		saturation temperature [K]

Outputs

Type	Name	Description
AbsolutePressure	psat	saturation pressure [Pa]

Modelica definition

redeclare function extends saturationPressure 
  "Saturation curve valid for 223.16 <= T <= 373.16 (and slightly outside with less accuracy)"

algorithm 
  psat := Buildings.Utilities.Math.Functions.spliceFunction(
                                                  saturationPressureLiquid(Tsat),sublimationPressureIce(Tsat),Tsat-273.16,1.0);
end saturationPressure;

Buildings.Media.PerfectGases.MoistAir.pressure

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
AbsolutePressure	p	Pressure [Pa]

Modelica definition

redeclare function pressure "Gas pressure"
   extends Modelica.Media.Air.MoistAir.pressure;
end pressure;

Buildings.Media.PerfectGases.MoistAir.temperature

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
Temperature	T	Temperature [K]

Modelica definition

redeclare function temperature "Gas temperature"
   extends Modelica.Media.Air.MoistAir.temperature;
end temperature;

Buildings.Media.PerfectGases.MoistAir.density

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
Density	d	Density [kg/m3]

Modelica definition

redeclare function density "Gas density"
   extends Modelica.Media.Air.MoistAir.density;
end density;

Buildings.Media.PerfectGases.MoistAir.specificEntropy

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificEntropy	s	Specific entropy [J/(kg.K)]

Modelica definition

redeclare function specificEntropy 
  "Specific entropy (liquid part neglected, mixing entropy included)"
   extends Modelica.Media.Air.MoistAir.specificEntropy;
end specificEntropy;

Buildings.Media.PerfectGases.MoistAir.enthalpyOfVaporization

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]

Outputs

Type	Name	Description
SpecificEnthalpy	r0	vaporization enthalpy [J/kg]

Modelica definition

redeclare function extends enthalpyOfVaporization 
  "Enthalpy of vaporization of water"
algorithm 
 r0 := 2501014.5;
end enthalpyOfVaporization;

Buildings.Media.PerfectGases.MoistAir.HeatCapacityOfWater

Information

Inputs

Type	Name	Default	Description
Temperature	T		[K]

Outputs

Type	Name	Description
SpecificHeatCapacity	cp_fl	[J/(kg.K)]

Modelica definition

function HeatCapacityOfWater 
  "Specific heat capacity of water (liquid only) which is constant"
  extends Modelica.Icons.Function;
  input Temperature T;
  output SpecificHeatCapacity cp_fl;
algorithm 
  cp_fl := 4186;
end HeatCapacityOfWater;

Buildings.Media.PerfectGases.MoistAir.enthalpyOfLiquid

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]

Outputs

Type	Name	Description
SpecificEnthalpy	h	liquid enthalpy [J/kg]

Modelica definition

redeclare replaceable function extends enthalpyOfLiquid 
  "Enthalpy of liquid (per unit mass of liquid) which is linear in the temperature"
  annotation(derivative=der_enthalpyOfLiquid);

algorithm 
  h := (T - 273.15)*4186;
end enthalpyOfLiquid;

Buildings.Media.PerfectGases.MoistAir.der_enthalpyOfLiquid

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]
Real	der_T		temperature derivative

Outputs

Type	Name	Description
Real	der_h	derivative of liquid enthalpy

Modelica definition

replaceable function der_enthalpyOfLiquid 
  "Temperature derivative of enthalpy of liquid per unit mass of liquid"
  extends Modelica.Icons.Function;
  input Temperature T "temperature";
  input Real der_T "temperature derivative";
  output Real der_h "derivative of liquid enthalpy";
algorithm 
  der_h := 4186*der_T;
end der_enthalpyOfLiquid;

Buildings.Media.PerfectGases.MoistAir.enthalpyOfCondensingGas

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]

Outputs

Type	Name	Description
SpecificEnthalpy	h	steam enthalpy [J/kg]

Modelica definition

redeclare function enthalpyOfCondensingGas 
  "Enthalpy of steam per unit mass of steam"
  annotation(derivative=der_enthalpyOfCondensingGas);
  extends Modelica.Icons.Function;

  input Temperature T "temperature";
  output SpecificEnthalpy h "steam enthalpy";
algorithm 
  h := (T-273.15) * steam.cp + enthalpyOfVaporization(T);
end enthalpyOfCondensingGas;

Buildings.Media.PerfectGases.MoistAir.der_enthalpyOfCondensingGas

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]
Real	der_T		temperature derivative

Outputs

Type	Name	Description
Real	der_h	derivative of steam enthalpy

Modelica definition

replaceable function der_enthalpyOfCondensingGas 
  "Derivative of enthalpy of steam per unit mass of steam"
  extends Modelica.Icons.Function;
  input Temperature T "temperature";
  input Real der_T "temperature derivative";
  output Real der_h "derivative of steam enthalpy";
algorithm 
  der_h := steam.cp*der_T;
end der_enthalpyOfCondensingGas;

Buildings.Media.PerfectGases.MoistAir.enthalpyOfNonCondensingGas

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]

Outputs

Type	Name	Description
SpecificEnthalpy	h	enthalpy [J/kg]

Modelica definition

redeclare function enthalpyOfNonCondensingGas 
  "Enthalpy of non-condensing gas per unit mass of steam"
  annotation(derivative=der_enthalpyOfNonCondensingGas);
  extends Modelica.Icons.Function;

  input Temperature T "temperature";
  output SpecificEnthalpy h "enthalpy";
algorithm 
  h := enthalpyOfDryAir(T);
end enthalpyOfNonCondensingGas;

Buildings.Media.PerfectGases.MoistAir.der_enthalpyOfNonCondensingGas

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]
Real	der_T		temperature derivative

Outputs

Type	Name	Description
Real	der_h	derivative of steam enthalpy

Modelica definition

replaceable function der_enthalpyOfNonCondensingGas 
  "Derivative of enthalpy of non-condensing gas per unit mass of steam"
  extends Modelica.Icons.Function;
  input Temperature T "temperature";
  input Real der_T "temperature derivative";
  output Real der_h "derivative of steam enthalpy";
algorithm 
  der_h := der_enthalpyOfDryAir(T, der_T);
end der_enthalpyOfNonCondensingGas;

Buildings.Media.PerfectGases.MoistAir.enthalpyOfGas

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]
MassFraction	X[:]		vector of mass fractions [kg/kg]

Outputs

Type	Name	Description
SpecificEnthalpy	h	specific enthalpy [J/kg]

Modelica definition

redeclare replaceable function extends enthalpyOfGas 
  "Enthalpy of gas mixture per unit mass of gas mixture"
algorithm 
  h := enthalpyOfCondensingGas(T)*X[Water]
       + enthalpyOfDryAir(T)*(1.0-X[Water]);
end enthalpyOfGas;

Buildings.Media.PerfectGases.MoistAir.enthalpyOfDryAir

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]

Outputs

Type	Name	Description
SpecificEnthalpy	h	dry air enthalpy [J/kg]

Modelica definition

replaceable function enthalpyOfDryAir 
  "Enthalpy of dry air per unit mass of dry air"
  annotation(derivative=der_enthalpyOfDryAir);
  extends Modelica.Icons.Function;

  input Temperature T "temperature";
  output SpecificEnthalpy h "dry air enthalpy";
algorithm 
  h := (T - 273.15)*dryair.cp;
end enthalpyOfDryAir;

Buildings.Media.PerfectGases.MoistAir.der_enthalpyOfDryAir

Information

Inputs

Type	Name	Default	Description
Temperature	T		temperature [K]
Real	der_T		temperature derivative

Outputs

Type	Name	Description
Real	der_h	derivative of dry air enthalpy

Modelica definition

replaceable function der_enthalpyOfDryAir 
  "Derivative of enthalpy of dry air per unit mass of dry air"
  extends Modelica.Icons.Function;
  input Temperature T "temperature";
  input Real der_T "temperature derivative";
  output Real der_h "derivative of dry air enthalpy";
algorithm 
  der_h := dryair.cp*der_T;
end der_enthalpyOfDryAir;

Buildings.Media.PerfectGases.MoistAir.specificHeatCapacityCp

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificHeatCapacity	cp	Specific heat capacity at constant pressure [J/(kg.K)]

Modelica definition

redeclare replaceable function extends specificHeatCapacityCp 
  "Specific heat capacity of gas mixture at constant pressure"
algorithm 
  cp := dryair.cp*(1-state.X[Water]) +steam.cp*state.X[Water];
end specificHeatCapacityCp;

Buildings.Media.PerfectGases.MoistAir.specificHeatCapacityCv

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificHeatCapacity	cv	Specific heat capacity at constant volume [J/(kg.K)]

Modelica definition

redeclare replaceable function extends specificHeatCapacityCv 
  "Specific heat capacity of gas mixture at constant volume"
algorithm 
  cv:= dryair.cv*(1-state.X[Water]) +steam.cv*state.X[Water];
end specificHeatCapacityCv;

Buildings.Media.PerfectGases.MoistAir.dynamicViscosity

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
DynamicViscosity	eta	Dynamic viscosity [Pa.s]

Modelica definition

redeclare function extends dynamicViscosity 
  "dynamic viscosity of dry air"
algorithm 
  eta := 1.85E-5;
end dynamicViscosity;

Buildings.Media.PerfectGases.MoistAir.thermalConductivity

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
ThermalConductivity	lambda	Thermal conductivity [W/(m.K)]

Modelica definition

redeclare function extends thermalConductivity 
  "Thermal conductivity of dry air as a polynomial in the temperature"
algorithm 
  lambda := Modelica.Media.Incompressible.TableBased.Polynomials_Temp.evaluate(
               {(-4.8737307422969E-008), 7.67803133753502E-005, 0.0241814385504202},
               Modelica.SIunits.Conversions.to_degC(state.T));
end thermalConductivity;

Buildings.Media.PerfectGases.MoistAir.h_pTX

Information

Inputs

Type	Name	Default	Description
Pressure	p		Pressure [Pa]
Temperature	T		Temperature [K]
MassFraction	X[:]		Mass fractions of moist air [1]

Outputs

Type	Name	Description
SpecificEnthalpy	h	Specific enthalpy at p, T, X [J/kg]

Modelica definition

function h_pTX 
  "Compute specific enthalpy from pressure, temperature and mass fraction"
  extends Modelica.Icons.Function;
  input SI.Pressure p "Pressure";
  input SI.Temperature T "Temperature";
  input SI.MassFraction X[:] "Mass fractions of moist air";
  output SI.SpecificEnthalpy h "Specific enthalpy at p, T, X";

protected 
  SI.AbsolutePressure p_steam_sat "Partial saturation pressure of steam";
  SI.MassFraction x_sat "steam water mass fraction of saturation boundary";
  SI.MassFraction X_liquid "mass fraction of liquid water";
  SI.MassFraction X_steam "mass fraction of steam water";
  SI.MassFraction X_air "mass fraction of air";
  SI.SpecificEnthalpy hDryAir "Enthalpy of dry air";
algorithm 
  p_steam_sat :=saturationPressure(T);
  x_sat    :=k_mair*p_steam_sat/(p - p_steam_sat);
  X_liquid :=max(X[Water] - x_sat/(1 + x_sat), 0.0);
  X_steam  :=X[Water] - X_liquid;
  X_air    :=1 - X[Water];

/* THIS DOES NOT WORK --------------------------    
  h := enthalpyOfDryAir(T) * X_air + 
       Modelica.Media.Air.MoistAir.enthalpyOfCondensingGas(T) * X_steam + enthalpyOfLiquid(T)*X_liquid;
--------------------------------- */

/* THIS WORKS!!!! +++++++++++++++++++++
  h := (T - 273.15)*dryair.cp * X_air + 
       Modelica.Media.Air.MoistAir.enthalpyOfCondensingGas(T) * X_steam + enthalpyOfLiquid(T)*X_liquid;
 +++++++++++++++++++++*/

  hDryAir := (T - 273.15)*dryair.cp;
  h := hDryAir * X_air +
       ((T-273.15) * steam.cp + 2501014.5) * X_steam +
       (T - 273.15)*4186*X_liquid;
end h_pTX;

Buildings.Media.PerfectGases.MoistAir.specificEnthalpy

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificEnthalpy	h	Specific enthalpy [J/kg]

Modelica definition

redeclare function extends specificEnthalpy "Specific enthalpy"
algorithm 
  h := h_pTX(state.p, state.T, state.X);
end specificEnthalpy;

Buildings.Media.PerfectGases.MoistAir.specificInternalEnergy

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificEnergy	u	Specific internal energy [J/kg]

Modelica definition

redeclare function extends specificInternalEnergy 
  "Specific internal energy"
  extends Modelica.Icons.Function;
algorithm 
  u := h_pTX(state.p,state.T,state.X) - gasConstant(state)*state.T;
end specificInternalEnergy;

Buildings.Media.PerfectGases.MoistAir.specificGibbsEnergy

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificEnergy	g	Specific Gibbs energy [J/kg]

Modelica definition

redeclare function extends specificGibbsEnergy 
  "Specific Gibbs energy"
  extends Modelica.Icons.Function;
algorithm 
  g := h_pTX(state.p,state.T,state.X) - state.T*specificEntropy(state);
end specificGibbsEnergy;

Buildings.Media.PerfectGases.MoistAir.specificHelmholtzEnergy

Information

Inputs

Type	Name	Default	Description
ThermodynamicState	state		thermodynamic state record

Outputs

Type	Name	Description
SpecificEnergy	f	Specific Helmholtz energy [J/kg]

Modelica definition

redeclare function extends specificHelmholtzEnergy 
  "Specific Helmholtz energy"
  extends Modelica.Icons.Function;
algorithm 
  f := h_pTX(state.p,state.T,state.X) - gasConstant(state)*state.T - state.T*specificEntropy(state);
end specificHelmholtzEnergy;

Buildings.Media.PerfectGases.MoistAir.T_phX

Information

Inputs

Type	Name	Default	Description
AbsolutePressure	p		Pressure [Pa]
SpecificEnthalpy	h		Specific enthalpy [J/kg]
MassFraction	X[:]		Mass fractions of composition [kg/kg]

Outputs

Type	Name	Description
Temperature	T	Temperature [K]

Modelica definition

function T_phX 
  "Compute temperature from specific enthalpy and mass fraction"
  input AbsolutePressure p "Pressure";
  input SpecificEnthalpy h "Specific enthalpy";
  input MassFraction X[:] "Mass fractions of composition";
  output Temperature T "Temperature";

protected 
package Internal 
    "Solve h(data,T) for T with given h (use only indirectly via temperature_phX)"
  extends Modelica.Media.Common.OneNonLinearEquation;

  redeclare record extends f_nonlinear_Data 
      "Data to be passed to non-linear function"
    extends Modelica.Media.IdealGases.Common.DataRecord;
  end f_nonlinear_Data;

  redeclare function extends f_nonlinear
  algorithm 
      y := h_pTX(p,x,X);
  end f_nonlinear;

  // Dummy definition has to be added for current Dymola
  redeclare function extends solve
  end solve;
end Internal;
protected 
constant Modelica.Media.IdealGases.Common.DataRecord steam=
              Modelica.Media.IdealGases.Common.SingleGasesData.H2O;
protected 
 SI.AbsolutePressure p_steam_sat "Partial saturation pressure of steam";
 SI.MassFraction x_sat "steam water mass fraction of saturation boundary";

algorithm 
  T := 273.15 + (h - 2501014.5 * X[Water])/((1 - X[Water])*dryair.cp + X[Water] *
     Buildings.Media.PerfectGases.Common.SingleGasData.H2O.cp);
  // check for saturation
  p_steam_sat :=saturationPressure(T);
  x_sat    :=k_mair*p_steam_sat/(p - p_steam_sat);
  // If the state is in the fog region, then the above equation is not valid, and
  // T is computed by inverting h_pTX(), which is much more costly.
  // For Buildings.Fluid.HeatExchangers.Examples.WetEffectivenessNTUPControl, the
  // computation above reduces the computing time by about a factor of 2.
  if (X[Water] > x_sat/(1 + x_sat)) then
     T := Internal.solve(h, TMin, TMax, p, X[1:nXi], steam);
  end if;
end T_phX;