Buildings.Media.Specialized.Air.PerfectGas

Model for air as a perfect gas

Information

This package contains a thermally perfect model of moist air.

A medium is called thermally perfect if

In addition, this medium model is calorically perfect, i.e., the specific heat capacities at constant pressure cp and constant volume cv are both constant (Bower 1998).

This medium uses the ideal gas law

ρ = p ⁄(R T),

where ρ is the density, p is the pressure, R is the gas constant and T is the temperature.

The enthalpy is computed using the convention that h=0 if T=0 °C and no water vapor is present.

Note that for typical building simulations, the media Buildings.Media.Air should be used as it leads generally to faster simulation.

References

Bower, William B. A primer in fluid mechanics: Dynamics of flows in one space dimension. CRC Press. 1998.

Extends from Modelica.Media.Interfaces.PartialCondensingGases (Base class for mixtures of condensing and non-condensing gases), Modelica.Icons.Package (Icon for standard packages).

Package Content

Name Description
Water=1 Index of water (in substanceNames, massFractions X, etc.)
Air=2 Index of air (in substanceNames, massFractions X, etc.)
Buildings.Media.Specialized.Air.PerfectGas.ThermodynamicState ThermodynamicState ThermodynamicState record for moist air
Buildings.Media.Specialized.Air.PerfectGas.BaseProperties BaseProperties  
Buildings.Media.Specialized.Air.PerfectGas.Xsaturation Xsaturation Steam water mass fraction of saturation boundary in kg_water/kg_moistair
Buildings.Media.Specialized.Air.PerfectGas.setState_pTX setState_pTX Thermodynamic state as function of p, T and composition X
Buildings.Media.Specialized.Air.PerfectGas.setState_phX setState_phX Thermodynamic state as function of p, h and composition X
Buildings.Media.Specialized.Air.PerfectGas.setState_dTX setState_dTX Thermodynamic state as function of d, T and composition X
Buildings.Media.Specialized.Air.PerfectGas.gasConstant gasConstant Gas constant
Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid saturationPressureLiquid Return saturation pressure of water as a function of temperature T in the range of 273.16 to 373.16 K
Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid_der saturationPressureLiquid_der Time derivative of saturationPressureLiquid
Buildings.Media.Specialized.Air.PerfectGas.sublimationPressureIce sublimationPressureIce Saturation curve valid for 223.16 <= T <= 273.16. Outside of these limits a (less accurate) result is returned
Buildings.Media.Specialized.Air.PerfectGas.sublimationPressureIce_der sublimationPressureIce_der Derivative function for 'sublimationPressureIce'
Buildings.Media.Specialized.Air.PerfectGas.saturationPressure saturationPressure Saturation curve valid for 223.16 <= T <= 373.16 (and slightly outside with less accuracy)
Buildings.Media.Specialized.Air.PerfectGas.pressure pressure Gas pressure
Buildings.Media.Specialized.Air.PerfectGas.temperature temperature Gas temperature
Buildings.Media.Specialized.Air.PerfectGas.density density Gas density
Buildings.Media.Specialized.Air.PerfectGas.specificEntropy specificEntropy Specific entropy (liquid part neglected, mixing entropy included)
Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfVaporization enthalpyOfVaporization Enthalpy of vaporization of water
Buildings.Media.Specialized.Air.PerfectGas.HeatCapacityOfWater HeatCapacityOfWater Specific heat capacity of water (liquid only) which is constant
Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfLiquid enthalpyOfLiquid Enthalpy of liquid (per unit mass of liquid) which is linear in the temperature
Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfLiquid der_enthalpyOfLiquid Temperature derivative of enthalpy of liquid per unit mass of liquid
Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfCondensingGas enthalpyOfCondensingGas Enthalpy of steam per unit mass of steam
Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfCondensingGas der_enthalpyOfCondensingGas Derivative of enthalpy of steam per unit mass of steam
Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfNonCondensingGas enthalpyOfNonCondensingGas Enthalpy of non-condensing gas per unit mass of steam
Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfNonCondensingGas der_enthalpyOfNonCondensingGas Derivative of enthalpy of non-condensing gas per unit mass of steam
Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfGas enthalpyOfGas Enthalpy of gas mixture per unit mass of gas mixture
Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfDryAir enthalpyOfDryAir Enthalpy of dry air per unit mass of dry air
Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfDryAir der_enthalpyOfDryAir Derivative of enthalpy of dry air per unit mass of dry air
Buildings.Media.Specialized.Air.PerfectGas.specificHeatCapacityCp specificHeatCapacityCp Specific heat capacity of gas mixture at constant pressure
Buildings.Media.Specialized.Air.PerfectGas.der_specificHeatCapacityCp der_specificHeatCapacityCp Derivative of specific heat capacity of gas mixture at constant pressure
Buildings.Media.Specialized.Air.PerfectGas.specificHeatCapacityCv specificHeatCapacityCv Specific heat capacity of gas mixture at constant volume
Buildings.Media.Specialized.Air.PerfectGas.der_specificHeatCapacityCv der_specificHeatCapacityCv Derivative of specific heat capacity of gas mixture at constant volume
Buildings.Media.Specialized.Air.PerfectGas.dynamicViscosity dynamicViscosity dynamic viscosity of dry air
Buildings.Media.Specialized.Air.PerfectGas.thermalConductivity thermalConductivity Thermal conductivity of dry air as a polynomial in the temperature
Buildings.Media.Specialized.Air.PerfectGas.specificEnthalpy specificEnthalpy Specific enthalpy
Buildings.Media.Specialized.Air.PerfectGas.specificEnthalpy_pTX specificEnthalpy_pTX Specific enthalpy
Buildings.Media.Specialized.Air.PerfectGas.specificInternalEnergy specificInternalEnergy Specific internal energy
Buildings.Media.Specialized.Air.PerfectGas.specificGibbsEnergy specificGibbsEnergy Specific Gibbs energy
Buildings.Media.Specialized.Air.PerfectGas.specificHelmholtzEnergy specificHelmholtzEnergy Specific Helmholtz energy
Buildings.Media.Specialized.Air.PerfectGas.temperature_phX temperature_phX Compute temperature from specific enthalpy and mass fraction
Buildings.Media.Specialized.Air.PerfectGas.GasProperties GasProperties Coefficient data record for properties of perfect gases
dryair Dry air properties
steam Steam properties
k_mair=steam.MM/dryair.MM Ratio of molar weights
h_fg=Buildings.Utilities.Psychrometrics.Constants.h_fg Latent heat of evaporation of water
cpWatLiq=Buildings.Utilities.Psychrometrics.Constants.cpWatLiq Specific heat capacity of liquid water
Buildings.Media.Specialized.Air.PerfectGas.s_pTX s_pTX Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)
Buildings.Media.Specialized.Air.PerfectGas.s_pTX_der s_pTX_der Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)
Inherited
fluidConstants={Modelica.Media.IdealGases.Common.FluidData.H2O,Modelica.Media.IdealGases.Common.FluidData.N2} Constant data for the fluid
Modelica.Media.Interfaces.PartialMixtureMedium.moleToMassFractions moleToMassFractions Return mass fractions X from mole fractions
Modelica.Media.Interfaces.PartialMixtureMedium.massToMoleFractions massToMoleFractions Return mole fractions from mass fractions X
ThermoStates=Modelica.Media.Interfaces.Choices.IndependentVariables.pTX Enumeration type for independent variables
mediumName="Moist air unsaturated perfect gas" Name of the medium
substanceNames={"water","air"} 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=false = 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=273.15 Reference temperature of Medium: default 25 deg Celsius
reference_X={0.01,0.99} 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
Modelica.Media.Interfaces.PartialMedium.FluidConstants FluidConstants Critical, triple, molecular and other standard data of fluid
Modelica.Media.Interfaces.PartialMedium.setState_psX setState_psX Return thermodynamic state as function of p, s and composition X or Xi
Modelica.Media.Interfaces.PartialMedium.setSmoothState setSmoothState Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b
Modelica.Media.Interfaces.PartialMedium.prandtlNumber prandtlNumber Return the Prandtl number
Modelica.Media.Interfaces.PartialMedium.heatCapacity_cp heatCapacity_cp Alias for deprecated name
Modelica.Media.Interfaces.PartialMedium.heatCapacity_cv heatCapacity_cv Alias for deprecated name
Modelica.Media.Interfaces.PartialMedium.isentropicExponent isentropicExponent Return isentropic exponent
Modelica.Media.Interfaces.PartialMedium.isentropicEnthalpy isentropicEnthalpy Return isentropic enthalpy
Modelica.Media.Interfaces.PartialMedium.velocityOfSound velocityOfSound Return velocity of sound
Modelica.Media.Interfaces.PartialMedium.isobaricExpansionCoefficient isobaricExpansionCoefficient Return overall the isobaric expansion coefficient beta
Modelica.Media.Interfaces.PartialMedium.beta beta Alias for isobaricExpansionCoefficient for user convenience
Modelica.Media.Interfaces.PartialMedium.isothermalCompressibility isothermalCompressibility Return overall the isothermal compressibility factor
Modelica.Media.Interfaces.PartialMedium.kappa kappa Alias of isothermalCompressibility for user convenience
Modelica.Media.Interfaces.PartialMedium.density_derp_h density_derp_h Return density derivative w.r.t. pressure at const specific enthalpy
Modelica.Media.Interfaces.PartialMedium.density_derh_p density_derh_p Return density derivative w.r.t. specific enthalpy at constant pressure
Modelica.Media.Interfaces.PartialMedium.density_derp_T density_derp_T Return density derivative w.r.t. pressure at const temperature
Modelica.Media.Interfaces.PartialMedium.density_derT_p density_derT_p Return density derivative w.r.t. temperature at constant pressure
Modelica.Media.Interfaces.PartialMedium.density_derX density_derX Return density derivative w.r.t. mass fraction
Modelica.Media.Interfaces.PartialMedium.molarMass molarMass Return the molar mass of the medium
Modelica.Media.Interfaces.PartialMedium.specificEntropy_pTX specificEntropy_pTX Return specific enthalpy from p, T, and X or Xi
Modelica.Media.Interfaces.PartialMedium.density_pTX density_pTX Return density from p, T, and X or Xi
Modelica.Media.Interfaces.PartialMedium.density_phX density_phX Return density from p, h, and X or Xi
Modelica.Media.Interfaces.PartialMedium.temperature_psX temperature_psX Return temperature from p,s, and X or Xi
Modelica.Media.Interfaces.PartialMedium.density_psX density_psX Return density from p, s, and X or Xi
Modelica.Media.Interfaces.PartialMedium.specificEnthalpy_psX specificEnthalpy_psX Return specific enthalpy from p, s, and X or Xi
Modelica.Media.Interfaces.PartialMedium.MassFlowRate MassFlowRate Type for mass flow rate with medium specific attributes
Modelica.Media.Interfaces.Types.AbsolutePressure AbsolutePressure Type for absolute pressure with medium specific attributes
Modelica.Media.Interfaces.Types.Density Density Type for density with medium specific attributes
Modelica.Media.Interfaces.Types.DynamicViscosity DynamicViscosity Type for dynamic viscosity with medium specific attributes
Modelica.Media.Interfaces.Types.EnthalpyFlowRate EnthalpyFlowRate Type for enthalpy flow rate with medium specific attributes
Modelica.Media.Interfaces.Types.MassFraction MassFraction Type for mass fraction with medium specific attributes
Modelica.Media.Interfaces.Types.MoleFraction MoleFraction Type for mole fraction with medium specific attributes
Modelica.Media.Interfaces.Types.MolarMass MolarMass Type for molar mass with medium specific attributes
Modelica.Media.Interfaces.Types.MolarVolume MolarVolume Type for molar volume with medium specific attributes
Modelica.Media.Interfaces.Types.IsentropicExponent IsentropicExponent Type for isentropic exponent with medium specific attributes
Modelica.Media.Interfaces.Types.SpecificEnergy SpecificEnergy Type for specific energy with medium specific attributes
Modelica.Media.Interfaces.Types.SpecificInternalEnergy SpecificInternalEnergy Type for specific internal energy with medium specific attributes
Modelica.Media.Interfaces.Types.SpecificEnthalpy SpecificEnthalpy Type for specific enthalpy with medium specific attributes
Modelica.Media.Interfaces.Types.SpecificEntropy SpecificEntropy Type for specific entropy with medium specific attributes
Modelica.Media.Interfaces.Types.SpecificHeatCapacity SpecificHeatCapacity Type for specific heat capacity with medium specific attributes
Modelica.Media.Interfaces.Types.SurfaceTension SurfaceTension Type for surface tension with medium specific attributes
Modelica.Media.Interfaces.Types.Temperature Temperature Type for temperature with medium specific attributes
Modelica.Media.Interfaces.Types.ThermalConductivity ThermalConductivity Type for thermal conductivity with medium specific attributes
Modelica.Media.Interfaces.Types.PrandtlNumber PrandtlNumber Type for Prandtl number with medium specific attributes
Modelica.Media.Interfaces.Types.VelocityOfSound VelocityOfSound Type for velocity of sound with medium specific attributes
Modelica.Media.Interfaces.Types.ExtraProperty ExtraProperty Type for unspecified, mass-specific property transported by flow
Modelica.Media.Interfaces.Types.CumulativeExtraProperty CumulativeExtraProperty Type for conserved integral of unspecified, mass specific property
Modelica.Media.Interfaces.Types.ExtraPropertyFlowRate ExtraPropertyFlowRate Type for flow rate of unspecified, mass-specific property
Modelica.Media.Interfaces.Types.IsobaricExpansionCoefficient IsobaricExpansionCoefficient Type for isobaric expansion coefficient with medium specific attributes
Modelica.Media.Interfaces.Types.DipoleMoment DipoleMoment Type for dipole moment with medium specific attributes
Modelica.Media.Interfaces.Types.DerDensityByPressure DerDensityByPressure Type for partial derivative of density with respect to pressure with medium specific attributes
Modelica.Media.Interfaces.Types.DerDensityByEnthalpy DerDensityByEnthalpy Type for partial derivative of density with respect to enthalpy with medium specific attributes
Modelica.Media.Interfaces.Types.DerEnthalpyByPressure DerEnthalpyByPressure Type for partial derivative of enthalpy with respect to pressure with medium specific attributes
Modelica.Media.Interfaces.Types.DerDensityByTemperature DerDensityByTemperature Type for partial derivative of density with respect to temperature with medium specific attributes
Modelica.Media.Interfaces.Types.DerTemperatureByPressure DerTemperatureByPressure Type for partial derivative of temperature with respect to pressure with medium specific attributes
Modelica.Media.Interfaces.Types.SaturationProperties SaturationProperties Saturation properties of two phase medium
Modelica.Media.Interfaces.Types.FluidLimits FluidLimits Validity limits for fluid model
Modelica.Media.Interfaces.Types.FixedPhase FixedPhase Phase of the fluid: 1 for 1-phase, 2 for two-phase, 0 for not known, e.g., interactive use
Modelica.Media.Interfaces.Types.Basic Basic The most basic version of a record used in several degrees of detail
Modelica.Media.Interfaces.Types.IdealGas IdealGas The ideal gas version of a record used in several degrees of detail
Modelica.Media.Interfaces.Types.TwoPhase TwoPhase The two phase fluid version of a record used in several degrees of detail

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 GasProperties dryair(
    R =    Modelica.Media.IdealGases.Common.SingleGasesData.Air.R,
    MM =   Modelica.Media.IdealGases.Common.SingleGasesData.Air.MM,
    cp =   Buildings.Utilities.Psychrometrics.Constants.cpAir,
    cv =   Buildings.Utilities.Psychrometrics.Constants.cpAir
             -Modelica.Media.IdealGases.Common.SingleGasesData.Air.R)
    "Dry air properties";
  constant GasProperties steam(
    R =    Modelica.Media.IdealGases.Common.SingleGasesData.H2O.R,
    MM =   Modelica.Media.IdealGases.Common.SingleGasesData.H2O.MM,
    cp =   Buildings.Utilities.Psychrometrics.Constants.cpSte,
    cv =   Buildings.Utilities.Psychrometrics.Constants.cpSte
             -Modelica.Media.IdealGases.Common.SingleGasesData.H2O.R)
    "Steam properties";
  constant Real k_mair =  steam.MM/dryair.MM "Ratio of molar weights";
  constant Modelica.SIunits.SpecificEnergy h_fg=
    Buildings.Utilities.Psychrometrics.Constants.h_fg
    "Latent heat of evaporation of water";
  constant Modelica.SIunits.SpecificHeatCapacity cpWatLiq=
    Buildings.Utilities.Psychrometrics.Constants.cpWatLiq
    "Specific heat capacity of liquid water";

Buildings.Media.Specialized.Air.PerfectGas.ThermodynamicState Buildings.Media.Specialized.Air.PerfectGas.ThermodynamicState

ThermodynamicState record for moist air

Information

Extends from (Thermodynamic state variables).

Modelica definition

redeclare record extends ThermodynamicState( p(start=p_default), T(start=T_default), X(start=X_default)) "ThermodynamicState record for moist air" end ThermodynamicState;

Buildings.Media.Specialized.Air.PerfectGas.BaseProperties Buildings.Media.Specialized.Air.PerfectGas.BaseProperties

Information

Extends from (Base properties (p, d, T, h, u, R, MM and, if applicable, X and Xi) of a medium).

Parameters

TypeNameDefaultDescription
BooleanstandardOrderComponentstrueIf true, and reducedX = true, the last element of X will be computed from the other ones
Advanced
BooleanpreferredMediumStatesfalse= true if StateSelect.prefer shall be used for the independent property variables of the medium

Modelica definition

redeclare replaceable model extends BaseProperties( p(stateSelect=if preferredMediumStates then StateSelect.prefer else StateSelect.default), Xi(each stateSelect=if preferredMediumStates then StateSelect.prefer else StateSelect.default), final standardOrderComponents=true) /* 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. */ protected constant Modelica.SIunits.MolarMass[2] MMX = {steam.MM,dryair.MM} "Molar masses of components"; MassFraction X_steam "Mass fraction of steam water"; MassFraction X_air "Mass fraction of air"; equation assert(T >= 200.0, " In " + getInstanceName() + ": Temperature T exceeded its minimum allowed value of -73.15 degC (200 Kelvin) as required from medium model \"" + mediumName + "\"."); assert(T <= 423.15, " In " + getInstanceName() + ": Temperature T exceeded its maximum allowed value of 150 degC (423.15 Kelvin) as required from medium model \"" + mediumName + "\"."); MM = 1/(Xi[Water]/MMX[Water]+(1.0-Xi[Water])/MMX[Air]); X_steam = Xi[Water]; X_air = 1-Xi[Water]; h = (T - reference_T)*dryair.cp * (1 - Xi[Water]) + ((T-reference_T) * steam.cp + h_fg) * Xi[Water]; R = dryair.R*(1 - X_steam) + steam.R*X_steam; // 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 negligible with respect to the volume of air and of steam */ state.p = p; state.T = T; state.X = X; end BaseProperties;

Buildings.Media.Specialized.Air.PerfectGas.Xsaturation Buildings.Media.Specialized.Air.PerfectGas.Xsaturation

Steam water mass fraction of saturation boundary in kg_water/kg_moistair

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
MassFractionX_satSteam 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.Specialized.Air.PerfectGas.setState_pTX Buildings.Media.Specialized.Air.PerfectGas.setState_pTX

Thermodynamic state as function of p, T and composition X

Information

Extends from Modelica.Media.Air.MoistAir.setState_pTX (Return thermodynamic state as function of pressure p, temperature T and composition X).

Inputs

TypeNameDefaultDescription
AbsolutePressurep Pressure [Pa]
TemperatureT Temperature [K]
MassFractionX[:]reference_XMass fractions [kg/kg]

Outputs

TypeNameDescription
ThermodynamicStatestateThermodynamic 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.Specialized.Air.PerfectGas.setState_phX Buildings.Media.Specialized.Air.PerfectGas.setState_phX

Thermodynamic state as function of p, h and composition X

Information

Function to set the state for given pressure, enthalpy and species concentration.

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

Inputs

TypeNameDefaultDescription
AbsolutePressurep Pressure [Pa]
SpecificEnthalpyh Specific enthalpy [J/kg]
MassFractionX[:] Mass fractions [kg/kg]

Outputs

TypeNameDescription
ThermodynamicStatestate 

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=temperature_phX(p,h,X),X=X) else ThermodynamicState(p=p,T=temperature_phX(p,h,X), X=cat(1,X,{1-sum(X)})); end setState_phX;

Buildings.Media.Specialized.Air.PerfectGas.setState_dTX Buildings.Media.Specialized.Air.PerfectGas.setState_dTX

Thermodynamic state as function of d, T and composition X

Information

The thermodynamic state record is computed from density d, temperature T and composition X.

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

Inputs

TypeNameDefaultDescription
Densityd Density [kg/m3]
TemperatureT Temperature [K]
MassFractionX[:]reference_XMass fractions [kg/kg]

Outputs

TypeNameDescription
ThermodynamicStatestateThermodynamic state

Modelica definition

redeclare function setState_dTX "Thermodynamic state as function of d, T and composition X" extends Modelica.Icons.Function; input Density d "Density"; input Temperature T "Temperature"; input MassFraction X[:]=reference_X "Mass fractions"; output ThermodynamicState state "Thermodynamic state"; algorithm state := if size(X, 1) == nX then ThermodynamicState( p=d*({steam.R,dryair.R}*X)*T, T=T, X=X) else ThermodynamicState( p=d*({steam.R,dryair.R}*cat( 1, X, {1 - sum(X)}))*T, T=T, X=cat( 1, X, {1 - sum(X)})); end setState_dTX;

Buildings.Media.Specialized.Air.PerfectGas.gasConstant Buildings.Media.Specialized.Air.PerfectGas.gasConstant

Gas constant

Information

Extends from (Return the gas constant of the mixture (also for liquids)).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state

Outputs

TypeNameDescription
SpecificHeatCapacityRMixture gas constant [J/(kg.K)]

Modelica definition

redeclare function extends gasConstant "Gas constant" algorithm R := dryair.R*(1 - state.X[Water]) + steam.R*state.X[Water]; end gasConstant;

Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid

Return saturation pressure of water as a function of temperature T in the range of 273.16 to 373.16 K

Information

Saturation pressure of water above the triple point temperature is computed from temperature. It's range of validity is between 273.16 and 373.16 K. Outside these limits a less accurate result is returned.

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

Inputs

TypeNameDefaultDescription
TemperatureTsat saturation temperature [K]

Outputs

TypeNameDescription
AbsolutePressurepsatsaturation 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=Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid_der); extends Modelica.Icons.Function; input Modelica.SIunits.Temperature Tsat "saturation temperature"; output Modelica.SIunits.AbsolutePressure psat "saturation pressure"; // This function is declared here explicitly, instead of referencing the function in its // base class, since otherwise Dymola 7.3 does not find the derivative for the model // Buildings.Fluid.Sensors.Examples.MassFraction algorithm psat := 611.657*Modelica.Math.exp(17.2799 - 4102.99/(Tsat - 35.719)); end saturationPressureLiquid;

Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid_der Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid_der

Time derivative of saturationPressureLiquid

Information

Derivative function of Buildings.Media.Specialized.Air.PerfectGas.saturationPressureLiquid

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

Inputs

TypeNameDefaultDescription
TemperatureTsat Saturation temperature [K]
RealdTsatdTsat( unit...Saturation temperature derivative [K/s]

Outputs

TypeNameDescription
Realpsat_derSaturation pressure [Pa/s]

Modelica definition

function saturationPressureLiquid_der "Time derivative of saturationPressureLiquid" extends Modelica.Icons.Function; input Modelica.SIunits.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.Specialized.Air.PerfectGas.sublimationPressureIce Buildings.Media.Specialized.Air.PerfectGas.sublimationPressureIce

Saturation curve valid for 223.16 <= T <= 273.16. Outside of these limits a (less accurate) result is returned

Inputs

TypeNameDefaultDescription
TemperatureTsat Sublimation temperature [K]

Outputs

TypeNameDescription
AbsolutePressurepsatSublimation 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.Specialized.Air.PerfectGas.sublimationPressureIce_der Buildings.Media.Specialized.Air.PerfectGas.sublimationPressureIce_der

Derivative function for 'sublimationPressureIce'

Inputs

TypeNameDefaultDescription
TemperatureTsat Sublimation temperature [K]
RealdTsat Sublimation temperature derivative [K/s]

Outputs

TypeNameDescription
Realpsat_derSublimation pressure derivative [Pa/s]

Modelica definition

function sublimationPressureIce_der = Modelica.Media.Air.MoistAir.sublimationPressureIce_der "Derivative function for 'sublimationPressureIce'";

Buildings.Media.Specialized.Air.PerfectGas.saturationPressure Buildings.Media.Specialized.Air.PerfectGas.saturationPressure

Saturation curve valid for 223.16 <= T <= 373.16 (and slightly outside with less accuracy)

Information

Extends from (Return saturation pressure of condensing fluid).

Inputs

TypeNameDefaultDescription
TemperatureTsat Saturation temperature [K]

Outputs

TypeNameDescription
AbsolutePressurepsatSaturation 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.regStep( y1=saturationPressureLiquid(Tsat), y2=sublimationPressureIce(Tsat), x=Tsat-273.16, x_small=1.0); end saturationPressure;

Buildings.Media.Specialized.Air.PerfectGas.pressure Buildings.Media.Specialized.Air.PerfectGas.pressure

Gas pressure

Information

Pressure is returned from the thermodynamic state record input as a simple assignment.

Extends from (Return pressure).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
AbsolutePressurepPressure [Pa]

Modelica definition

redeclare function extends pressure "Gas pressure" algorithm p := state.p; end pressure;

Buildings.Media.Specialized.Air.PerfectGas.temperature Buildings.Media.Specialized.Air.PerfectGas.temperature

Gas temperature

Information

Temperature is returned from the thermodynamic state record input as a simple assignment.

Extends from (Return temperature).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
TemperatureTTemperature [K]

Modelica definition

redeclare function extends temperature "Gas temperature" algorithm T := state.T; end temperature;

Buildings.Media.Specialized.Air.PerfectGas.density Buildings.Media.Specialized.Air.PerfectGas.density

Gas density

Information

Density is computed from pressure, temperature and composition in the thermodynamic state record applying the ideal gas law.

Extends from (Return density).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
DensitydDensity [kg/m3]

Modelica definition

redeclare function extends density "Gas density" algorithm d := state.p/(gasConstant(state)*state.T); end density;

Buildings.Media.Specialized.Air.PerfectGas.specificEntropy Buildings.Media.Specialized.Air.PerfectGas.specificEntropy

Specific entropy (liquid part neglected, mixing entropy included)

Information

Specific entropy is calculated from the thermodynamic state record, assuming ideal gas behavior and including entropy of mixing. Liquid or solid water is not taken into account, the entire water content X[1] is assumed to be in the vapor state (relative humidity below 1.0).

Extends from (Return specific entropy).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificEntropysSpecific entropy [J/(kg.K)]

Modelica definition

redeclare function extends specificEntropy "Specific entropy (liquid part neglected, mixing entropy included)" algorithm s := s_pTX( state.p, state.T, state.X); end specificEntropy;

Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfVaporization Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfVaporization

Enthalpy of vaporization of water

Information

Extends from (Return vaporization enthalpy of condensing fluid).

Inputs

TypeNameDefaultDescription
TemperatureT Temperature [K]

Outputs

TypeNameDescription
SpecificEnthalpyr0Vaporization enthalpy [J/kg]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.HeatCapacityOfWater Buildings.Media.Specialized.Air.PerfectGas.HeatCapacityOfWater

Specific heat capacity of water (liquid only) which is constant

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT [K]

Outputs

TypeNameDescription
SpecificHeatCapacitycp_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 := cpWatLiq; end HeatCapacityOfWater;

Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfLiquid Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfLiquid

Enthalpy of liquid (per unit mass of liquid) which is linear in the temperature

Information

Extends from (Return liquid enthalpy of condensing fluid).

Inputs

TypeNameDefaultDescription
TemperatureT Temperature [K]

Outputs

TypeNameDescription
SpecificEnthalpyhLiquid 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 - reference_T)*cpWatLiq; end enthalpyOfLiquid;

Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfLiquid Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfLiquid

Temperature derivative of enthalpy of liquid per unit mass of liquid

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]
Realder_T temperature derivative

Outputs

TypeNameDescription
Realder_hderivative 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 := cpWatLiq*der_T; end der_enthalpyOfLiquid;

Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfCondensingGas Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfCondensingGas

Enthalpy of steam per unit mass of steam

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]

Outputs

TypeNameDescription
SpecificEnthalpyhsteam 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-reference_T) * steam.cp + enthalpyOfVaporization(T); end enthalpyOfCondensingGas;

Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfCondensingGas Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfCondensingGas

Derivative of enthalpy of steam per unit mass of steam

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]
Realder_T temperature derivative

Outputs

TypeNameDescription
Realder_hderivative 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.Specialized.Air.PerfectGas.enthalpyOfNonCondensingGas Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfNonCondensingGas

Enthalpy of non-condensing gas per unit mass of steam

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]

Outputs

TypeNameDescription
SpecificEnthalpyhenthalpy [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.Specialized.Air.PerfectGas.der_enthalpyOfNonCondensingGas Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfNonCondensingGas

Derivative of enthalpy of non-condensing gas per unit mass of steam

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]
Realder_T temperature derivative

Outputs

TypeNameDescription
Realder_hderivative 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.Specialized.Air.PerfectGas.enthalpyOfGas Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfGas

Enthalpy of gas mixture per unit mass of gas mixture

Information

Extends from (Return enthalpy of non-condensing gas mixture).

Inputs

TypeNameDefaultDescription
TemperatureT Temperature [K]
MassFractionX[:] Vector of mass fractions [kg/kg]

Outputs

TypeNameDescription
SpecificEnthalpyhSpecific 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.Specialized.Air.PerfectGas.enthalpyOfDryAir Buildings.Media.Specialized.Air.PerfectGas.enthalpyOfDryAir

Enthalpy of dry air per unit mass of dry air

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]

Outputs

TypeNameDescription
SpecificEnthalpyhdry 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 - reference_T)*dryair.cp; end enthalpyOfDryAir;

Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfDryAir Buildings.Media.Specialized.Air.PerfectGas.der_enthalpyOfDryAir

Derivative of enthalpy of dry air per unit mass of dry air

Information

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

Inputs

TypeNameDefaultDescription
TemperatureT temperature [K]
Realder_T temperature derivative

Outputs

TypeNameDescription
Realder_hderivative 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.Specialized.Air.PerfectGas.specificHeatCapacityCp Buildings.Media.Specialized.Air.PerfectGas.specificHeatCapacityCp

Specific heat capacity of gas mixture at constant pressure

Information

Extends from (Return specific heat capacity at constant pressure).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificHeatCapacitycpSpecific heat capacity at constant pressure [J/(kg.K)]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.der_specificHeatCapacityCp

Derivative of specific heat capacity of gas mixture at constant pressure

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate  
ThermodynamicStateder_state  

Outputs

TypeNameDescription
Realder_cp[J/(kg.K.s)]

Modelica definition

replaceable function der_specificHeatCapacityCp "Derivative of specific heat capacity of gas mixture at constant pressure" input ThermodynamicState state; input ThermodynamicState der_state; output Real der_cp(unit="J/(kg.K.s)"); algorithm der_cp := (steam.cp-dryair.cp)*der_state.X[Water]; end der_specificHeatCapacityCp;

Buildings.Media.Specialized.Air.PerfectGas.specificHeatCapacityCv Buildings.Media.Specialized.Air.PerfectGas.specificHeatCapacityCv

Specific heat capacity of gas mixture at constant volume

Information

Extends from (Return specific heat capacity at constant volume).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificHeatCapacitycvSpecific heat capacity at constant volume [J/(kg.K)]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.der_specificHeatCapacityCv

Derivative of specific heat capacity of gas mixture at constant volume

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate  
ThermodynamicStateder_state  

Outputs

TypeNameDescription
Realder_cv[J/(kg.K.s)]

Modelica definition

replaceable function der_specificHeatCapacityCv "Derivative of specific heat capacity of gas mixture at constant volume" input ThermodynamicState state; input ThermodynamicState der_state; output Real der_cv(unit="J/(kg.K.s)"); algorithm der_cv := (steam.cv-dryair.cv)*der_state.X[Water]; end der_specificHeatCapacityCv;

Buildings.Media.Specialized.Air.PerfectGas.dynamicViscosity Buildings.Media.Specialized.Air.PerfectGas.dynamicViscosity

dynamic viscosity of dry air

Information

Extends from (Return dynamic viscosity).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
DynamicViscosityetaDynamic viscosity [Pa.s]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.thermalConductivity Buildings.Media.Specialized.Air.PerfectGas.thermalConductivity

Thermal conductivity of dry air as a polynomial in the temperature

Information

Extends from (Return thermal conductivity).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
ThermalConductivitylambdaThermal 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.Specialized.Air.PerfectGas.specificEnthalpy Buildings.Media.Specialized.Air.PerfectGas.specificEnthalpy

Specific enthalpy

Information

Extends from (Return specific enthalpy).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificEnthalpyhSpecific enthalpy [J/kg]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.specificEnthalpy_pTX Buildings.Media.Specialized.Air.PerfectGas.specificEnthalpy_pTX

Specific enthalpy

Information

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

Inputs

TypeNameDefaultDescription
Pressurep Pressure [Pa]
TemperatureT Temperature [K]
MassFractionX[:] Mass fractions of moist air [1]

Outputs

TypeNameDescription
SpecificEnthalpyhSpecific enthalpy at p, T, X [J/kg]

Modelica definition

redeclare replaceable function specificEnthalpy_pTX "Specific enthalpy" extends Modelica.Icons.Function; input Modelica.SIunits.Pressure p "Pressure"; input Modelica.SIunits.Temperature T "Temperature"; input Modelica.SIunits.MassFraction X[:] "Mass fractions of moist air"; output Modelica.SIunits.SpecificEnthalpy h "Specific enthalpy at p, T, X"; protected Modelica.SIunits.SpecificEnthalpy hDryAir "Enthalpy of dry air"; algorithm hDryAir := (T - reference_T)*dryair.cp; h := hDryAir * (1 - X[Water]) + ((T-reference_T) * steam.cp + h_fg) * X[Water]; end specificEnthalpy_pTX;

Buildings.Media.Specialized.Air.PerfectGas.specificInternalEnergy Buildings.Media.Specialized.Air.PerfectGas.specificInternalEnergy

Specific internal energy

Information

Extends from Modelica.Icons.Function (Icon for functions), (Return specific internal energy).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificEnergyuSpecific internal energy [J/kg]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.specificGibbsEnergy Buildings.Media.Specialized.Air.PerfectGas.specificGibbsEnergy

Specific Gibbs energy

Information

Extends from Modelica.Icons.Function (Icon for functions), (Return specific Gibbs energy).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificEnergygSpecific Gibbs energy [J/kg]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.specificHelmholtzEnergy Buildings.Media.Specialized.Air.PerfectGas.specificHelmholtzEnergy

Specific Helmholtz energy

Information

Extends from Modelica.Icons.Function (Icon for functions), (Return specific Helmholtz energy).

Inputs

TypeNameDefaultDescription
ThermodynamicStatestate Thermodynamic state record

Outputs

TypeNameDescription
SpecificEnergyfSpecific Helmholtz energy [J/kg]

Modelica definition

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

Buildings.Media.Specialized.Air.PerfectGas.temperature_phX Buildings.Media.Specialized.Air.PerfectGas.temperature_phX

Compute temperature from specific enthalpy and mass fraction

Information

Temperature as a function of specific enthalpy and species concentration. The pressure is input for compatibility with the medium models, but the temperature is independent of the pressure.

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

Inputs

TypeNameDefaultDescription
AbsolutePressurep Pressure [Pa]
SpecificEnthalpyh specific enthalpy [J/kg]
MassFractionX[:] mass fractions of composition [kg/kg]

Outputs

TypeNameDescription
TemperatureTtemperature [K]

Modelica definition

redeclare replaceable function temperature_phX "Compute temperature from specific enthalpy and mass fraction" extends Modelica.Icons.Function; input AbsolutePressure p "Pressure"; input SpecificEnthalpy h "specific enthalpy"; input MassFraction[:] X "mass fractions of composition"; output Temperature T "temperature"; algorithm T := reference_T + (h - h_fg * X[Water]) /((1 - X[Water])*dryair.cp + X[Water] * steam.cp); end temperature_phX;

Buildings.Media.Specialized.Air.PerfectGas.GasProperties Buildings.Media.Specialized.Air.PerfectGas.GasProperties

Coefficient data record for properties of perfect gases

Information

This data record contains the coefficients for perfect gases.

Extends from Modelica.Icons.Record (Icon for records).

Modelica definition

record GasProperties "Coefficient data record for properties of perfect gases" extends Modelica.Icons.Record; Modelica.SIunits.MolarMass MM "Molar mass"; Modelica.SIunits.SpecificHeatCapacity R "Gas constant"; Modelica.SIunits.SpecificHeatCapacity cp "Specific heat capacity at constant pressure"; Modelica.SIunits.SpecificHeatCapacity cv = cp-R "Specific heat capacity at constant volume"; end GasProperties;

Buildings.Media.Specialized.Air.PerfectGas.s_pTX Buildings.Media.Specialized.Air.PerfectGas.s_pTX

Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)

Inputs

TypeNameDefaultDescription
Pressurep Pressure [Pa]
TemperatureT Temperature [K]
MassFractionX[:] Mass fractions of moist air [1]

Outputs

TypeNameDescription
SpecificEntropysSpecific entropy at p, T, X [J/(kg.K)]

Modelica definition

function s_pTX = Modelica.Media.Air.MoistAir.s_pTX "Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)";

Buildings.Media.Specialized.Air.PerfectGas.s_pTX_der Buildings.Media.Specialized.Air.PerfectGas.s_pTX_der

Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)

Inputs

TypeNameDefaultDescription
Pressurep Pressure [Pa]
TemperatureT Temperature [K]
MassFractionX[:] Mass fractions of moist air [1]
Realdp Derivative of pressure [Pa/s]
RealdT Derivative of temperature [K/s]
RealdX[nX] Derivative of mass fractions [1/s]

Outputs

TypeNameDescription
RealdsSpecific entropy at p, T, X [J/(kg.K.s)]

Modelica definition

function s_pTX_der = Modelica.Media.Air.MoistAir.s_pTX_der "Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)";