ReferenceMoistAirReferenceMoistAir: Detailed moist air model (143.15 ... 2000 K) 
ThermodynamicState record for moist air 

Moist air base properties record 

Return thermodynamic state as function of pressure p, temperature T and composition X 

Return thermodynamic state as function of pressure p, specific enthalpy h and composition X 

Return thermodynamic state as function of pressure p, specific enthalpy h and composition X 

Return thermodynamic state as function of density d, temperature T and composition X 

Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b 

Return absolute humitity per unit mass of moist air at saturation as a function of the thermodynamic state record 

Return absolute humitity per unit mass of dry air at saturation as a function of the thermodynamic state record 

Return mass fractions as a function of pressure, temperature and relative humidity 

Return mass fraction of water vapor 

Return mass fraction of liquid and solid water 

Return saturation mass fractions 

Return mass fvraction at saturation boundary given pressure and saturation pressure 

Return mass fractions as a function of pressure, temperature and absolute humidity in kg(water)/kg(dry air) 

Return water content in kg(water)/kg(dry air) given mass fractions 

Return relative humidity 

Return ideal gas constant as a function from thermodynamic state, only valid for phi<1 

Return saturation pressure of water as a function of temperature T 

Return sublimation pressure of water as a function of temperature T between 223.16 and 273.16 K 

Return saturation pressure of condensing fluid 

Return saturation temperature of condensing fluid 

Return enthalpy of vaporization of water 

Return enthalpy of liquid water 

Return specific enthalpy of gas (air and steam) 

Return specific enthalpy of steam 

Return specific enthalpy of dry air 

Return specific enthalpy of dry air 

Return specific enthalpy of water (solid + liquid + steam) 

Return specific enthalpy of steam 

Return enthalpy of liquid and solid water 

Returns pressure of ideal gas as a function of the thermodynamic state record 

Return temperature of ideal gas as a function of the thermodynamic state record 

Returns density as a function of the thermodynamic state record 

Return specific enthalpy of moist air as a function of the thermodynamic state record 

Return specific internal energy of moist air as a function of the thermodynamic state record 

Return specific entropy from thermodynamic state record, only valid for phi<1 

Return specific Gibbs energy as a function of the thermodynamic state record, only valid for phi<1 

Return specific Helmholtz energy as a function of the thermodynamic state record, only valid for phi<1 

Return specific heat capacity at constant pressure as a function of the thermodynamic state record 

Return specific heat capacity at constant volume as a function of the thermodynamic state record 

Return isentropic exponent 

Return isentropic enthalpy 

Return velocity of sound 

Return the molar mass of the medium 

Return dynamic viscosity as a function of the thermodynamic state record, valid from 73.15 K to 373.15 K 

Return thermal conductivity as a function of the thermodynamic state record, valid from 73.15 K to 373.15 K 

Utility package for moist air 
ThermoStates 
Value: Modelica.Media.Interfaces.Choices.IndependentVariables.pTX Type: IndependentVariables Description: Enumeration type for independent variables 

mediumName 
Value: "Moist air" Type: String Description: Name of the medium 
substanceNames 
Value: {"Water", "Air"} Type: String[:] Description: Names of the mixture substances. Set substanceNames={mediumName} if only one substance. 
extraPropertiesNames 
Value: fill("", 0) Type: String[:] Description: Names of the additional (extra) transported properties. Set extraPropertiesNames=fill("",0) if unused 
singleState 
Value: false Type: Boolean Description: = true, if u and d are not a function of pressure 
reducedX 
Value: true Type: Boolean Description: = true if medium contains the equation sum(X) = 1.0; set reducedX=true if only one substance (see docu for details) 
fixedX 
Value: false Type: Boolean Description: = true if medium contains the equation X = reference_X 
reference_p 
Value: 101325 Type: AbsolutePressure (Pa) Description: Reference pressure of Medium: default 1 atmosphere 
reference_T 
Value: 298.15 Type: Temperature (K) Description: Reference temperature of Medium: default 25 deg Celsius 
reference_X 
Value: {0.01, 0.99} Type: MassFraction[nX] (kg/kg) Description: Default mass fractions of medium 
p_default 
Value: 101325 Type: AbsolutePressure (Pa) Description: Default value for pressure of medium (for initialization) 
T_default 
Value: Modelica.SIunits.Conversions.from_degC(20) Type: Temperature (K) Description: Default value for temperature of medium (for initialization) 
h_default 
Value: specificEnthalpy_pTX(p_default, T_default, X_default) Type: SpecificEnthalpy (J/kg) Description: Default value for specific enthalpy of medium (for initialization) 
X_default 
Value: reference_X Type: MassFraction[nX] (kg/kg) Description: Default value for mass fractions of medium (for initialization) 
C_default 
Value: fill(0, nC) Type: ExtraProperty[nC] Description: Default value for trace substances of medium (for initialization) 
nS 
Value: size(substanceNames, 1) Type: Integer Description: Number of substances 
nX 
Value: nS Type: Integer Description: Number of mass fractions 
nXi 
Value: if fixedX then 0 else if reducedX then nS  1 else nS Type: Integer Description: Number of structurally independent mass fractions (see docu for details) 
nC 
Value: size(extraPropertiesNames, 1) Type: Integer Description: Number of extra (outside of standard massbalance) transported properties 
C_nominal 
Value: 1.0e6 * ones(nC) Type: Real[nC] Description: Default for the nominal values for the extra properties 
fluidConstants 
Value: {Utilities.Water95_Utilities.waterConstants, Modelica.Media.Air.ReferenceAir.airConstants} Type: FluidConstants[nS] Description: Constant data for the fluid 
Water 
Value: 1 Type: Integer Description: Index of water (in substanceNames, massFractions X, etc.) 
Air 
Value: 2 Type: Integer Description: Index of air (in substanceNames, massFractions X, etc.) 
useEnhancementFactor 
Value: false Type: Boolean Description: Use the enhancement factor in the calculations 
useDissociation 
Value: true Type: Boolean Description: Take dissociation into account for high temperatures 
k_mair 
Value: steam.MM / dryair.MM Type: Real Description: Ratio of molar weights 
dryair 
Value: ReferenceAir.Air_Utilities.Basic.Constants Type: FundamentalConstants 
steam 
Value: Utilities.Water95_Utilities.Constants Type: FundamentalConstants 
MMX 
Value: {steam.MM, dryair.MM} Type: MolarMass[2] (kg/mol) Description: Molar masses of components 
This information is part of the Modelica Standard Library maintained by the Modelica Association.
Calculation of fluid properties for moist air in the region from 143.15 Kelvin to 2000 Kelvin at pressures up to 10 MPa. This model of moist air is based on the diploma thesis of Hellriegel [10] with small modifications. Moist air is treated as an ideal mixture of the real fluids air and water.
The functions provided by this package shall be used inside of the restricted limits according to the referenced literature.
The package MoistAir can be used as any other medium model (see User's Guide of Media Library for further information). The package defines two boolean constants useEnhancementFactor and useDissociation, which give the user fine grained control of the calculations.
Constant  Default Value  Meaning 
useEnhancementFactor  false  The enhancement factor is used in the calculation of the saturation partial pressure of water in moist air. It is always very close to 1 except for high pressures (>2 MPa) and low temperatures (<233.15 K). For pressures less than 1 MPa this factor can be safely set to 1. Its calculation is very expensive, since it can only be calculated by an iterative method. 
useDissociation  true  The effect of dissociation is taken into account for temperatures greater than 773.15 K. 
p  Mixture pressure in Pa 
T  Temperature in K 
x_{w}  Absolutue humidity in kg(water)/kg(dry air) 
x_{ws}  Absolutue humidity on saturation boundary in kg(water)/kg(dry air) 
φ  Relative humidity (only defined for unsaturated humid air) 
Ideal mixture of dry air and steam
Liquid fog (x_{w} > x_{wsw}) and T ≥ 273.16 K
Ideal mixture of saturated humid air and water
Ice fog (x_{w} > x_{wsw}) and T < 273.16 K
Ideal mixture of saturated humid air and ice
The saturation pressure p_{ds} of water in moist air is calculated by p_{ds} = f*p_{sat}, where
For temperatures above 773.15 K effects of dissociation are taken into account. Dissociation is modeled according to [11]. For high temperatures the calculated values for moist air with 0 kg(water)/kg(dry air) (i.e. dry air) may differ from those calculated by the package Modelica.Media.Air.ReferenceAir, because there no dissociation is considered.
The verification report for the development of this library is provided here.
This library was developed by XRG Simulation GmbH as part of the Clean Sky JTI project (Project title: MoMoLibModelica Model Library Development for Media, Magnetic Systems and Wavelets; Project number: 296369; Theme: JTICS20111SGO02026: Modelica Model Library Development Part I). The partial financial support for the development of this library by the European Union is highly appreciated.
Some parts of this library refer to the ThermoFluid library developed at Lund University (http://thermofluid.sourceforge.net).
Copyright © 20132019, Modelica Association and contributors
Modelica.Media.Examples.ReferenceAir.MoistAir Medium model 