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.

**611.2 Pa ≤ p ≤ 10 MPa****143.15 K ≤ T ≤ 2000 K**

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

- Dry air:
- d,h,u,s,c
_{p}from [1] - λ, η from [2]

- d,h,u,s,c
- Steam:
- d,h,u,s,c
_{p}from [4] - λ, η for 273.15 K ≤ T ≤ 1073.15 K from [5] and [6]
- λ, η for T < 273.15 K or T > 1073.15 K from [12]

- d,h,u,s,c

**Liquid fog (x _{w} > x_{wsw}) and T ≥
273.16 K**

Ideal mixture of saturated humid air and water

- Saturated humid air (see above)
- d,h,u,s of liquid droplets from [4]
- c
_{p}is not defined - λ, η of liquid droplets from [5] and [6]

**Ice fog (x _{w} > x_{wsw}) and T <
273.16 K**

Ideal mixture of saturated humid air and ice

- Saturated humid air (see above)
- d,h,u,s of ice crystals from [7]
- c
_{p}is not defined - λ of ice as constant value
- η of ice is neglected

The saturation pressure p_{ds} of water in moist air is
calculated by p_{ds} = f*p_{sat}, where

- f is the enhancement factor from [9] and [3]
- p
_{sat}for T ≥ 273.16 K is the saturation pressure from [4] - p
_{sat}for T < 273.16 K is the saturation pressure from [8]

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.

- [1]
**Thermodynamic Properties of Air and Mixtures of Nitrogen, Argon, and Oxygen From 60 to 2000 K at Pressures to 2000 MPa**. J. Phys. Chem. Ref. Data, Vol. 29, No. 3, 2000. - [2]
**Viscosity and Thermal Conductivity Equations for Nitrogen, Oxygen, Argon, and Air**. International Journal of Thermophysics, Vol. 25, No. 1, January 2004 - [3]
**Revised Release on the IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use**. 2009 International Association for the Properties of Water and Steam. - [4]
**Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam**. 2007 International Association for the Properties of Water and Steam. - [5]
**Release on the IAPWS Formulation 2008 for the Viscosity of Ordinary Water Substance**. 2008 International Association for the Properties of Water and Steam - [6]
**Release on the IAPWS Formulation 2011 for the Thermal Conductivity of Ordinary Water Substance**. 2011 International Association for the Properties of Water and Steam. - [7]
**Revised Release on the Equation of State 2006 for H2O Ice Ih**. 2009 International Association for the Properties of Water and Steam. - [8]
**Revised Release on the Pressure along the Melting and Sublimation Curves of Ordinary Water Substance**. 2011 International Association for the Properties of Water and Steam. - [9]
**Determination of Thermodynamic and Transport Properties of Humid Air for Power-Cycle Calculations**. 2009 PTB, Braunschweig, Germany. - [10]
**Berechnung der thermodynamischen Zustandsfunktionen von feuchter Luft in energietechnischen Prozessmodellierungen**. 2001 Diplomarbeit, Zittau. - [11]
**Thermodynamische Stoffwerte von feuchter Luft und Verbrennungsgasen**. 2003 VDI-Richtlinie 4670. - [12]
**Wärmeübertragung in Dampferzeugern und Wärmetauschern**. 1985 FDBR-Fachbuchreihe, Bd. 2, Vulkan Verlag Essen.

- Lemmon, E. W., Jacobsen, R. T., Penoncello, S. G., Friend, D. G.:
**Thermodynamic Properties of Air and Mixtures of Nitrogen, Argon, and Oxygen From 60 to 2000 K at Pressures to 2000 MPa**. J. Phys. Chem. Ref. Data, Vol. 29, No. 3, 2000.- Lemmon, E. W., Jacobsen, R. T.:
**Viscosity and Thermal Conductivity Equations for Nitrogen, Oxygen, Argon, and Air**. International Journal of Thermophysics, Vol. 25, No. 1, January 2004

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: MoMoLib-Modelica Model Library Development for Media, Magnetic Systems and Wavelets; Project number: 296369; Theme: JTI-CS-2011-1-SGO-02-026: 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 © 2013-2019, Modelica Association and contributors

Name | Description |
---|---|

ThermodynamicState | ThermodynamicState record for moist air |

BaseProperties | Moist air base properties record |

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

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

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

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

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

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

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

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

massFractionWaterVapor | Return mass fraction of water vapor |

massFractionWaterNonVapor | Return mass fraction of liquid and solid water |

massFractionSaturation | Return saturation mass fractions |

massFractionSaturation_ppsat | Return mass fvraction at saturation boundary given pressure and saturation pressure |

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

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

relativeHumidity | Return relative humidity |

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

saturationPressureLiquid | Return saturation pressure of water as a function of temperature T |

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

saturationPressure | Return saturation pressure of condensing fluid |

saturationTemperature | Return saturation temperature of condensing fluid |

enthalpyOfVaporization | Return enthalpy of vaporization of water |

enthalpyOfLiquid | Return enthalpy of liquid water |

enthalpyOfGas | Return specific enthalpy of gas (air and steam) |

enthalpyOfCondensingGas | Return specific enthalpy of steam |

enthalpyOfNonCondensingGas | Return specific enthalpy of dry air |

enthalpyOfDryAir | Return specific enthalpy of dry air |

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

enthalpyOfWaterVapor | Return specific enthalpy of steam |

enthalpyOfWaterNonVapor | Return enthalpy of liquid and solid water |

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

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

density | Returns density as a function of the thermodynamic state record |

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

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

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

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

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

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

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

isentropicExponent | Return isentropic exponent |

isentropicEnthalpy | Return isentropic enthalpy |

velocityOfSound | Return velocity of sound |

molarMass | Return the molar mass of the medium |

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

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

Utilities | Utility package for moist air |

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