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 |
| xw | Absolute humidity in kg(water)/kg(dry air) |
| xws | Absolute 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 (xw > xwsw) and T ≥ 273.16 K
Ideal mixture of saturated humid air and water
Ice fog (xw > xwsw) and T < 273.16 K
Ideal mixture of saturated humid air and ice
The saturation pressure pds of water in moist air is calculated by pds = f*psat, 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: 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 © 2013-2020, 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 humidity per unit mass of moist air at saturation as a function of the thermodynamic state record |
| xsaturation | Return absolute humidity 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 |