Modelica.Media.Air.MoistAir

Information

Thermodynamic Model

This package provides a full thermodynamic model of moist air including the fog region and temperatures below zero degC. The governing assumptions in this model are:

• the perfect gas law applies
• water volume other than that of steam is neglected

All extensive properties are expressed in terms of the total mass in order to comply with other media in this library. However, for moist air it is rather common to express the absolute humidity in terms of mass of dry air only, which has advantages when working with charts. In addition, care must be taken, when working with mass fractions with respect to total mass, that all properties refer to the same water content when being used in mathematical operations (which is always the case if based on dry air only). Therefore two absolute humidities are computed in the BaseProperties model: X denotes the absolute humidity in terms of the total mass while x denotes the absolute humidity per unit mass of dry air. In addition, the relative humidity phi is also computed.

At the triple point temperature of water of 0.01 °C or 273.16 K and a relative humidity greater than 1 fog may be present as liquid and as ice resulting in a specific enthalpy somewhere between those of the two isotherms for solid and liquid fog, respectively. For numerical reasons a coexisting mixture of 50% solid and 50% liquid fog is assumed in the fog region at the triple point in this model.

Range of validity

From the assumptions mentioned above it follows that the pressure should be in the region around atmospheric conditions or below (a few bars may still be fine though). Additionally a very high water content at low temperatures would yield incorrect densities, because the volume of the liquid or solid phase would not be negligible anymore. The model does not provide information on limits for water drop size in the fog region or transport information for the actual condensation or evaporation process in combination with surfaces. All excess water which is not in its vapour state is assumed to be still present in the air regarding its energy but not in terms of its spatial extent.

The thermodynamic model may be used for temperatures ranging from 190 ... 647 K. This holds for all functions unless otherwise stated in their description. However, although the model works at temperatures above the saturation temperature it is questionable to use the term "relative humidity" in this region. Please note, that although several functions compute pure water properties, they are designed to be used within the moist air medium model where properties are dominated by air and steam in their vapor states, and not for pure liquid water applications.

Transport Properties

Several additional functions that are not needed to describe the thermodynamic system, but are required to model transport processes, like heat and mass transfer, may be called. They usually neglect the moisture influence unless otherwise stated.

Application

The model's main area of application is all processes that involve moist air cooling under near atmospheric pressure with possible moisture condensation. This is the case in all domestic and industrial air conditioning applications. Another large domain of moist air applications covers all processes that deal with dehydration of bulk material using air as a transport medium. Engineering tasks involving moist air are often performed (or at least visualized) by using charts that contain all relevant thermodynamic data for a moist air system. These so called psychrometric charts can be generated from the medium properties in this package. The model PsychrometricData may be used for this purpose in order to obtain data for figures like those below (the plotting itself is not part of the model though).

Legend: blue - constant specific enthalpy, red - constant temperature, black - constant relative humidity

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=IdealGases.Common.SingleGasesData.Air
steam=IdealGases.Common.SingleGasesData.H2O
MMX={steam.MM,dryair.MM}	Molar masses of components
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_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
xsaturation_pT	Return absolute humidity per unit mass of dry air at saturation as a function of pressure p and temperature T
massFraction_pTphi	Return steam mass fraction as a function of relative humidity phi and temperature T
relativeHumidity_pTX	Return relative humidity as a function of pressure p, temperature T and composition X
relativeHumidity	Return relative humidity as a function of the thermodynamic state record
gasConstant	Return ideal gas constant as a function from thermodynamic state, only valid for phi<1
gasConstant_X	Return ideal gas constant as a function from composition X
saturationPressureLiquid	Return saturation pressure of water as a function of temperature T in the range of 273.16 to 647.096 K
saturationPressureLiquid_der	Derivative function for 'saturationPressureLiquid'
sublimationPressureIce	Return sublimation pressure of water as a function of temperature T between 190 and 273.16 K
sublimationPressureIce_der	Derivative function for 'sublimationPressureIce'
saturationPressure	Return saturation pressure of water as a function of temperature T between 190 and 647.096 K
saturationPressure_der	Derivative function for 'saturationPressure'
saturationTemperature	Return saturation temperature of water as a function of (partial) pressure p
enthalpyOfVaporization	Return enthalpy of vaporization of water as a function of temperature T, 273.16 to 647.096 K
HeatCapacityOfWater	Return specific heat capacity of water (liquid only) as a function of temperature T
enthalpyOfLiquid	Return enthalpy of liquid water as a function of temperature T(use enthalpyOfWater instead)
enthalpyOfGas	Return specific enthalpy of gas (air and steam) as a function of temperature T and composition X
enthalpyOfCondensingGas	Return specific enthalpy of steam as a function of temperature T
enthalpyOfNonCondensingGas	Return specific enthalpy of dry air as a function of temperature T
enthalpyOfWater	Computes specific enthalpy of water (solid/liquid) near atmospheric pressure from temperature T
enthalpyOfWater_der	Derivative function of enthalpyOfWater
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
T_phX	Return temperature as a function of pressure p, specific enthalpy h and composition X
density	Returns density of ideal gas as a function of the thermodynamic state record
specificEnthalpy	Return specific enthalpy of moist air as a function of the thermodynamic state record
h_pTX	Return specific enthalpy of moist air as a function of pressure p, temperature T and composition X
h_pTX_der	Derivative function of h_pTX
isentropicExponent	Return isentropic exponent (only for gas fraction!)
isentropicEnthalpyApproximation	Approximate calculation of h_is from upstream properties, downstream pressure, gas part only
specificInternalEnergy	Return specific internal energy of moist air as a function of the thermodynamic state record
specificInternalEnergy_pTX	Return specific internal energy of moist air as a function of pressure p, temperature T and composition X
specificInternalEnergy_pTX_der	Derivative function for specificInternalEnergy_pTX
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
dynamicViscosity	Return dynamic viscosity as a function of the thermodynamic state record, valid from 123.15 K to 1273.15 K
thermalConductivity	Return thermal conductivity as a function of the thermodynamic state record, valid from 123.15 K to 1273.15 K
Utilities	Utility functions
PsychrometricData	Produces plot data for psychrometric charts
velocityOfSound
isobaricExpansionCoefficient
isothermalCompressibility
density_derp_h
density_derh_p
density_derp_T
density_derT_p
density_derX
molarMass
T_psX	Return temperature as a function of pressure p, specific entropy s and composition X
setState_psX
s_pTX	Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)
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)
isentropicEnthalpy	Isentropic enthalpy (only valid for phi<1)
Inherited
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
FluidConstants	Critical, triple, molecular and other standard data of fluid
prandtlNumber	Return the Prandtl number
heatCapacity_cp	Alias for deprecated name
heatCapacity_cv	Alias for deprecated name
beta	Alias for isobaricExpansionCoefficient for user convenience
kappa	Alias of isothermalCompressibility for user convenience
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
MassFlowRate	Type for mass flow rate with medium specific attributes
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
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 respect to pressure with medium specific attributes
DerDensityByEnthalpy	Type for partial derivative of density with respect to enthalpy with medium specific attributes
DerEnthalpyByPressure	Type for partial derivative of enthalpy with respect to pressure with medium specific attributes
DerDensityByTemperature	Type for partial derivative of density with respect to temperature with medium specific attributes
DerTemperatureByPressure	Type for partial derivative of temperature with respect to pressure with medium specific attributes
SaturationProperties	Saturation properties of two phase medium
FluidLimits	Validity limits for fluid model
FixedPhase	Phase of the fluid: 1 for 1-phase, 2 for two-phase, 0 for not known, e.g., interactive use
Basic	The most basic version of a record used in several degrees of detail
IdealGas	The ideal gas version of a record used in several degrees of detail
TwoPhase	The two phase fluid version of a record used in several degrees of detail

Modelica.Media.Air.MoistAir.ThermodynamicState

Information

Modelica.Media.Air.MoistAir.BaseProperties

Information

This model computes thermodynamic properties of moist air from three independent (thermodynamic or/and numerical) state variables. Preferred numerical states are temperature T, pressure p and the reduced composition vector Xi, which contains the water mass fraction only. As an EOS the ideal gas law is used and associated restrictions apply. The model can also be used in the fog region, when moisture is present in its liquid state. However, it is assumed that the liquid water volume is negligible compared to that of the gas phase. Computation of thermal properties is based on property data of dry air and water (source: VDI-Wärmeatlas), respectively. Besides the standard thermodynamic variables absolute and relative humidity, x_water and phi, respectively, are given by the model. Upper case X denotes absolute humidity with respect to mass of moist air while absolute humidity with respect to mass of dry air only is denoted by a lower case x throughout the model. See package description for further information.

Parameters

Name	Description
standardOrderComponents	If true, and reducedX = true, the last element of X will be computed from the other ones
Advanced
preferredMediumStates	= true if StateSelect.prefer shall be used for the independent property variables of the medium

Modelica.Media.Air.MoistAir.setState_pTX

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]
X[:]	Mass fractions [kg/kg]

Outputs

Name	Description
state	Thermodynamic state

Modelica.Media.Air.MoistAir.setState_phX

Information

Inputs

Name	Description
p	Pressure [Pa]
h	Specific enthalpy [J/kg]
X[:]	Mass fractions [kg/kg]

Outputs

Name	Description
state	Thermodynamic state

Modelica.Media.Air.MoistAir.setState_dTX

Information

Inputs

Name	Description
d	Density [kg/m3]
T	Temperature [K]
X[:]	Mass fractions [kg/kg]

Outputs

Name	Description
state	Thermodynamic state

Modelica.Media.Air.MoistAir.setSmoothState

Information

Inputs

Name	Description
x	m_flow or dp
state_a	Thermodynamic state if x > 0
state_b	Thermodynamic state if x < 0
x_small	Smooth transition in the region -x_small < x < x_small

Outputs

Name	Description
state	Smooth thermodynamic state for all x (continuous and differentiable)

Modelica.Media.Air.MoistAir.Xsaturation

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

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

Modelica.Media.Air.MoistAir.xsaturation

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
x_sat	Absolute humidity per unit mass of dry air [kg/kg]

Modelica.Media.Air.MoistAir.xsaturation_pT

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]

Outputs

Name	Description
x_sat	Absolute humidity per unit mass of dry air [kg/kg]

Modelica.Media.Air.MoistAir.massFraction_pTphi

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]
phi	Relative humidity (0 ... 1.0)

Outputs

Name	Description
X_steam	Absolute humidity, steam mass fraction [kg/kg]

Modelica.Media.Air.MoistAir.relativeHumidity_pTX

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]
X[:]	Composition [1]

Outputs

Name	Description
phi	Relative humidity

Modelica.Media.Air.MoistAir.relativeHumidity

Information

Inputs

Name	Description
state	Thermodynamic state

Outputs

Name	Description
phi	Relative humidity

Modelica.Media.Air.MoistAir.gasConstant

Information

Inputs

Name	Description
state	Thermodynamic state

Outputs

Name	Description
R	Mixture gas constant [J/(kg.K)]

Modelica.Media.Air.MoistAir.gasConstant_X

Information

Inputs

Name	Description
X[:]	Gas phase composition [1]

Outputs

Name	Description
R	Ideal gas constant [J/(kg.K)]

Modelica.Media.Air.MoistAir.saturationPressureLiquid

Information

Saturation pressure of water above the triple point temperature is computed from temperature.

Source: A Saul, W Wagner: "International equations for the saturation properties of ordinary water substance", equation 2.1

Inputs

Name	Description
Tsat	Saturation temperature [K]

Outputs

Name	Description
psat	Saturation pressure [Pa]

Modelica.Media.Air.MoistAir.saturationPressureLiquid_der

Information

Saturation pressure of water above the triple point temperature is computed from temperature.

Source: A Saul, W Wagner: "International equations for the saturation properties of ordinary water substance", equation 2.1

Inputs

Name	Description
Tsat	Saturation temperature [K]
dTsat	Saturation temperature derivative [K/s]

Outputs

Name	Description
psat_der	Saturation pressure derivative [Pa/s]

Modelica.Media.Air.MoistAir.sublimationPressureIce

Information

Sublimation pressure of water below the triple point temperature is computed from temperature.

Source: W Wagner, A Saul, A Pruss: "International equations for the pressure along the melting and along the sublimation curve of ordinary water substance", equation 3.5

Inputs

Name	Description
Tsat	Sublimation temperature [K]

Outputs

Name	Description
psat	Sublimation pressure [Pa]

Modelica.Media.Air.MoistAir.sublimationPressureIce_der

Information

Sublimation pressure of water below the triple point temperature is computed from temperature.

Source: W Wagner, A Saul, A Pruss: "International equations for the pressure along the melting and along the sublimation curve of ordinary water substance", equation 3.5

Inputs

Name	Description
Tsat	Sublimation temperature [K]
dTsat	Sublimation temperature derivative [K/s]

Outputs

Name	Description
psat_der	Sublimation pressure derivative [Pa/s]

Modelica.Media.Air.MoistAir.saturationPressure

Information

Inputs

Name	Description
Tsat	Saturation temperature [K]

Outputs

Name	Description
psat	Saturation pressure [Pa]

Modelica.Media.Air.MoistAir.saturationPressure_der

Information

Inputs

Name	Description
Tsat	Saturation temperature [K]
dTsat	Time derivative of saturation temperature [K/s]

Outputs

Name	Description
psat_der	Saturation pressure [Pa/s]

Modelica.Media.Air.MoistAir.saturationTemperature

Information

Inputs

Name	Description
p	Pressure [Pa]
T_min	Lower boundary of solution [K]
T_max	Upper boundary of solution [K]

Outputs

Name	Description
T	Saturation temperature [K]

Modelica.Media.Air.MoistAir.enthalpyOfVaporization

Information

Enthalpy of vaporization of water is computed from temperature in the region of 273.16 to 647.096 K.

Source: W Wagner, A Pruss: "International equations for the saturation properties of ordinary water substance. Revised according to the international temperature scale of 1990" (1993).

Inputs

Name	Description
T	Temperature [K]

Outputs

Name	Description
r0	Vaporization enthalpy [J/kg]

Modelica.Media.Air.MoistAir.HeatCapacityOfWater

Information

Inputs

Name	Description
T	Temperature [K]

Outputs

Name	Description
cp_fl	Specific heat capacity of liquid [J/(kg.K)]

Modelica.Media.Air.MoistAir.enthalpyOfLiquid

Information

Inputs

Name	Description
T	Temperature [K]

Outputs

Name	Description
h	Liquid enthalpy [J/kg]

Modelica.Media.Air.MoistAir.enthalpyOfGas

Information

Inputs

Name	Description
T	Temperature [K]
X[:]	Vector of mass fractions [kg/kg]

Outputs

Name	Description
h	Specific enthalpy [J/kg]

Modelica.Media.Air.MoistAir.enthalpyOfCondensingGas

Information

Inputs

Name	Description
T	Temperature [K]

Outputs

Name	Description
h	Specific enthalpy [J/kg]

Modelica.Media.Air.MoistAir.enthalpyOfNonCondensingGas

Information

Inputs

Name	Description
T	Temperature [K]

Outputs

Name	Description
h	Specific enthalpy [J/kg]

Modelica.Media.Air.MoistAir.enthalpyOfWater

Information

• heat capacity of liquid water:4200 J/kg
• heat capacity of solid water: 2050 J/kg
• enthalpy of fusion (liquid=>solid): 333000 J/kg

Inputs

Name	Description
T	Temperature [K]

Outputs

Name	Description
h	Specific enthalpy of water [J/kg]

Modelica.Media.Air.MoistAir.enthalpyOfWater_der

Information

Inputs

Name	Description
T	Temperature [K]
dT	Time derivative of temperature [K/s]

Outputs

Name	Description
dh	Time derivative of specific enthalpy [J/(kg.s)]

Modelica.Media.Air.MoistAir.pressure

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
p	Pressure [Pa]

Modelica.Media.Air.MoistAir.temperature

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
T	Temperature [K]

Modelica.Media.Air.MoistAir.T_phX

Information

Inputs

Name	Description
p	Pressure [Pa]
h	Specific enthalpy [J/kg]
X[:]	Mass fractions of composition [kg/kg]

Outputs

Name	Description
T	Temperature [K]

Modelica.Media.Air.MoistAir.density

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
d	Density [kg/m3]

Modelica.Media.Air.MoistAir.specificEnthalpy

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
h	Specific enthalpy [J/kg]

Modelica.Media.Air.MoistAir.h_pTX

Information

Inputs

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

Outputs

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

Modelica.Media.Air.MoistAir.h_pTX_der

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]
X[:]	Mass fractions of moist air [1]
dp	Pressure derivative [Pa/s]
dT	Temperature derivative [K/s]
dX[:]	Composition derivative [1/s]

Outputs

Name	Description
h_der	Time derivative of specific enthalpy [J/(kg.s)]

Modelica.Media.Air.MoistAir.isentropicExponent

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
gamma	Isentropic exponent [1]

Modelica.Media.Air.MoistAir.isentropicEnthalpyApproximation

Information

Inputs

Name	Description
p2	Downstream pressure [Pa]
state	Thermodynamic state at upstream location

Outputs

Name	Description
h_is	Isentropic enthalpy [J/kg]

Modelica.Media.Air.MoistAir.specificInternalEnergy

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
u	Specific internal energy [J/kg]

Modelica.Media.Air.MoistAir.specificInternalEnergy_pTX

Information

Inputs

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

Outputs

Name	Description
u	Specific internal energy [J/kg]

Modelica.Media.Air.MoistAir.specificInternalEnergy_pTX_der

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]
X[:]	Mass fractions of moist air [1]
dp	Pressure derivative [Pa/s]
dT	Temperature derivative [K/s]
dX[:]	Mass fraction derivatives [1/s]

Outputs

Name	Description
u_der	Specific internal energy derivative [J/(kg.s)]

Modelica.Media.Air.MoistAir.specificEntropy

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

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

Modelica.Media.Air.MoistAir.specificGibbsEnergy

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
g	Specific Gibbs energy [J/kg]

Modelica.Media.Air.MoistAir.specificHelmholtzEnergy

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
f	Specific Helmholtz energy [J/kg]

Modelica.Media.Air.MoistAir.specificHeatCapacityCp

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

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

Modelica.Media.Air.MoistAir.specificHeatCapacityCv

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

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

Modelica.Media.Air.MoistAir.dynamicViscosity

Information

Dynamic viscosity is computed from temperature using a simple polynomial for dry air. Range of validity is from 123.15 K to 1273.15 K. The influence of pressure and moisture is neglected.

Source: VDI Waermeatlas, 8th edition.

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
eta	Dynamic viscosity [Pa.s]

Modelica.Media.Air.MoistAir.thermalConductivity

Information

Thermal conductivity is computed from temperature using a simple polynomial for dry air. Range of validity is from 123.15 K to 1273.15 K. The influence of pressure and moisture is neglected.

Source: VDI Waermeatlas, 8th edition.

Inputs

Name	Description
state	Thermodynamic state record

Outputs

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

Modelica.Media.Air.MoistAir.PsychrometricData

Information

This model produces psychrometric data from the moist air model in this library to be plotted in charts. The two most common chart varieties are the Mollier Diagram and the Psychrometric Chart. The first is widely used in some European countries while the second is more common in the Anglo-American world. Specific enthalpy is plotted over absolute humidity in the Mollier Diagram, it is the other way round in the Psychrometric Chart.
It must be noted that the relationship of both axis variables is not right-angled, the absolute humidity follows a slope which equals the enthalpy of vaporization at 0 °C. For better reading and in order to reduce the fog region the humidity axis is rotated to obtain a right-angled plot. Both charts usually contain additional information as isochores or auxiliary scales for e.g., heat ratios. Those information are omitted in this model and the charts below. Other important features of psychrometric chart data are that all mass specific variables (like absolute humidity, specific enthalpy etc.) are expressed in terms of kg dry air and that their baseline of 0 enthalpy is found at 0 °C and zero humidity.

Legend: blue - constant specific enthalpy, red - constant temperature, black - constant relative humidity

The model provides data for lines of constant specific enthalpy, temperature and relative humidity in a Mollier Diagram or Psychrometric Chart as they were used for the figures above. For limitations and ranges of validity please refer to the MoistAir package description. Absolute humidity x is increased with time in this model. The specific enthalpies adjusted for plotting are then obtained from:

• y_h: constant specific enthalpy
• y_T: constant temperature
• y_phi: constant relative humidity

Parameters

Name	Description
p_const	Pressure [Pa]
n_T	Number of isotherms
T_min	Lowest isotherm [K]
T_step	Temperature step between two isotherms [K]
n_h	Number of lines with constant specific enthalpy
h_min	Lowest line of constant enthalpy [J/kg]
h_step	Enthalpy step between two lines of constant enthalpy [J/kg]
n_phi	Number of lines with constant relative humidity
phi_min	Lowest line of constant humidity
phi_step	Step between two lines of constant humidity
x_min	Minimum diagram absolute humidity [1]
x_max	Maximum diagram absolute humidity [1]
t	Simulation time [s]

Modelica.Media.Air.MoistAir.velocityOfSound

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
a	Velocity of sound [m/s]

Modelica.Media.Air.MoistAir.isobaricExpansionCoefficient

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
beta	Isobaric expansion coefficient [1/K]

Modelica.Media.Air.MoistAir.isothermalCompressibility

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
kappa	Isothermal compressibility [1/Pa]

Modelica.Media.Air.MoistAir.density_derp_h

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
ddph	Density derivative w.r.t. pressure [s2/m2]

Modelica.Media.Air.MoistAir.density_derh_p

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
ddhp	Density derivative w.r.t. specific enthalpy [kg.s2/m5]

Modelica.Media.Air.MoistAir.density_derp_T

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
ddpT	Density derivative w.r.t. pressure [s2/m2]

Modelica.Media.Air.MoistAir.density_derT_p

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
ddTp	Density derivative w.r.t. temperature [kg/(m3.K)]

Modelica.Media.Air.MoistAir.density_derX

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
dddX[nX]	Derivative of density w.r.t. mass fraction [kg/m3]

Modelica.Media.Air.MoistAir.molarMass

Information

Inputs

Name	Description
state	Thermodynamic state record

Outputs

Name	Description
MM	Mixture molar mass [kg/mol]

Modelica.Media.Air.MoistAir.T_psX

Information

Inputs

Name	Description
p	Pressure [Pa]
s	Specific entropy [J/(kg.K)]
X[:]	Mass fractions of composition [kg/kg]

Outputs

Name	Description
T	Temperature [K]

Modelica.Media.Air.MoistAir.setState_psX

Information

Inputs

Name	Description
p	Pressure [Pa]
s	Specific entropy [J/(kg.K)]
X[:]	Mass fractions [kg/kg]

Outputs

Name	Description
state	Thermodynamic state record

Modelica.Media.Air.MoistAir.s_pTX

Information

Inputs

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

Outputs

Name	Description
s	Specific entropy at p, T, X [J/(kg.K)]

Modelica.Media.Air.MoistAir.s_pTX_der

Information

Inputs

Name	Description
p	Pressure [Pa]
T	Temperature [K]
X[:]	Mass fractions of moist air [1]
dp	Derivative of pressure [Pa/s]
dT	Derivative of temperature [K/s]
dX[nX]	Derivative of mass fractions [1/s]

Outputs

Name	Description
ds	Specific entropy at p, T, X [J/(kg.K.s)]

Modelica.Media.Air.MoistAir.isentropicEnthalpy

Information

Inputs

Name	Description
p_downstream	Downstream pressure [Pa]
refState	Reference state for entropy

Outputs

Name	Description
h_is	Isentropic enthalpy [J/kg]