IdealGasMixtureFluidProperties

This is a VaporMixtureFluidProperties where each of the components are assumed to be ideal gases, such as IdealGasFluidProperties or NASA7IdealGasFluidProperties. A fluid properties class can be a component if it implements IdealGasMixtureInterface, which tells the mixture whether its specific heats are constant and at which temperature Newton's method should start.

commentnote

Components can have different references for the internal energy. For example, that of IdealGasFluidProperties is plus a user-supplied reference value, whereas that of NASA7IdealGasFluidProperties includes the enthalpy of formation. Only a reference that includes the enthalpy of formation accounts for the heat of reaction when the composition changes by reaction.

First note the following definitions and relations:

where

  • is the mass of component ,

  • is the mixture mass,

  • is the number of moles of component ,

  • is the mixture number of moles,

  • is the molar mass of component , and

  • is the mixture molar mass.

Due to Dalton's law of partial pressures,

where is the partial pressure of component and is the mixture pressure.

Mixture mass-specific properties, such as specific volume and specific internal energy are computed as mass-fraction-weighted sums of the component properties evaluated at the mixture temperature and pressure:

Mixture entropy is an exception to this rule, as the component entropies must be evaluated at their partial pressures, rather than the mixture pressure, in accordance with the Gibbs' theorem, which accounts for the entropy of mixing (Çengel and Boles, 2008):

Components with a zero molar fraction do not contribute to this sum.

The temperature is computed from the specific volume and the specific internal energy by solving

for ; the internal energy of an ideal gas does not depend on pressure. When all components have constant specific heats, the internal energy is linear in temperature and follows explicitly. Otherwise, is found with the 1D Newton solver of the fluid properties utilities, starting at the lowest of the start temperatures of the components whose specific heats are not constant. For NASA 7-coefficient components, these are the upper ends of the temperature ranges of their data, above the solution, for the reasons given in NASA7IdealGasFluidProperties. The equation is offset by a constant that makes both of its sides close to , where is the mixture isochoric specific heat, so that the convergence test of the solver bounds the relative error in temperature even where the internal energy is close to zero. The pressure then follows from the ideal gas law, , where is the universal gas constant.

Transport properties such as dynamic viscosity and thermal conductivity are combined from the component properties evaluated at the mixture temperature and pressure with the rule selected by "transport_mixing_rule". The default, mole_fraction_average, computes molar-fraction-weighted sums:

This average is a rough estimate when the molar masses of the components differ widely. For a mixture of N, O, H, and CO with molar fractions 0.4, 0.1, 0.3, and 0.2 at 1000 K, for example, it gives a viscosity 15% below that of the rule of Wilke, which Cantera also uses. The option wilke applies the rule of Wilke to the viscosity and the rule of Mason and Saxena to the thermal conductivity (Poling et al., 2001):

where is the molar mass of component . The rule of Mason and Saxena has the same interaction factors when its ratio of translational thermal conductivities is written with viscosities and its empirical constant is one.

The binary diffusion coefficient of a pair of components, binaryDiffusionCoefficient(p, T, i, j), follows from Chapman-Enskog kinetic theory with the Lennard-Jones parameters of the components, as described with the gas transport utilities. It is available for components that provide these parameters through IdealGasMixtureInterface, such as NASA7IdealGasFluidProperties, but not for IdealGasFluidProperties.

In the gas-mixture flow channels of the thermal hydraulics module, the material FluidPropertiesBinaryDiffusionCoefMaterial provides this coefficient for mixtures of NASA7IdealGasFluidProperties components.

Input Parameters

  • component_fluid_propertiesName of component fluid properties user objects. The first entry should be the primary component.

    C++ Type:std::vector<UserObjectName>

    Controllable:No

    Description:Name of component fluid properties user objects. The first entry should be the primary component.

Required Parameters

  • emit_on_nannoneWhether to raise a warning, an exception (usually triggering a retry with a smaller time step) or an error (ending the simulation)

    Default:none

    C++ Type:MooseEnum

    Options:none, warning, exception, error

    Controllable:No

    Description:Whether to raise a warning, an exception (usually triggering a retry with a smaller time step) or an error (ending the simulation)

  • transport_mixing_rulemole_fraction_averageRule that combines the viscosities and thermal conductivities of the components

    Default:mole_fraction_average

    C++ Type:MooseEnum

    Options:mole_fraction_average, wilke

    Controllable:No

    Description:Rule that combines the viscosities and thermal conductivities of the components

Optional Parameters

  • allow_imperfect_jacobiansFalsetrue to allow unimplemented property derivative terms to be set to zero for the AD API

    Default:False

    C++ Type:bool

    Controllable:No

    Description:true to allow unimplemented property derivative terms to be set to zero for the AD API

  • control_tagsAdds user-defined labels for accessing object parameters via control logic.

    C++ Type:std::vector<std::string>

    Controllable:No

    Description:Adds user-defined labels for accessing object parameters via control logic.

  • enableTrueSet the enabled status of the MooseObject.

    Default:True

    C++ Type:bool

    Controllable:Yes

    Description:Set the enabled status of the MooseObject.

  • fp_typeunspecified-typeType of the fluid property object

    Default:unspecified-type

    C++ Type:FPType

    Controllable:No

    Description:Type of the fluid property object

Advanced Parameters

  • prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Unit:(no unit assumed)

    Controllable:No

    Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

  • use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

    Default:False

    C++ Type:bool

    Controllable:No

    Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Material Property Retrieval Parameters

Input Files

References

  1. Bruce E. Poling, John M. Prausnitz, and John P. O'Connell. The Properties of Gases and Liquids. McGraw-Hill, New York, 5 edition, 2001.[Export]
  2. Yunus A. Çengel and Michael A. Boles. Thermodynamics: An Engineering Approach. McGraw-Hill, New York, 6th edition, 2008. ISBN 9780073305370.[Export]