humidityTemperatureCoupledMixed

Description

The humidityTemperatureCoupledMixed is a mixed coupled boundary condition for temperature to be used at the coupling interface between fluid and solid regions.

Various governing equations of this boundary condition are based on Bergman et al.1.

The condition assumes a drop-wise type of condensation, whereby its heat transfer Nusselt number is calculated using:

$$Nu = 51104 + 2044 (T - 273.15) \, \text{if} \, \, T > 295 \, \, \& \, \, T < 373$$ $$Nu = 255510 \, \, \text{if} \, \, T > 373$$

The mass transfer correlation used is:

$$h_m = D_{ab} \frac{Sh}{L}$$

The Sherwood number is calculated using:

$$Sh = 0.664 Re^\frac{1}{2} Sc^\frac{1}{3} \, \, \text{if} \, \, Re < 5.0E+05$$ $$Sh = 0.037 Re^\frac{4}{5} Sc^\frac{1}{3} \, \, \text{if} \, \, Re > 5.0E+05$$

where:

Property	Description
$D_{ab}$	Mass vapour difussivity
$L$	Characteristic length
$Sh$	Sherwood number
$Re$	Reynolds number
$Sc$	Schmidt number
$Nu$	Nusselt number

Usage

The condition requires entries in both the boundary and field files.

Boundary file

<patchName>
{
    type            patch;
    ...
}

Field file

On the fluid side:

<patchName>
{
    // Mandatory entries
    type            humidityTemperatureCoupledMixed;
    mode            <word>;

    // Optional entries
    p               <word>;
    U               <word>;
    rho             <word>;
    mu              <word>;
    Tnbr            <word>;
    qrNbr           <word>;
    qr              <word>;
    specie          <word>;
    thicknessLayers <scalarList>;

    // Conditional entries

        // when 'thicknessLayers' entry is present
        kappaLayers         <scalarList>;

        // when 'mode' == 'constantMass'
        thickness           <scalarField>;
        cp                  <scalarField>;
        rho                 <scalarField>;

        // when 'mode' != 'constantMass'
        carrierMolWeight    <scalar>;
        L                   <scalar>;
        Tvap                <scalar>;
        liquid              <dict>;
        thickness           <scalarField>;

    // Inherited entries
    ...
}

On the solid side:

<patchName>
{
    // Mandatory entries
    type            humidityTemperatureCoupledMixed;

    // Optional entries
    p               <word>;
    U               <word>;
    rho             <word>;
    mu              <word>;
    Tnbr            <word>;
    qrNbr           <word>;
    qr              <word>;
    specie          <word>;
    thicknessLayers <scalarList>;

    // Conditional entries

        // when 'thicknessLayers' entry is present
        kappaLayers         <scalarList>;

    // Inherited entries
    ...
}

where:

Property	Description	Type	Required	Default
type	Type name: humidityTemperatureCoupledMixed	word	yes	-
mode	Operation mode	word	yes	-
p	Name of pressure field	word	no	p
U	Name of velocity field	word	no	U
rho	Name of density field	word	no	rho
mu	Name of dynamic viscosity field	word	no	thermo:mu
Tnbr	Name of neighbour temperature field	word	no	T
qrNbr	Name of neighbour radiative heat flux field	word	no	none
qr	Name of radiative heat flux field	word	no	none
specie	Name of specie field	word	no	none
thicknessLayers	List of kappa-layer thicknesses	scalarList	no	-
kappaLayers	List of kappas corresponding to thicknesses	scalarList	conditional	-
thickness	Thickness field	scalarField	conditional	-
cp	Specific heat capacity field	scalarField	conditional	-
rho	Density field	scalarField	conditional	-
carrierMolWeight	Carrier molecular weight	scalar	conditional	-
L	Characteristic length of the wall	scalar	conditional	-
Tvap	Vaporisation temperature	scalar	conditional	-
liquid	Liquid properties	dict	conditional	-

The inherited entries are elaborated in:

• Foam::mixedFvPatchField
• Foam::temperatureCoupledBase
• Foam::liquidProperties

Options for the mode entry:

Property	Description
constantMass	Thermal inertia only
condensation	Condensation only
evaporation	Evaporation only
condensationAndEvaporation	Simultaneous condensation and evaporation

• The correlation used to calculate Tdew is for water vapour.
• A scalar transport equation for the carrier specie is required, e.g. supplied via a function object or in the main solver. This specie transports the vapour phase in the main ragion.
• The boundary condition of this specie on the coupled wall must be fixedGradient in order to allow condensation or evaporation of the vapour in or out of this wall.
• There is no mass flow on the wall, i.e. the mass condensed on a face remains on that face. It uses a 'lumped mass' model to include thermal inertia effects.
• With mode==condensation, when the wall temperature (Tw) is below the dew temperature (Tdew) condesation takes place and the resulting condensed mass is stored on the wall.
• With mode==evaporation, initial mass is vaporized when the wall temperature (Tw) is above the input vaporization temperature (Tvap).

Further information

Tutorial:

• windshieldCondensation

Source code:

• humidityTemperatureCoupledMixed

API:

• Foam::compressible::humidityTemperatureCoupledMixedFvPatchScalarField

History: Introduced in version v1706