Description🔗

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

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
    ...
}

The inherited entries are elaborated in:

• mixedFvPatchFields.H
• temperatureCoupledBase.H
• liquidProperties.H

where:

Options for the mode entry:

• 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).

Method🔗

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:

Further information🔗

Tutorial:

• $FOAM_TUTORIALS/heatTransfer/chtMultiRegionFoam/windshieldCondensation

Source code:

• $FOAM_SRC/thermoTools/derivedFvPatchFields/humidityTemperatureCoupledMixed

API:

• Foam::compressible::humidityTemperatureCoupledMixedFvPatchScalarField

History:

• Introduced in version v1706