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:

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:

The inherited entries are elaborated in:

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

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).

Further information🔗

Tutorial:

• $FOAM_TUTORIALS/heatTransfer/chtMultiRegionFoam/windshieldCondensation

Source code:

• $FOAM_SRC/thermoTools/derivedFvPatchFields/humidityTemperatureCoupledMixed

API:

• Foam::compressible::humidityTemperatureCoupledMixedFvPatchScalarField

History:

• Introduced in version v1706