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humidityTemperatureCoupledMixedFvPatchScalarField Class Reference

Mixed boundary condition for temperature to be used at the coupling interface between fluid solid regions. More...

## Detailed Description

Mixed boundary condition for temperature to be used at the coupling interface between fluid solid regions.

This boundary condition can operate in four modes:

• constantMass: thermal inertia only
• requires rho, thickness and cp
• condensation: condensation only
• when the wall temperature (Tw) is below the dew temperature (Tdew) condesation takes place and the resulting condensed mass is stored on the wall
• evaporation: evaporation only
• initial mass is vaporized when Tw is above the input vaporization temperature (Tvap).
• condensationAndEvaporation : condensation and evaporation take place simultaneously.

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.

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

\begin{eqnarray*} 51104 + 2044 (T - 273.15) & T > 295 & T < 373 \\ 255510 & T > 373 & \end{eqnarray*}

References:

    Standard models (tag:BLID):
Bergman, T. L., Lavine, A. S.,
Incropera, F. P., & Dewitt, D. P. (2011).
Fundamentals of heat and mass transfer.
John Wiley & Sons. 7th Edition. Chapter 10.
ISBN:9780470501979


The mass transfer correlation used is:

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

where:

 $$D_{ab}$$ = mass vapour difussivity $$L$$ = characteristic length $$Sh$$ = Sherwood number

The Sherwood number is calculated using:

\begin{eqnarray*} 0.664 Re^\frac{1}{2} Sc^\frac{1}{3} & Re < 5.0E+05 \\ 0.037 Re^\frac{4}{5} Sc^\frac{1}{3} & Re > 5.0E+05 \end{eqnarray*}

where:

 $$Re$$ = Reynolds number $$Sc$$ = Schmidt number

NOTE:

• 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
• Addition of extra layers in possible using thicknessLayers and kappaLayers

Example usage:

On the fluid side

    myInterfacePatchName
{
type            thermalHumidityCoupledMixed;
kappaMethod     fluidThermo;
kappa           none;

// Modes of operation: inert, condensation, vaporization, condEvap
mode            condEvap;

// Carrier species name
specieName      H2O;

// Carrier molecular weight
carrierMolWeight           28.9;

// Characteristic length of the wall
L               0.1;

// Vaporisation temperature
Tvap            273;

// Liquid properties for the condensed mass
liquid
{
H2O
{
defaultCoeffs       yes;
}
}

thicknessLayers (0.1 0.2 0.3 0.4);
kappaLayers     (1 2 3 4);

// thickness, density and cp required for inert and condensation
// modes

//thickness       uniform 0;
//cp              uniform 0;
//rho             uniform 0;

value           \$internalField;
}

On the solid side:

    myInterfacePatchName
{
type            thermalInertiaMassTransferCoupledMixed;
kappaMethod     solidThermo;
kappa           none;
value           uniform 260;
}
Source files

The documentation for this class was generated from the following file: