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:

$\begin{eqnarray*} 51104 + 2044 T & T > 295 & T < 373 \\ 255510 & T > 373 & \end{eqnarray*}$

Reference:

T. Bergam, A.Lavine, F. Incropera and D. Dewitt. Heat and Mass Transfer. 7th Edition. Chapter 10.

The mass transfer correlation used is:

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

where:

$D_{ab}$	=	mass vapour difussivity
	=	characteristic length
	=	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:

	=	Reynolds number
	=	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:

src/thermophysicalModels/thermophysicalPropertiesFvPatchFields/liquidProperties/humidityTemperatureCoupledMixed/humidityTemperatureCoupledMixedFvPatchScalarField.H