variableHeatTransfer.H

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    Copyright (C) 2020 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.

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Class
    Foam::fv::variableHeatTransfer

Group
    grpFvOptionsSources

Description
    Applies a variable heat transfer model depending
    on local values for inter-region heat exchanges.

    The area of contact between regions (area) must be provided.
    The Nu number is calculated as:

    \f[
        Nu = a \, \textrm{Re}^b \, \textrm{Pr}^c
    \f]

    and the heat transfer coefficient as:

    \f[
        htc = \frac{\textrm{Nu} \, K}{ds}
    \f]

    where
    \vartable
      htc     | Heat transfer coefficient
      Nu      | Nusselt number
      Re      | Reynolds number
      Pr      | Fluid Prandtl number
      K       | Heat conduction
      ds      | Strut diameter
      a, b, c | Model constants
    \endvartable

    Required fields:
    \verbatim
      AoV       | Area per unit volume of heat exchanger    [1/m]
    \endverbatim

Usage
    Minimal example by using \c constant/fvOptions:
    \verbatim
    variableHeatTransfer1
    {
        // Mandatory entries (unmodifiable)
        type             variableHeatTransfer;

        // Optional entries (runtime modifiable)
        UNbr             U;
        a                0.0;
        b                0.0;
        c                0.0;
        ds               0.0;
        Pr               0.0;

        // Mandatory/Optional (inherited) entries
        ...
    }
    \endverbatim

    where the entries mean:
    \table
      Property  | Description                     | Type  | Reqd | Dflt
      type      | Type name: variableHeatTransfer | word  | yes  | -
      UNbr      | Name of operand neighbour velocity field | word | no | U
      a         | Model constant                  | scalar | no  | 0
      b         | Model constant                  | scalar | no  | 0
      c         | Model constant                  | scalar | no  | 0
      ds        | Struct diameter                 | scalar | no  | 0
      Pr        | Fluid Prandtl number            | scalar | no  | 0
      \endtable

    The inherited entries are elaborated in:
     - \link interRegionHeatTransfer.H \endlink

Notes
  - With v2512, the denominator of the Reynolds number calculation has been
    changed from 'mut' to 'muEff'. For fully turbulent regions, there should be
    no significant difference as mut >> mu, thus muEff ~ mut. However, in
    porous/laminar regions, this change prevents the Reynolds number from
    blowing up due to very low turbulent viscosity. Instead, the classical
    laminar Reynolds number is now used in such regions.

SourceFiles
    variableHeatTransfer.C

\*---------------------------------------------------------------------------*/

#ifndef variableHeatTransfer_H
#define variableHeatTransfer_H

#include "interRegionHeatTransferModel.H"
#include "autoPtr.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

namespace Foam
{
namespace fv
{

/*---------------------------------------------------------------------------*\
                    Class variableHeatTransfer Declaration
\*---------------------------------------------------------------------------*/

class variableHeatTransfer
:
    public interRegionHeatTransferModel
{

    // Private Data

        //- Name of operand neighbour velocity field
        word UNbrName_;

        //- Model constants
        scalar a_;
        scalar b_;
        scalar c_;

        //- Strut diameter
        scalar ds_;

        //- Fluid Prandtl number
        scalar Pr_;

        //- Area per unit volume of heat exchanger
        autoPtr<volScalarField> AoV_;


public:

    //- Runtime type information
    TypeName("variableHeatTransfer");


    // Constructors

        //- Construct from dictionary
        variableHeatTransfer
        (
            const word& name,
            const word& modelType,
            const dictionary& dict,
            const fvMesh& mesh
        );

        //- No copy construct
        variableHeatTransfer(const variableHeatTransfer&) = delete;

        //- No copy assignment
        void operator=(const variableHeatTransfer&) = delete;


    //- Destructor
    virtual ~variableHeatTransfer() = default;


    // Public Functions

        //- Calculate the heat transfer coefficient
        virtual void calculateHtc();

        //- Read dictionary
        virtual bool read(const dictionary& dict);
};


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace fv
} // End namespace Foam

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#endif

// ************************************************************************* //