LiquidEvaporationBoil.C

Go to the documentation of this file.

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | www.openfoam.com
     \\/     M anipulation  |
-------------------------------------------------------------------------------
    Copyright (C) 2011-2016 OpenFOAM Foundation
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
\*---------------------------------------------------------------------------*/
 
#include "LiquidEvaporationBoil.H"
#include "specie.H"
#include "mathematicalConstants.H"
 
using namespace Foam::constant::mathematical;
 
// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
 
template<class CloudType>
Foam::tmp<Foam::scalarField> Foam::LiquidEvaporationBoil<CloudType>::calcXc
(
    const label celli
) const
{
    scalarField Xc(this->owner().thermo().carrier().Y().size());
 
    forAll(Xc, i)
    {
        Xc[i] =
            this->owner().thermo().carrier().Y()[i][celli]
           /this->owner().thermo().carrier().W(i);
    }
 
    return Xc/sum(Xc);
}
 
 
template<class CloudType>
Foam::scalar Foam::LiquidEvaporationBoil<CloudType>::Sh
(
    const scalar Re,
    const scalar Sc
) const
{
    return 2.0 + 0.6*Foam::sqrt(Re)*cbrt(Sc);
}
 
 
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
template<class CloudType>
Foam::LiquidEvaporationBoil<CloudType>::LiquidEvaporationBoil
(
    const dictionary& dict,
    CloudType& owner
)
:
    PhaseChangeModel<CloudType>(dict, owner, typeName),
    liquids_(owner.thermo().liquids()),
    activeLiquids_(this->coeffDict().lookup("activeLiquids")),
    liqToCarrierMap_(activeLiquids_.size(), -1),
    liqToLiqMap_(activeLiquids_.size(), -1)
{
    if (activeLiquids_.size() == 0)
    {
        WarningInFunction
            << "Evaporation model selected, but no active liquids defined"
            << nl << endl;
    }
    else
    {
        Info<< "Participating liquid species:" << endl;
 
        // Determine mapping between liquid and carrier phase species
        forAll(activeLiquids_, i)
        {
            Info<< "    " << activeLiquids_[i] << endl;
            liqToCarrierMap_[i] =
                owner.composition().carrierId(activeLiquids_[i]);
        }
 
        // Determine mapping between model active liquids and global liquids
        const label idLiquid = owner.composition().idLiquid();
        forAll(activeLiquids_, i)
        {
            liqToLiqMap_[i] =
                owner.composition().localId(idLiquid, activeLiquids_[i]);
        }
    }
}
 
 
template<class CloudType>
Foam::LiquidEvaporationBoil<CloudType>::LiquidEvaporationBoil
(
    const LiquidEvaporationBoil<CloudType>& pcm
)
:
    PhaseChangeModel<CloudType>(pcm),
    liquids_(pcm.owner().thermo().liquids()),
    activeLiquids_(pcm.activeLiquids_),
    liqToCarrierMap_(pcm.liqToCarrierMap_),
    liqToLiqMap_(pcm.liqToLiqMap_)
{}
 
 
// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
template<class CloudType>
Foam::LiquidEvaporationBoil<CloudType>::~LiquidEvaporationBoil()
{}
 
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
template<class CloudType>
void Foam::LiquidEvaporationBoil<CloudType>::calculate
(
    const scalar dt,
    const label celli,
    const scalar Re,
    const scalar Pr,
    const scalar d,
    const scalar nu,
    const scalar T,
    const scalar Ts,
    const scalar pc,
    const scalar Tc,
    const scalarField& X,
    scalarField& dMassPC
) const
{
    // immediately evaporate mass that has reached critical condition
    if ((liquids_.Tc(X) - T) < SMALL)
    {
        if (debug)
        {
            WarningInFunction
                << "Parcel reached critical conditions: "
                << "evaporating all available mass" << endl;
        }
 
        forAll(activeLiquids_, i)
        {
            const label lid = liqToLiqMap_[i];
            dMassPC[lid] = GREAT;
        }
 
        return;
    }
 
    // droplet surface pressure assumed to surface vapour pressure
    scalar ps = liquids_.pv(pc, Ts, X);
 
    // vapour density at droplet surface [kg/m3]
    scalar rhos = ps*liquids_.W(X)/(RR*Ts);
 
    // construct carrier phase species volume fractions for cell, celli
    const scalarField XcMix(calcXc(celli));
 
    // carrier thermo properties
    scalar Hsc = 0.0;
    scalar Hc = 0.0;
    scalar Cpc = 0.0;
    scalar kappac = 0.0;
    forAll(this->owner().thermo().carrier().Y(), i)
    {
        scalar Yc = this->owner().thermo().carrier().Y()[i][celli];
        Hc += Yc*this->owner().thermo().carrier().Ha(i, pc, Tc);
        Hsc += Yc*this->owner().thermo().carrier().Ha(i, ps, Ts);
        Cpc += Yc*this->owner().thermo().carrier().Cp(i, ps, Ts);
        kappac += Yc*this->owner().thermo().carrier().kappa(i, ps, Ts);
    }
 
    // calculate mass transfer of each specie in liquid
    forAll(activeLiquids_, i)
    {
        const label gid = liqToCarrierMap_[i];
        const label lid = liqToLiqMap_[i];
 
        // boiling temperature at cell pressure for liquid species lid [K]
        const scalar TBoil = liquids_.properties()[lid].pvInvert(pc);
 
        // limit droplet temperature to boiling/critical temperature
        const scalar Td = min(T, 0.999*TBoil);
 
        // saturation pressure for liquid species lid [Pa]
        const scalar pSat = liquids_.properties()[lid].pv(pc, Td);
 
        // carrier phase concentration
        const scalar Xc = XcMix[gid];
 
 
        if (Xc*pc > pSat)
        {
            // saturated vapour - no phase change
        }
        else
        {
            // vapour diffusivity [m2/s]
            const scalar Dab = liquids_.properties()[lid].D(ps, Ts);
 
            // Schmidt number
            const scalar Sc = nu/(Dab + ROOTVSMALL);
 
            // Sherwood number
            const scalar Sh = this->Sh(Re, Sc);
 
 
            if (pSat > 0.999*pc)
            {
                // boiling
 
                const scalar deltaT = max(T - TBoil, 0.5);
 
                // vapour heat of formation
                const scalar hv = liquids_.properties()[lid].hl(pc, Td);
 
                // empirical heat transfer coefficient W/m2/K
                scalar alphaS = 0.0;
                if (deltaT < 5.0)
                {
                    alphaS = 760.0*pow(deltaT, 0.26);
                }
                else if (deltaT < 25.0)
                {
                    alphaS = 27.0*pow(deltaT, 2.33);
                }
                else
                {
                    alphaS = 13800.0*pow(deltaT, 0.39);
                }
 
                // flash-boil vaporisation rate
                const scalar Gf = alphaS*deltaT*pi*sqr(d)/hv;
 
                // model constants
                // NOTE: using Sherwood number instead of Nusselt number
                const scalar A = (Hc - Hsc)/hv;
                const scalar B = pi*kappac/Cpc*d*Sh;
 
                scalar G = 0.0;
                if (A > 0.0)
                {
                    // heat transfer from the surroundings contributes
                    // to the vaporisation process
                    scalar Gr = 1e-5;
 
                    for (label i=0; i<50; i++)
                    {
                        scalar GrDash = Gr;
 
                        G = B/(1.0 + Gr)*log(1.0 + A*(1.0 + Gr));
                        Gr = Gf/G;
 
                        if (mag(Gr - GrDash)/GrDash < 1e-3)
                        {
                            break;
                        }
                    }
                }
 
                dMassPC[lid] += (G + Gf)*dt;
            }
            else
            {
                // evaporation
 
                // surface molar fraction - Raoult's Law
                const scalar Xs = X[lid]*pSat/pc;
 
                // molar ratio
                const scalar Xr = (Xs - Xc)/max(SMALL, 1.0 - Xs);
 
                if (Xr > 0)
                {
                    // mass transfer [kg]
                    dMassPC[lid] += pi*d*Sh*Dab*rhos*log(1.0 + Xr)*dt;
                }
            }
        }
    }
}
 
 
template<class CloudType>
Foam::scalar Foam::LiquidEvaporationBoil<CloudType>::dh
(
    const label idc,
    const label idl,
    const scalar p,
    const scalar T
) const
{
    scalar dh = 0;
 
    scalar TDash = T;
    if (liquids_.properties()[idl].pv(p, T) >= 0.999*p)
    {
        TDash = liquids_.properties()[idl].pvInvert(p);
    }
 
    typedef PhaseChangeModel<CloudType> parent;
    switch (parent::enthalpyTransfer_)
    {
        case (parent::etLatentHeat):
        {
            dh = liquids_.properties()[idl].hl(p, TDash);
            break;
        }
        case (parent::etEnthalpyDifference):
        {
            scalar hc = this->owner().composition().carrier().Ha(idc, p, TDash);
            scalar hp = liquids_.properties()[idl].h(p, TDash);
 
            dh = hc - hp;
            break;
        }
        default:
        {
            FatalErrorInFunction
                << "Unknown enthalpyTransfer type" << abort(FatalError);
        }
    }
 
    return dh;
}
 
 
template<class CloudType>
Foam::scalar Foam::LiquidEvaporationBoil<CloudType>::Tvap
(
    const scalarField& X
) const
{
    return liquids_.Tpt(X);
}
 
 
template<class CloudType>
Foam::scalar Foam::LiquidEvaporationBoil<CloudType>::TMax
(
    const scalar p,
    const scalarField& X
) const
{
    return liquids_.pvInvert(p, X);
}
 
 
// ************************************************************************* //