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ENH: Extended the effectiveness heat exchanger source to enable target

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heat rejection

The new optional entry targetQdot can be used to specify a target heat
rejection.  This is additionally controlled using the
targetQdotCalcInterval  and targetQdotRelax entries which default to
values of 5 and 0.5, respectively.
This commit is contained in:
Andrew Heather
2017-12-18 19:41:33 +00:00
parent 19c3875a14
commit c6433e32c2
2 changed files with 85 additions and 35 deletions
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75
src/fvOptions/sources/derived/effectivenessHeatExchangerSource/effectivenessHeatExchangerSource.C
View File

@ -3,7 +3,7 @@
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2013-2015 OpenFOAM Foundation
\\/ M anipulation | Copyright (C) 2016 OpenCFD Ltd.
\\/ M anipulation | Copyright (C) 2016-2017 OpenCFD Ltd.
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
@ -142,6 +142,10 @@ Foam::fv::effectivenessHeatExchangerSource::effectivenessHeatExchangerSource
secondaryInletT_(0),
primaryInletT_(0),
userPrimaryInletT_(false),
targetQdotActive_(false),
targetQdot_(0),
targetQdotCalcInterval_(5),
targetQdotRelax_(0.5),
eTable_(),
UName_("U"),
TName_("T"),
@ -225,48 +229,52 @@ void Foam::fv::effectivenessHeatExchangerSource::addSup
reduce(CpfMean, sumOp<scalar>());
reduce(sumPhi, sumOp<scalar>());
reduce(sumMagPhi, sumOp<scalar>());
reduce(primaryInletTfMean, sumOp<scalar>());
primaryInletTfMean /= sumMagPhi + ROOTVSMALL;
CpfMean /= sumMagPhi + ROOTVSMALL;
scalar primaryInletT = primaryInletT_;
if (!userPrimaryInletT_)
{
primaryInletT = primaryInletTfMean;
reduce(primaryInletTfMean, sumOp<scalar>());
primaryInletT = primaryInletTfMean/(sumMagPhi + ROOTVSMALL);
}
scalar Qt =
const scalar alpha =
eTable_()(mag(sumPhi), secondaryMassFlowRate_)
*(secondaryInletT_ - primaryInletT)
*CpfMean*mag(sumPhi);
const scalar Qt = alpha*(secondaryInletT_ - primaryInletT);
if
(
targetQdotActive_
&& (mesh_.time().timeIndex() % targetQdotCalcInterval_ == 0)
)
{
scalar dT = (targetQdot_ - Qt)/(alpha + ROOTVSMALL);
secondaryInletT_ += targetQdotRelax_*dT;
}
const scalarField TCells(T, cells_);
scalar Tref = 0;
if (Qt > 0)
{
Tref = max(TCells);
reduce(Tref, maxOp<scalar>());
}
else
{
Tref = min(TCells);
reduce(Tref, minOp<scalar>());
}
scalarField deltaTCells(cells_.size(), 0);
forAll(deltaTCells, i)
{
if (Qt > 0)
{
Tref = gMax(TCells);
forAll(deltaTCells, i)
{
deltaTCells[i] = max(Tref - TCells[i], 0.0);
}
}
else
{
Tref = gMin(TCells);
forAll(deltaTCells, i)
{
deltaTCells[i] = max(TCells[i] - Tref, 0.0);
}
}
const volVectorField& U = mesh_.lookupObject<volVectorField>(UName_);
const scalarField& V = mesh_.V();
scalar sumWeight = 0;
@ -293,6 +301,7 @@ void Foam::fv::effectivenessHeatExchangerSource::addSup
Info<< type() << ": " << name() << nl << incrIndent
<< indent << "Net mass flux [Kg/s] : " << sumPhi << nl
<< indent << "Total energy exchange [W] : " << Qt << nl
<< indent << "Secondary inlet T [K] : " << secondaryInletT_ << nl
<< indent << "Tref [K] : " << Tref << nl
<< indent << "Effectiveness : "
<< eTable_()(mag(sumPhi), secondaryMassFlowRate_) << decrIndent
@ -314,7 +323,7 @@ bool Foam::fv::effectivenessHeatExchangerSource::read(const dictionary& dict)
if (coeffs_.readIfPresent("primaryInletT", primaryInletT_))
{
Info<< type() << " " << this->name() << ": "
Info<< type() << " " << this->name() << ": " << indent << nl
<< "employing user-specified primary flow inlet temperature: "
<< primaryInletT_ << endl;
@ -322,11 +331,33 @@ bool Foam::fv::effectivenessHeatExchangerSource::read(const dictionary& dict)
}
else
{
Info<< type() << " " << this->name() << ": "
Info<< type() << " " << this->name() << ": " << indent << nl
<< "employing flux-weighted primary flow inlet temperature"
<< endl;
}
if (coeffs_.readIfPresent("targetQdot", targetQdot_))
{
targetQdotActive_ = true;
Info<< indent << "employing target heat rejection of "
<< targetQdot_ << nl;
coeffs_.readIfPresent
(
"targetQdotCalcInterval",
targetQdotCalcInterval_
);
Info<< indent << "updating secondary inlet temperature every "
<< targetQdotCalcInterval_ << " iterations" << nl;
coeffs_.readIfPresent("targetQdotRelax", targetQdotRelax_);
Info<< indent << "temperature relaxation: "
<< targetQdotRelax_ << endl;
}
return true;
}
else

43
src/fvOptions/sources/derived/effectivenessHeatExchangerSource/effectivenessHeatExchangerSource.H
View File

@ -3,7 +3,7 @@
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2013-2017 OpenFOAM Foundation
\\/ M anipulation | Copyright (C) 2016 OpenCFD Ltd.
\\/ M anipulation | Copyright (C) 2016-2017 OpenCFD Ltd.
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
@ -28,8 +28,8 @@ Group
grpFvOptionsSources
Description
Heat exchanger source model, in which the heat exchanger is defined as a
selection of cells.
Heat exchanger source model, in which the heat exchanger is defined as an
energy source using a selection of cells.
The total heat exchange source is given by:
\f[
@ -75,13 +75,21 @@ Usage
secondaryMassFlowRate 1.0;
secondaryInletT 336;
// primaryInletT 293; // Constrain to this T if present
faceZone facesZoneInletOriented;
outOfBounds clamp;
file "effTable";
// Optional
// primaryInletT 293;
// targetQdot 1500;
}
\endverbatim
Optional entries:
- \c primaryInletT : sets the primary inlet temperature. If not set, the
flux-averaged temperature is used.
- \c targetQdot : target heat rejection
The effectiveness table is described in terms of the primary and secondary
mass flow rates. For example, the table:
@ -95,7 +103,7 @@ Usage
\endverbatim
Is specified by the following:
is specified by the following:
\verbatim
(
@ -121,9 +129,9 @@ Usage
\endverbatim
Note
- the table with name "file" should have the same units as the
- the table with name \c file should have the same units as the
secondary mass flow rate and kg/s for phi
- faceZone is the faces at the inlet of the cellzone, it needs to be
- \c faceZone is the faces at the inlet of the \c cellzone, it needs to be
created with flip map flags. It is used to integrate the net mass flow
rate into the heat exchanger
@ -133,8 +141,8 @@ SourceFiles
\*---------------------------------------------------------------------------*/
#ifndef effectivenessHeatExchangerSource_H
#define effectivenessHeatExchangerSource_H
#ifndef fv_effectivenessHeatExchangerSource_H
#define fv_effectivenessHeatExchangerSource_H
#include "cellSetOption.H"
#include "autoPtr.H"
@ -172,6 +180,18 @@ protected:
//- Flag to use a user-specified primary inlet temperature
bool userPrimaryInletT_;
//- Flag to use target heat rejection
bool targetQdotActive_;
//- Target heat rejection
scalar targetQdot_;
//- Target heat rejection calculation interval
label targetQdotCalcInterval_;
//- Target heat rejection temperature under-relaxation coefficient
scalar targetQdotRelax_;
//- 2D look up table efficiency = function of primary and secondary
// mass flow rates [kg/s]
autoPtr<interpolation2DTable<scalar>> eTable_;
@ -214,7 +234,7 @@ private:
//- Initialise heat exchanger source model
void initialise();
//- Calculate total area of faceZone accross processors
//- Calculate total area of faceZone across processors
void calculateTotalArea(scalar& area);
@ -237,8 +257,7 @@ public:
//- Destructor
virtual ~effectivenessHeatExchangerSource()
{}
virtual ~effectivenessHeatExchangerSource() = default;
// Member Functions