View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0001329 | OpenFOAM | Bug | public | 2014-06-17 16:02 | 2014-06-19 15:27 |
| Reporter | dkxls | Assigned To | henry | ||
| Priority | normal | Severity | minor | Reproducibility | N/A |
| Status | resolved | Resolution | fixed | ||
| Platform | Linux x86_64 | OS | openSUSE | OS Version | 12.2 |
| Summary | 0001329: [PengRobinsonGas]: Bad mixture expression for critical pressure Pc | ||||
| Description | A mole-fraction averaged mixture expression gives normally a good approximation for critical temperature, volume and acentric factor. However, for the critical pressure, a mole-fraction average of pure-component critical pressures is normally unsatisfactory. This is because the critical pressure for most systems goes through a maximum or minimum with composition. The simplest rule which can give acceptable Pc values for a cubic EOS is the modified rule of Prausnitz and Gunn (1958), as it is also implemented in the liquidMixtureProperties class. For a more detailed discussion on this topic see Poling (2001); chapter 5-3. The changes required for the mixing rule of Prausnitz and Gunn are small and a patch that implements them is attached. | ||||
| Additional Information | Kay, W. "Gases and Vapors At High Temperature and Pressure - Density of Hydrocarbon." Industrial & Engineering Chemistry 28, no. 9 (September 1, 1936): 1014–19. doi:10.1021/ie50321a008. Prausnitz, J. M., and R. D. Gunn. "Volumetric Properties of Nonpolar Gaseous Mixtures." AIChE Journal 4, no. 4 (December 1, 1958): 430–35. doi:10.1002/aic.690040410. Poling, B.E., J.M. Prausnitz, and J.P. O’Connell. The Properties of Gases and Liquids. McGraw-Hill, 2001. | ||||
| Tags | No tags attached. | ||||
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PengRobinsonGas.patch (5,880 bytes)
diff --git a/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.C b/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.C
index e2b99d0..c3fefab 100644
--- a/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.C
+++ b/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.C
@@ -33,6 +33,8 @@ Foam::PengRobinsonGas<Specie>::PengRobinsonGas(Istream& is)
:
Specie(is),
Tc_(readScalar(is)),
+ Vc_(readScalar(is)),
+ Zc_(readScalar(is)),
Pc_(readScalar(is)),
omega_(readScalar(is))
{
@@ -48,9 +50,13 @@ Foam::PengRobinsonGas<Specie>::PengRobinsonGas
:
Specie(dict),
Tc_(readScalar(dict.subDict("equationOfState").lookup("Tc"))),
+ Vc_(readScalar(dict.subDict("equationOfState").lookup("Vc"))),
+ Zc_(1.0),
Pc_(readScalar(dict.subDict("equationOfState").lookup("Pc"))),
omega_(readScalar(dict.subDict("equationOfState").lookup("omega")))
-{}
+{
+ Zc_ = Pc_*Vc_/(specie::RR*Tc_);
+}
// * * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * //
@@ -74,6 +80,8 @@ Foam::Ostream& Foam::operator<<
{
os << static_cast<const Specie&>(pg)
<< token::SPACE << pg.Tc_
+ << token::SPACE << pg.Vc_
+ << token::SPACE << pg.Zc_
<< token::SPACE << pg.Pc_
<< token::SPACE << pg.omega_;
diff --git a/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.H b/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.H
index 7d1df11..568b35a 100644
--- a/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.H
+++ b/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGas.H
@@ -98,10 +98,16 @@ class PengRobinsonGas
//- Critical Temperature [K]
scalar Tc_;
+ //- Critical volume [m^3/kmol]
+ scalar Vc_;
+
+ //- Critical compression factor [-]
+ scalar Zc_;
+
//- Critical Pressure [Pa]
scalar Pc_;
- //- Accentric factor [-]
+ //- Acentric factor [-]
scalar omega_;
@@ -114,6 +120,8 @@ public:
(
const Specie& sp,
const scalar& Tc,
+ const scalar& Vc,
+ const scalar& Zc,
const scalar& Pc,
const scalar& omega
);
@@ -163,7 +171,7 @@ public:
//- Return compressibility rho/p [s^2/m^2]
inline scalar psi(scalar p, scalar T) const;
- //- Return compression factor []
+ //- Return compression factor [-]
inline scalar Z(scalar p, scalar T) const;
//- Return (cp - cv) [J/(kmol K]
diff --git a/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGasI.H b/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGasI.H
index aae0b92..125ce88 100644
--- a/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGasI.H
+++ b/src/thermophysicalModels/specie/equationOfState/PengRobinsonGas/PengRobinsonGasI.H
@@ -34,12 +34,16 @@ inline Foam::PengRobinsonGas<Specie>::PengRobinsonGas
(
const Specie& sp,
const scalar& Tc,
+ const scalar& Vc,
+ const scalar& Zc,
const scalar& Pc,
const scalar& omega
)
:
Specie(sp),
Tc_(Tc),
+ Vc_(Vc),
+ Zc_(Zc),
Pc_(Pc),
omega_(omega)
{}
@@ -57,6 +61,8 @@ inline Foam::PengRobinsonGas<Specie>::PengRobinsonGas
Specie(name, pg),
Tc_(pg.Tc),
Pc_(pg.Pc),
+ Vc_(pg.Vc),
+ Zc_(pg.Zc),
omega_(pg.omega)
{}
@@ -214,7 +220,9 @@ inline void Foam::PengRobinsonGas<Specie>::operator+=
scalar molr2 = pg.nMoles()/this->nMoles();
Tc_ = molr1*Tc_ + molr2*pg.Tc_;
- Pc_ = molr1*Pc_ + molr2*pg.Pc_;
+ Vc_ = molr1*Vc_ + molr2*pg.Vc_;
+ Zc_ = molr1*Zc_ + molr2*pg.Zc_;
+ Pc_ = specie::RR*Zc_*Tc_/Vc_;
omega_ = molr1*omega_ + molr2*pg.omega_;
}
@@ -233,7 +241,9 @@ inline void Foam::PengRobinsonGas<Specie>::operator-=
scalar molr2 = pg.nMoles()/this->nMoles();
Tc_ = molr1*Tc_ - molr2*pg.Tc_;
- Pc_ = molr1*Pc_ - molr2*pg.Pc_;
+ Vc_ = molr1*Vc_ - molr2*pg.Vc_;
+ Zc_ = molr1*Zc_ - molr2*pg.Zc_;
+ Pc_ = specie::RR*Zc_*Tc_/Vc_;
omega_ = molr1*omega_ - molr2*pg.omega_;
}
@@ -259,12 +269,18 @@ Foam::PengRobinsonGas<Specie> Foam::operator+
scalar molr1 = pg1.nMoles()/nMoles;
scalar molr2 = pg2.nMoles()/nMoles;
+ const scalar Tc = molr1*pg1.Tc_ + molr2*pg2.Tc_;
+ const scalar Vc = molr1*pg1.Vc_ + molr2*pg2.Vc_;
+ const scalar Zc = molr1*pg1.Zc_ + molr2*pg2.Zc_;
+
return PengRobinsonGas<Specie>
(
static_cast<const Specie&>(pg1)
+ static_cast<const Specie&>(pg2),
- molr1*pg1.Tc_ + molr2*pg2.Tc_,
- molr1*pg1.Pc_ + molr2*pg2.Pc_,
+ Tc,
+ Vc,
+ Zc,
+ specie::RR*Zc*Tc/Vc,
molr1*pg1.omega_ + molr2*pg2.omega_
);
}
@@ -281,12 +297,18 @@ Foam::PengRobinsonGas<Specie> Foam::operator-
scalar molr1 = pg1.nMoles()/nMoles;
scalar molr2 = pg2.nMoles()/nMoles;
+ const scalar Tc = molr1*pg1.Tc_ + molr2*pg2.Tc_;
+ const scalar Vc = molr1*pg1.Vc_ + molr2*pg2.Vc_;
+ const scalar Zc = molr1*pg1.Zc_ + molr2*pg2.Zc_;
+
return PengRobinsonGas<Specie>
(
static_cast<const Specie&>(pg1)
- static_cast<const Specie&>(pg2),
- molr1*pg1.Tc_ - molr2*pg2.Tc_,
- molr1*pg1.Pc_ - molr2*pg2.Pc_,
+ Tc,
+ Vc,
+ Zc,
+ specie::RR*Zc*Tc/Vc,
molr1*pg1.omega_ - molr2*pg2.omega_
);
}
@@ -303,6 +325,8 @@ Foam::PengRobinsonGas<Specie> Foam::operator*
(
s*static_cast<const Specie&>(pg),
pg.Tc_,
+ pg.Vc_,
+ pg.Zc_,
pg.Pc_,
pg.omega_
);
|
|
|
Thanks for the excellent detailed bug-report and patch. This is resolved by commit 372326bbfc081ff2df635c1a64ef529c0f60255f |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2014-06-17 16:02 | dkxls | New Issue | |
| 2014-06-17 16:02 | dkxls | File Added: PengRobinsonGas.patch | |
| 2014-06-19 15:25 | henry | Note Added: 0003136 | |
| 2014-06-19 15:25 | henry | Status | new => resolved |
| 2014-06-19 15:25 | henry | Resolution | open => fixed |
| 2014-06-19 15:25 | henry | Assigned To | => henry |
