research/cantera
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

MaskellSolidPhaseSoln thermo updates.

Browse source 
Fix sign error in chemical potentials and update
activity coefficients accordingly.

Correct implementation of getActivityConcentrations()

Additional unit tests.
This commit is contained in:
Victor Brunini 2014-03-07 17:14:13 +00:00
parent 0981391ac4
commit 1565bad198
3 changed files with 49 additions and 42 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

27
include/cantera/thermo/MaskellSolidSolnPhase.h
View file

@ -57,33 +57,6 @@ public:
* concentration divided by the standard concentration is also
* equal to the activity of species.
*
* For this implementation the activity is defined to be the
* mole fraction of the species. The generalized concentration
* is defined to be equal to the mole fraction divided by
* the partial molar volume. The generalized concentrations
* for species in this phase therefore have units of
* kmol m<SUP>-3</SUP>. Rate constants must reflect this fact.
*
* On a general note, the following must be true.
* For an ideal solution, the generalized concentration must consist
* of the mole fraction multiplied by a constant. The constant may be
* fairly arbitrarily chosen, with differences adsorbed into the
* reaction rate expression. 1/V_N, 1/V_k, or 1 are equally good,
* as long as the standard concentration is adjusted accordingly.
* However, it must be a constant (and not the concentration, btw,
* which is a function of the mole fractions) in order for the
* ideal solution properties to hold at the same time having the
* standard concentration to be independent of the mole fractions.
*
* In this implementation the form of the generalized concentrations
* depend upon the member attribute, #m_formGC.
*
* HKM Note: We have absorbed the pressure dependence of the pure species
* state into the thermodynamics functions. Therefore the
* standard state on which the activities are based depend
* on both temperature and pressure. If we hadn't, it would have
* appeared in this function in a very awkward exp[] format.
*
* @param c Pointer to array of doubles of length m_kk, which on exit
* will contain the generalized concentrations.
*/

16
src/thermo/MaskellSolidSolnPhase.cpp
View file

@ -68,10 +68,10 @@ getActivityConcentrations(doublereal* c) const
{
std::vector<doublereal> pmv(m_kk);
getPartialMolarVolumes(&pmv[0]);
const doublereal* const dtmp = moleFractdivMMW();
const double mmw = meanMolecularWeight();
for (size_t k = 0; k < m_kk; k++) {
c[k] = dtmp[k] * mmw / pmv[k];
getActivityCoefficients(c);
for(unsigned sp=0; sp < m_kk; ++sp)
{
c[sp] *= moleFraction(sp) / pmv[sp];
}
}
@ -174,8 +174,8 @@ getActivityCoefficients(doublereal* ac) const
const doublereal A = (std::pow(1 - rfm, pval) * std::pow(rfm, pval) * std::pow(r - rfm, 1 - pval)) /
(std::pow(1 - r - rfm, 1 + pval) * (1 - r));
const doublereal B = pval * h_mixing / RT;
ac[product_species_index] = 1 / (A * r * r) * std::exp(-B);
ac[reactant_species_index] = A * r / (1 - r) * std::exp(B);
ac[product_species_index] = A * std::exp(B);
ac[reactant_species_index] = 1 / (A * r * (1-r) ) * std::exp(-B);
}
void MaskellSolidSolnPhase::
@ -191,8 +191,8 @@ getChemPotentials(doublereal* mu) const
GasConstant * temperature() *
std::log( (std::pow(1 - rfm, pval) * std::pow(rfm, pval) * std::pow(r - rfm, 1 - pval) * r) /
(std::pow(1 - r - rfm, 1 + pval) * (1 - r)) );
mu[product_species_index] = RT * m_g0_RT[product_species_index] - DgbarDr;
mu[reactant_species_index] = RT * m_g0_RT[reactant_species_index] + DgbarDr;
mu[product_species_index] = RT * m_g0_RT[product_species_index] + DgbarDr;
mu[reactant_species_index] = RT * m_g0_RT[reactant_species_index] - DgbarDr;
}
void MaskellSolidSolnPhase::

48
test/thermo/MaskellSolidSolnPhase_Test.cpp
View file

@ -37,8 +37,8 @@ public:
const double r = 0.1 * (i+1);
set_r(r);
test_phase->getChemPotentials(&chemPotentials[0]);
EXPECT_NEAR(expected_result[i], chemPotentials[0], 1.e-6);
EXPECT_NEAR(1000.-expected_result[i], chemPotentials[1], 1.e-6);
EXPECT_NEAR(-expected_result[i], chemPotentials[0], 1.e-6);
EXPECT_NEAR(1000.+expected_result[i], chemPotentials[1], 1.e-6);
}
}
};
@ -78,6 +78,18 @@ TEST_F(MaskellSolidSolnPhase_Test, chem_potentials)
check_chemPotentials(expected_result_minus_5000);
}
TEST_F(MaskellSolidSolnPhase_Test, partialMolarVolumes)
{
const std::string valid_file("../data/MaskellSolidSolnPhase_valid.xml");
initializeTestPhaseWithXML(valid_file);
ASSERT_TRUE(dynamic_cast<MaskellSolidSolnPhase *>(test_phase) != NULL);
std::vector<double> pmv(2);
test_phase->getPartialMolarVolumes(&pmv[0]);
EXPECT_EQ(0.005, pmv[0]);
EXPECT_EQ(0.01, pmv[1]);
}
TEST_F(MaskellSolidSolnPhase_Test, activityCoeffs)
{
const std::string valid_file("../data/MaskellSolidSolnPhase_valid.xml");
@ -105,16 +117,38 @@ TEST_F(MaskellSolidSolnPhase_Test, activityCoeffs)
}
}
TEST_F(MaskellSolidSolnPhase_Test, partialMolarVolumes)
TEST_F(MaskellSolidSolnPhase_Test, standardConcentrations)
{
const std::string valid_file("../data/MaskellSolidSolnPhase_valid.xml");
initializeTestPhaseWithXML(valid_file);
ASSERT_TRUE(dynamic_cast<MaskellSolidSolnPhase *>(test_phase) != NULL);
std::vector<double> pmv(2);
test_phase->getPartialMolarVolumes(&pmv[0]);
EXPECT_EQ(0.005, pmv[0]);
EXPECT_EQ(0.01, pmv[1]);
EXPECT_DOUBLE_EQ(1.0 / 0.005, test_phase->standardConcentration(0));
EXPECT_DOUBLE_EQ(1.0 / 0.01, test_phase->standardConcentration(1));
}
TEST_F(MaskellSolidSolnPhase_Test, activityConcentrations)
{
const std::string valid_file("../data/MaskellSolidSolnPhase_valid.xml");
initializeTestPhaseWithXML(valid_file);
ASSERT_TRUE(dynamic_cast<MaskellSolidSolnPhase *>(test_phase) != NULL);
// Check to make sure activityConcentration_i == standardConcentration_i * gamma_i * X_i
std::vector<double> standardConcs(2);
std::vector<double> activityCoeffs(2);
std::vector<double> activityConcentrations(2);
for(int i=0; i < 9; ++i)
{
const double r = 0.1 * (i+1);
set_r(r);
test_phase->getActivityCoefficients(&activityCoeffs[0]);
standardConcs[0] = test_phase->standardConcentration(0);
standardConcs[1] = test_phase->standardConcentration(1);
test_phase->getActivityConcentrations(&activityConcentrations[0]);
EXPECT_NEAR(standardConcs[0] * r * activityCoeffs[0], activityConcentrations[0], 1.e-6);
EXPECT_NEAR(standardConcs[1] * (1-r) * activityCoeffs[1], activityConcentrations[1], 1.e-6);
}
}
};