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Replaced coeffThermExp() with an analytical derivative.

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This commit is contained in:
Harry Moffat 2008-09-03 22:40:14 +00:00
parent 0f57869240
commit 71393768bf
5 changed files with 40 additions and 54 deletions
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14
Cantera/src/thermo/PDSS_Water.cpp
View file

@ -435,16 +435,22 @@ namespace Cantera {
* \f]
*/
doublereal PDSS_Water::thermalExpansionCoeff() const {
doublereal pres = pressure();
doublereal val = m_sub->coeffThermExp(m_temp, pres);
doublereal val = m_sub->coeffThermExp();
return val;
}
doublereal PDSS_Water::dthermalExpansionCoeffdT() const {
doublereal pres = pressure();
doublereal dens_save = m_dens;
double tt = m_temp - 0.04;
doublereal vald = m_sub->coeffThermExp(tt, pres);
doublereal val2 = m_sub->coeffThermExp(m_temp, pres);
doublereal dd = m_sub->density(tt, pres, m_iState, m_dens);
if (dd < 0.0) {
throw CanteraError("PDSS_Water::dthermalExpansionCoeffdT",
"unable to solve for the density at T = " + fp2str(tt) + ", P = " + fp2str(pres));
}
doublereal vald = m_sub->coeffThermExp();
m_sub->setState_TR(m_temp, dens_save);
doublereal val2 = m_sub->coeffThermExp();
doublereal val = (val2 - vald) / 0.04;
return val;
}

15
Cantera/src/thermo/WaterProps.cpp
View file

@ -442,14 +442,21 @@ namespace Cantera {
}
double WaterProps::coeffThermalExp_IAPWS(double temp, double press) {
double cte;
cte = m_waterIAPWS->coeffThermExp(temp, press);
double dens = m_waterIAPWS->density(temp, press, WATER_LIQUID);
if (dens < 0.0) {
throw CanteraError("WaterProps::coeffThermalExp_IAPWS",
"Unable to solve for density at T = " + fp2str(temp) + " and P = " + fp2str(press));
}
double cte = m_waterIAPWS->coeffThermExp();
return cte;
}
double WaterProps::isothermalCompressibility_IAPWS(double temp, double press) {
m_waterIAPWS->density(temp, press, WATER_LIQUID);
double dens = m_waterIAPWS->density(temp, press, WATER_LIQUID);
if (dens < 0.0) {
throw CanteraError("WaterProps::isothermalCompressibility_IAPWS",
"Unable to solve for density at T = " + fp2str(temp) + " and P = " + fp2str(press));
}
double kappa = m_waterIAPWS->isothermalCompressibility();
return kappa;
}

46
Cantera/src/thermo/WaterPropsIAPWS.cpp
View file

@ -257,45 +257,6 @@ double WaterPropsIAPWS::psat_est(double temperature) {
return ps;
}
/*
* Returns the coefficient of thermal expansion as a function
* of temperature and pressure.
* alpha = d (ln V) / dT at constant P.
*
* Currently this function is calculated using a differencing scheme.
*/
double WaterPropsIAPWS::coeffThermExp(double temperature, double pressure) {
double deltaT = 0.01;
double psat_at=0.0;
double rhoguess = -1;
int phase = -1;
if (temperature > T_c) {
rhoguess = pressure * M_water / (Rgas * temperature);
} else {
psat_at = psat(temperature);
if (pressure >= psat_at) {
phase = WATER_LIQUID;
deltaT = -0.01;
} else
phase = WATER_GAS;
}
double dens_base = density(temperature, pressure, phase, rhoguess);
if (dens_base == -1.0) {
printf("problems\n");
exit(-1);
}
double temp_del = temperature + deltaT;
double dens_del = density(temp_del, pressure, phase, dens_base);
double Vavg = 0.5 * (1./dens_del + 1./dens_base);
double retn = 1.0 / Vavg * (1./dens_del - 1.0/dens_base)/deltaT;
return retn;
}
/*
* Returns the coefficient of isothermal compressibility
* of temperature and pressure.
@ -315,6 +276,13 @@ double WaterPropsIAPWS:: coeffPresExp() const {
return (retn);
}
double WaterPropsIAPWS:: coeffThermExp() const {
double kappa = isothermalCompressibility();
double beta = coeffPresExp();
double dens = delta * Rho_c;
return (kappa * dens * Rgas * beta / M_water);
}
/*
* Calculate the Gibbs free energy in mks units of
* J kmol-1 K-1.

4
Cantera/src/thermo/WaterPropsIAPWS.h
View file

@ -307,7 +307,7 @@ public:
*/
double density() const;
//! Returns the coefficient of thermal expansion as a function of temperature and pressure.
//! Returns the coefficient of thermal expansion.
/*!
* alpha = d (ln V) / dT at constant P.
*
@ -316,7 +316,7 @@ public:
* @return
* Returns the coefficient of thermal expansion
*/
double coeffThermExp(double temperature, double pressure);
double coeffThermExp() const;
//! Returns the isochoric pressure-temperature coefficient
/*!

15
Cantera/src/thermo/WaterSSTP.cpp
View file

@ -508,18 +508,23 @@ namespace Cantera {
* \f]
*/
doublereal WaterSSTP::thermalExpansionCoeff() const {
doublereal pres = pressure();
double T = temperature();
doublereal val = m_sub->coeffThermExp(T, pres);
doublereal val = m_sub->coeffThermExp();
return val;
}
doublereal WaterSSTP::dthermalExpansionCoeffdT() const {
doublereal pres = pressure();
doublereal dens_save = density();
double T = temperature();
double tt = T - 0.04;
doublereal vald = m_sub->coeffThermExp(tt, pres);
doublereal val2 = m_sub->coeffThermExp(T, pres);
doublereal dd = m_sub->density(tt, pres, WATER_LIQUID, dens_save);
if (dd < 0.0) {
throw CanteraError("WaterSSTP::dthermalExpansionCoeffdT",
"Unable to solve for the density at T = " + fp2str(tt) + ", P = " + fp2str(pres));
}
doublereal vald = m_sub->coeffThermExp();
m_sub->setState_TR(T, dens_save);
doublereal val2 = m_sub->coeffThermExp();
doublereal val = (val2 - vald) / 0.04;
return val;
}