doublereal WaterPropsIAPWS::psat(doublereal temperature, int waterState) {
doublereal densLiq = -1.0, densGas = -1.0, delGRT = 0.0;
doublereal dp, pcorr;
if (temperature >= T_c) {
densGas = density(temperature, P_c, WATER_SUPERCRIT);
setState_TR(temperature, densGas);
return P_c;
}
doublereal p = psat_est(temperature);
bool conv = false;
for (int i = 0; i < 30; i++) {
if (method == 1) {
corr(temperature, p, densLiq, densGas, delGRT);
doublereal delV = M_water * (1.0/densLiq - 1.0/densGas);
dp = - delGRT * Rgas * temperature / delV;
} else {
corr1(temperature, p, densLiq, densGas, pcorr);
dp = pcorr - p;
}
p += dp;
if ((method == 1) && delGRT < 1.0E-8) {
conv = true;
break;
} else {
if (fabs(dp/p) < 1.0E-9) {
conv = true;
break;
}
}
}
// Put the fluid in the desired end condition
if (waterState == WATER_LIQUID) {
setState_TR(temperature, densLiq);
} else if (waterState == WATER_GAS) {
setState_TR(temperature, densGas);
} else {
throw Cantera::CanteraError("WaterPropsIAPWS::psat",
"unknown water state input: " + Cantera::int2str(waterState));
}
return p;
}
doublereal WaterPropsIAPWS::densSpinodalSteam() const
{
doublereal temperature = T_c/tau;
doublereal delta_save = delta;
// return the critical density if we are above or even just a little below
// the critical temperature. We just don't want to worry about the critical
// point at this juncture.
if (temperature >= T_c - 0.001) {
return Rho_c;
}
doublereal p = psat_est(temperature);
doublereal rho_low = 0.0;
doublereal rho_high = 1000;
doublereal densSatGas = density_const(p, WATER_GAS);
doublereal dens_old = densSatGas;
delta = dens_old / Rho_c;
m_phi.tdpolycalc(tau, delta);
doublereal dpdrho_old = dpdrho();
if (dpdrho_old < 0.0) {
rho_high = std::min(dens_old, rho_high);
} else {
rho_low = std::max(rho_low, dens_old);
}
doublereal dens_new = densSatGas * (0.99);
delta = dens_new / Rho_c;
m_phi.tdpolycalc(tau, delta);
doublereal dpdrho_new = dpdrho();
if (dpdrho_new < 0.0) {
rho_high = std::min(dens_new, rho_high);
} else {
rho_low = std::max(rho_low, dens_new);
}
bool conv = false;
for (int it = 0; it < 50; it++) {
doublereal slope = (dpdrho_new - dpdrho_old)/(dens_new - dens_old);
if (slope >= 0.0) {
slope = dpdrho_new;
// shouldn't be here for gas spinodal
} else {
slope = std::min(slope, dpdrho_new *5.0 / dens_new);
}
doublereal delta_rho = - dpdrho_new / slope;
if (delta_rho > 0.0) {
delta_rho = std::min(delta_rho, dens_new * 0.1);
} else {
delta_rho = std::max(delta_rho, - dens_new * 0.1);
}
doublereal dens_est = dens_new + delta_rho;
if (dens_est < rho_low) {
dens_est = 0.5 * (rho_low + dens_new);
}
if (dens_est > rho_high) {
dens_est = 0.5 * (rho_high + dens_new);
}
dens_old = dens_new;
dpdrho_old = dpdrho_new;
dens_new = dens_est;
delta = dens_new / Rho_c;
m_phi.tdpolycalc(tau, delta);
dpdrho_new = dpdrho();
if (dpdrho_new < 0.0) {
rho_high = std::min(dens_new, rho_high);
} else if (dpdrho_new > 0.0) {
rho_low = std::max(rho_low, dens_new);
} else {
conv = true;
break;
}
if (fabs(dpdrho_new) < 1.0E-5) {
conv = true;
break;
}
}
if (!conv) {
throw CanteraError("WaterPropsIAPWS::densSpinodalSteam()",
"convergence failure");
}
// Restore the original delta
delta = delta_save;
m_phi.tdpolycalc(tau, delta);
return dens_new;
}
