Phase boundaries

Critical curve of H2O-NaCl system

P_X_Critical

P_X_Critical calculate the critical pressure (P) and salinity (X) given temperature.

Chart

python

import pyswEOS
from pyswEOS import H2ONaCl
from pyswEOS import H2O
sw=H2ONaCl.cH2ONaCl()
# calculate critical curve by giving temperature
T=np.linspace(H2O.T_Critic,H2ONaCl.TMAX_C,100)
p,x = sw.P_X_Critical(T)
x,p = np.array(x)*100,np.array(p)

c++

#include "H2ONaCl.H"
H2ONaCl::cH2ONaCl eos;
double dT = (H2ONaCl::TMAX_C - H2O::T_Critic)/100;
for (double T = H2O::T_Critic; T <= H2ONaCl::TMAX_C; T=T+dT)
{
    double P,X;
    eos.P_X_Critical(T,P,X);
    cout<<T<<" "<<P<<" "<<X<<endl;
}

Below water critical point

The critical salinity at critical point of water is zero, so what’s the relationship between critical pressure given by Equation 5a of Driesner(2007a) and boiling pressure given by IAPWS formula (e.g. IAPWS-IF97 TSat_P) ? The calculation results are quite different (up to 9 bar).