87 lines
2.4 KiB
C++
87 lines
2.4 KiB
C++
// Lee-Kesler equation of state
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#include "RedlichKwong.h"
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#include <math.h>
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namespace tpx {
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//--------------------------- member functions ------------------
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double RedlichKwong::up() {
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double u = -Pp()/Rho + hresid() + m_energy_offset;
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//cout << "up = " << u << endl;
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return u;
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}
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double RedlichKwong::hresid(){
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double hh = m_b * (Rho/m_mw);
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double hresid_mol_RT = z() - 1.0
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- (1.5*m_a/(m_b*8314.3*T*sqrt(T)))*log(1.0 + hh);
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return 8314.3*T*hresid_mol_RT/m_mw;
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}
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double RedlichKwong::sresid(){
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double hh = m_b * (Rho/m_mw);
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//cout << "hh = " << hh << endl;
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double sresid_mol_R = log(z()*(1.0 - hh))
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- (0.5*m_a/(m_b*8314.3*T*sqrt(T)))*log(1.0 + hh);
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double sp = 8314.3*sresid_mol_R/m_mw;
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//cout << "sresid = " << sp << endl;
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return sp;
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}
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double RedlichKwong::sp() {
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const double Pref = 101325.0;
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double rgas = 8314.3/m_mw;
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//cout << "P = " << Rho*rgas*T << endl;
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double ss = rgas*(log(Pref/(Rho*rgas*T)));
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double sr = sresid();
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double p = Pp();
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double s = rgas*(log(Pref/p)) + sr + m_entropy_offset;
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//cout << "sp = " << s << " " << ss << " " << sr << " " << m_entropy_offset << endl;
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return s;
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}
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double RedlichKwong::z() {
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return Pp()*m_mw/(Rho*8314.3*T);
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}
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double RedlichKwong::Pp() {
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double R = 8314.3;
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double V = m_mw/Rho;
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double pp = R*T/(V - m_b) - m_a/(sqrt(T)*V*(V+m_b));
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//cout << "molar V, T, P = " << V << " " << T << " " << pp << endl;
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return pp;
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//cout << "Rho, T, Pp = " << pp << endl;
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}
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double RedlichKwong::Psat(){
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double tt = m_tcrit/T;
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double lpr = -0.8734*tt*tt - 3.4522*tt + 4.2918;
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return m_pcrit*exp(lpr);
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}
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double RedlichKwong::ldens(){
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double c;
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int i;
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double sqt = sqrt(T);
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double v = m_b, vnew;
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double pp = Psat();
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double Rhsave = Rho;
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for (i = 0; i < 50; i++) {
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//pp = Pp();
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c = m_b*m_b + m_b*GasConstant*T/pp - m_a/(pp*sqt);
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vnew = (1.0/c)*(v*v*v - GasConstant*T*v*v/pp - m_a*m_b/(pp*sqt));
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v = vnew;
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//Rho = m_mw/v;
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//cout << "ldens Rho = " << Rho << " " << z() << " " << Pp() << endl;
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}
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Rho = Rhsave;
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//cout << "ldens: " << m_mw/vnew << endl;
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return m_mw/vnew;
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}
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}
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