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Fixed humid air properties to take into account reference state for air and water to close https://github.com/CoolProp/CoolProp/issues/47

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Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
This commit is contained in:
Ian Bell
2014-07-28 10:49:24 +02:00
parent 5d3fa2761c
commit db3515007b
1 changed files with 41 additions and 11 deletions
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52
src/HumidAirProp.cpp
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@@ -640,19 +640,35 @@ double IdealGasMolarEnthalpy_Water(double T, double vmolar)
double hbar_w_0, tau, rhomolar, hbar_w;
// Ideal-Gas contribution to enthalpy of water
hbar_w_0 = -0.01102303806; //[J/mol]
// Calculate the offset in the water enthalpy from a given state with a known (desired) enthalpy
double Tref = 473.15, vmolarref = 0.038837428192186184, href = 51885.582451893446;
Water->update(CoolProp::DmolarT_INPUTS,1/vmolarref,Tref);
double tauref = Water->keyed_output(CoolProp::iT_reducing)/Tref; //[no units]
double href_EOS = R_bar*Tref*(1+tauref*Water->keyed_output(CoolProp::idalpha0_dtau_constdelta));
double hoffset = href_EOS - href;
tau = Water->keyed_output(CoolProp::iT_reducing)/T;
rhomolar = 1/vmolar; //[mol/m^3]
Water->update(CoolProp::DmolarT_INPUTS, rhomolar, T);
hbar_w = hbar_w_0+R_bar*T*(1+tau*Water->keyed_output(CoolProp::idalpha0_dtau_constdelta));
hbar_w = hbar_w_0 + hoffset + R_bar*T*(1+tau*Water->keyed_output(CoolProp::idalpha0_dtau_constdelta));
return hbar_w;
}
double IdealGasMolarEntropy_Water(double T, double p)
{
double sbar_w, tau, R_bar;
R_bar = 8.314371; //[J/mol/K]
// Calculate the offset in the water entropy from a given state with a known (desired) entropy
double Tref = 473.15, pref = 101325, sref = 141.18297895840303;
Water->update(CoolProp::DmolarT_INPUTS,pref/(R_bar*Tref),Tref);
double tauref = Water->keyed_output(CoolProp::iT_reducing)/Tref; //[no units]
double sref_EOS = R_bar*(tauref*Water->keyed_output(CoolProp::idalpha0_dtau_constdelta)-Water->keyed_output(CoolProp::ialpha0));
double soffset = sref_EOS - sref;
tau = Water->keyed_output(CoolProp::iT_reducing)/T;
Water->update(CoolProp::DmolarT_INPUTS,p/(R_bar*T),T);
sbar_w = R_bar*(tau*Water->keyed_output(CoolProp::idalpha0_dtau_constdelta)-Water->keyed_output(CoolProp::ialpha0)); //[kJ/kmol/K]
sbar_w = soffset + R_bar*(tau*Water->keyed_output(CoolProp::idalpha0_dtau_constdelta)-Water->keyed_output(CoolProp::ialpha0)); //[kJ/kmol/K]
return sbar_w;
}
double IdealGasMolarEnthalpy_Air(double T, double vmolar)
@@ -660,13 +676,21 @@ double IdealGasMolarEnthalpy_Air(double T, double vmolar)
double hbar_a_0, tau, rhomolar, hbar_a, R_bar_Lemmon;
// Ideal-Gas contribution to enthalpy of air
hbar_a_0 = -7914.149298; //[J/mol]
R_bar_Lemmon = 8.314510; //[J/mol/K]
// Calculate the offset in the air enthalpy from a given state with a known (desired) enthalpy
double Tref = 473.15, vmolarref = 0.038837428192186184, href = 13782.240592933371;
Air->update(CoolProp::DmolarT_INPUTS, 1/vmolarref, Tref);
double tauref = 132.6312/Tref; //[no units]
double href_EOS = R_bar_Lemmon*Tref*(1+tauref*Air->keyed_output(CoolProp::idalpha0_dtau_constdelta));
double hoffset = href_EOS - href;
// Tj is given by 132.6312 K
tau = 132.6312/T;
rhomolar = 1/vmolar; //[mol/m^3]
R_bar_Lemmon = 8.314510; //[J/mol/K]
// Now calculate it based on the given inputs
Air->update(CoolProp::DmolarT_INPUTS, rhomolar, T);
double dd = Air->keyed_output(CoolProp::idalpha0_dtau_constdelta);
hbar_a = hbar_a_0 + R_bar_Lemmon*T*(1+tau*Air->keyed_output(CoolProp::idalpha0_dtau_constdelta)); //[J/mol]
hbar_a = hbar_a_0 + hoffset + R_bar_Lemmon*T*(1+tau*Air->keyed_output(CoolProp::idalpha0_dtau_constdelta)); //[J/mol]
return hbar_a;
}
double IdealGasMolarEntropy_Air(double T, double vmolar_a)
@@ -674,16 +698,22 @@ double IdealGasMolarEntropy_Air(double T, double vmolar_a)
double sbar_0_Lem, tau, sbar_a, R_bar_Lemmon = 8.314510, T0=273.15, p0=101325, vmolar_a_0;
// Ideal-Gas contribution to entropy of air
sbar_0_Lem=-196.1375815; //[J/mol/K]
// Tj and rhoj are given by 132.6312 and 302.5507652 respectively
tau = 132.6312/T; //[no units]
sbar_0_Lem = -196.1375815; //[J/mol/K]
vmolar_a_0 = R_bar_Lemmon*T0/p0; //[m^3/mol]
// Calculate the offset in the air entropy from a given state with a known (desired) entropy
double Tref = 473.15, vmolarref = 0.038837605637863169, sref = 212.22365283759311;
Air->update(CoolProp::DmolarT_INPUTS, 1/vmolar_a_0, Tref);
double tauref = 132.6312/Tref; //[no units]
double sref_EOS = R_bar_Lemmon*(tauref*Air->keyed_output(CoolProp::idalpha0_dtau_constdelta)-Air->keyed_output(CoolProp::ialpha0))+R_bar_Lemmon*log(vmolarref/vmolar_a_0);
double soffset = sref_EOS - sref;
// Tj and rhoj are given by 132.6312 and 302.5507652 respectively
tau = 132.6312/T; //[no units]
Air->update(CoolProp::DmolarT_INPUTS,1/vmolar_a_0,T);
sbar_a=sbar_0_Lem+R_bar_Lemmon*(tau*Air->keyed_output(CoolProp::idalpha0_dtau_constdelta)-Air->keyed_output(CoolProp::ialpha0))+R_bar_Lemmon*log(vmolar_a/vmolar_a_0); //[J/mol/K]
sbar_a=sbar_0_Lem + soffset + R_bar_Lemmon*(tau*Air->keyed_output(CoolProp::idalpha0_dtau_constdelta)-Air->keyed_output(CoolProp::ialpha0))+R_bar_Lemmon*log(vmolar_a/vmolar_a_0); //[J/mol/K]
return sbar_a; //[J/mol/K]
}