Implemented psat_max and Tsat_max for pseudo-pure fluids to close https://github.com/CoolProp/CoolProp/issues/89

include/CoolPropFluid.h

@@ -265,7 +265,9 @@ public:
     SimpleState reduce, ///< Reducing state used for the EOS (usually, but not always, the critical point)
                 sat_min_liquid, ///< The saturated liquid state at the minimum saturation temperature
                 sat_min_vapor, ///< The saturated vapor state at the minimum saturation temperature
-                hs_anchor; ///< A fixed anchor state at Tc*1.1 and rhoc*0.9 used as a reference state for enthalpy and entropy ancillary curves
+                hs_anchor, ///< A fixed anchor state at Tc*1.1 and rhoc*0.9 used as a reference state for enthalpy and entropy ancillary curves
+                max_sat_T, ///< The state at the maximum saturation temperature for pseudo-pure
+                max_sat_p; ///< The state at the maximum saturation pressure for pseudo-pure
     EOSLimits limits; ///< Limits on the EOS
     double R_u, ///< The universal gas constant used for this EOS (usually, but not always, 8.314472 J/mol/K)
            molar_mass, ///< The molar mass in kg/mol (note NOT kg/kmol)
@@ -328,7 +330,6 @@ public:
         return alphar.dTau3(tau, delta);
     };
 
-
     long double base0(const long double &tau, const long double &delta) throw()
     {
         return alpha0.base(tau, delta);

src/Backends/Helmholtz/FlashRoutines.cpp

@@ -131,6 +131,18 @@ void FlashRoutines::PQ_flash(HelmholtzEOSMixtureBackend &HEOS)
             throw NotImplementedError("PQ_flash not implemented for pseudo-pure fluids yet");
         }
         else{
+            // Critical point for pure fluids, slightly different for pseudo-pure, very different for mixtures
+            long double pmax_sat = HEOS.calc_pmax_sat();
+            
+            // Check what the minimum limits for the equation of state are
+            long double pmin_satL, pmin_satV, pmin_sat;
+            HEOS.calc_pmin_sat(pmin_satL, pmin_satV);
+            pmin_sat = std::max(pmin_satL, pmin_satV);
+            
+            // Check limits
+            if (!is_in_closed_range(pmin_sat, pmax_sat, static_cast<long double>(HEOS._p))){
+                throw ValueError(format("Temperature to PQ_flash [%6g Pa] must be in range [%8g Pa, %8g Pa]",HEOS._p, pmin_sat, pmax_sat));
+            }
             // ------------------
             // It is a pure fluid
             // ------------------

src/Backends/Helmholtz/Fluids/FluidLibrary.h

@@ -337,6 +337,21 @@ protected:
             EOS.hs_anchor.hmolar = cpjson::get_double(hs_anchor, "hmolar");
             EOS.hs_anchor.smolar = cpjson::get_double(hs_anchor, "smolar");
         }
+        
+        if (EOS_json["STATES"].HasMember("pressure_max_sat")){
+            rapidjson::Value &s = EOS_json["STATES"]["pressure_max_sat"];
+            EOS.max_sat_T.T = cpjson::get_double(s, "T");
+            EOS.max_sat_T.p = cpjson::get_double(s, "p");
+            EOS.max_sat_T.rhomolar = cpjson::get_double(s, "rhomolar");
+        }
+        
+        if (EOS_json["STATES"].HasMember("temperature_max_sat")){
+            rapidjson::Value &s = EOS_json["STATES"]["temperature_max_sat"];
+            EOS.max_sat_p.T = cpjson::get_double(s, "T");
+            EOS.max_sat_p.p = cpjson::get_double(s, "p");
+            EOS.max_sat_p.rhomolar = cpjson::get_double(s, "rhomolar");
+        }
+        
 
         // Validate the equation of state that was just created
         EOS.validate();

src/Backends/Helmholtz/HelmholtzEOSMixtureBackend.cpp

@@ -419,7 +419,7 @@ long double HelmholtzEOSMixtureBackend::calc_pmax_sat(void)
 	{
 		if (components[0]->pEOS->pseudo_pure)
 		{
-			throw ValueError("calc_pmax_sat not yet defined for pseudo-pure");
+			return components[0]->pEOS->max_sat_p.p;
 		}
 		else{
 			return p_critical();
@@ -435,7 +435,7 @@ long double HelmholtzEOSMixtureBackend::calc_Tmax_sat(void)
 	{
 		if (components[0]->pEOS->pseudo_pure)
 		{
-			throw ValueError("calc_Tmax_sat not yet defined for pseudo-pure");
+			return components[0]->pEOS->max_sat_T.T;
 		}
 		else{
 			return T_critical();
@@ -459,6 +459,19 @@ void HelmholtzEOSMixtureBackend::calc_Tmin_sat(long double &Tmin_satL, long doub
 	}
 }
 
+void HelmholtzEOSMixtureBackend::calc_pmin_sat(long double &pmin_satL, long double &pmin_satV)
+{
+	if (is_pure_or_pseudopure)
+	{
+		pmin_satL = components[0]->pEOS->sat_min_liquid.p;
+		pmin_satV = components[0]->pEOS->sat_min_vapor.p;
+		return;
+	}
+	else{
+		throw ValueError("calc_pmin_sat not yet defined for mixtures");
+	}
+}
+
 // Minimum allowed saturation temperature the maximum of the saturation temperatures of liquid and vapor
 		// For pure fluids, both values are the same, for pseudo-pure they are probably the same, for mixtures they are definitely not the same
 

src/Backends/Helmholtz/HelmholtzEOSMixtureBackend.h

@@ -144,6 +144,7 @@ public:
 	long double calc_pmax_sat(void);
 	long double calc_Tmax_sat(void);
 	void calc_Tmin_sat(long double &Tmin_satL, long double &Tmin_satV);
+    void calc_pmin_sat(long double &pmin_satL, long double &pmin_satV);
 
     long double calc_T_critical(void);
     long double calc_p_critical(void);