Predefined mixtures are added, can be accessed with a fluid name like R410A.mix

Closes https://github.com/CoolProp/CoolProp/issues/153

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>

src/AbstractState.cpp

@@ -22,7 +22,7 @@ AbstractState * AbstractState::factory(const std::string &backend, const std::st
     if (!backend.compare("HEOS"))
     {
         if (fluid_string.find('&') == std::string::npos){
-            return new HelmholtzEOSBackend(&get_fluid(fluid_string));
+            return new HelmholtzEOSBackend(fluid_string);
         }
         else{
             // Split at the '&'

src/Backends/Helmholtz/HelmholtzEOSBackend.h

@@ -11,6 +11,7 @@
 #include <vector>
 #include "HelmholtzEOSMixtureBackend.h"
 #include "Fluids/FluidLibrary.h"
+#include "MixtureParameters.h"
 
 namespace CoolProp {
 
@@ -18,7 +19,28 @@ class HelmholtzEOSBackend : public HelmholtzEOSMixtureBackend  {
 public:
     HelmholtzEOSBackend();
     HelmholtzEOSBackend(CoolPropFluid *pFluid){set_components(std::vector<CoolPropFluid*>(1,pFluid));};
-    HelmholtzEOSBackend(const std::string &name){set_components(std::vector<CoolPropFluid*>(1,&(get_library().get(name))));};
+    HelmholtzEOSBackend(const std::string &name){
+        Dictionary dict;
+        std::vector<double> mole_fractions;
+        std::vector<CoolPropFluid*> components;
+        if (is_predefined_mixture(name, dict)){
+            std::vector<std::string> fluids = dict.get_string_vector("fluids");
+            mole_fractions = dict.get_double_vector("mole_fractions");
+            
+            components.resize(fluids.size());
+            for (unsigned int i = 0; i < components.size(); ++i){
+                components[i] = &(get_library().get(fluids[i]));
+            }
+        }
+        else{
+            components = std::vector<CoolPropFluid*>(1,&(get_library().get(name)));
+            mole_fractions = std::vector<double>(1,1);
+        }
+        // Set the components
+        set_components(components);
+        // Set the mole fractions
+        set_mole_fractions(std::vector<long double>(mole_fractions.begin(), mole_fractions.end()));
+    };
     virtual ~HelmholtzEOSBackend(){};
 };
 

src/Backends/Helmholtz/MixtureParameters.cpp

@@ -1,9 +1,51 @@
 #include "MixtureParameters.h"
 #include "mixture_departure_functions_JSON.h" // Creates the variable mixture_departure_functions_JSON
 #include "mixture_binary_pairs_JSON.h" // Creates the variable mixture_binary_pairs_JSON
+#include "predefined_mixtures_JSON.h" // Makes a std::string variable called predefined_mixtures_JSON
 
 namespace CoolProp{
 
+/** \brief A library of predefined mixtures
+ * 
+ * Each entry in the predefined mixture library contains the names and mole fractions for the binary pairs
+ */
+class PredefinedMixturesLibrary{
+    public:
+    std::map<std::string, Dictionary> predefined_mixture_map;
+    
+    PredefinedMixturesLibrary(){
+        rapidjson::Document doc;
+
+        doc.Parse<0>(predefined_mixtures_JSON.c_str());
+        if (doc.HasParseError()){throw ValueError();}
+        
+        // Iterate over the papers in the listing
+        for (rapidjson::Value::ValueIterator itr = doc.Begin(); itr != doc.End(); ++itr)
+        {
+            // Instantiate the empty dictionary to be filled
+            Dictionary dict;
+            // Get the name
+            std::string name = cpjson::get_string(*itr, "name")+".mix";
+            // Get the fluid names
+            dict.add_string_vector("fluids", cpjson::get_string_array(*itr, "fluids"));
+            // Get the mole fractions            
+            dict.add_double_vector("mole_fractions", cpjson::get_double_array(*itr,"mole_fractions"));
+            
+            predefined_mixture_map.insert(std::pair<std::string, Dictionary >(name, dict));
+        }
+    }
+};
+static PredefinedMixturesLibrary predefined_mixtures_library;
+
+bool is_predefined_mixture(const std::string name, Dictionary &dict){
+    if (predefined_mixtures_library.predefined_mixture_map.find(name) != predefined_mixtures_library.predefined_mixture_map.end()){
+        dict = predefined_mixtures_library.predefined_mixture_map[name];
+        return true;
+    }
+    else{
+        return false;
+    }
+}
     
 /** \brief A library of binary pair parameters for the mixture
  * 

src/Backends/Helmholtz/MixtureParameters.h

@@ -11,6 +11,11 @@ namespace CoolProp{
  */
 std::string get_csv_mixture_binary_pairs();
 
+/** \brief Get the parameters for a predefined mixture - R410A, R404A, etc.
+ * 
+ */
+bool is_predefined_mixture(const std::string name, Dictionary &dict);
+    
 /** \brief Get a string for the given binary pair
  * 
  *