From 5dcf810f0b0388bd654317edbc6a242e4fd21045 Mon Sep 17 00:00:00 2001
From: Ian Bell <ian.h.bell@gmail.com>
Date: Thu, 18 Sep 2014 19:16:52 +0200
Subject: [PATCH] Added cp0 and dpdT|rho for REFPROP backend for use in PDSim

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
---
 .../REFPROP/REFPROPMixtureBackend.cpp         | 20 +++++++++++++++++++
 src/Backends/REFPROP/REFPROPMixtureBackend.h  |  4 ++++
 2 files changed, 24 insertions(+)

diff --git a/src/Backends/REFPROP/REFPROPMixtureBackend.cpp b/src/Backends/REFPROP/REFPROPMixtureBackend.cpp
index be068859..e79a5227 100644
--- a/src/Backends/REFPROP/REFPROPMixtureBackend.cpp
+++ b/src/Backends/REFPROP/REFPROPMixtureBackend.cpp
@@ -770,6 +770,26 @@ void REFPROPMixtureBackend::calc_phase_envelope(const std::string &type)
                &ierr, herr, errormessagelength);       // Error message
     if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); }
 }
+long double REFPROPMixtureBackend::calc_cpmolar_idealgas(void)
+{
+    double rho_mol_L = 0.001*_rhomolar;
+    double p0, e0, h0, s0, cv0, cp0, w0, A0, G0;
+    THERM0dll(&_T,&rho_mol_L,&(mole_fractions[0]),&p0,&e0,&h0,&s0,&cv0,&cp0,&w0,&A0,&G0);
+    return static_cast<long double>(cp0);
+}
+long double REFPROPMixtureBackend::calc_first_partial_deriv(parameters Of, parameters Wrt, parameters Constant)
+{
+    if (Of == iP && Wrt == iT && (Constant == iDmolar || Constant == iDmass))
+    {
+        double rho_mol_L = 0.001*_rhomolar;
+        double dpt;
+        DPDTdll(&_T, &rho_mol_L, &(mole_fractions[0]), &dpt);
+        return static_cast<long double>(dpt*1000);
+    }
+    else{
+        throw ValueError(format("These derivative terms are not supported"));
+    }
+}
 
 void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double value1, double value2)
 {
diff --git a/src/Backends/REFPROP/REFPROPMixtureBackend.h b/src/Backends/REFPROP/REFPROPMixtureBackend.h
index 43b6bc4c..525e15cf 100644
--- a/src/Backends/REFPROP/REFPROPMixtureBackend.h
+++ b/src/Backends/REFPROP/REFPROPMixtureBackend.h
@@ -55,6 +55,10 @@ public:
 
 	/// Returns true if REFPROP is supported on this platform
 	bool REFPROP_supported(void);
+    
+    long double calc_cpmolar_idealgas(void);
+    
+    long double calc_first_partial_deriv(parameters Of, parameters Wrt, parameters Constant);
 
 	/// Set the fluids in REFPROP DLL by calling the SETUPdll function
 	/**