function derSpecificInternalEnergy_derP_derh
input Units.SI.AbsolutePressure P "Pressure (Pa)";
input Units.SI.SpecificEnthalpy h "Specific enthalpy";
input Integer fluid "<html>Fluid number: <br>1 - Water/Steam <br>2 - C3H3F5 <br>3 - FlueGases <br>4 - MoltenSalt <br>5 - Oil <br>6 - DryAirIdealGas <br>7 - WaterSteamSimple </html>";
input Integer mode "IF97 region - 0:automatic computation";
input Real Xco2 "CO2 mass fraction";
input Real Xh2o "H2O mass fraction";
input Real Xo2 "O2 mass fraction";
input Real Xso2 "SO2 mass fraction";
input Real der_P "Pressure time derivative (J/(kg*s))";
input Real der_h "Specific Enthalpy time derivative (J/(kg*s))";
input Real der_Xco2 = 0 "CO2 mass fraction";
input Real der_Xh2o = 0 "H2O mass fraction";
input Real der_Xo2 = 0 "O2 mass fraction";
input Real der_Xso2 = 0 "SO2 mass fraction";
output Real der_u "Specific Internal Energy time derivative (J/kg/s)";
end derSpecificInternalEnergy_derP_derh;
.ThermoSysPro.Properties.Fluid.derSpecificInternalEnergy_derP_derh