Derivative of density wrt. pressure at constant specific enthalpy in steam region for given pressure and specific enthalpy
function dd2ph_Ph input Units.SI.AbsolutePressure p "Pressure"; input Units.SI.SpecificEnthalpy h "Specific enthalpy"; output Units.SI.DerDensityByPressure ddph "Derivative of density wrt. pressure at constant specific enthalpy"; end dd2ph_Ph;