function density_derp_T_phX input Modelica.SIunits.AbsolutePressure p "pressure"; input Modelica.SIunits.SpecificEnthalpy h "specific enthalpy"; input Modelica.SIunits.MassFraction X[nC] = reference_X "Mass fraction"; input Properties state; output Real ddpT "Density derivative wrt p at constant temperature"; end density_derp_T_phX;