derivative function of rho_ph
function rho_ph_der extends Modelica.Icons.Function; input SI.Pressure p "pressure"; input SI.SpecificEnthalpy h "specific enthalpy"; input ThermalSeparation.Media.WaterBasedLiquid.BaseClasses.Common.IF97BaseTwoPhase aux "auxiliary record"; input Real p_der "derivative of pressure"; input Real h_der "derivative of specific enthalpy"; output Real rho_der "derivative of density"; end rho_ph_der;