function prop4_Ph_der input Units.SI.AbsolutePressure p "Pressure"; input Units.SI.SpecificEnthalpy h "Specific enthalpy"; input Real p_der "derivative of Pressure"; input Real h_der "derivative of Specific enthalpy"; output ThermoSysPro.Properties.WaterSteamSimple.ThermoProperties_ph der_pro "Derivative"; end prop4_Ph_der;