function specificInternalEnergy_pTX_der extends Modelica.Icons.Function; input SI.Pressure p "Pressure"; input SI.Temperature T "Temperature"; input SI.MassFraction X[:] "Mass fractions of moist air"; input SI.PressureSlope dp "Pressure derivative"; input SI.TemperatureSlope dT "Temperature derivative"; input Real dX[:](each unit = "1/s") "Mass fraction derivatives"; output Real u_der(unit = "J/(kg.s)") "Specific internal energy derivative"; end specificInternalEnergy_pTX_der;