Inappropriate velocity outcome
 

Hi All,

I am trying to design a nitrogen fluid flow through convergent-divergent nozzle. I set 1.4MPa total pressure and 550 degC total temp boundary conditions at inlet.Now it is believed that maximum velocity will occur at throat section of the nozzle. The results show max. velocity 12290m/s. This is too much. This is surely not real and crazy velocity.
I don't know what's wrong with my model.
Can anyone help and identify the potential mistake and correct my output maximum velocity at throat section.
I have attached the picture as well...plzz help...