Ansys Employee

Real gas doesn't behave well around the phase change. You're generally safer with a multiphase model to handle the phase change. Unless you really need real gas I'd always favour ideal gas + phase change: note I don't tend to model much in this application area so can't comment in great detail (I'm also limited by the forum rules). 

I'm a little surprised the model ran with that mesh, you're going to need a lot more cells to pick up the boundary layer effects and all the other fun stuff when real gases start flowing.