[SebastianSchuster]

Hello everybody,

I want to simulate flow through a nozzle. At the inlet I have liquid CO2 which evaporates in the nozzle.

I use the Peng-Robinsion equation of state.
At first I did a homogenous simulation and get an exit vapour volume fraction from 0.3. Based on this simulation I create an inhomogeneous simulation. Liquid CO2 as continuous phase and vapour CO2 as dispersed phase. To simulate boiling I use the "Thermal Phase Change Model".

I follow the modelling instructions in the CFX Help and set the Nusselt Number on the dispersed side to 1000 and on the continuous side set it to Ranz-Marshall Correlation.

The result of my simulation is that I have superheated liquid at the outlet of the nozzle and no vapour. During the simulation the liquid CO2 Temperature remains constant form inlet to outlet.

First I thought the liquid is not in thermodynamic equilibrium, so I set a very long tube at the nozzle outlet (50 times the length of the nozzle). Result is that liquid temperature at the outlet of the tube is still the same then at the inlet. Also there is no boiling in the tube.


At the moment I can not imagine where I did the mistake. So I hope somebody has experience with such simulation and can help me.

So if anybody knows about a mistake in my setup or about a general problem in the phase change model please tell me.


Best regards

Sebastian Schuster