Temperature distribution over a boiling surface
 

Hello everyone,
I am trying to model phase change in starccm. The system is the following :
There is a cylindrical vessel with water in it upto certain height. The top is open to atmosphere whereas the Boltom is heated from below (like a pan containing water kept on a heated stove). The water will boil and evaporate into steam which mixes with air. The ultimate goal is to find the temperature distribution over the water surface (water air interface) in the vessel. I know this a complex phenomena to model with CFD but here is my approach.

1. Made and meshed a cylindrical geometry
2. Chose a multi phase model (vof) and boiling model along with other relevant models
3. Defined three eulerian phases- water (liquid), steam/water vapor (gas), air (gas)
4. Prescribed the initial distribution of the phases in the vessel. Initially water is present in the vessel upto a certain height and above it, there is air and steam
5. Boundary conditions: bottom temp of vessel maintained at high temp (400 K) , vessel top was given outlet pressure condition (open to atmosphere) and side walls were made adiabatic.

The results I get is unexpected. It seems all water (initially upto a certain height) redistributes within the entire vessel. The temperature in the system also reaches high values (5000 k). I can't seem to diagnose the problem.

How would you model this problem. Are my boundary conditions correct or do I need to take a completely different aproach.

I would appreciate any help I can get regarding this and I thank you on advance for it.