I am using the General finite-rate species model, where I am trying to solve combustion inside a furnace and a water cooling circulation outside of that volume. I added H2O(L) to my mixture spices. I have set the inlet Conditions for the combustion; mass fraction 0.32 wood volatiles and 0.68 air, For the water circulation inlet I have simply set mass fraction H2O(L) to 1 however fluent does not seem to understand that inside that volume should be liquid phase, density results show that, and the velocity magnitude is extremely high near the water inlet.

So the question is; is it possible with Fluent to solve a combustion with a water cooling, if so how?

I'm curious as to more details on how you are setting up your problem. Quite often we model hog fuel combustion in a boiler, and also calculate circulation in the boiler wall tubes, but in two completely separate calculations. And, the circulation is not CFD-based.

Since the water circulation is unlikely to influence combustion (i.e. the combustion chamber wall will stay close to the saturation temperature) there seems to be little benefit in linking the calculations. Combustion, of course, will have big influence on the water circulation, but that can be treated as a boundary condition.

Hey friends... I did solve a similar problem in the past using CFX. I can tell you how I did it... maybe the method will be helpful, especially to Allan. First of all I had 2 separate domains: One for the combustion and the other for the coolant. I had the combustion going with an 18 step chemistry reaction. Using both a gaseous phase and a partciel phase. Through the other domain I had the coolant running. Of course, as Allan noted, the combustion is not significantly influenced by the coolant, but the coolant is influenced by the combustion. So it seems like that you might want to separate your water domain from the combustion domain. This is probably practical too, since one would expect a wall between a combustion chamber and a water inlet, although this could be otherwise. A few more things to look at would be: What BC are you using to define your inlet? Are you using the ideal gas law?

Hope this helps, - Phil