Simulation of Stirling Engine

Hello everybody

I'm currently trying to simulate the fluid flow in a stirling engine (beta) which I've built from the following video:
www.youtube.com/watch?v=X2qssmxA82U
You should try building it;-)

My problem is that I'm not very experienced using COMSOL (only made one model before using the CFD-module) so I'm having quite a bit of difficulty setting the model up. I'm following a CFD course (no heat transfer course though) at my university but we don't use COMSOL but MATLAB. I wanna start off slow with the COMSOL model by trying to just model the free convective flow which occurs when heat is added to the bottom of the "can" and water cooling to the sides at the top.

My questions are as follows:

I) Which physics should be used? Conjugate heat transfer or non-isothermal flow or some other?
II) In the model I've tried using the Convective Cooling but should I just use a negative heat flux instead?
III) Why is the wall condition (no slip) not satisfied?
IV) Do the initial values act as a boundary condition or are they just a guess for the solver to initiate the calculations?

I've added a model which shows the geometry and what I've tried to add to the model but pay no heap to the number/parameters as I've just been playing around a bit.

Thanks

Mikael