Hi Amal,

If you only need to solve equations in a fluid domain, then buoyantSimpleFoam (steady solver) or buoyantPimpleFoam (transient solver) should do the job.

If you also need to solve the heat transfer in solids in addition to the fluid region(s), you should go for the chtMultiRegionFoam solver (Conjugate Heat Transfer).

If you are new to OpenFOAM and CFD, I strongly suggest to start reading the user guide and running tutorials in order to understand how OpenFOAM works before moving on to your own case. It is important to understand the basics before trying to work on your own cases. It can sound like a waste of time but I can guarantee you it could save you hours or days of struggle.

For the same reason, I would suggest to start heat transfer with the buoyantSimpleFoam solver before moving to CHT if required.

I hope this helps,
Yann