Hey Bili,
I took a course at the University of Manitoba last term that covered some of this type of material. Generally I believe Finite Difference Method is used. Simply put you divide the area you want to analyze into a finite mesh, and then establish Boundary conditions around the edges of the mesh, and initial conditions at each node on the mesh. Each 'cell' of the mesh has 4 sides, and is called an element, (I suppose it could have any number of sides). Next an energy balance equation is written for each element, and you end up with a system of equations that can be solved, usually by writing a computer program.
The course only covered the methods for solids, I assume because in fluids all sorts of fluid mechanic properties play a role, and make it more complicated. I have heard of commercial programs that do thermofluid simulations though.
Hope that helps.
- Mike