Has anybody worked on Icepak and Fluent both? What are the differences between them? Which one is better for Heat transfer ( Forced, Natural and radiation ) problems? Which one would give faster results for complex geometries?

regards, Ashutosh

Fluent is a general-purpose code. Icepak is a purpose-specific core for thermal evaluation of integrated circuits and other electronic packaging. Which one is better depends on whether or not you are evaluating electronics packaging.

There is absolutely no difference between the two as far as computation is concerned. The only difference is on the geometry and mesh generation, which is automatic in icepak (or airpak). The solver is exactly the same solver. Ask Fluent Inc. They will tell you.