grid independence in ansys fluent
 

how can i do grid independence?
what parameters should i use?
averege nusselet number / number of element?
temperature / number of element?

Look up Grid Convergence Index. It's simple and understanding it gives you a basic understanding of how grid sensitivity can be measured.

A good place to start is to pick a single parameter (average nusselt number is a good one) and compare that across simulations. Once you master how to do grid convergence index for a single parameter, you can apply it to multi-parameter scenarios. But you should start with basics.