Is it possible to model two phase flow in porous media using fluent .I am simulating boiling in porous region? what problems can one face?

You will need to write your own UDF to handle this, the basic model is single-phase only.

thanks for the reply .Can u be more specific .what i have to include in my udf to modify the porous model?

The built-in porous model is just a fluid region with an extra momentum sink term. You would need to write a UDF that looks at the two phases and computes an appropriate sink term. I've never done this, so I can't help you with the actual writing.