how to define bc for circular tube having internal tappered fin
 

dear frnds..
i'm currently dng my master's degree project....entitled as
"effect of fin geometry on heat transfer performance in internal finned tube"....
i'm using gambit nd fluent software to find bulk temperature and nusselt number...
my b.c is constant heat flux is applied over the outer surface of tube(externally),,,inlet velocity is given..
i having doubt,,,,how to define constant heat flux area in gambit
As well as i need to find bulk temperature...but there is no option in fluent is there any other word related to bulk temperature.