I want to simulate 2-phase heat transfer charcteristics of AC condenser and evaporator. However, due to very fine fin spacing, it is very difficult to model the complete condenser.

Is there any simpler approach to model the tune/fin and their contact as the material is different and they are mechanically joined?

Thanks, AMOD

Write an anlytical model for the fin heat transfer. It may be explicit or implict (in terms of temperature variable itself) model. Add this heat transport as a source term of the thermal energy equation by writing a small function or subroutine where source term, S_T = f(x,y,z,T,h,...), is modeled to fit exactly the locations where your fins are.

Hope this helps