Counter flow HX

moh

Hello guys, I am trying to simulate a counter flow heat exchanger with known inlet temperatures and velocities. wall thickness is to be considered as well.

I am having a problem in setting the outlets bc. if i set them to pressure outlets i have to key in the outlet pressure which is one of the things i am looking for in this simulation.

one more problem is in the walls between the 2 fluids (the wall and the shadow wall)what is the best bc to be used here?.

I would really appreciate your help in these problems

Thanks