gas/gas heat exchanger

[mb89]

Hello everyone, I have to deal with the study of a gas/gas heat exchanger countercurrent. I tried the 3d approach directly, but I had problems. So, thinking about solving the problem, I schematized the exchanger with a 2d approach: the problems are left.
briefly, we say that geometry (made with gambit) is gross this:

on the left is the cold fluid to be heated (both 465k and 3.5bar) with a flow of 0.1 kg/s, on the right instead it flows in countercurrent the hot fluid (both 1500k and 1 bar). the fluid in question is air, so I need to use the ideal gas model. I expect out for the cold fluid a t of about 1100k and for the hot fluid a t of about 900k.

I used as boundary conditions two mass-flow-inlet for inputs and two pressure-outlet.
I think I have problems with the insertion of pressure values (supersonic/initial gauge pressure and gauge pressure) because I cannot carry out the simulation (the temperature diverges and the simulation stops).

Can someone help me?

thank you very much to all:finger:

 

[l.eonardo]

Hi, I read the discussion again. I hope you solved the matter!
I wanted to ask you how you set the boundary conditions on the exchange surface?

Thank you.