Without getting into too many details, I'm attempting to model a two-fluid heat exchanger, with the fluids as hot air and cold liquid. In the system, the liquid would start at 25°C, go through the heat exchanger (heating up), run through a series of other components and return back to the inlet of the heat exchanger. However, when it comes back around, it won't be at 25°C anymore, it will be warmer. For the sake of reason, let's say the liquid comes back at the temperature at the exit of the heat exchanger.
I haven't come across any way to link the temperature of the entrance boundary condition to that of the exit (can I create a variable from the bulk average leaving temperature?), leading me to believe that in the current configuration it isn't possible.
My only other alternative would be to connect the inlet and outlet with a pipe. If this is done, how would a boundary condition be set such that the flow would in fact, flow?
Any other work-arounds?