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Hi all!

I'd like to evaluate the pressure drop and heat transfer characteristics of a periodic heat exchange surface.

I assume the fluid properties to be constant. By doing so, I was hoping to be able to assess HT characteristics this way:
1. Solve for flow only (no HT), using cyclic BC's and a momentum source.
2. Map the results onto a new model where the flow is frozen, HT solved, and the cyclic BC's replaced by inlet/outlet BC's.

I've succeeded with step one, and with the mapping step, but the second model diverges quickly. The mesh is quite coarse but I believe the quality is decent, and the HT is solved without a problem if just solve the model like it's done in the tutorials (one shot, no periodicity). I've played a bit with relaxation factors, no luck.

Unfortunately I am traveling and can't post more details at the moment. But maybe someone knowledgeable can comment on my strategy. What do you think? Something wrong with the setup in step 2, or is my general strategy just wrong?

I've seen posts which involve solver modification but I would really prefer to stay away from this type of solution strategy at this point, for a collection of reasons.

Many thanks, and a bit ahead of schedule: best wishes for 2017!!

/JB