Problem making a periodic boundary in helical coil

Mikael

I'm trying to estimate the heat transfer (Nu number) in a helical coil at fully developed flow. As I dont have a tube that is sufficiently long to get fully developed flow I need to make the boundaries periodic instead. I have coupled the surfaces in Gambit (added them both to one surface that is periodic) and exported the geometry to FLUENT. Under the periodic conditions menu I have chosen -specify mass flow = 2.45 -pressure gradient = 0 flow direction z=1 (the flow enters in the z-direction and leaves in z-direction) Relaxation = 0.5 Number of iterations = 2

When Im doing the simulations I get a mass flow of approx 10e-7 kg/s...Very far from 2.45 kg/s

Somebody knows what could be wrong? And is it even possible to use periodic boundaries for such a geometry?

Greatful for an answear!