C. Castelain et al., RESIDENCE TIME DISTRIBUTION IN TWISTED PIPE FLOWS - HELICALLY COILED SYSTEM AND CHAOTIC SYSTEM, Experiments in fluids, 22(5), 1997, pp. 359-368
This study compares residence time distributions in a helically coiled
tube and a spatially chaotic system. The chaotic system consists of a
n array of bends, the plane of curvature of each one makes a 90 degree
s angle with that of its neighbors. Chaotic trajectories are obtained
by the switch in the symmetry plane of the Dean vortices which appear
in the bends. Mixing in the two configurations is compared by modeling
the residence time distributions, experimentally determined by means
of a two-measurement-point technique, using the axial dispersion plug-
flow model. For Reynolds numbers greater than 2500, axial dispersion i
n the chaotic system is more than 20% less than in a helically coiled
tube having the same number of bends. The decrease in axial dispersion
is due to the generation of chaotic trajectories, which also contribu
te to an increase in transverse dispersion. Thus, the chaotic curved p
ipes system appears very promising in producing good mixing, especiall
y in a laminar flow regime.