In this work, the two-phase flow
behavior of a falling film on
horizontal smooth and finned tube systems was investigated and compared
using a three-dimensional computational fluid dynamics model based
on the volume of fluid method. The model was established to capture
the microscopic gas–liquid interface of the falling film for
smooth and finned tubes. The three-dimensional flow behavior of the
falling film, including the liquid film spreading, the film thickness,
the velocity distribution, and the effect of Reynolds number (Re) on the film distribution, was investigated systematically.
The results show that the liquid film spreads on the smooth tube rapidly
and forms a film thickness distribution of “crest-stable-crest”,
while the axial spreading of the liquid film is significantly restricted
and hindered by the fins on the finned tubes. The falling films of
the smooth tube and the finned tube present a staggered column flow
and an in-line column flow, respectively. Besides, the axial liquid
film spreading on the smooth tube is more sensitive to the Re compared with the finned tubes. The finned tube with
a lower fin density achieves better axial spreading, and the finned
tube is completely covered by the liquid film at Re = 521 with an optimized liquid column spacing.