  In the last several decades, heat transfer enhancements using extended
surface (fins) has received considerable attentions. A new heat transfer
enhancement technique, longitudinal vortex generators (LVG), has received
significant attention since the 1990s. It is activated by a special type of
extended surface that can generate vortices with axes parallel to the main flow
direction. The vortices result from strong swirling secondary flow caused by
flow separation and friction. The state-of-the-art on research and applications
of LVG are described here. The topical coverage includes heat transfer
enhancement in straight channels and in heat exchangers. Among the latter are
plate and wavy fin-and-tube heat exchangers, fin-and-oval-tube heat exchangers,
and fin-and-tube heat exchangers with multiple rows of tubes. The trends and
future directions of heat transfer enhancement by means of LVG are discussed.

Fluid Dynamics