  Theoretical results on a conventional approach to the dark energy (DE)
concept are reviewed and discussed. According to them, there is absolutely no
need for a novel DE component in the Universe, provided that the associated
matter-energy content is represented by a perfect fluid whose volume elements
perform polytropic flows. When the thermodynamic energy of this fluid's
internal motions is also considered as a source of the universal gravitational
field, it compensates the DE needed to compromise spatial flatness in an
accelerating Universe. The cosmological model with matter-energy content in the
form of a polytropic fluid not only interprets the observations associated to
the recent history of Universe expansion, but successfully confronts with all
the current cosmological issues, thus arising as a viable alternative to
$\Lm$CDM model.
