Recent astronomical observations suggest that the bulk of energy in the Universe is repulsive and appears like a dark energy component (which accounts for ~2/3 of the energy content of the Universe) with negative pressure (ω ≡ px/ρx < 0). In this work, we discuss the thermodynamic behavior by considering three different parametrizations, describing the dark energy component: (1) Model 1: ; (2) Model 2: ω(z) = ω0 + ω2 z; (3) Model 3: ω(z) = ω0 - ω3 ln(1 + z). It is found that its energy and temperature grow during the evolution of the Universe since work is done on the system. The case of phantom energy (ω < -1), however, seems to be physically meaningless because its entropy is negative. Our analysis also implies that the ultimate fate of the Universe may be considerably modified. Actually, the future of the Universe depends on the kind of parametrization. For Models 1 and 3, the Universe will becoming increasingly hot, while for Model 2 it cools during evolution.
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