  In this paper, the effect of the space-time dimension on effective
thermodynamic quantities in (n+2)-dimensional Reissoner-Nordstrom-de Sitter
space has been stud ied. Based on derived effective thermodynamic quantities,
conditions for the phase transition are obtained. The result shows that the
accelerating cosmic expansion can be attained by the entropy force arisen from
the interaction between horizons of black holes and our universe, which
provides a possible way to explain the physical mechanism for the accelerating
cosmic expansion.
