Internal energy and condensate fraction of a trapped interacting Bose   gas
  We present a semiclassical two-fluid model for an interacting Bose gas confined in an anisotropic harmonic trap and solve it in the experimentally relevant region for a spin-polarized gas of Rb-87 atoms, obtaining the temperature dependence of the internal energy and of the condensate fraction. Our results are in agreement with recent experimental observations by Ensher et al. 
A. Minguzzi, S. Conti and M. P. Tosi (Scuola Normale Superiore, Pisa,   Italy)