The natural stratification of turbulent flows in an axisymmetric, cylindrical, chilled-water storage tank has been investigated numerically. The calculations involve the injection of cold water through a slot in the base of an insulated tank, within which the fluid is initially at rest and at constant temperature. Calculations are presented for inlet Reynolds numbers ranging from 500-3000, and Archimedes numbers ranging from 0.5-5.0. Results obtained by employing both k-epsilon and full Reynolds stress turbulence closure models are presented and contrasted, and indicate that to ensure stratified flow the Archimedes number should be greater than two, independent of the inlet Reynolds number. In addition, considerable differences were found in terms of the thickness of the evolving thermocline between the predictions of the k-epsilon and Reynolds stress models.