Dispersion of immiscible fluids in a Couette device, in which the inner cylinder rotates whereas the outer one is immobile, is modelled. The developer's version of the STARCCM+ commercial CFD code is employed for simulations. The CFD-population balance technique, recently implemented into the code, is a basis for the computations. The Reynolds stress turbulence model along with the Daly and Harlow transport model are employed for modelling two-dimensional axisymmetric flow field. Formation of a stable emulsion (no coalescence) is considered. Computational results are compared with experimental data available in the literature. A low-rate coalescence is formally introduced for accurately fitting these data. Effects of both the Couette device height and the inner to outer radius ratio on droplet size distributions are also studied using the STAR-CCM+ CFD code. Different physical phenomena influencing the dispersion process are discussed.