CFD analysis has been performed to observe the efficient numerical scheme for non-standard impeller (CD-6) in stirred tanks. Three families of k-e turbulence model (standard, realizable and renormalization group) have been employed for modeling. Multiple reference frames (MRF) impeller model and k-e turbulence model coupled with first and second order discretization schemes are used in this study. Fluent^® is being used to simulate turbulent flow in a pilot unbaffled tank agitated by a CD-6 impeller rotating at a speed of 296 rpm. The axial, radial, tangential velocities, turbulent kinetic energy and turbulent dissipation rate of the three families of k-e turbulence model have been analyzed and it is ascertained that standard k-e turbulence model may be adopted as an efficient turbulence model for numerical designing of stirred tanks.