Flow in annuli has wide application in industry. The modelling of the flow field improves design of such equipment and reduces the experimental cost. The entropy minimization can be used as a very useful tool in process optimization. In the present study, a laminar flow generated due to outer cylinder rotation in an annuli is considered. The velocity profiles, shear stress, torque required for the rotation, and the mean entropy generation are formulated for an isothermal case. The parametric study for the torque required and the mean entropy generation is conducted with water as the fluid medium. The parameters include the outer cylinder radius, the radius ratio and rotational speed. It is found that at large outer radii and large radius ratios, the rate of increase of torque exceeds the rate of increase of entropy generation. Consequently, the energy distribution reduces while torque increases under this condition. Copyright (C) 2001 John Wiley & Sons, Ltd.