A new mixing unit, based on a modification of the classical Taylor-Couette (TC) unit is proposed, where a lobed profile of the inner cylinder cross section is used. The shear rate distribution of the lobed Taylor-Couette (LTC) unit have been computed through computational fluid dynamic simulations and compared with those of the TC unit and a standard stirred tank (ST). It is found that since the flow pattern of the LTC units becomes temporal-periodic at each point with respect to the nonrotational outer cylinder, it reduces the formation of the low velocity gradient (low shear rate) region, typically generated in the vortex core of the TC units. The obtained distributions of the shear rate are substantially narrower than those of the TC and the ST units. Variation of the ratio between the maximum and the minimum gap widths can lead to significant changes in the shear rate distribution, and there exists an optimal range of such ratio, where the shear rate distribution is not only very narrow but also insensitive to the variation of the gap widths. (c) 2007 American Institute of Chemical Engineers.