A new method was developed to evaluate rheological properties of polymer melts such as shear stress, shear rate, apparent viscosity and other rheological parameters in internal mixers. It is based on the classical power law model where the power law index n is directly evaluated from a set of data containing speed S, torque M, and the consistency index m is indirectly determined by an empirical relation. The method is based on a model with only one geometrical parameter (alpha), which involves a chamber radius R-2 and an equivalent radius R-e. It is assumed that the measuring head consists of two adjacent sets of coaxial cylinders. This method has advantages over previously reported models that use two parameters and do not propose a straightforward method to evaluate m The pseudoplastic nature of the polymer melt decreases as the rate of loss of structural points, i.e., molecular entanglements and network junctions, increases, which produces greater mobility of the melt. A relationship between alpha and C(n) is found, which is simpler than other models previously reported. These results further demonstrate the feasibility of evaluating rheological properties of polymer melts in internal mixers.