A model linking the circulation rate of charge particles with physical mill parameters (load fraction, shoulder angle and friction) has been developed and tested using experimental data derived from positron emission particle tracking (PEPT). The model parameters are obtained directly from the in situ flow field of the PEPT tracer particles. The model formulation, methodology for model parameter correlations and comparison of circulation rate model with direct measurement from PEPT forms the focus of this paper. (C) 2010 Elsevier Ltd. All rights reserved.