CFD-DEM algorithm which couples the macroscopic governing equations for gas phase and the second law of motions for individual particles in the system, is more accurate than the continuum based description of the particle phase. However, certain key challenges still remain which are the massive computational time and the selection of appropriate drag correlation. In the present work, coupled CFD-DEM simulations of two and three dimensional fluidized beds are carried out using the open source code MFIX, first, to understand the performance of different drag laws and second to investigate the effect of scaling down the actual geometry on fluidization behavior. The average gas and solid phase properties such as bed pressure drop, and the mean particle velocity, are determined and compared with the experimental results to benchmark the numerical simulations. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.