The chemical vapor synthesis (CVS) reactor for the preparation of WC nanopowder from tungsten hexachloride was simulated by a two-dimensional multiphase computational fluid dynamics (CFD) model. The model solves the gas-phase governing equations of overall continuity, momentum, energy, and species mass transport inside a tubular reactor system. The population balance model is coupled with the gas-phase equations to describe the formation and growth of WC nanoparticles. The model has been validated with experimental data in terms of average particle size and concentration of unreacted precursor at the outlet. The contours of temperature, velocity, species concentration and particle size distribution (PSD) inside the tubular reactor were computed. (C) 2009 Elsevier Ltd. All rights reserved.