The influence of extended single- and multi-jet nozzles in a fluidized bed reactor on growth of granular polysilicon was studied, experimentally and numerically. Three-dimensional (3D) unsteady computational fluid dynamics (CFD) calculations were performed using the Fluent commercial CFD package. The Eulerian-Eulerian multiphase model was applied for the bulk motion of the two-phase flow, and the kinetic theory of granular flow was used to predict the solid-phase interactions. 3D cold-model reactor experiments were performed to validate the models and conditions used for the CFD simulations. The CFD-predicted pressure drop and bed expansion agreed reasonably well with the cold-model reactor test data. For a single-jet nozzle, superimposed bubbling and spouting behavior were observed in the bed. The effects of the single-jet intensity were also examined. For multi-jet nozzles, the mixing performance was much improved in the reaction zone and the dead reaction zone was reduced compared to the single-jet nozzle. Furthermore, determining the optimal configuration of multi-jets nozzles is necessary to minimize or avoid wall deposition as well as enlarging reaction zone. (C) 2014 Elsevier B.V. All rights reserved.