In this study, a mathematical model was presented for prediction of the plug-flow fluidized bed drying process under dynamic conditions resulted from the transient of inlet dry solids mass flow rate. The model previously developed and successfully validated for plug-flow fluidized bed drying process under steady-state condition was the starting point of this study. This model was extended in order to account for the mass and energy transfers between solids and gas phases at dynamic conditions. Additionally, a mass balance equation of dry-based solid holdup and a mass flow rate relationship for outlet solids were developed to predict the transient response of outlet dry solids mass flow rate. The model equations were solved numerically using the finite difference method. To validate the model, drying of rough rice in a laboratory-scale plug-flow fluidized bed dryer was investigated under dynamic conditions. A very satisfactory agreement between simulated and measured results was achieved. (C) 2014 Elsevier Ltd. All rights reserved,