Simulation of Three-dimensional Vibrated Fluidized Bed Dryer Using Distinct Element Method

Abstract

The particle motion, temperature behavior, and drying rate of particle inside a vibrated fluidized bed dryer were numerically investigated in this work. In the simulation, the Distinct Element Method (DEM) based on the Newton’s second law of motion was used to solve the particle motion. The physical aspects of fluid motion and heat transfer were obtained by applying Computational Fluid Dynamics (CFD) technique. For the drying of particle, only the constant rate period was considered in order to save the computational time. Programming was developed in Standard-C language and using MATLAB to visualize the results. In the simulation, 2,000 particles with stiffness 800 N m-1 were simulated in a rectangular bed. The developed model was validated with an experimental result of Gupta et al. [1]. The program was then used to study the effect of superficial gas velocity (U0), frequency of vibration (f) and amplitude of vibration (a) in fluidized bed dryer. At low velocities and no vibration of bed, articles in the bed were not fluidized but smoothly circulated. Thus, the heat transfer occurred only near the orifice. When superficial gas velocity increased, the fluidization of the particles was observed. The fluidization and drying rate improved with increased in superficial velocity for both vibrated fluidized bed and stationary bed. With introducing of vibration, the fluidization behavior of the particle was improved. The particles in the bed were well mixed and also increased the drying rate. From the simulation results, increasing of frequency and amplitude could not significantly improve rate of drying.