Prediction of the non-uniform drying of wet grain in a fluidised-bed based on a modified CFD-DEM drying model

Abstract

The diversity in grain shapes results in complex interactions among flow, heat and mass transfer, which constrains the rational selection of process conditions to improve the uniformity of grain drying and enhance drying quality. A Computational Fluid Dynamics Discrete Element Method model, suitable for describing wet grains drying was developed. The effects of particle shape and fluid velocity on the interaction of flow, heat, and mass transfer were revealed, and an evaluation system for drying quality was established. The results showed that a nonlinear trend can be observed in the drying non-uniformity. The presence of localised high temperature regions within the bed and the differential interphase heat transfer under mesoscale structures were the primary factors contributing to the drying non-uniformity. When the aspect ratio increases from 1 to 3 and the fluid velocity increases from 3.3 m s−1 to 4.2 m s−1, the temperature lumped parameter increases by 13.16% and 17.48%, respectively. The mixing mechanism of particles underwent a transformation from a convective to a diffusive, which enhanced the circulation capacity of particles and improved the uniformity of the drying process. These research findings can provide guidance for improving the design, control and operation of fluidised drying equipment.