CFD-DEM simulation of drying of food grains with particle shrinkage

• Published in: Powder technology 2019-02, Vol.343, p.792-802
• Main Authors: Azmir, Jannatul, Hou, Qinfu, Yu, Aibing
• Format: Article
• Language: English
• Subjects: Aerodynamics; Air temperature; CFD-DEM; Computational fluid dynamics; Computer applications; Computer simulation; Discrete element method; Drying; Fluid dynamics; Food; Food grain drying; Grain size distribution; Hydrodynamics; Mathematical models; Model testing; Moisture content; Particle diameter distribution; Particle shrinkage; Particle size; Reduction; Shrinkage; Shrinkage rate; Temperature effects; Velocity; Water content; Wheat
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2018.11.097

Food grains naturally undergo physical and structural changes during a drying process. The volumetric change of particles or particle shrinkage is one of the important and complicated physical changes in drying. In this work, a shrinkage model for particle diameter reduction is incorporated into the computational fluid dynamics- discrete element method (CFD-DEM) drying model for food grains. First, mixing, general drying and shrinkage characteristics including particle and air moisture content, and particle diameter variation are reproduced. Then, the model is tested by comparing the predicted moisture reduction and volume shrinkage curve with the experimental data of wheat from the literature. The results demonstrate the capability of the current model in predicting drying and particle shrinkage characteristics. Finally, the effects of inlet air temperature and velocity on drying and particle shrinkage are studied. It is revealed that the shrinkage rate increases significantly with increasing air temperature but increases slightly with increasing inlet air velocity. The uniformity of grain size, quantified here by the standard deviation of the particle diameter distribution, increases with decreasing air temperature or increasing air velocity. This grain scale drying model with particle shrinkage should be useful for the design and control of many drying processes. [Display omitted] •A CFD-DEM model with particle shrinkage is developed for food grain drying.•Particle size reduction leads to higher drying rate and particle temperature.•A higher air temperature or air velocity leads to a higher shrinkage rate.•A higher air velocity or a lower air temperature improves the uniformity of particle size and product quality.