Numerical modelling of drying processes in a mixed-flow grain dryer based on coupled discrete element and computational fluid dynamics method
| dc.contributor.author | Wu, Xinyi | |
| dc.contributor.examiningcommittee | Jian, Fuji (Biosystems engineering) | |
| dc.contributor.examiningcommittee | Koksel, Filiz (Food and Human Nutritional Sciences) | |
| dc.contributor.examiningcommittee | Sosa Morales, Maria Elena (University of Guanajuato) | |
| dc.contributor.supervisor | Cenkowski, Stefan | |
| dc.contributor.supervisor | Zhang, Qiang | |
| dc.date.accessioned | 2024-11-20T18:25:58Z | |
| dc.date.available | 2024-11-20T18:25:58Z | |
| dc.date.issued | 2024-10-21 | |
| dc.date.submitted | 2024-10-21T15:20:24Z | en_US |
| dc.date.submitted | 2024-10-24T14:55:37Z | en_US |
| dc.date.submitted | 2024-11-20T18:23:27Z | en_US |
| dc.degree.discipline | Biosystems Engineering | |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | |
| dc.description.abstract | The main objective of this research was to develop a numerical model to simulate the transport phenomena involved in the grain drying processes in mixed-flow grain dryers by coupling the discrete element method (DEM) and computational fluid dynamics (CFD), and utilize the proposed model for the design assessment and optimization of mixed-low grain dryers. The formation of the grain bed and the movement of the grain kernels were simulated by the proposed DEM model which was developed using a commercial software package PFC3D (Particle Flow Code in Three Dimension, Itasca Consulting Group, Inc. Minneapolis, MN). Heat and mass transfer, as well as the air flow pattern were solved in the proposed CFD model, which was developed in ANSYS Fluent 2022. The coupling between the DEM and CFD models was realized by custom-coded algorithms in Matlab (Version 8.4) following a quasi-static fashion, i.e., each simulation was run incrementally in the time domain and the simulation results (data) were transferred between the CFD and DEM models after each time increment. The coupled CFD-DEM, as well as component DEM and CFD models, was validated against experimental data extracted from the literature in terms of grain temperature and moisture content distribution, as well as grain movement and airflow pattern. Close agreements were achieved between simulated results of the coupled CFD-DEM model and published experimental data, with an average difference of 4.3% for grain temperature and 2.5% for grain moisture content. The model revealed the detailed distribution patterns of grain movement, temperature and moisture content. Specifically, the grain movement was slowed down by the air ducts and dryer walls, causing nonuniform distribution of grain velocity across the dryer, with the lowest velocity at about 43% of the highest velocity. The low-velocity zones were found underneath the air ducts. This nonuniform distribution of grain velocity resulted in large disparities in the residence time of drying, with the longest residence time (66 min) being 3.3 times the shortest one (20 min) while the median time was 36 min. There were considerable variations in grain temperature within the drying column, with the highest grain temperature underneath the inlet air ducts, while “cold zones” existed in the near-wall region. The grain moisture content was not uniform across the dryer, with the lowest moisture content underneath the inlet air duct and the higher moisture near the dryer walls. Using empirical models in the literature, the potential reduction in grain quality during drying was estimated in terms of risks of germination reduction and fissure (stress cracking) of grain kernels, which were predicted based on the grain temperature and moisture simulated by the coupled CFD-DEM model. A valuable function of the model was the ability to predict the zones within the dryer where grain could potentially experience quality losses. These zones were generally located underneath the inlet air ducts. The model was also applied to assessment of different duct designs and layouts in mixed-flow grain dryers. It was found that the air ducts with 60-degree angles resulted in the best drying performance among the five duct geometries that were simulated. The best layout had the ratio of vertical distance to duct height of 1.35 and the ratio of horizontal distance to duct width of 1.5. | |
| dc.description.note | February 2025 | |
| dc.identifier.uri | http://hdl.handle.net/1993/38673 | |
| dc.language.iso | eng | |
| dc.subject | Grain drying | |
| dc.subject | DEM | |
| dc.subject | CFD | |
| dc.subject | Couple DEM-CFD | |
| dc.subject | Porous media | |
| dc.subject | Airflow | |
| dc.subject | Heat and mass transfer | |
| dc.subject | Mixed-flow grain dryer | |
| dc.subject | Grain quality | |
| dc.subject | Design optimization | |
| dc.title | Numerical modelling of drying processes in a mixed-flow grain dryer based on coupled discrete element and computational fluid dynamics method | |
| local.subject.manitoba | yes |