Experimental and Numerical Study of Pressure Drop Characteristics of Soybean Grain under Vertical Pressure

Abstract

The vertical pressure lead to increased airflow resistance through the grain bulk, which affected the efficiency of ventilation and drying. The effects of vertical pressures at 50, 150, and 250 kPa on the pressure drop characteristics of soybeans were studied using experiment and numerical simulation. The random packing and different compression states for soybean packed beds were generated by the Discrete Element Method (DEM). The Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) were coupled to investigate the radial velocity and pressure drop of soybean bulk. The simulation results showed that the radial porosity had an oscillating distribution, and the radial average dimensionless velocity was consistent with the distribution trend of porosity. The increase in vertical pressure causes a decrease in porosity and an increase in local velocity. The PathFinder code was used as a supplementary method to calculate the pore path and pore characterization parameters, and the resistance coefficient term in the Forchheimer equation was determined. The compression of soybeans measured by the experiment mainly occurred within two hours after loading. The pressure drop of soybeans increased with the vertical pressure, with the average pressure drop at vertical pressures of 50, 150, and 250 kPa being 36%, 57%, and 92% higher than the uncompressed state (0 kPa). The pressure drop of soybeans calculated by the DEM-CFD method and the Forchheimer equation under different vertical pressures were in close agreement with the experimental results, and an average relative difference was found to be less than 10%. These results provide guidance for estimating the pressure drop of soybeans at different grain depths.

Genetic algorithm in the design of soybean silos for airflow homogenization

“…Figure 6 shows the comparison of the OpenFOAM simulations using the Darcy-Forchheimer model with experimental data from Khatchatourian & Savicki (2004). The experimental data showed that the relationship between airflow velocity and airflow pressure drop depends on the grain layer height (H); it happens because of the compaction in the lower regions, which decreases the porosity, as evidenced by Liu et al (2022) and Nwaizu & Zhang (2021). The prediction from the OpenFOAM software using Darcy-Forchheimer model shows good agreement with the experimental data.…”

“…Both parameters have a nonlinear dynamic, and both curve-fitting procedures obtained a R² above 0.95. Liu et al (2022) used a different method to estimate the parameters D and F, based on Discrete Element Method (DEM), and obtained D in the range from 17740438 to 47576815, and F in the range from 382 to 659. These parameters were not obtained as function of grain layer height, therefore, a direct comparison cannot be possible; but there is an intersection for the parameter D in both studies, whereas the range of the parameter F in Liu et al ( 2022) is smaller and outside the range of these results.…”

“…These parameters were not obtained as function of grain layer height, therefore, a direct comparison cannot be possible; but there is an intersection for the parameter D in both studies, whereas the range of the parameter F in Liu et al ( 2022) is smaller and outside the range of these results. One possible explanation is the difference in soybean grains: the equivalent particle diameter used by Liu et al (2022) to represent the soybean as a sphere was 7.24 mm, whereas in Brazil, a typical equivalent diameter would range from 5.40 to 6.40 mm (Lorenzoni et al, 2020).…”

Numerical and experimental investigation of flow and heat transfer in a fixed bed of non‐spherical grains using the DEM‐CFD method

“…However, the effect of pore structure on the temperature field remains neglected. Few researchers have constructed pore structures and analyzed the airflow distribution within the grain pile using the DEM packing model (Liu, Dhamankar, et al, 2022; Liu et al, 2022). To simplify CFD pretreatment models, in studies of near‐spherical food products such as apples (Delele et al, 2008; Han et al, 2017) and pomegranates (Ambaw et al, 2017), scholars have mainly used spheres instead of real food shapes to obtain data on local airflow distribution and temperature variation.…”

An improved anisotropic continuum model for the flow and heat transfer in grain aeration system

“…They accomplished this by modifying the granary structure, inlet duct configurations, inlet velocity conditions, and grain packing forms (Alagusundaram et al, 1990; Kashaninejad et al, 2010; Khatchatourian & De Oliveira, 2006; Nawi et al, 2010; Zhang, Xia, et al, 2022; Zhang, Zhang, et al, 2022). Although the particle‐resolved computational fluid dynamics (PRCFD) method, which restores the packing structure and porosity distribution of particles in a fixed bed, and solves the heat and mass transfer inside particles, was available, its high computational cost made it unsuitable for large‐scale practical production (Ambaw et al, 2017; Liu et al, 2022). Consequently, developing an improved homogeneous continuous numerical models with appropriate computational efficiency and accuracy is essential to investigate the actual flow and heat transfer processes in grain piles.…”