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

Abstract

AbstractFixed‐bed drying of grains is a widely used method for determining temperature and humidity changes and pressure drop characteristics during aeration. In this study, an accurate particle‐resolved computational fluid dynamics (CFD) numerical model was developed to investigate the flow and heat transfer in fixed beds of soybean, wheat, and maize grains. A randomly filled non‐spherical grain fixed bed structure was generated using the discrete element method (DEM), and the contact areas between the packed particles are automated. The distribution of grain particles near the wall surface was approximately circular, and the circle became more regular with increase grain sphericity. Compared with the fixed beds of soybean and maize, there was no significant stratification in the fixed beds of wheat, and the difference between the peaks and troughs of porosity oscillations was smaller. Detailed particle‐resolved CFD simulations of the flow and heat transfer in fixed beds with different grains were performed. The results showed that the pressure drop results of the DEM–CFD simulation of different grain shapes were in good agreement with the Nemec–Levec equation and experimental results. The velocity and temperature distribution in the fixed bed have obvious non‐uniform distribution characteristics, which are more visible in the maize pile. Regions with high porosity have a higher average velocity, and the temperature near the wall is higher than that at the center when the heat transfer is unbalanced. The DEM‐CFD model includes the heat conduction process between the fluid and solid phases, which is consistent with the experimental temperature results.Practical ApplicationsIn this work, an accurate particle‐resolved computational fluid dynamics numerical model was developed to investigate the flow and heat transfer in fixed beds of soybean, wheat, and maize grains. The randomly filled non‐spherical grain fixed bed structure is generated by the discrete element method (DEM), and the contact areas between the packed particles are automated treated. The pressure drop and heat transfer processes of different grains were measured using the fixed bed drying experimental platform. The results show that the pressure drop results of DEM–CFD simulation of different grain shapes are in good agreement with Nemec–Levec equation results and experimental results. The DEM‐CFD model includes the heat conduction process between fluid and solid phases, which is in close agreement with the experimental temperature results.