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

To investigate the influence of pore structure distribution on the flow and heat transfer during the aeration process of a grain pile, an anisotropic continuous model (ACM) was developed based on the homogeneous continuous model (HCM). The improved ACM includes spatial resistance factors and effective thermal conductivity correction coefficients. The experimental results were compared with the particle-resolved computational fluid dynamics (PRCFD) and ACM simulation results to verify the accuracy. At higher inlet velocities, the HCM underestimated the pressure drop in the wheat fixed bed, with an average deviation of 21%. In contrast, the improved ACM incorporates the effect of resistance factors and had an average deviation of less than 10% from the experimental. By simulating the pilot-scale bin aeration system, the accuracy of the improved ACM applied to the real bin was ensured, considering the change in the porosity of the grain pile along the center of the bin to the bin wall and the grain pile height direction. The range of variable porosity distribution was set at .35-.45, and the total average deviation between the ACM simulation static pressure and the experimental value was 9.7% when the inlet airflow velocity was .019 m/s. The simulated temperature of the ACM matches the measured temperature better compared to the temperature values of the grain pile at different heights in the HCM with a constant porosity of .45. Therefore, the impact of four central air collection duct forms on airflow and temperature was discussed, and it was determined that the pipe with a larger diameter at the top and a smaller diameter at the bottom air collection duct was more advantageous when used in a horizontal aeration system by applying the improved ACM to different scenarios.Practical ApplicationsThis study introduces the resistance factor and effective thermal conductivity in a laboratory-scale fixed bed of wheat. An improved anisotropic continuous model was established for simulating the flow and heat transfer in the fixed bed during the aeration process. The improved anisotropic continuous model accurately reflected the non-uniformity of fixed bed flow and temperature transfer in the fixed bed. This model can be employed for simulating flow and heat transfer in large-scale actual storage systems characterized by heterogeneous pore distribution, while ensuring appropriate computational efficiency and precision.