Study of air flow and heat transfer in soybean piles based on CT

Abstract

The airflow within the grain pile is directly influenced by the 3D structure of the pores. The airflow distribution will further induce temperature changes within the grain pile, ultimately affecting the safety of grain storage. A quantitative analysis of the porosity, pore size and fractal dimension of the soybean grain pile is performed using computed tomography (CT). Then, the geometric modeling of the soybean grain pile is established by iterative reconstruction technology. Finally, the distribution of airflow and temperature fields in soybean grain piles is analyzed by finite element numerical simulation. It is found that the pore equivalent diameter, throat diameter and throat length are mainly within the 2–5 mm, 0–2 mm, and 3–6 mm, respectively. The results of the numerical simulation of the pressure drop of soybean grain piles are well agreed with the Nemec formula and the measurement values. Pressure diminishes along the airflow direction, with a substantially greater drop observed in vertical ventilation compared to horizontal ventilation. The airflow traverses the channel with a larger radius, while the velocity in a single pore gradually diminishes from the center to the wall. The intricate features of the pore structure significantly influence the distribution of airflow within the grain pile. This phenomenon results in an imbalance of heat transfer within the grain pile, thereby manifesting as discernible heterogeneity in both velocity and temperature distributions. The relevant research methods and conclusions can provide theoretical support and guidance for the multifield coupling theory of grain storage and grain storage safety research.