Simulating the circulation and longitudinal ventilation of corn storage silos using EDEM-Fluent

This study aims to improve the storage efficiency of longitudinal ventilation in vertical silos during mechanical ventilation of grain storage. A circulation ventilation silo model was established to combine the longitudinal and transverse ventilation. EDEM Fluent software was used to simulate the velocity and temperature fields of air duct structures in a grain storage silo under mechanical ventilation. The results show that the velocity uniformity indexes of the circulating and longitudinal ventilation were 0.92 and 0.88, respectively. The average velocities of circulating and longitudinal ventilation airflow were 2.51 and 1.91m/s, respectively. The circulation ventilation airflow was more evenly distributed in the grain silo. In the simulation of the temperature field, the temperature of the grain pile near the inlet of the longitudinal ventilation initially decreased in a gradient, which was significantly lower than the initial temperature. There was no outstanding heat transfer caused by longitudinal ventilation in the upper layer of the grain layer. But the temperature of the grain surface was lower than that inside the grain pile, due mainly to the environmental temperature at the top of the warehouse. Specifically, the upper layer of grain started the heat exchange in the early stage of circulation ventilation, thus generating a temperature gradient. Furthermore, the temperature of the longitudinal ventilation chamber dropped to 27.35℃ at H=0.5 m and 28.85 ℃ at H=0.8 m after ventilating for 20 s. There was no significant variation in the temperature of the grain pile near the warehouse wall. Correspondingly, the temperatures of the circulating ventilation warehouse were 26.85 ℃ and 28.35 ℃, respectively. When ventilated for 30 s, the temperature of the longitudinal ventilation chamber dropped to 26.85 ℃ at H=0.5 m, and to 28.35 ℃ at H=0.8 m. The temperature of the circulating ventilation chamber were 25.35 ℃ and 27.35 ℃, respectively. After the ventilation was completed, the longitudinal ventilation was maintained at a temperature of 26.85 ℃ at H =0.5 m, and the temperature dropped to 27.85 ℃ at H =0.8 m. The temperature values of the circulating ventilation chamber were 24.85 ℃ and 25.85 ℃, respectively; The overall average temperature dropped to 24.77 ℃ and 23.43 ℃, respectively, at the end of ventilation in the longitudinal and circulating ventilation. The cooling performance of circulating ventilation was significantly improved with the high and more uniform cooling rate, compared with the longitudinal one. In the simulation of the particle temperature field, the temperature of the lower half of the particles in the silo was relatively low after longitudinal ventilation, with an average particle temperature of 21.20 ℃ and an average particle temperature of 22.85 ℃ after circulating ventilation. There was relatively low cooling in the upper part of the particles after longitudinal ventilation. There was no significant change in the temperature of the particles near the warehouse wall. The average temperature of particles was 27.34 ℃ after ventilation. There was more significant cooling of the particles in the upper part of the warehouse after circulating ventilation, where the average temperature of particles was 23.07 ℃ after ventilation. Compared with longitudinal ventilation, the temperature difference of particles between the upper and lower parts of the circulating ventilation warehouse was relatively small, indicating uniform cooling. In the temperature changes in different layers of grain silos under the same ventilation conditions with different heights of grain piles, the temperature of circulating ventilation was lower than that of longitudinal ventilation grain piles. After ventilation, the average temperature of the circulating and longitudinal ventilation chamber dropped to 23.43 ℃, and 24.77 ℃, respectively. The temperature of circulating ventilation decreased significantly, where the average temperature of each layer was lower than that of longitudinal ventilation, resulting in better cooling. The grain pile in the vertical silo with a circulating air duct was better cooling than that of the longitudinal ventilation. This finding can provide an important basis to optimize the air duct in the vertical silo for better ventilation in grain storage.