Grain drying and aeration in a solar hexagonal silo

The processes involved in the drying and aeration of grain in a silo were s tudied. Experiments were performed on a model silo based on the design rece ntly proposed by Hernandez-Cordero et al. (2000), capable of minimizing the dynamic stresses during the emptying process, therefore reducing the amoun t of grain losses due to mechanical damage during storage. This study addre ssed the second most important factor for grain losses, the grain loss resu lting from lack of aeration and excess moisture. Air was injected into the interior of the model silo to study the grain drying time. The temperature of the air was controlled with an electrical heater that simulated a solar energy source. Day and night operating conditions were simulated by switchi ng the heating on and off alternatively for periods of approximately 12 hou rs. The moisture of grain samples was monitored over time to obtain the rat e of moisture decrease. The experimental results compared very well with th e predictions of an established model. The mean difference between the expe riments and the model was within in 1%. It is shown that a significant decrease in the drying time is achieved with the proposed system. A system operated with day solar heating achieved dry ing times 100% shorter than those obtained with a system with no heating. W hen, in addition to day heating, night aeration was used reductions of the order of 300% in the drying time were obtained. Comparisons between differe nt operating conditions show that this system is a viable option to reduce the drying times and cost of operation for drying processes.