Experimental Comparison of Ventilation Strategies for Condensation Risk in Underground Wheat Granaries

Underground granaries offer natural insulation for long-term grain storage, yet spatial heterogeneity in temperature and humidity can drive condensation and degrade grain quality. To address this issue, mechanical ventilation is commonly employed, yet evidence remains limited on whether pretreating the inlet air before ventilation can further reduce the risk of condensation. In order to bridge this gap, a custom-designed small-scale underground granary was employed, in which temperature and relative humidity of the grain pile, surrounding soil, and ambient air were monitored at 28 sampling points. The effectiveness of mechanical ventilation and ventilation pretreatment in reducing condensation was also assessed. Results demonstrated that during static storage, the granary was minimally affected by external conditions. Yet, a high temperature and humidity area developed at the top of the grain pile over the 24-day period of static storage. Under mechanical ventilation, local relative humidity decreased but grain temperature still responded to ambient conditions. In contrast, ventilation pretreatment stabilized inlet air, lowered peak grain temperature by 1 °C, and improved relative humidity reduction from 6% to 12%. This produced a more uniform temperature–humidity profile and markedly reduced condensation risk.