Heat and mass transfer in the semi-underground double-storey squat silo: a numerical analysis during static grain storage

The semi-underground double-storey squat silo (SDSS) is innovative storage structure. The underground section of SDSS uses shallow geologic energy for low-temperature storage, indicating its potential suitability for long-term grain storage under appropriate insulation and management conditions. The above-ground section of the SDSS has a high efficiency storage and transit functions. Two important elements influencing the safety of stored grain are temperature and relative humidity (T-RH) in a grain pile. Using conservation equations, a mathematical model of T-RH flow in the grain pile has been generated in order to examine the spatiotemporal evolution of T-RH in the SDSS. The model's validity was confirmed through experiments. Meanwhile, a T-RH transfer model was further developed for the static grain storage process in a SDSS, and the spatiotemporal distribution patterns of T-RH in the grain pile were analyzed. The results revealed: 1) Seasonal fluctuations have a significant impact on the grain pile temperature (GT) changes in the above-ground section and the upper air of the SDSS. 2) As the external climate changes, the T-RH of the peripheral zone of the above-ground grain pile show an approximate negative correlation. 3) The GT changes of the above-ground storey are related to the initial GT and environmental conditions. 4) The GT changes of the underground storey are significantly influenced by the constant environmental GT. The findings provide useful insights into the temperature–humidity evolution characteristics in SDSS and offer a reference for further research and optimization of SDSS design.