Research Progress on Moisture and Heat Transfer Model for Ventilation Drying of Grain under Bulk Storage
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Abstract:
Food security has been at the forefront of state governance throughout history. The safety of grain storage is particularly important, which is related to the national security of a country. A large amount of grain is lost after harvest every year owing to reasons such as the primitive grain drying and storage methods and the backward drying technology. The uneven distribution of moisture and heat in stored grain will not only lower the quality of grain, but also seriously affect the food safety of grain caused by mildew, insect pests and other problems. Therefore, how to reduce quickly and uniformly the moisture content or temperature of bulk grain piles with low energy consumption to ensure grain quality while saving energy is an important direction for grain drying and storage research, which has profound theoretical and practical significance. Ventilation drying is an important measure to ensure the uniform distribution of moisture and heat in stored grain, and constructing a drying model to predict the moisture and heat distribution of grain pile is an important means to study the moisture and heat transfer during the drying process of grain piles. This paper reviewed three models of moisture and heat transfer in bulk grain piles, the empirical model, continuum model and discrete model. The empirical model is easy to obtain but rarely used. The continuum model is widely used, but it cannot reflect the pore characteristics of grain piles. The discrete model reflects well the pore structure of grain piles, though it relies on large amounts of calculations and is difficult to understand and construct. Finally, it is pointed out in this paper that corresponding models can be established in combination with advanced calculation methods and processing techniques according to different moisture and heat transfer processes to meet different simulation requirements. In addition, the future research direction of moisture and heat transfer models for ventilation drying of grain pile under storage is also prospected in this paper.
