Study on three-dimensional model of ventilation drying and heat and mass transfer of bulk grain pile based on discrete-continuous media

In order to ensure the safety of grain storage and explore the mechanisms of water and heat transfer during the drying process of grain piles, this paper takes wheat as the research object, uses a thermal conductivity analyzer to measure the thermal conductivity and specific heat capacity of wheat, and obtains a linear relationship between the heat constant and water content of wheat. COMSOL software was used to establish a three-dimensional model of ventilation drying and heat and mass transfer of bulk grain piles based on discrete continuum media, which simulated the temperature and humidity changes during the drying process of the grain pile. The model was verified by a thin layer drying experiment. The results show that the simulated values of temperature and water content obtained by the wet heat transfer model are in good agreement with the experimental values, and the maximum errors are 2.14 % and 5.68 % respectively. During the drying process, the grain temperature of wheat at the bottom of the grain pile increased rapidly, compared with that at the top of the grain pile, and the temperature of the wheat at the center was higher than that at the edge. At the end of drying, the moisture content from highest to lowest was top edge > top center > bottom edge > bottom center. Therefore, the model can be used to further study the changes of grain pile temperature gradient and water gradient.