Numerical simulation of rice drying process in a deep bed under an angular air duct

Abstract The deep‐bed drying process of rice grains was investigated through numerical simulation, employing the porous medium flow field theory and the local thermal nonequilibrium method. Moisture field of rice grains described using thin‐layer equations. On this basis, the deep‐bed drying of rice grains modeled with COMSOL, and verified its plausibility. The results showed that the drying rate of rice grains was significantly accelerated when the hot air temperature was increased from 40°C to 70°C, but the inhomogeneity of rice grains temperature increased by 29.79%, 22.31%, and 17.41% for every 10°C increase. Drying grains faster with vertically arranged an angular air duct, with a 4.88% increase in drying speed in 300 min. The temperature difference between the top and the bottom of an angular air duct with a small width is smaller, about 11°C, and the heating efficiency is better at the top, by 31.28%. Practical Applications Grain dryers are often used in high‐volume grain drying operations and it has been a great challenge to save the energy consumption of the drying process. It is necessary to use numerical simulation to design a reasonable structure of the heating section to improve the energy utilization efficiency of the heating section of the grain dryer. The numerical model proposed in this article can effectively simulate the spatial distribution of moisture content of rice under different structures of grain drying units, which can be used not only for the prediction of drying time but also for analyzing the optimal heating structure from it. A technical basis is provided for the design of grain dryers.