The influence of the stacking characteristics of paddy on the distribution of temperature and humidity fields during microwave drying

This study investigates the main causes of uneven drying induced by stacking during industrial drying through rice stacking experiments. Experiments were conducted under conditions of a stacking diameter of 85 mm, stacking depth of 40–70 mm, and initial moisture content of 20%–25% to analyze the temperature distribution mechanisms in different layers of rice. The results show that variations in initial moisture content affect the drying process, and the moisture content changes of each layer are influenced by the initial moisture content. The mechanisms by which stacking depth influences the temperature of each rice layer vary. The temperature distribution of the surface layer is strongly affected by the microwave distribution within the cavity, whereas the middle layer is governed by stacking characteristics. At a stacking depth less than 55 mm, the attenuation of microwave energy during propagation through the medium results in a temperature distribution that is higher around the central region and lower at the center point. When the stacking depth exceeds 60 mm, the temperature at the central point rises more rapidly than that at the peripheral points, because the stacking effect gradually becomes prominent with increasing stacking depth.