Abstract This study was conducted to determine the effective moisture diffusivity of walnuts for the understanding of drying mechanism and improved drying simulation. The drying characteristics of walnut shell and kernel were investigated during the single layer drying of in-shell walnuts at 43, 55, 65 and 75 °C with hot air. The values of average effective moisture diffusivity for walnut shell and kernel ranged from 1.51 × 10−9 to 9.28 × 10−9 m2/s and 1.13 × 10−9 to 2.85 × 10−9 m2/s, respectively. The 3rd order polynomial-exponential relationship well correlated the effective moisture diffusivity with sample moisture content (MC) and temperature (Radj2 > 0.983). A mathematical model with changing moisture diffusivity and heterogeneous components was developed. It simulated the in-shell walnut drying characteristics using finite element approach with good accuracy (Radj2 > 0.985). The outcomes provide important information for the understanding of moisture transfer mechanisms and have practical value for the optimization of operating conditions in the walnut drying industry.

中文翻译：

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核桃在热风下的有效水分扩散和干燥模拟

摘要 本研究旨在确定核桃的有效水分扩散率，以了解干燥机理和改进干燥模拟。研究了带壳核桃在43、55、65和75°C热风单层干燥过程中核桃壳和仁的干燥特性。核桃壳和核桃仁的平均有效水分扩散率值分别为 1.51 × 10-9 至 9.28 × 10-9 m2/s 和 1.13 × 10-9 至 2.85 × 10-9 m2/s。三阶多项式指数关系将有效水分扩散率与样品水分含量 (MC) 和温度 (Radj2 > 0.983) 很好地相关联。开发了具有变化的水分扩散率和异质成分的数学模型。它使用有限元方法以良好的精度（Radj2 > 0.985）模拟了带壳核桃干燥特性。研究结果为理解水分传递机制提供了重要信息，对优化核桃干燥行业的操作条件具有实用价值。