Numerical Simulation and Uniformity Analysis of the Rewetting Process of Flue-cured Tobacco in Box-type Curing

To analyze the uniformity of flue-cured tobacco rewetting in a box-type barn, this study constructed a theoretical model of moisture transfer during the rewetting process. Through comparative analysis, the accuracy of rewetting simulations under instantaneous equilibrium rewetting model (IE) and dynamic equilibrium rewetting model (DE) boundary conditions was evaluated, with both simulations calibrated against environmental data from the box-type rewetting system. Results demonstrate that compared with the IE, the DE introduces the moisture absorption equilibrium characteristic parameters of the leaf with τ=1 580 and the main vein with τ=9 372, reducing the maximum simulation errors of the leaf and the main vein from 14.1% and 36.1% to 7.4% and 7.1% respectively, which significantly improves the prediction accuracy. At the scale of single leaf, the rewetting rate of leaf is much higher than that of the main vein. At the scale of a single box, the uniformity of the rewetting process of flue-cured tobacco first decreased and then increased. The moisture gradually penetrates from the outer layer to the inner layer, and the moisture content of the tobacco leaves at the lower part of the box is higher than that at the upper part. At the scale of barn, as the distance from the humidifier increases, the moisture level gradually decreases, with the central area of all ten boxes showing the lowest moisture levels. In addition, rewetting uniformity was optimal in boxes 1–3. In conclusion, the rewetting model with two-component (leaf and vein) dynamic equilibrium boundary conditions constructed based on the humidity field and material properties is used to analyze the rewetting uniformity of flue-cured tobacco, which provides a scientific foundation for optimizing future flue-cured tobacco rewetting processes in box-type barns.