初烤烟叶回潮过程传质模拟与均匀性分析

Mass Transfer Simulation and Uniformity Analysis of Cured Tobacco Leaves during Rewetting

为充分掌握初烤烟叶回潮特性,提高回潮均匀性,借助COMSOL多物理场仿真软件,基于初烤烟叶单组分同质性(OH)和两组分异质性(TH)两种假设分别构建了回潮模型。经回潮试验验证后,以TH模型模拟了单片烟叶叶基、叶中和叶尖的水分分布;基于18个位点温湿度实测数据,通过插值法导入回潮12 h内装烟室不同位点的温湿度,进一步模拟了回潮后装烟室内烟叶的含水率,以云图的形式展示其分布。结果表明:OH和TH模型的最大相对误差分别为12.92%和9.74%,TH模型的模拟效果更好。经TH模型模拟发现,装烟室内烟叶含水率模拟值与实测值的相对误差介于4.55%~14.75%;烟叶回潮过程中,水分由烟叶表面向内部梯度扩散,同一时间叶片不同位置的含水率基本一致,而主脉含水率由叶尖至叶基逐渐增大,表面与内部中心的水分梯度差亦增大;装烟室内,烟叶的含水率由下棚(Z=2.6 m)向上棚(Z=1 m)逐渐降低,平均含水率降低7.53%,由烤房后端(X=6 m)向前端(X=2 m)逐渐降低,平均含水率降低8.76%。综上,本研究建立的TH模型能够根据烤房内温湿度准确模拟烟叶含水率,今后应通过对装烟室内温湿度更加精准的预测来提高模型的模拟准确度。

To fully understand the rewetting characteristics of cured tobacco leaves and improve the uniformity of rewetting,with the help of COMSOL multi-physics simulation software,two rewetting models were constructed based on the one-component homogeneity(OH)and the two-component heterogeneity(TH)of cured tobacco leaves.After verification by the rewetting test,the moisture distribution at the base,middle and tip of single cured tobacco leaf was simulated by the TH model.Based on the measured temperature and humidity data from 18 locations in the curing barn,the temperature and humidity of different locations after 12 hours of rewetting were imported through the interpolation method.The moisture content of cured tobacco leaves in curing barn after rewetting was further simulated,and its distribution was displayed in the form of a cloud map.The results showed that the maximum relative errors of the OH and TH models were 12.92%and 9.74%respectively,and the simulation results of the TH model were better.The results of the TH model simulation indicated that the relative error between the simulated and measured values of moisture content in the curing barn ranged from 4.55%to 14.75%.During the rewetting of tobacco leaves,moisture diffused in a gradient from the surface to the interior.At the same time,the moisture content at different positions of leaf blade was basically the same,while the moisture content of the main vein gradually increased from the leaf tip to the leaf base,and the difference in moisture gradient between the surface and the interior center also increased.In curing barn,the moisture content of cured tobacco leaves gradually decreased from the lower shed(Z=2.6 m)to the upper shed(Z=1 m),with an average moisture content decrease of 7.53%.Moisture also gradually decreased from the rear end(X=6 m)to the front end(X=2 m)of the curing barn,with an average moisture content decrease of 8.76%.In summary,the TH model established in this study could accurately simulate the moisture content of cured tobacco leaves based on the temperature and humidity inside the curing barn.In the future,the simulation accuracy of the model should be improved by more accurate prediction of temperature and humidity in curing barn.