热风干燥甘薯片的热质传递分析

Analysis of Heat and Mass Transfer in Hot Air Drying of Sweet Potato Slices

为探究甘薯片在热风干燥过程中的温度和水分分布,建立数值模型来模拟不同恒定干燥温度(50,60,70,80℃)的传热、传质过程。由于物料在热风干燥过程中会发生较为明显的收缩效应,其有效水分扩散系数会发生改变,对模拟的精准度产生影响,因此对比了依赖温度、收缩相关扩散系数两种方式的传热、传质过程。结果表明,基于收缩相关的有效水分扩散系数能准确地描述甘薯片的热风干燥过程,其中依赖收缩的水分比以及温度的模拟值与试验值的决定系数(R~2)在0.976~0.994和0.961~0.981之间。为了分析不同热风温度对甘薯片干燥后质量的影响,从色差、复水率及感官评分方面分析,得出60℃为甘薯片热风干燥的最佳温度。模拟试验结果表明,有效水分扩散系数随热风温度的升高而上升,传热、传质系数对甘薯片温度变化以及干燥过程的影响十分显著。所开发的模型可为不同干燥温度下模拟研究其它农作物的干燥过程提供借鉴。

In order to investigate the temperature and moisture distribution in sweet potato slices during hot air drying,a numerical model was established to simulate the heat and mass transfer processes at different constant drying temperatures(50,60,70,80℃).Due to the significant shrinkage effect of the materials during hot air drying,the effective moisture diffusion coefficient changed,which affected the accuracy of simulation.Therefore,this study compared the heat and mass transfer processes,accounting for both temperature and shrinkage-related diffusion coefficients.The results showed that the shrinkage-related effective moisture diffusion coefficient can describe the hot air drying process of sweet potato chips more accurately.The coefficient of determination(R2)between the simulated value and the experimental value,based on the shrinkage moisture ratio and temperature,ranged from 0.976 to 0.994 and 0.961 to 0.981,respectively.To determine the influence of different hot air temperatures on the quality of dried sweet potato slices,the optimal temperature for hot air drying of sweet potato slices was 60℃based on the analysis of color difference,rehydration rate and sensory score.From the simulation test results,it concluded that the effective moisture diffusion coefficient increases with the increase of hot air temperature,and the heat and mass transfer coefficients were significantly affected by the change of sweet potato chip temperature and drying process.The developed model can serve as a reference for simulating the drying process of other agricultural crops under various drying temperatures.