胡萝卜薄层干燥动力学模型研究

Dynamic Modeling of Thin Layer Drying of Carrots

为探索胡萝卜热风干燥过程中水分的变化规律,本研究以胡萝卜为干燥对象,进行薄层干燥特性及模型研究,探讨不同温度、风速及物料厚度条件下胡萝卜水分比与干燥时间的关系,建立动力学模型;以Fick扩散定律为依据,确定胡萝卜一维传热传质的有效水分扩散系数并建立其数学模型。结果表明：胡萝卜薄层干燥动力学模型可用Page方程来描述,并通过回归分析确定方程系数m、k,通过多元线性回归方法得到有效水分扩散系数（Deff）与温度、风速和厚度的表达式,实验得到的Deff值在0.84×10^-9~6.69×10^-9 m^2/s范围内随着干燥温度、风速和物料厚度的升高而增大。

The thin layer drying characteristics of carrot slices were investigated and moisture content （relative to dry matter） was modeled as a function of drying time under different conditions of temperature, air flow rate and sample thickness. Meanwhile, based on Fick＇s diffusion law, the effective diffusion coefficients of water （Deff） in carrots were calculated and modeled as well. Results showed that the thin layer drying kinetics of carrots could be described by the Page equation, the coefficients of equation were obtained through regression analysis, and the equations of Doff vs. air temperature, air flow rate and sample thickness were obtained by multiple linear regression. The experimentally observed Deff values increased from 0.84 × 10^-9 to 6.69 × 10^-9m^2/s with increasing drying temperature, air flow rate and sample thickness.