生物介质传质系数Bi-G模型可靠性实验测定

Reliability of Bi-G Model for Experimental Determination of Mass Transfer Coefficient of Biological Materials

为验证分析Biot数-迟滞因子(Bi-G)关系式估算生物介质热风干燥的对流传质系数与水分扩散系数可靠性,首先采用指数函数对胡萝卜切片干燥实验数据进行拟合,利用Bi-G关系式估算其对流传质系数与水分扩散系数;然后采用该估算值,通过生物介质内部水分扩散遵循Fick第二扩散定律、生物介质-热空气间遵循对流传质的干燥模型,对热风对流干燥胡萝卜切片水分变化进行了数值模拟计算,并对数值模拟计算值与干燥实验数据进行了比较。结果表明:指数函数对干燥实验数据拟合曲线与干燥实验数据吻合不是Bi-G关系式精确估算对流传质系数与水分扩散系数的充分条件,Bi-G关系式不能用来精确估算对流传质系数与水分扩散系数。

In order to validate and analyze the reliability of Biot number-lag factor （Bi - G） correlation to estimate convective mass transfer coefficient and moisture diffusion coefficient of biological material under hot air drying, the drying experiment data of carrot slice is fitted by the exponential function, and the convective mass transfer coefficient and the moisture diffusion coefficient are estimated by Bi - G correlation. Then, the estimated values are used to simulate moisture change of carrot slice in the drying model, in which the internal moisture diffusion follows the Fick＇ s second law of diffusion, and the mass transfer between the biological medium and hot air follows the convective boundary condition. The calculated values are compared to the drying experiment data. The results show that the exponential function fitting drying experimental data well is not the sufficient condition for the Bi - G correlation to accurately estimate the convective mass transfer coefficient and the moisture diffusion coefficient. Bi - G correlation can not be used to accurately estimate the convective mass transfer coefficient and the moisture diffusion coefficient.