MODELLING FOR VACUUM DRYING CHARACTERISTICS OF REHMANNIAE

摘要

The experiments on vacuum drying of Rehmanniae were carried out. Through single factor experiments, the influences of drying temperature and sample thickness on vacuum drying characteristics of Rehmanniaewere studied.Drying rate increased when the drying temperature was increased or sample thickness decreased.Seven empirical drying models, given in literature for describing time dependence of the moisture ratio change, were fitted to experimental data. The models were compared based on the coefficient of determination, mean bias error and root mean square error between the observed and predicted moisture ratios. The modified Page model was found to give better predictions than the other models.Effective moisture diffusivity, computed on the basis of Fick’s law, varied between 3.7938 and 15.289 ×10-9 m2/s over the temperature and tinckness range. The temperature and thickness dependence of effective moisture diffusivity was expressed by an Arrhenius type equation.