Modelling and analysis of the moisture dynamic process of Codonopsis Radix with different drying methods

To realize an effective prediction of the drying process and select the appropriate drying method for Codonopsis Radix, Weibull distribution was applied for modelling the dynamic drying curves of Codonopsis Radix and the effects of drying method and temperature on the drying process were investigated.Results showed that Weibull distribution did well in simulating the drying curves of Codonopsis Radix under the experimental conditions.Drying rate was found to present a rising trend at the beginning but a downward trend as time went on. The scale parameter ( α) was decreased with the increasing of drying temperature.The shape parameter ( β) was scarcely influenced by temperature. The activation energy ( Ea) for Codonopsis Radix obtained with hot-air drying and infrared drying was 40.40 and 70.21 k J/mol, respectively.From the aspect of moisture removal efficiency, hot-air drying would be preferable for the drying of Codonopsis Radix at temperatures under 51.51 ℃ because drying time consumed for 63% of the complete drying process was shortened than infrared drying by over 20%.On the contrast, infrared drying would be better when temperature was higher than 63.88 ℃ as consumption of drying time for 63% of the complete drying process was shortened than hot-air drying by over 20%.When the temperature was in the range from 51.51 ℃and 63.88 ℃, either would be appropriate.The study provided the data support for the establishment and optimization of modern drying methods on Codonopsis Radix from the aspect of moisture removal efficiency.