Simulation and experiment of temperature uniformity of Erzhi Pills during hot air drying process / 中草药

ABSTRACT

Objective: To explore the law of temperature change in hot air drying process, and provide a theoretical basis for improving the drying efficiency and uniformity of Erzhi Pills (EP). Methods: Heat and mass transfer models were established to simulate the temperature distribution of the drying process of EP with no hole bottom and screen hole bottom based on COMSOL Multiphysics. The drying process of EP layer at 60, 80 and 100 ℃ was studied. The effective water diffusion coefficient (Deff) of EP layer was calculated by Fick’s second law plate model. A probe temperature sensor was used to monitor the temperature changes of the intermediate surface and interior of EP layer during the drying process to verify the drying model. Results: The surface and internal temperature of EP layer showed a trend of first sharp rise and then slow rise in the drying process of different hot air temperature. The inner temperature range of the drying model with no hole bottom and screen hole bottom was 55.3-56.0 ℃ and 57.5-57.7 ℃ respectively. The uniformity of drying temperature of EP can be improved by using drying plate with screen hole. The Deff range of the two model experiments were 0.76 × 10-7-2.82 × 10-7 m2/s and 1.15 × 10-7-3.94 × 10-7 m2/s, respectively. The experimental results showed that the model could well reflect the temperature variation of EP layer drying process within a certain drying temperature range. Conclusion: The change of drying temperature was directly reflected through the reliable hot air drying model of EP layer. The study provides reference for the optimization of EP drying process.