Hot-air drying characteristics of Millettia speciosa Champ. slice and establishment of the kinetic model

【Objective】To explore the influence of different hot air temperatures, slice thicknesses and material loads on Millettia speciosa Champ.slice hot air drying rate, establish model of thermal wind drying kinetic, and provide reference for perfecting M.Champ.drying processing technology.【Method】 Taking hot air temperature(50, 60, 70, 80℃), slice thickness(2, 4, 6, 8 mm) and material load(100, 200, 300 g) as investigating factors, real-time measurement of moisture changes during hot air drying of M. speciosa Champ.slices under various conditions.The 5 kinds of drying models were screened and fitted, calculated the effective water diffusion coefficient and theactivation energy in the drying process.【Result】 With the increase of the hot air temperature, the slice thickness and material load decreased, the moisture content of dry basis was greatly reduced, and the drying rate was greatly increased.The hot-air drying process of M. speciosa Champ.slices was divided into two stages:acceleration and deceleration, and most of the drying process was the deceleration stage.The kinetic model of hot-air drying of M. speciosa Champ.slices conformed to the Page model, and the predicted value of the Page model had a good fit with the experimental value(R²=0.969).the fitting equation ln(-lnMR) =-3.174-0.242H+0.02 9 T-0.006L+(0.721+0.015H+0.002T) lnt, k=e^{-3.174-0.242H+0.029T-0.006L}, n=0.721+0.015H+0.002T, the effective diffusion coefficient D_eff of M. speciosa Champ.under different drying conditions was 1.62114×10^-10-12.96913×10^-10 m²/s, with the increase of hot air temperature and slice thickness, the material load decreased, and the overall trend was increasing, and the activation energy was 60.7388 kJ/mol.【Conclusion】The Page model can better reflect the moisture change law of hot air drying process of M. speciosa Champ.slice with different slice thicknesses, and by fitting the equation, the content of water ratio in the hot air drying process at a certain time can be accurately predicted.