Modeling and Moisture Content Prediction of Vacuum Pulsating Drying of Paddy Rice

The vacuum pulsating drying characteristics of paddy rice, on industrial scale, were mathematically modeled, theoretically analyzed and experimentally evaluated.The influence of the drying conditions, including the drying temperature, pressure and low-pressure holding time, on the drying rate and time, was investigated in orthogonal experiment, least squares support vector machine (LS-SVM) and grid search and cross-validation methods for optimization of drying conditions.The results show that the drying temperature and drying pressure significantly affected the fissure-ratio and drying time, and their impact factor can be listed in a descending order:drying temperature>drying pressure>low pressure holding time.Dried at 55℃, 80 kPa for 3 min, the optimized effective moisture coefficient was found to be (1.7371~3.1285)×10^-10 m²/s with an activation energy of 35.59 kJ/(mol·K).Predicted with the newly-formulated LS-SVM model, the average accuracy in moisture content was estimated to be 99.4425%.