Mathematical modelling of drying kinetics of paddy in sun drying and air inflated solar dryer

A solar powered air inflated grain dryer was developed at Indian Agricultural Research Institute, New Delhi. The developed dryer works on principle of greenhouse effect. The thin layer drying experiments were carried out by drying the freshly harvested paddy in the developed dryer and sun drying. The time required for drying of paddy up to milling moisture content of 14% in the developed dryer ranged from 7.5-9 hours and 11-12.8 hours in sun drying respectively. The drying curves obtained from the experiments were fitted to eight commonly used thin layer drying models. The selected models were compared based on coefficient of determination (R2) and Root mean square error (RMSE). The page model (R²=0.9954 and RMSE = 0.007245) had the best fit for the drying of paddy in the developed dryer. Wang and Singh model (R²=0.995 and RMSE = 0.0064) followed by approximation of diffusion model were other models which suitably described the drying kinetics of paddy in the dryer. Sun drying of paddy was found to yield similar results with page model (R²=0.9990 and RMSE = 0.0007) and Wang and Singh model (R²=0.998 and RMSE= 0.01035)) as two best fit models.