Mathematical modelling of paddy drying using fluidized bed dryer

Abstract

Several mathematical models have been developed to illustrate the drying process of crops, and one of them is thin-layer modelling. However, there are still limited information about mathematical modelling in paddy drying. In this paper, thin layer modelling of paddy drying curve on drying using fluidized bed dryer is presented. The drying paddy was done with drying temperature variations of 50, 60, 70, 80, and 90 °C. The initial paddy moisture content is 33 % dry basis. The drying process was done for 1,5 hours. Paddy moisture was measured every 10 minutes using grain moisture meter. The thin layer models used are Newton, Page, Modified Page, Henderson and Pabis, Logarithmic, Two-term, and Wang and Singh models. Model fittings were done using MATLAB 2015 software by sum square error minimization. Experimental results showed that Modified Page model gave the best results, evidenced by the highest average R2 value of 0.9949 and lowest average RMSE (Root Mean Square Error) value of 0.0631, followed by Page model and Henderson and Pabis model. The plotting of MR (Moisture Ratio) and time at five drying temperatures showed that effective diffusivity (Deff) value ranged from 1.0334 x 10−8 m2/s to 2.1983 x 10−8 m2/s and the value increases as drying temperature increases. The plotting results of ln Deff and 1/T (absolute temperature) showed that the value of diffusivity factor (Do) is 8.5293 x 10−6 m2/s and activation energy (Ea) is 18.11 kJ/mol.