Optimization of process parameters and numerical modeling of heat and mass transfer during simulated solar drying of paddy

Abstract

Present study aims to optimize the process parameters and to develop a 3-dimensional, multi-layered finite element model for predicting moisture and temperature profile during simulated solar drying of paddy. Drying of paddy was conducted in an in-house designed photovoltaic integrated hybrid solar dryer. Design expert software was employed for optimization of drying process parameters (power level, air velocity and moisture content). Analysis of variance (ANOVA) was performed at significance level (P < 0.05) for the linear and interaction effects of the variables on various quality parameters. The simulation studies were performed using COMSOL Multiphysics platform. Optimum parameters for drying paddy were found at 700 W, 3.5 m/s and 12% moisture with optimal temperature, milling yield and drying time of 46 °C, 71.48% and 90 min, respectively, having the desirability factor of 0.92. Milling yield was observed to vary linearly with moisture content. Furthermore, the three dimensional model was successfully developed for paddy loaded in bulk as well as, accounting husk, bran and endosperm layers. Diffusion coefficient of endosperm, bran and husk was found to be 2.95 × 10−11, 8.66 × 10−12 and 6.00 × 10−12 m2/s, respectively. The optimized parameters can be successfully used to dry paddy to ensure maximum throughput and uniform quality of products in every drying batch. Additionally, the developed model was validated and can be employed for monitoring the drying parameters to standardize the hybrid solar drying process.