Energy efficiency investigation of intermittent paddy rice dryer: Modeling and experimental study

Abstract

In this study, energy consumption of intermittent drying of paddy rice is considered. Firstly, a mathematical model consists of two parts is established to describe the moisture distribution within a grain for both drying and tempering stages. The model, which is solved analytically, is proposed based on Fick's second law of diffusion within a sphere. Effects of different parameters namely air temperature and velocity are experimentally investigated utilizing a lab-scale fluidized bed dryer. Thereafter, moisture diffusivity is estimated in Arrhenius form using experimental results. Finally, the model is utilized in an optimization problem to minimize the total energy consumption. Based on experimental results, impact of air velocity on drying characteristics is found to be negligible. The optimization results shows that employing the tempering stages substantially reduces the energy consumption. Not only that, it dictates a process beginning with longer drying stages and lower temperatures while the subsequent stages are shorter with higher temperatures.