Generalized Single-Layer Rice Drying Models

An experimental dryer with a data acquisition system to analyze single-layer rice drying was built and tested. Data of moisture content and time were collected for long grain rough rice representing on-farm and commercial drying conditions. Four different drying models were evaluated for the single-layer rice drying data. The first two were based on the solution of the diffusion equation and the others were empirical. The first empirical model was of a quadratic form, while the second empirical model was developed in a form analogous to the diffusion equation and assumes a linear dependence of the drying constant on the moisture content, as the drying proceeds. The two-term exponential form of the diffusion model and the second empirical model were determined to be best, and a generalized form was developed with the aid of non-linear regression techniques for the on-farm conditions. For the commercial drying conditions, the second empirical model proved to be the best for a generalized model.