Deep‐bed drying kinetics and thermodynamic parameters of high‐moisture parboiled paddy (ASD‐16) in a reversible airflow fixed bed dryer

Abstract

AbstractReversible airflow fixed bed dryer (RAFBD) is an energy‐efficient, cost‐effective, and dependable dryer for using renewable energy sources in parboiling mills. In this study, a medium‐sized and high‐moisture parboiled paddy, ASD‐16, was dried in the RAFBD to determine its deep drying characteristics and thermodynamic properties. The chosen paddy variety is a commonly cultivated paddy in the southern region of Tamil Nadu, India. The RAFBD experimental setup was designed to dry 30 kg of parboiled paddy. For the statistical analysis, the experimental data for the deep‐bed drying at hot air temperatures 50–80°C and velocities of 0.1 and 0.15 m/s were used at constant specific humidity. To predict drying characteristics, 12 drying models were compared. Based on their statistical parameters, the Midilli et al. model was selected. For the tested conditions, the coefficients for effective moisture diffusion, heat transfer, and mass transfer were between 9.82 × 10−8 and 2.13 × 10−7 m2/s, 0.3802 and 1.325 W/m2 K, and 0.375 × 10−4 and 1.26 × 10−4 m/s, respectively. Furthermore, the determined activation energy ranged from 20.4964 to 20.4390 kJ/mol.Practical ApplicationsASD‐16 is one of the popular paddy varieties cultivated and used in parboiling mills in the study region. The outcome of this research can contribute to the application of a cost‐effective dryer for drying high‐moisture paddy. Furthermore, the drying time and bed height proposed in this work can reduce the drying time in the mills and improve energy efficiency. The drying kinetics and suitability of the models found in this study will contribute to the design and development of low‐cost dryers for the local parboiling industries. As rice husk, which is a waste from paddy processing, is used for the heating process, industries can reduce the cost of energy for closed‐roof drying. This study provides a clear insight to the researchers and designers in standardizing the capacity of the dryer, drying temperature, and airflow rate for any similar kind of paddy variety.