Optimization of Hot Air Inlet Position in a Biomass-Fueled Rotary Drum Dryer Using CFD Simulation and Experimental Validation

Abstract

This study evaluates the impact of hot air inlet positioning on heat transfer efficiency within a biomass-fueled rotary drum dryer system using Computational Fluid Dynamics (CFD) simulation combined with experimental validation. Three inlet configurations - at the drum head, at one-third of the drum length, and at the center of the drum - were compared based on velocity distribution, temperature fields, and energy loss characteristics. Simulation results using ANSYS Fluent indicate that the head-inlet configuration leads to non-uniform thermal distribution and high exhaust velocities $(\approx 3 mathrm{m} / \mathrm{s})$. Conversely, the internal-inlet configuration optimizes airflow circulation with lower velocities $(\approx \mathbf{1} \mathrm{m} / \mathrm{s})$, enhancing heat transfer efficiency to the material bed and minimizing energy loss to the environment. Experimental drying of agricultural products within a temperature range of 60-80°C confirmed the accuracy of the simulation model, with deviations in final temperature and moisture content below 5%. The results demonstrate that the internal-inlet configuration shortens drying time and improves product uniformity. This research confirms the critical role of CFD simulation in designing and optimizing renewable energy drying systems, particularly for decentralized small-scale production.