Drying Performance and Computational Fluid Dynamics Analysis of a Circular-Pipe Conical-Floor Paddy In-Store Dryer

Abstract

The in-store dryer (ISD) is a well-established convective drying-storage system; however, conventional designs often suffer from uneven airflow distribution and inefficient heat transfer. To address this gap, this study introduces a novel configuration featuring a circular-pipe conical floor and an improved hot-air supply arrangement through axial-blower repositioning and inlet-air regulation to enhance airflow uniformity. Drying experiments were conducted using 300 kg of paddy over an 8-h drying period. The measured operating condition was then applied as the boundary condition for Computational Fluid Dynamics (CFD) simulation. The improved ISD maintained relatively stable drying conditions, with a mean chamber temperature of 37.13 °C, internal RH of 57.32%, and an inlet airflow rate of 0.66 m³ s⁻¹ (corresponding to a velocity of 5.35 m s⁻¹ during blower operation). Paddy moisture content decreased from 17.78% to 10.44% (w.b.), corresponding to an apparent moisture reduction rate of 0.92 percentage points h⁻¹. The estimated total specific energy consumption was 20.98 MJ kg⁻¹ water evaporated. CFD validation, performed by comparing simulated data with measured values at specific sensor points inside the drying chamber, showed acceptable to good agreement, with RMSE values of 0.54 °C for temperature, 1.73% for RH, and 0.38 m s⁻¹ for airflow velocity, and correlation coefficients of 0.81, 0.76, and 0.84, respectively. These results indicate that the improved ISD achieved effective bulk paddy drying and that the validated CFD model adequately represented the internal airflow and thermal-humidity behavior of the system.