Modelling and CFD Simulation of Temperature and Airflow Distribution Inside a Forced Convection Mixed-Mode Solar Grain Dryer with a Preheater

In this study, a 3D Computational Fluid Dynamics (CFD) model was developed to simulate the drying process of maize ears/cobs in a mixed-mode solar grain dryer. The dryer system is aimed to operate under forced convection and is integrated with a preheater to heat air prior to entering the solar collector. The 3D model was developed with great accuracy using SolidWorks software and the CFD simulation was carried out using ANSYS Fluent software. The study was aimed at analyzing and predicting temperature and airflow distribution in the mixed-mode solar dryer system. The CFD simulation was conducted at different airflow velocities varying from 0.5 m/s to 2 m/s for different temperature values of the preheater. Results from the simulation of the solar collector were satisfactory, indicating a minimum and maximum temperature of 59.7 ℃ and 70.5 ℃ at minimum and maximum drying conditions, respectively. The variation of temperature inside the drying chamber was predicted with an average maximum of 64.1 ℃ at the inlets. Results of airflow distribution in the solar collector and drying chamber indicated high turbulence and flow recirculation. This is a desirable flow combination that promotes good moisture evaporation from the maize ears during the drying process. This study proves that the use of computer software can allow one to clearly gain an understanding of the development, heat and mass transfer process, and performance of dryers used in the food drying industry. This approach can promote improvements in existing drying processes and increase food productivity.