Effect of different arrangements of globe particles on radio frequency heating uniformity: Using black pepper as an example

Different arrangements of stacked globe particles may result in various heating patterns in radio frequency heating. In this study, black pepper particles with an identical diameter (5 mm) and four different arrangements subjected to radio frequency heating were modeled and the heating rate and temperature distribution were compared. The four arrangements were simple cubic, body centered cubic, rhombohedral and face centered cubic. Within different arrangements, as the porosity increased from 0.25 to 0.47, the heating time increased from 500 to 780 s for reaching a target temperature of 70 °C. For heating rates comparison at the sample center and corners, rhombohedral model had the highest R2 (0.9953, 0.9975) and lowest RMSE (1.0709, 0.7642), respectively, among all arrangements. For temperature distribution on the top surface, the highest similarity of heating pattern between simulation and experiment was also found in rhombohedral model with an RMSE of 124.30. Therefore, the optimal prediction results was obtained in an arrangement with the closest porosity to randomly stacked globe particles in experiment. This study verified the importance of porosity and arrangement of particles in RF heating, and expanded the usage of RMSE for modeling accuracy evaluation.