Numerical and experimental studies on drying behavior of radio frequency assisted convective drying for thin-layer corn kernels

Radio frequency assisted convective drying (RFCD) has been considered as an alternative method to grain convective drying. In order to obtain a comprehensive understanding of the drying behavior, a 3D coupled electromagnetic and heat-mass model was developed to describe the RFCD process of thin-layer corn kernels. The RFCD of thin-layer corn kernels with chaotic (CH) placement was equivalent to that with orderly (OR) placement. The overheating of corn kernels at the corner and edge of the rectangular container caused the continuous deterioration of non-uniform drying. The temperature gradient in corn kernels treated by RFCD was much larger than that by convective drying, and its direction was the same as that of moisture gradient, which was more conducive to moisture diffusion. What's more, RF heating acted as the dominant heat source in RFCD process with an absorbed ratio of more than 94%, which reduced with the increase of hot air temperature. The convection played a cooling role for a long time during RFCD, resulting in the efficiency of RF energy less than 13.3%, which meant most of RF energy and convective energy were wasted. The findings in this work provide a useful performance information of RFCD.