Radio frequency disinfestation treatments for dried fruit: Model development and validation

Abstract

Non-uniform heating is one of the most important challenges during the development of radio frequency (RF) heat treatments for pest control and other applications. A computer simulation model using finite element-based commercial software, COMSOL, was developed to investigate the heating uniformity of raisins packed in a rectangular plastic container (25.5×15.0×10.0cm3) and treated in a 6kW, 27.12MHz RF system. The developed model was then experimentally validated. Simulated and experimental temperature distributions in raisins after RF heating were compared in three different horizontal layers (top, middle, and bottom) within the container. Simulated and experimental average and standard deviation of the temperature values were highest in the middle layer, followed by the top and bottom layers. A sensitivity study indicated that the heating uniformity of the samples was most affected by the density of the raisins followed by the top electrode voltage, the dielectric properties, the thermal conductivity and the heat transfer coefficient. Corners and edges were heated more than the centers in each layer of the RF treated raisins. The model developed here can be used for future investigations to improve the heating uniformity for insect disinfection of dried fruit and other similar applications.