Computer simulation of heat transfer for disinfestation of red flour beetle, Tribolium castaneum (Herbst) in stored canola seeds (Brassica napus L.) by radio frequency heating

To control insect pests in the stored grains effectively, radio frequency (RF) treatment is one of the novel alternative methods over the existing methods, such as pesticides, fumigations, and heat and cold treatments. The RF selective heating of red flour beetle, Tribolium castaneum (Herbst) in two different volumes of bulk canola seeds at 5%, 7%, 9%, and 11% moisture contents (MC) using a 1.5 kW, 27.12 MHz RF heating unit was simulated using a finite element method based commercial simulation package (COMSOL Multi-physics). The electric field formation, dielectric heat generation, non-isothermal fluid flow, and heat transfer including surface to surface radiation were coupled. The simulated and the measured temperatures of the seeds were compared with the different MCs and volumes of the seeds. Similar comparison was also conducted for the insects and the seeds. The differences between the simulated and the measured temperatures of the seeds were not more than 17.4%, 13.4%, 8.08%, and 19.0% for the small volume seeds and 14.8%, 15.6%, 19.5%, and 18.8% for the large volume seeds at 5%, 7%, 9%, and 11% MCs, respectively. Non-uniform RF heating of the seeds was observed regardless of the MC and the volume of the seeds. The RF selective heating of the insects was most effective for the small volume seeds at 11% MC. The temperature of the insects was 14.6 °C (maximum) higher than the temperature of the seeds. The RF selective heating of the T. castaneum in the canola seeds could be improved with a proper design of RF applicator that minimizes the non-uniformity of heating.