Modeling radio frequency heating of food moving on a conveyor belt

A multiphysics model that coupled electric fields and heat transfer was developed to simulate the radio frequency (RF) heating of food moving on a conveyor belt. A discrete moving step approach was used in the simulation. The total power absorption increased considerably during the entry of the sample into the RF system, remained stable when the sample was fully covered by the top and bottom electrodes, and decreased when the sample moved out of the system. Edge and corner heating was observed from the power absorption distribution and electric field distribution. The model was validated by heating a rectangular container of wheat kernels moving on a conveyor belt in a RF system (27.12 MHz, 6 kW). The predicted spatial temperatures in top, middle, and bottom layers showed less than 3.5 °C lower prediction than the experimental result. The measured anode current showed a good linear correlation with the predicted total power absorption. The optimum number of discrete moving steps was determined to be nine for accurate temperature prediction with total conveyor belt movement distance of 1.13 m which is equivalent to optimize step size of 0.1256 m/step (0.3 m for entry and exit, respectively, and 0.53 m for fully covered by electrodes) at speed of 14.23 m h−1. The movement of food product could help improve the heating uniformity of RF heating process.