Analysis of radio frequency (RF) power distribution in dry food materials

Abstract

The objectives of this research were to investigate the influence of various factors on radio frequency (RF) power distribution in dry food materials, placed in a 12 kW, 27.12 MHz parallel plate RF system, using a validated finite element computer model. The factors investigated were sample size, shape, relative position between the RF electrodes, and dielectric properties (DPs) of the sample and the surrounding medium. Effects of electrode gap and top electrode configuration on the RF power distribution behavior of the sample were also studied. The RF power uniformity in the samples was compared using RF power density uniformity index (PUI). Simulated results showed that the RF power uniformity in cuboid shaped samples, placed on the bottom electrode, first decreased and then increased with the increase in sample size. The sample shape and its vertical position between the fixed gap parallel plate electrodes also affected the RF power distribution and uniformity. A cuboid sample had higher RF power densities at the edges, while an ellipsoid had higher power densities in the center parts. Simulated results showed that the smaller values of DPs resulted in better RF power uniformities in the samples. Reducing the electrode gap improved the RF power uniformity of the sample. While studying the influence of the top electrode configuration on the RF power distribution and uniformity, the results showed that optimum RF power uniformity in a particular sample size could be achieved with a particular top electrode bending position and angle. The results are useful in understanding complex RF heating, designing and scaling up of efficient RF systems.