Experimental Studies on Leaked Electromagnetic Fields around Radio Frequency Heating Systems

Abstract

A safe operational environment is critical for industrial pasteurization and disinfestation applications of radio frequency (RF) treatments. To determine the maximum electric and magnetic field intensities around inlet and outlet openings for 27.12 MHz Strayfield and Jiyuan RF systems, an electromagnetic detector was used to measure the leakage electric or magnetic field intensity and estimate power density as a function of the distance from the opening, load type and electrode gap with shielding conditions in inlet and outlet openings. Results showed that both electric and magnetic field intensities increased with decreasing distance and electrode gap. With a load of 1 kg water, the RF power increased but the leaked electric or magnetic field intensity decreased, especially for the Strayfield system. After shielding was added around inlet and outlet openings for Jiyuan RF system, the leaked electric field intensity and the estimated power density were significantly reduced (P<0.05) at each location under each of the distances and electrode gaps. The averaged electric field intensity without shielding was 19.9 V/m for these two RF systems and the average magnetic one was 0.12 A/m for Strayfield system at the electrode gap of 130 mm, which were lower than the limited values allowed by International Commission on Non-Ionizing Radiation Protection (ICNIRP) and Institute of Electrical and Electronics Engineers (IEEE) standards. During the daily operations of the RF systems, the measures to reduce operators’ radiation exposure include additional shielding of the interaction area, reducing exposure time, increasing the distance between the operator and the electrode, and avoiding empty-load running.