An Experimental Study on the Heating Performance Evaluation of Bean Specimens

Abstract

Radio Frequency (RF) heating is an emerging alternative way of heating, drying, sterilizing/pasteurizing processes. Rapid and relatively even heat transfer and high quality end products make RF heating preferable. A well-designed RF heating unit plays a major role on the efficiency of the process. Different parameters affect the heating performance of the system such as dielectric and geometrical properties of the material, electrode gap and so on. Designing the heating unit of the system for a specified material, one should measure the effectiveness of the proposed parameters. In this study, bean specimens were heated in a parallel plate 13.56 MHz frequency and 5 kW RF oven. 20 mm and 40 mm height of bulk bean specimens were exposed to RF process at three different electrode gaps (65, 75 and 85 mm). To determine the heating performance, heating performance index (HPI) was proposed. The thermal images were evaluated in the light of HPI and heating rate (HR) values. According to the results, electrode gap and material height (thickness) affects differently the HPI and HR. So both values should be considered while designing an effective RF oven.