Abstract

Non-uniform heating is a significant challenge in radiofrequency (RF) heating of low moisture foods. Previous experiments showed that the immersion of fluids (air, deionized water, and soybean oil) changed the RF heating uniformity and rate of cornflour. However, the behind mechanism is not well understood. This study developed a finite-element-based model that incorporated quasi-static electromagnetics and Fourier’s heat transfer to understand the effect of the three immersion fluids on the RF heating performance of cornflour. The model was validated and showed good agreement with experimental thermal images. The simulation results showed that the immersion of soybean oil increased the average heating rate and improved the heating uniformity compared to immersions of air and deionized water. Less distortion of electric potential reduced the fringe effect of edge heating and thus improved the heating uniformity. The higher heating rate was attributed to more dissipated power within the cornflour sample and less surface heat loss from cornflour to the surrounding fluid than the immersion of air or water. The use of soybean oil as immersion fluid could be a promising strategy to be implemented with RF technology to improve heating performance of low moisture food products.

摘要

非均匀加热是射频 (RF) 加热低水分食品的一个重大挑战。先前的实验表明，液体（空气、去离子水和大豆油）的浸泡改变了玉米粉的射频加热均匀性和速率。然而，背后的机制还不是很清楚。本研究开发了一个基于有限元的模型，该模型结合了准静态电磁学和傅里叶传热，以了解三种浸没流体对玉米粉射频加热性能的影响。该模型经过验证，与实验热图像显示出良好的一致性。模拟结果表明，与空气和去离子水浸泡相比，大豆油浸泡提高了平均加热速率，提高了加热均匀性。较小的电位畸变降低了边缘加热的边缘效应，从而提高了加热均匀性。与浸入空气或水相比，较高的加热速率归因于玉米粉样品内更多的耗散功率以及从玉米粉到周围流体的较少表面热损失。使用大豆油作为浸液可能是一种很有前途的策略，可以通过射频技术实施，以提高低水分食品的加热性能。