低湿玉米籽粒的射频加热模拟与试验  

Simulation and experimental study of radio frequency heating of low-moisture maize kernels

作　　者：魏硕 谢为俊 郑招辉 范奔 杨德勇[1] Wei Shuo;Xie Weijun;Zheng Zhaohui;Fan Ben;Yang Deyong(College of Engineering,China Agricultural University,Beijing 100083,China)

机构地区：[1]中国农业大学工学院,北京100083

出　　处：《农业工程学报》2021年第4期11-17,I0003,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金面上项目(No.31171772)。

摘　　要：为了准确预测射频加热过程低湿(含水率13.0%~20.0%)玉米籽粒的温度分布变化,该研究结合玉米籽粒的多组分结构特征、热物理特性及介电特性的异质性,建立了玉米籽粒的三维二组分物理几何模型和射频加热数学模型,并利用验证后的模型研究不同姿态和含水率玉米籽粒的射频选择性加热。结果表明:射频加热过程中平放玉米籽粒温度的模拟值与试验值最大相对误差仅为3.47%,玉米籽粒中胚的温度高于胚乳,该模型能很好地预测籽粒内部的选择性加热现象。射频加热过程直立玉米籽粒的几何效应最强,显著提高了胚的电场强度和功率密度,导致其优先加热程度最大,其次是斜放和侧立玉米籽粒的,平放玉米籽粒中胚的优先加热程度最小。射频加热过程含水率为13.0%的玉米籽粒中胚与胚乳的温差逐渐增大,而含水率为16.5%和20.0%的玉米籽粒中胚与胚乳的温差先增大后减小;当玉米籽粒被加热至55℃时,含水率为16.5%的玉米籽粒中胚的优先加热程度最大,其次是含水率为13.0%玉米籽粒的,含水率为20.0%的玉米籽粒中胚的优先加热程度最小。研究结果揭示了玉米籽粒的姿态和含水率对其射频选择性加热的影响规律,可为射频加热技术应用于低湿玉米籽粒的热处理过程提供有益借鉴。Radio frequency(RF)heating has been expected as an alternative to traditional thermal treatments for postharvest pasteurization and disinfestation,due to its rapid heating,high thermal efficiency,volumetric heating,and selective heating.Corn is one of the most primary food crops in terms of both large yield and wide use in the world.Since a large amount of postharvest loss was caused by the invasion of mold and insects every year,especially in developing countries,it is highly urgent to develop RF heating for corn kernels.However,it needs to accurately predict the temperature when formulating parameters for the process of RF heating,where the corn temperature is the primary determinant of product quality.In this study,a three-dimensional geometric model of corn kernels was constructed using the simplified structure of germ and endosperm,and an RF heating mathematical model for corn kernels was developed using the heterogeneity of thermos-physical and dielectric properties in the COMSOL multi-physics software.A validated model was used to simulate the distribution of temperature and electric field,thereby exploring the changes of RF selective heating in corn kernels with different postures and moisture content.The results showed that the simulated and experimental temperatures were highly consistent,with a maximum relative error of 3.47%,indicating that the model could well predict the behavior of RF selective heating in corn kernels.The cold spots appeared in the center of the rectangular container,while the hot spots occurred in its corners and edges during RF heating,showing non-uniform heating.Specifically,the temperature difference between the corn kernels at the corner and center gradually increased as time proceeded.In surface temperature,the temperature of the germ was higher than that of endosperm,indicating the preferential heating of the germ.The geometric effect of the upright corn kernel was the largest,followed by the oblique and side-standing ones,where the preferential heating of germ was the great

关 键 词：射频加热 模型 玉米籽粒 多组分结构 介电异质性 

分 类 号：TS255[轻工技术与工程—农产品加工及贮藏工程] TQ028[轻工技术与工程—食品科学与工程]