冬枣片热风干燥过程介电参数变化规律研究  

Study on variation rules of dielectric parameters during hot-air drying process of winter jujube slices

作　　者：刘欢 王吉强 牛玉宝 曹玉雪 肖红伟[3] 姚雪东[1,2] 郑霞 王强[1,2] LIU Huan;WANG Jiqiang;NIU Yubao;CAO Yuxue;XIAO Hongwei;YAO Xuedong;ZHENG Xia;WANG Qiang(College of Mechanical and Electrical Engineering,Shihezi University,Shihezi 832000,China;Northwest Key Laboratory of Agricultural Equipment,Ministry of Agriculture,Shihezi 832000,China;College of Engineering,China Agricultural University,BeiJing 100083,China)

机构地区：[1]石河子大学机械电气工程学院,新疆石河子832000 [2]农业部西北农业装备重点实验室,新疆石河子832000 [3]中国农业大学工学院,北京100083

出　　处：《包装与食品机械》2021年第5期13-19,共7页Packaging and Food Machinery

基　　金：国家自然科学基金项目(31960488)。

摘　　要：为确定冬枣片热风与射频联合干燥射频介入的适宜条件,以冬枣为试验材料,应用终端开路同轴电缆技术测量不同频率(1~300 MHz)、温度(25℃、40℃、55℃、70℃和85℃)以及含水率(20%、35%、45%、60%和80%)条件下冬枣片在热风干燥过程中介电参数的变化规律。试验结果表明:1~300 MHz频段内,各温度条件下,冬枣片的介电常数与介电损耗因子均随频率的增大而逐渐减小;对比射频加热常用频段,27.12 MHz时的介电常数与介电损耗因子均明显高于40.68 MHz。射频频率为27.12 MHz时,各含水率条件下,冬枣片介电常数和介电损耗因子均随温度的升高而增大;各温度条件下,冬枣片介电常数随含水率先增大后趋于稳定,介电损耗因子随含水率的增大而增大。通过对各条件下介电参数变化规律的分析与比较,确定冬枣片热风与射频联合干燥中射频介入的适宜条件:频率27.12 MHz、温度55~75℃、含水率(湿基)45%~80%,为后续冬枣片热风与射频联合干燥技术与工艺研究提供理论依据。In order to determine the suitable conditions for combined intervention of hot air drying and RF drying to the winter jujube chips,by using the winter jujube as the experimental material,the variation rules of dielectric parameters of winter jujube chips were measured and studied at different frequencies(1~300 MHz),temperature(25℃,40℃,55℃,70℃ and 85℃)and moisture content(20%,35%,45%,60% and 80%)by the open-ended coaxial cable technology during the hot air drying.The experimental results indicate that the dielectric constant and dielectric loss factor of the winter jujube chips decreased as frequency increased over the frequency range of 1~300 MHz at various temperatures;The dielectric constant and dielectric loss factor of jujube chips at 27.12 MHz were higher than that of the samples at 40.68 MHz compared to the common frequency band for RF heating;when the RF frequency was 27.12 MHz,the dielectric constant and dielectric loss factor of winter jujube chips increased with temperature increase at various moisture contents;the dielectric constant of winter jujube chips first increased with moisture content and then tended to be stable,and the dielectric loss factor increased with moisture content at different temperatures;Based on the analysis and comparison of the change behavior of dielectric parameters under various conditions,the suitable conditions of RF intervention in the combined drying of hot air and radio frequency were determined as follows:frequency 27.12 MHz,temperature 55~75℃,and moisture content(wet basis)45%~80%.The experimental results provide a theoretical basis for subsequent research on the technology of combined drying of hot air and RF of winter jujube chips.

关 键 词：冬枣片 介电参数 频率 温度 含水率 热风干燥 

分 类 号：TS255.36[轻工技术与工程—农产品加工及贮藏工程]