基于加热均匀性的射频干燥系统结构优化与试验  

Structure optimization and experiment of radio frequency dryer based on heating uniformity

作　　者：谢永康 林雅文 朱广飞 于贤龙 薛令阳[1] 高振江[1] 刘嫣红[1] 

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》2018年第5期248-255,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：大北农项目-玉米种子射频保质干燥技术研究(1071-2415002)

摘　　要：针对现有射频干燥系统存在装料量大时射频加热不均匀、干燥过程无法实时称重等问题,该文设计了一种热风对流加热装置、装料装置和称量装置。热风对流加热装置主要由热源供给系统、风温风速控制系统和气流分配室组成;装料装置由特制的多层料盘组成;称量装置由称量传感器、称量托盘和支柱等组成。采用计算流体力学软件对气流分配室进行模拟,结果显示改变气流分配室为喇叭口形状及增加分流圆柱体后,条形出风口处风速均匀性提高,其速度偏差比从31%降为10.5%,速度不均匀系数从19%降为7.6%。以玉米种子为例进行了优化后的性能验证试验,结果表明:热风对流加热装置可以提供均匀的温度和风速;自动称量装置能够实时监测物料的质量,其最大量程为24 kg,分层后的薄层物料最大处理量为18 kg,偏差范围为1~5 g;在热风和射频合适的匹配参数下,采用射频干燥结合热风对流技术,以及分层装料的方法,可解决射频干燥大装载量玉米种子产生的热偏移问题和边角效应问题,进而提高射频加热均匀性。该研究避免了干燥过程中外界温湿度的影响,减少了10%的干燥时间,为改善射频加热均匀性提供了参考。Drying of agricultural products immediately after harvest is critical to preserve their quality and prevent mildew deterioration. Fresh agricultural products must be dried to the required moisture content level for long-time storage in an ambient environment. Considering its great penetration depth and volumetric heating advantages, radio frequency(RF) technology can be used in agricultural products drying for its high efficiency, quick speed and high quality. However, the heating non-uniformity caused by the edge or corner effect and the thermal runaway heating restrict its industrial applications. Therefore, the structure of RF system need be optimized. In order to solve the problems of non-uniform heating during RF drying caused by internal heat and moisture accumulation due to large material thickness and caused by the edge or corner effect due to bending electric field lines, a convective hot air heating device and a charge device were designed. The convective hot air heating device was composed of heat source supplying system, hot air velocity and temperature control system and air distribution room. The charging device was composed of many trays. The automatic weighing system, which was composed of weighing sensor, weighing trays and supporting pillars, was also designed in order to realize real-time weighing during drying process. The air distribution performance, inlet diameter, size and shape of shunt cylinder were simulated using computational fluid dynamics software named Flow Simulation. When changing shape of the air distribution room to trumpet with tilt angle of 19.3° as well as length of 500 mm and adding 3 shunt cylinders with diameter of 20 mm, the air distribution uniformity could be improved, with the velocity deviation ratio decreasing from 31% to 10.5% and the velocity non-uniformity index decreasing from 19% to 7.6%. The result showed that the velocity magnitude of simulation seemed to be basically equal to the velocity magnitude of measurement. Taking corn seeds as an example, the optimi

关 键 词：干燥 结构优化 射频 热风对流 分层装料 自动称重 

分 类 号：S226.6[农业科学—农业机械化工程] S126[农业科学—农业工程]