【作者】 谈浩；

【导师】 陈君若；

【作者基本信息】 昆明理工大学 ， 机械制造及其自动化， 2009， 硕士

【摘要】 微波干燥技术自上世纪四十年代产生以来,经过几十年的研究和实践,理论研究获得长足进步,应用范围已日趋广泛。由于微波干燥独特的干燥机理,决定了其具有效率高、耗时短、能源利用率高、低污染以及优良的产品质量等特点,已经逐渐得到广泛的认可和应用。本文首先叙述了微波干燥基础知识,对微波的概念及特性,微波干燥的原理及特点以及介质的相关情况有了较为全面的综述和分析；然后介绍了模拟微波干燥过程所要用到的有关传热传质的理论知识,最后主要围绕着矩形谐振腔的设计、矩形谐振腔内电场和磁场的矢量分布以及微波干燥过程数值模拟三部分内容进行研究。微波干燥过程中,微波场的均匀性对干燥的结果有着十分重要的影响。为了得到均匀的微波场,方法之一就是使谐振腔内微波谐振模式数取得最大值。在特定的微波谐振频率下,谐振模式数主要取决于谐振腔的尺寸。通过编程求出在特定谐振频率下的最大模式数,从而得出相应的谐振腔体尺寸。在上述矩形谐振腔结构尺寸设计的基础上,借助于ANSYS软件模拟出微波场内电场和磁场的矢量分布,并对电场和磁场的矢量分布进行理论分析。微波干燥过程主要是在谐振腔内发生,是一个非常复杂的传热传质过程。本文采用近似的处理方式,选择胡萝卜作为干燥介质进行微波干燥过程数值模拟,通过改变微波功率、频率及介质介电常数等参数得出相应的介质温度、含水率等随时间的变化情况,并与热风干燥方式作比较,得出微波干燥较热风干燥具有升温快、干燥时间短、物料含水率低等特点。更多还原

【Abstract】 The microwave drying technology appeared in 1940s. Through several dozens of years’research and practice, the fundamental research has made great strides, and the application scope has already spreaded widely day by day. Because of microwave drying’s unique mechanism, which makes it have many special characteristics, such as high efficiency, short time, high energy usage rate, low pollution, good product quality and so on, it has already gradually obtained widespread approval and application.At first, this article introduces some elementary knowledge of microwave drying, summarizes and analyses comprehensively the relative information about the concept and the characteristics of microwave, the principle and the characteristics of microwave drying. And then introducing some theory knowledge about heat transfer & mass transfer which is used in the simulation of microwave drying. Finally, this article conducts the research mainly about three parts of contents, which are the design of rectangular resonant cavity, the vector distribution of the electric field and the magnetic field in the rectangular resonant cavity vector as well as the numerical simulation of the microwave drying.In the process of microwave drying, the microwave field uniformity has an extremely important influence to the drying result. One of the methods for obtaining uniform microwave field is to maximize the resonant model number in the cavity. Under specific microwave resonance frequency, the resonant model number mainly is decided by the resonant cavity size. Through programming, extracting the most large model number under the specific resonance frequency, thus obtaining the corresponding resonant cavity size. In the foundation about the rectangular resonant cavity structure size design, simulating the vector distribution of the electric field and the magnetic field in the microwave field with the aid of ANSYS, and carries on the theoretical analysis to the electric field and the magnetic field vector distribution. The microwave drying process is an extremely complex heat transfer & mass transfer process which is mainly conducted in the resonant cavity. This article uses the approximate processing method, choosing carrot as drying medium to carry on the microwave drying numerical simulation. Through changing parameters, such as microwave power, frequency and medium coefficient and so on, to obtain the corresponding medium temperature and the moisture content which are changed with time, and then making the comparison with the hot air drying method, obtains that, comparing with the hot air drying, the microwave drying has some characteristics such as quick temperature rising, short drying time, low material moisture content and so on.更多还原