微波反应器加热效率及均匀性仿真优化

利用COMSOL Multiphysics多物理场仿真软件采用有限元分析方法建模仿真了负载半径、负载位置和馈入功率相关参数对微波反应器内负载温度分布均匀性及反应器加热效率的影响,探究表明:负载半径和负载位置的变化导致微波反应器中负载温度均匀性以及加热效率的改变,而波导馈入功率的改变则仅仅改变负载的升温速率,导致负载中的温差差异明显;优化出当负载半径为32 mm,负载位置为10 mm以及馈入功率为10 k W时,微波反应器获得最优的加热均匀性,加热效率达到99%以上。同时考察了不同速度下的连续式微波反应器内的温度分布,结果表明:负载运行速度越大,体系平均温度越低,同时连续式微波反应器出口的温度随负载运行速度增大而减小。     

波导管隔板对废旧橡胶裂解传输功率的影响

采用HFSS软件模拟分析2 450 MHz频率下在波导管中设置石英板对废旧橡胶微波裂解传输功率的影响。结果表明,设置双层石英板且保持合适间距有利于提高波导管能量传输效率,极大地减小能量损耗,解决了废旧橡胶微波裂解中出现的能耗过大及波源易损坏的难题,提高了微波裂解效率以及裂解设备的可靠性和安全性。     

波导对橡胶微波加热硫化的影响

采用ANSYS有限元分析软件分别模拟橡胶在圆波导和同轴波导两种模式下的微波加热硫化过程。结果表明:同轴波导模式下胶料的微波加热效率低于圆波导模式,但同轴波导模式下胶料经微波加热后,胶料的最高和最低温度的差值较小,即同轴波导模式下加热胶料内的温度分布较均匀。     

激光与微波协同加热碳纤维的温度与热应力分布规律

利用仿真软件建立微波加热-激光加热-热辐射-流动传热-固体力学多物理场模型，研究了激光加热直径1mm碳纤维丝束的温度场分布与热应力大小，以及不同激光功率对于温度场与热应力的影响。同时，首次提出激光加热与微波加热结合的方式调节温度场分布与热应力大小的方法，仿真结果显示激光加热与微波加热结合的方式可以改善碳纤维丝束温度场的分布，有效降低丝束加热过程中的热应力。     

陶瓷材料微波加热特性计算分析

为更清楚和准确了解材料微波加热行为,提出了球形陶瓷材料微波加热升温过程的一个数学模型。用有限差分隐式格式推导了离散方程,通过编程进行了数值迭代计算,得到了Si C陶瓷球加热升温过程动态温度曲线,并分析了其加热基本特性。在此基础上,探讨了材料热导率和微波功率的影响。计算结果表明,微波体积加热效应决定了物体内部温度分布比较均匀;与普通加热方式不同,微波加热的物体内部温差随时间逐渐增加,加热初期温差比较小,这一特性决定了微波加热特别适合快速加热;对每一微波功率,有一个最大稳定温度值,因此烧结不同材料,所用微波功率应不同。材料热导率越大,物体内部温度分布越均匀,但能达到的稳定温度越低;微波功率越大,物体能达到的稳定温度越高,但物体内部温度均匀性越差,因此,为保证材料均匀烧结,不宜用大功率。     

微波加热多层橡胶复合材料的温度场分布及界面特性研究

针对不同波源下微波加热多层橡胶复合材料,建立基于Maxwell方程的一维非稳态有源加热偏微分方程(PDE)模型,以丁苯橡胶材料和丁腈橡胶材料复合为例,采用时域有限差分法进行模拟仿真,研究多层(两层)橡胶复合材料在单/双波源下材料厚度和微波功率对加热温度场和界面特性的影响。结果表明:微波功率变化会影响多层橡胶复合材料加热温度分布;在叠加橡胶材料的交界面处,微波振幅会有微小变化;将介电损耗小的橡胶材料直接暴露于微波源,有利于微波穿过介电损耗小的橡胶材料向深处传播,且各层橡胶材料厚度宜控制在临界穿透深度以下;相对于单波源加热,多波源加热能改善多层橡胶复合材料加热的均匀性。与传统有限元模型的分析结果进行比较,验证了本研究模型的有效性。     

轮胎微波硫化圆柱谐振腔设计及数值模拟研究

根据圆柱形谐振腔频率公式,选择模式数大于或等于9、简并比为0的10组谐振腔尺寸,运用COMSOL Multiphysics软件对选定尺寸谐振腔内轮胎微波硫化过程进行数值模拟,得到微波硫化过程中轮胎温度分布、轮胎体平均温度、微波利用率和最大温差。数据分析表明:轮胎体平均温度与微波利用率呈现良好的一次函数关系;半径为652mm、高度为470 mm的圆柱形谐振腔内的轮胎最大温差最小,温度分布最为均匀,加热效果最优。     

多孔介质微波加热厚度的确定

简述了微波加热的机理，以湿木材为研究对象，通过理论计算确定了微波在木材中的穿透深度。计算表明：随着木材含水率和微波工作频率的增加，微波在木材中的穿透深度减小；当用频率为915MHz和2450MHz的微波加热或干燥具有高含水率的多孔介质时，多孔介质的最大厚度应分别控制在16cm和6cm以内。     

轮胎微波硫化圆柱谐振腔的设计及数值模拟研究

根据圆柱形谐振腔频率公式,选择模式数大于或等于9、简并比为0的10组谐振腔尺寸,运用COMSOL Multiphysics软件对选定尺寸谐振腔内轮胎微波硫化过程进行数值模拟,得到微波硫化过程中轮胎温度分布、轮胎体平均温度、微波利用率和最大温差。数据分析表明:轮胎体平均温度与微波利用率呈现良好的一次函数关系;半径为652mm、高度为470 mm的圆柱形谐振腔内的轮胎最大温差最小,温度分布最为均匀,加热效果最优。     

微波加热对活性炭表面性质的影响

采用了微波加热技术，在不同功率和加热时间下对BN-09颗粒炭进行改性，研究了改性前后活性炭的表面基团变化。结果表明，经微波加热处理后，活性炭表面酸性基团分解，同时碱性特征增强。微波功率越大，加热时间越长，氧含量减少越多，活性炭的碱性特征也越强。     

基于ANSYS的橡胶微波加热的数值分析

利用ANSYS有限元软件分析天然橡胶(NR)在传统加热方式和微波加热方式下的加热效果,得出NR在两种不同加热方式下温度随时间的变化曲线,以及NR胶料芯部与表面温差随时间的变化曲线。证明了微波加热技术比传统加热方式效率高、加热时间短,为微波加热技术应用于橡胶制品的加热硫化提供一定的参考。     

Theoretical investigation of temperature distribution uniformity in wood during microwave drying in three-port feeding circular resonant cavity

The temperature distribution within wood samples during microwave drying is significantly influenced by the dimensions of the wood sample, microwave frequency, heating time, and moisture content of the wood. Here, the temperature distribution inside the wood during microwave drying has been studied by finite element analysis in a three-port feeding circular resonant cavity. With an increasing radius of the wood, the calculated temperature variation coefficient decreased from 54.3 to 23.5% and the energy efficiency increased from 18 to 95%. When the radius of the wood was 0.8 times that of the circular cavity, the drying process was optimal. The theoretical calculations indicated that the length of the wood also affects the temperature variation coefficient. When the length of wood was more than the height of waveguide, the temperature variation coefficient was less than 40.5% and the energy efficiency was more than 90%. Other factors such as microwave frequency, heating time, and moisture content also influenced the uniformity of temperature distribution. This study helps to better understand the microwave drying process to facilitate its further applications for wood drying.     

胶料热物性对微波加热硫化温度场的影响

采用闪光导热分析仪和差示扫描量热仪对异戊橡胶(IR)在硫化过程中的热物性参数进行测量,得出热导率和比热容随温度的变化规律。同时采用ANSYS有限元分析软件对IR进行三维建模,并对其微波加热硫化过程进行数值模拟,得到热导率和比热容恒定或随温度变化等4种情况下胶料内部的焦耳热密度分布和温度分布。结果表明,热导率变化对胶料温度分布影响不大,而比热容变化的影响较大。     

微波加热技术在橡胶硫化中的应用研究

本文针对橡胶微波加热硫化所存在的问题,应用ANSYS有限元分析软件,在分析比较了传统加热硫化和微波加热硫化胶料温升特点的基础上,提出了微波间歇加热的方法。根据硫化历程,设计了间歇加热的流程图,并模拟分析了微波间歇加热硫化胶料的温度变化趋势,模拟结果显示：采用微波间歇加热硫化能有效的解决微波连续加热硫化升温过快、焦烧时间不足、胶料不能很好充满模型,以及胶料内外温差逐渐加大的问题,对实际工程具有一定的实用价值。     

废橡胶微波再生法的实验研究

对不同胶种、不同硫化形态的废硫化橡胶在微波辐射下的再生过程进行实验研究。结果表明，炭黑填充硫黄硫化的极性和非极性废橡胶都可采用微波辐射再生，在频率为９１５ＭＨｚ的微波场中，粒径为３—５ｍｍ的废胶约辐射５ｍｉｎ，即可充分破坏硫黄文联网络，从而获得性能十分接近原胶的再生胶。     

Microwave joining and repair of composite materials

A novel technique that uses microwave power for joining and repair of thermoplastic and thermoset composites and ceramics is discussed. Enhanced microwave heating resulting from the use of conducting polymers and chiral microinclusions shows considerable promise for joining and repair of composites. The method is attractive because it produces clean and reliable interfacial joints, it is fast, it does not entail alteration of the bulk materials, and it does not result in volumetric heating. System details, including magnetron, waveguides, circulators, coupling iris, and the applicator for delivering microwave power, are described. Material requirements for the efficient absorption of microwave power are discussed. Microwave heating can be increased by doping the components to be joined or by the use of microwave adhesive films. Recent developments in electromagnetic chirality for microwave absorption are introduced and the design of composite materials for enhanced absorptivity is discussed. Results are presented for the welding and repair of thermoplastic, thermoset, and ceramic components.     

Polymerization of diglycidyl ether of bisphenol A/ diaminodiphenyl sulfone epoxy resins using radio frequency fields

Curing of diglycidyl ether of bisphenol A/diaminodiphenyl sulfone (DGEBA/DDS) epoxy resin has been effected by heating with radio frequency (RF) radiation at frequencies of 30–99 MHz. The epoxy resins can be cured rapidly at low RF power levels. Comparison of the kinetics of the RF curing with thermal curing while maintaining the same curing temperature revealed no differences. Previous differences in rates of thermal and microwave curing are believed to be due to lack of temperature control during microwave curing. For RF curing, the rate of cure, at constant power level, increases at lower RF frequency, thus emphasizing one of the principal advantages of RF curing over microwave curing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2917–2923, 1999     

Temperature field simulation of polyolefin-absorber mixture by FDTD-FDM model during microwave heating

This work has performed a numerical simulation of the temperature field during microwave heating of polyolefin-absorber mixture by means of a combined electric and thermal model. A finite difference time domain was used to model the electric field distribution within the cavity, while the finite difference method was used to calculate the temperature field distribution in different reactors. This study has focused only on the process from room temperature to 500 K for reducing heating time and energy consumption. This temperature range is a process with high energy consumption, difficult to control and great influence on the follow-up reaction. Temperature dependence of dielectric properties and thermal properties of heated materials are fully considered and simulated through an iterative process. The simulation results show that input power, the size and location of the heated materials, the position of the waveguide, and the kinds of microwave absorbers are important factors affecting the heating process. As a result, the uniform temperature distribution (the temperature difference T_d < 10 K) can be achieved by choosing the appropriate input power (500-2000 W), the appropriate proportion of microwave absorber (the volume ratio of SiC to HDPE is 30:70), and combining with the moving and rotating of the heated materials. The uniform temperature field obtained without mechanical stirring is very important for reducing energy consumption and subsequent reactions.