基于束能推进的微波加热效率仿真

微波束能推进是一种新的微波能传输利用方式,使用高强度吸波材料将电磁能转化为热能。针对其热交换器系统构建了简化能量接收模型,对毫米波加热能量转换效率及最高温度进行了初步研究,并设计了三种结构进行模拟仿真,最高效率超过30%,稳定效率在23%左右。使用遗传算法对影响性能的参数进行了优化,结果表明热交换器性能受吸波材料有效损耗因子影响,应保持在一个适中的水平。     

高熵陶瓷吸波材料研究进展

吸波材料是指能吸收或者大幅减弱其表面接收到的电磁波能量，从而减少电磁波干扰的一类材料。近年来对吸波材料的探索中出现各种高熵陶瓷吸波材料，通过热力学的高熵效应、结构的晶格畸变效应、动力学的迟滞扩散效应以及组元的协同增效作用，获得高熵陶瓷材料的吸波性能优于单组元的吸波性能。基于近年来的研究成果，本文归纳总结了不同种类高熵吸波陶瓷的组元设计、制备与吸波性能关系的相关研究结果，分析了高熵效应对吸波性能的影响规律，最后，总结了目前研究工作中存在的关键科学难题与挑战，并展望了高熵吸波陶瓷的未来前景和发展方向。     

吸波材料包覆研究进展在雷达波低频上的应用

通过各种包覆手段形成的核壳结构吸波材料,不仅可增强吸收剂的耐高温性、抗氧化性、抗腐蚀性性能,还能通过降低介电常数,改善阻抗匹配,大大提高吸波材料的吸波性能。对铁氧体,陶瓷、金属及其合金作为包覆的核-壳结构吸波材料的国内外研究现状进行总结,并针对目前雷达波低频1~4GHz吸波材料的研究热点,探讨包覆研究对雷达波低频吸波材料吸波性能的影响,发现适当的对吸波材料进行包覆处理,有利于提高其在雷达波低频频段的吸波特性。     

添加MWCNTs的结构吸波材料的制备及其性能研究

采用炭纤维、玻璃纤维、环氧树脂和纳米碳管制备了结构吸波材料。通过实验和理论计算研究了MWCNTs含量对单层结构吸波材料的吸波性能的影响和层间排列方式对双层结构吸波材料吸收性能的影响。对于单层的结构吸波材料,当MWC-NTs的含量为9%时吸波效果最佳,吸收率超过-10dB的有效带宽为5.4GHz;对于双层结构吸波材料,当层间排列为MWCNTs15%MWCNTs3%时,最大吸收率为-39.3dB、吸收率超过-10dB的有效带宽为6.5GHz,涵盖了整个Ku频率范围(12～18GHz),更能满足"强、宽、薄"的要求。     

吸波涂层的制备及其与红外隐身涂料的兼容性研究

依据阻抗匹配原理制备了一种3层雷达吸波涂层，并在吸波涂层表面喷涂一定厚度的可见光、红外伪装涂料，比较了喷涂伪装涂料前后涂层吸波性能的变化。实验结果表明，三层结构的设计对提高涂层的吸波性能具有重要的影响，将电介质材料与磁介质材料复合所制备的吸波涂层具有厚度薄、面密度低、吸波频带宽的特点。雷达吸波涂层与可见光、红外隐身涂层复合后，其吸波性能基本保持不变。     

吸波材料吸波性能的评价测试方法研究进展

电磁污染已成为危害人类生存环境的重要污染源。吸波材料是一类能够吸收或大幅减弱投射到它表面的电磁波能量的材料,广泛应用于军事设备的隐身、电子电气设备及个体防护领域。传统的吸波材料通常在金属材料上敷设吸波层,以此来减少电磁波的反射,避免被雷达侦测到。然而,随着科学技术的发展以及实际使用环境的多元化,结构功能一体化材料以其优异的综合性能,被用于制备吸波材料。对吸波材料进行评价时,不能只考虑吸波材料的反射率,还需考虑吸波材料的透过率。因此,需要不断地完善吸波材料的评价测试方法,为吸波材料的研发与应用提供评价依据和数据支撑。根据相关测试标准,并结合近年吸波材料的相关研究,介绍了目前吸波材料吸波性能的评价指标及其主要测试方法。     

吸波材料的研究进展

吸渡材料的研究是隐身技术发展的关键,吸波剂的好坏对于吸波材料的性能有很大的影响。本文在对吸波材料以及其吸波原理进行介绍的基础上,大体阐述了有关吸波材料的研究进展,通过对几种常用的微波吸波剂的介绍,提出了未来吸波材料的发展将向着”薄、轻、宽、强”和耐腐蚀性等方面进行研究。     

偶联剂对炭黑/ABS复合平板材料吸波效能的影响

研究了钛酸酯偶联剂NDZ-105对炭黑／ABS吸波材料导电性能和吸波效能的影响，通过对吸波效能的分析，探讨了偶联剂影响吸波材料性能的机理。结果表明，加入偶联剂后吸波效能明显提高，吸波频率也明显变宽，最大吸收峰从15．63dB增加到21．76dB。     

碳团簇型材料含量对其吸波性能的影响

研究了碳团簇型材料含量对碳团簇／环氧树脂吸波材料吸波性能的影响，并由此制得了在8．2～12．4GHz范围内，最大吸收率为-23dB，吸收率超过-10dB的有效带宽接近100％的较高性能吸波材料，材料密度为1．16g/cm^3。同时采用有关电磁理论对实验结果进行了分析。合理利用材料的界面极化，可使材料的吸收频带大大加宽，提高材料的吸波性能。     

纳米吸波剂改性水泥基材料研究进展

水泥基吸波材料可以有效缓解电磁波辐射对人们日常生活的影响。传统吸波剂所制备的水泥基吸波材料因其有效带宽窄、吸波效率低和体积厚重等缺点，限制了其在工程中的应用。与之相比，纳米吸波剂具有量子尺寸效应、宏观量子隧道效应和界面效应等特点，因此纳米吸波剂改性水泥基材料为电磁辐射防护提供了一个新途径。根据纳米吸波剂种类的不同，从碳纳米管水泥基吸波材料、石墨烯水泥基吸波材料和磁性纳米颗粒水泥基吸波材料3个方面总结了国内外相关研究成果，并对未来该领域的发展进行了展望。     

Microwave-assisted epoxidation of styrene with molecular O2 over sulfated Co–Y–ZrO2 solid catalyst

The microwave-assisted styrene epoxidation reaction with molecular O₂ as an oxidant was studied over a sulfated Co–Y-doped ZrO₂ solid catalyst. The microwave irradiation (400 W) resulted in similar styrene conversion and styrene oxide selectivity, in reduced time, as compared to conventional thermal heating. Higher power (800 W) of microwave irradiation decreased the styrene oxide selectivity as well as leading to the formation of styrene glycol. DMF was found to be the most suitable solvent for epoxidation of styrene with molecular O₂ under microwave irradiation and yielded maximum oxide selectivity (91%) at 120 °C. The microwave-assisted oxidation reaction resulted in time saving and is energy conserving method.     

Energy efficiency of a scaled-up microwave-assisted transesterification for biodiesel production

We propose a scalable and energy-efficient microwave-assisted chemical reactor for biodiesel production, which is composed of a partially modified conventional 10-L stainless steel vessel and a microwave coupler to enable an optimized microwave injection of 99% power efficiency. The microwave power applied via a waveguide can be directly injected into the reaction vessel using a coupling rod clamped to a pressured microwave window, giving convenience of scale-up of the reactor volume because a conventional microwave transparent vessel like glass is not need. Microwave-assisted transesterification of triglycerides with potassium hydroxide catalyst achieved an accelerated conversion of 95% in 5 min. The precisely measured microwave energy consumption was only 87% of the calculated heat requirement for both the reactant and the vessel. Computer simulation studies indicated that the cause of the energy efficiency for microwave heating was the relatively low temperature of the vessel due to a reverse temperature gradient, in contrast to those done with conventional hot wall heating.     

Calculation of Critical Efficiency Factors of Microwave Energy Conversion into Heat

A modeling approach aimed at calculating critical efficiency factors of microwave energy conversion into heat for different operating conditions is presented. In the experimental part, an efficiency factor was determined for microwave heating of 13X zeolites in a multimode microwave cavity. A comparison of the obtained results with the results reported in the literature indicated that microwave heating (MH) can be more energy‐efficient than convective heating (CH). Moreover, it follows from the performed simulations that maintaining the same adsorbent bed temperatures in MH and CH for increasing gas flow rates rises energy consumptions in CH and decreases the critical efficiency factors, thereby improving the economic efficiency of MH.     

Performance experiment on solar energy and air dual-heat-source heat pump system

The flat micro heat pipe array photovoltaic-thermal module was retrofitted into a photovoltaic-thermal evaporator, and then a novel solar energy and air dual-heat-source heat pump system was developed. The operation performance of the system operating in the solar energy mode (S) as well as the solar energy and air dual-heat-source mode (SA) was studied in detail. Studies have shown that: affected by solar radiation and ambient temperature, the role of ambient air in the dual heat source heating mode will switch between heat release and heat absorption, and the temperature difference between ambient temperature and backplane temperature fluctuates between -3.1—3.5℃; the SA mode was suitable for low solar radiation condition, and its thermal efficiency, comprehensive performance efficiency and COP were 56.7%, 81.7% and 2.38 respectively, which were 20.3%, 25.0% and 6.7% higher than that of the S mode; under the high solar radiation condition, the SA mode would accelerate the heat dissipation of the system, but it could improve the electrical performance of the system. According to the above characteristics, it would get the better operation performance operating in SA mode when the backplane temperature was lower than the ambient temperature as well as operating in S mode when the backplane temperature was higher than the ambient temperature.     

太阳能-空气双热源热泵系统性能实验

将平板微热管光伏光热组件改造为新型光伏光热蒸发器,研发新型太阳能-空气双热源热泵系统,对太阳能供热模式和双热源供热模式下系统的运行性能进行研究。研究表明:受太阳辐射和环境温度影响,双热源供热模式下环境空气的作用会在放热和吸热之间转换,环境温度与背板温度的温差在-3.1～3.5℃之间波动;双热源供热模式适合在低辐照条件下运行,其热效率、综合性能效率和COP分别达56.7%、81.7%和2.38,比太阳能供热模式提升20.3%、25.0%和6.7%;在高辐射条件下,双热源供热模式会造成系统散热加快,但是对系统发电性能有提升作用。根据上述特性,当背板温度小于环境温度时启动双热源供热模式,反之启动太阳能供热模式,可以进一步提升系统的运行效果。     

微波与碳基催化剂协同促进果糖制5-羟甲基糠醛

生物质转化为高附加值的化学品是替代石化产品的有效途径,微波与催化剂的协同作用有助于提升糖类的转化效率。碳材料具有良好的化学稳定性和介电性,是微波反应过程中理想的催化剂载体和吸波剂。为了探究碳基催化剂对微波场的响应能力,本文以4种碳材料为载体应用于果糖转化过程,包括碳纳米管（CNT）、碳纳米纤维（CNF）、炭黑（CB）和活性炭（AC）。以果糖转化率和5-羟甲基糠醛（5-HMF）收率为评价指标,对比不同催化剂在常规和微波加热条件下的催化性能,探究微波与不同载体的耦合作用对反应的强化效果。在微波场中测量不同碳材料悬浮液的温度曲线,评价碳基催化剂在微波场中的加热能力。通过表征样品结构和介电参数,解释载体与微波间耦合作用差异的原因。结果表明,碳基催化剂的微波诱导热效应可以有效提升反应转化率和收率,拥有高损耗角正切值和电导率的催化剂把微波能转化为热量的能力较强,更有助于将微波能量传递至反应表面。高比表面积、高长径比、低密度和高石墨化度的碳基催化剂也有利于产生微波热效应。另外,由于显著的微波热效应,碳纳米管基催化剂CNT-SA在4类催化剂中催化性能最优,以110℃微波辐射10min,5-HMF收率可达96.30%,且催化剂具有良好的循环使用性能。     

Theoretical Study of Microwave Enhanced Thermal Decontamination of Oil Contaminated Waste

This paper demonstrates that microwave enhanced thermal decontamination of oil contaminated waste is a potentially important and highly efficiency approach to achieving the required environmental discharge limit. Numerical simulation of microwave thermal decontamination of oil contaminated wastes within an applicator known to support high electric field strengths was used to assess the influence of electric field and power loss density distributions on oil removal from the waste materials. It was found during this study that the water content plays the most important role in oil removal. As the microwave receptors within the material matrix, water molecules absorbed the bulk of the applied microwave energy. This energy was subsequently transferred to the oil in the form of heat, and was shown to cause thermal desorption. The boiling point of oil can also be reduced when it is mixed with water, since free water is beneficial to uniform heating, whilst bound water has a significant effect on the latter stages of oil removal. The experimental and simulation results suggest that the lowest residual oil levels were achieved when the sample material had a high dielectric loss factor and was placed in the position of maximum electric field strength. The cost of using a microwave technique for the remediation of oily waste can be up to 20 times lower than conventional heating.     

Methane aromatization using Mo-based catalysts prepared by microwave heating

Mo/HZSM-5 and Cu–Mo/HZSM-5 catalysts for the non-oxidative aromatization of methane have been prepared by microwave heating method. The effects of Mo loading, the molar ratio of Cu/Mo and preparation method on the catalytic performance of catalysts were studied. The results were compared with those for the methane aromatization over catalysts prepared by conventional heating. Both two kinds of catalysts have the maximum methane conversion when the Mo loading is 6%. The catalysts prepared by microwave heating exhibited higher selectivity to benzene than that prepared by conventional heating. The addition of metal Cu to Mo/HZSM-5 catalyst prepared by microwave heating enhanced the lifetime of catalyst, and gave rise to a little increase in methane conversion. The molar ratio of Cu/Mo influenced the methane conversion, and the maximum value was attained when Cu/Mo = 0.05, whereas no significant influence on the benzene selectivity was observed with the increase molar ratio of Cu/Mo. N₂ adsorption results showed that the catalysts prepared by microwave heating have the larger surface area and the similar pore volume compared with the catalysts prepared by conventional heating. This fact revealed that the more Mo species located on the outer surface of catalysts prepared by microwave heating is the main reason why they have better catalytic performance. XRD analysis indicated that the Mo species are highly dispersed on HZSM-5 zeolite. The addition of Cu influenced the dispersion. The actual active phase Mo₂C can be identified on the catalyst surface after reaction. TEM analysis revealed the carbonaceous deposition to have the form of carbon nanotube after reaction, with a uniform size range of 10–20 nm. TG analysis indicated that carbonaceous deposition on the catalysts prepared by microwave heating is lower than that by conventional heating, and the metal Cu further prompts the stability of catalyst. Most of the carbonaceous deposition on catalysts prepared by microwave heating is formed at low temperature and it is easy to burn-off. Coke accumulation at high temperature is the main reason of catalyst deactivation. The carbonaceous deposition formed on the catalysts for non-oxidative aromatization of methane is different from those formed on the catalysts for partial oxidation of methane.     

利用余热回收多能互补技术的原油蒸馏装置热集成系统的优化改造

针对换热网络（HEN）的优化改造,提出了一种利用公用热量实现多能互补理念的改造思路,通过充分利用热过程物流中的低温余热,完成热集成系统的优化改造。本文基于参考点非支配排序遗传算法（NSGA-Ⅲ）,通过综合评估集成废热回收（WHR）系统的换热网络的年度改造费用、年度改造收益、能耗（包含换热网络的冷/热公用工程和废热系统冷却水和电力消耗）和废热系统的有益产出,从而获得最优解决方案。对原油蒸馏系统（10H5C）的优化改造研究案例表明,通过权衡集成系统的能源消耗、WHR系统的产出、改造费用和改造收益4个目标,采用NSGA-Ⅲ算法求解获得了多维度的改造方案,相较于基础网络不仅有可以为用户最大节省22.9%能源消耗的改造方案,还有WHR系统最大输出为4.003×10⁴kW的解决方案,也有最小改造费用为1.848×10⁶USD/a的改造方案,还有最大改造收益和最大投资回报率分别为1.173×10⁷USD/a和121%的解决方案;最后通过比较集成WHR系统与单独HEN优化改造的性能,证明了集成WHR系统的实用性和可行性,以及余热回收多能互补技术对提高流程工业能量集成系统能量利用效率的重要作用。     

微波加热在毛条烘干中的应用研究

介绍了应用微波加热烘干毛条的基本原理,研究了微波干燥设备的烘干效率、节能效果及烘干效果,结果表明,微波加热可以应用于纺织印染行业,为微波加热在纺织印染行业的推广应用提供了研究基础。通过生产应用,在计算微波加热毛条烘干工艺参数时,微波烘干机的干燥效率可取1.1kg/kW﹒h,微波干燥后,毛条含水率均匀,颜色前后色差无变化,纤维的强度和手感得到改善,微波干燥节能效果,比射频烘干节能约20%。