Radiation of a TM mode from an open end of a three-layer dielectric capillary

Modern trends in beam-driven radiation sources include the interaction of Cherenkov wakefields in open-ended circular waveguides with complicated dielectric linings, with a three-layer dielectric capillary recently proposed to reduce radiation divergence being a representative example [Opt. Lett. 45 5416(2020)]. We present a rigorous approach that allows for an analytical description of the electromagnetic processes that occur when the structure is excited by a single waveguide TM mode. In other words, the corresponding canonical waveguide diffraction problem is solved in a rigorous formulation. This is a continuation of our previous papers which considered simpler cases with a homogeneous or two-layer dielectric filling. Here we use the same analytical approach based on the Wiener–Hopf–Fock technique and deal with the more complicated case of a three-layer dielectric lining. Using the obtained rigorous solution, we discuss the possibility of manipulating the far-field radiation pattern using a third layer made of a low permittivity material.

Thermal analysis of an innovative flat heat pipe radiator

An innovative flat heat pipe radiator was put forward, and it has the features of high efficiency of heat dissipation, compact construction, low thermal resistance, light weight, low cost, and anti-dust-deposition. The thermal analysis of the flat heat pipe radiator for cooling high-power light emitting diode （LED） array was conducted. The thermal characteristics of the flat heat pipe radiator under the different heat loads and incline angles were investigated experimentally in natural convection. An electro-thermal conversion method was used to measure the junction temperature of the LED chips. It is found that the integral temperature distribution of the flat heat pipe radiator is reasonable and uniform. The total thermal resistance of the flat heat pipe radiator varies in the range of 0.38-0.45 K/W. The junction temperatures of LED chips with the flat heat pipe radiator and with the aluminum board at the same forward current of 0.35 A are 52.5 and 75.2 ℃, respectively.

Thermal Design and Optimization of Heat Pipe Radiator for Satellites

Satellite＇s thermal control subsystem （TCS） has to maintain components and structure within their specified temperature limits during satellite service life. TCS designers have to face the challenge of reducing both the weight of the system and required heater power while keeping components temperature within their design range. For a space based heat pipe radiator system, several researchers have published different approaches to reach such goal. This paper presents a thermal design and optimization of a heat pipe radiator applied to a practical engineering design application. For this study, a prospective communication satellite payload panel with applied passive thermal control techniques was considered. The thermal passive techniques used in this design mainly include multilayer insulation （MLI） blankets, optical solar reflectors （OSR）, selected thermal coatings, interface fillers and constant conductance heat pipes. The heat pipe network is comprised of some heat pipes embedded in the panel and some mounted on inner surface of the panel. Embedded heat pipes are placed under high heat dissipation equipments and their size is fixed; minimum weight of the radiator is achieved by a minimum weight of the mounted heat pipes. Hence, size of the mounted heat pipes is optimized. A thermal model was built and parameterized for transient thermal analysis and optimization. Temperature requirements of components in both worst case conditions （Hot case and cold case） were satisfied under optimal sizing of mounted heat pipes.

Study on the squeezing effect of open-ended pipe piles

During the installation of a pipe pile,the soil around the pile will be squeezed out. This paper deals with this squeezing effect of open-ended pipe piles using the cylindrical cavity expansion theory. The characteristics of soil with different tension and compression moduli and dilation are involved by applying the elastic theory with different moduli and logarithmic strain. The closed-form solutions of the radius of the plastic region,the displacement of the boundary between the plastic region and the elastic region and the expansion pressure on the external surface of the pipe piles are obtained. When obtaining these solutions,the soil plug in the open-ended pipe pile is considered by employing an incremental filling ratio to quantify the degree of soil plugging. Moreover,the effects of the ratio of tension and compression moduli,angle of dilation and incremental filling ratio on the radius of the plastic region and the expansion pressure on the external surface of the pipe pile are investigated. The parametric analyses show that it is necessary and important to consider the difference between the tension modulus and compression modulus,dilation angle and incremental filling ratio for studying the squeezing effect of open-ended pipe pile installation. It is concluded that the analytical solutions presented in this paper are suitable for studying the squeezing effect of open-ended pipe piles.

某轻型客车加速工况进气噪声品质优化研究

针对某轻型客车发动机转速2 000~3 000 r/min范围内加速过程中存在类似“咆哮”声的异响问题,首先,采用滤波和主观评价相结合的方法确认异响的主要来源为发动机7~21阶次辐射噪声;然后,基于“源-路径-响应”模型,在台架上利用发动机倒拖方法分析可知,噪声产生的主要原因为发动机气缸活塞往复运动吸、排气过程产生的压力脉动,并采用声源覆盖法等方式识别出噪声辐射来自中冷器出气管。最后,通过优化中冷器出气管结构提高管壁的隔声能力,验证结果表明,问题发动机转速区间加速过程车内清晰度指数平均提高了5百分点,声品质得到明显改善。

低温辐射微槽道热管散热器传热性能研究

为研究低温辐射微槽道热管散热器的传热性能,首先,搭建了基于水-空气传热途径的微槽道热管散热器实验系统并进行了实测,结果显示,散热端热管阵列尺寸为0.9 m×0.5 m×0.003 m的散热器在测试条件下稳定工作时,其传热功率约为273W;然后,建立了该散热器传热过程的热阻分析模型,给出了微槽道热管散热器的三大部分热阻及其所包含的各个细分热阻的计算公式,以及依据实验数据计算了相应热阻值;最后,通过各个细分热阻的比较,分析了该系统传热过程的薄弱环节,并针对性地提出了强化传热措施。

Decoupled thermal–hydraulic analysis of an air-cooled separated heat pipe for spent fuel pools under natural convection

An investigation of the decoupled thermal–hydraulic analysis of a separated heat pipe spent fuel pool passive cooling system(SFS)is essential for practical engineering applications.Based on the principles of thermal and mass balance,this study decoupled the heat transfer processes in the SFS.In accordance with the decoupling conditions,we modeled the spent fuel pool of the CAP1400 pressurized water reactor in Weihai and used computational fluid dynamics to explore the heat dissipation capacity of the SFS under different air temperatures and wind speeds.The results show that the air-cooled separated heat pipe radiator achieved optimal performance at an air temperature of 10℃ or wind speed of 8 m/s.Fitted equations for the equivalent thermal conductivity of the separated heat pipes with the wind speed and air temperature we obtained according to the thermal resistance network model.This study is instructive for the actual operation of an SFS.

基于微热管阵列辐射板性能实验与模拟优化分析

基于微热管阵列辐射板具有传热效率高、供水温度低和结构简单等优点,本文对该辐射板应用于供暖房间的性能进行了实验和模拟优化研究。在供水温度45℃和流量200 L/h的工况下,辐射板的供热量为220.0 W/m^(2),辐射换热量占比67.6%,总传热系数为10.9 W/(m^(2)·K),高于传统辐射末端形式。分析了供水温度和流量对传热性能的影响,辐射板的供热量随供水温度的升高逐渐增大,随流量的升高而升高,但增速减缓。相较于对流换热量,供水温度和流量的变化对辐射换热量的影响更为显著。建立了辐射板传热过程的仿真模型,得到了辐射板各部分的温度分布和传热热阻,并对其结构进行了优化。通过在辐射板表面添加矩形封闭翅片引入强制对流,在相同工况下辐射板的供热量提高了31.3%。研究结果为基于微热管阵列辐射板的应用提供了实验数据与理论参考。

早期大体积混凝土温控原理综合研究

研究了大体积混凝土浇筑后产生的水化热引发的内部温升问题,该问题导致温度裂缝的产生,从而威胁结构的可靠性。针对这一问题,综合考虑了多种环境因素,包括水化热、环境温度周期变化、对流换热条件、太阳辐射热、冷却水管、弹模变化和徐变等,并对ABAQUS有限元软件进行了二次开发。通过编程模拟温度场和应力场,并进行参数分析,研究结果表明:采用冷却水管能够显著地降低混凝土内部温度,同时结合环境周期温度和太阳辐射热考虑的结果更加精确。所提出的温控方法所计算得到的混凝土里表温度与现场实际测量数据相符,为实际工程提供了可行的参考方法。对于解决大体积混凝土温度裂缝问题具有一定的理论和实际意义。

高寒地区平板热管式太阳能集热系统热性能研究

基于呼和浩特地区高寒气候条件,搭建两组完全一致的平板热管式太阳能集热系统,通过实验对比分析太阳辐射强度、传热工质流量、集热板表面积尘等因素对集热器瞬时集热效率以及系统热性能的影响。结果表明,在同等外界条件下,集热器的集热效率随着工质流量的增加而增大,集热效率与太阳辐射强度变化趋势相近,随积尘密度的增加,集热板表面积尘导致系统的得热量减少,集热性能下降。

地板辐射采暖系统建筑管材分析

建筑工程供暖形式多种多样,其中地板辐射采暖系统较为常用。不同的建筑管材在性能、成本、适用范围等方面存在差异,因此,需要根据具体情况选择合适的管材。文中介绍了几种常见的地板辐射采暖系统使用的建筑管材,并对地板辐射采暖管材进行研究分析。结果显示,常用的PE-RT管、PP-R管、PE-X管、XPAP管及PB管性能各有所长,均具有耐热性能好、耐腐蚀老化、无污染、光滑弹性好等优点,综合考量其均衡性与性价比等,选用PE-X管更为科学经济。

X光检测技术在输电检修作业中的应用

文章介绍了X光检技术在输电检修作业中,用来探究耐张线路压接管内部压接质量的重要作用,列举了在实际生产作业中发现的压接管典型缺陷;并对13353支压接管测量结果进行深入分析,得出耐热导线压接管钢芯断股断开、钢锚断裂的比例约为普通导线的84倍,且危急缺陷率为普通导线的6.4倍;随后通过机械性能(握力测试)、电气性能(温升、电阻测试)试验验证了通过安装备份线夹的方法处理钢芯断股、断开缺陷的可行性;最后针对X光射线源辐射剂量进行了检测,发现在正常工作中作业人员受到的辐射量为0.53~0.63 nSv/h,远低于工业标准规定2.5μSv/h,因此在日常检修作业中X光射线源辐射剂量对人体的伤害可以忽略不计。

基于CFD汽车散热器管口位置对性能影响的研究

文章研究对象为汽车散热器。通过CFD仿真分析,得出散热器的进出口管口设置在不同位置时散热器的内部流动阻力和流量分布均匀性的区别。基于CFD研究结果,通过制作不同进出口位置散热器的手工样件在台架进行测试,得到不同管口设置的散热器的实测性能区别。结果表明:当进出口水管位置设置不合理会对散热器水阻带来翻倍的影响。通过CFD研究和样件实测,为指导汽车散热器的进出口水管位置设计提供了优化方向。

基于TEC和平板热管的LED散热器结构优化设计

LED结温对其寿命和光效具有显著影响。高效的热管理对保持LED的性能稳定非常重要。为了有效降低LED结温、满足散热需求及特定场所的应用需求,结合热电冷却器(TEC)和平板热管(FPHP)重新设计了散热器结构,利用响应面法构建了针对散热器参数的双目标函数,通过非支配排序遗传算法(NSGA-II)求得Pareto最优解。基于散热器结构的最优值对TEC电流进行单因素优化分析,结果表明,优化后的LED最高结温比不采用TEC时的LED最高结温降低了23.3%,充分证明了优化散热器结构的有效性。

西安某综合体项目毛细管网辐射空调系统重难点问题浅析

本文结合西安某综合体毛细管网辐射空调系统设计实例,对毛细管网辐射空调系统的室内设计参数、送风状态、送风方式、水管管材等问题进行了浅析与归纳,为辐射空调系统在综合体项目中的应用提供参考借鉴。

风电变流器IGBT散热性能研究

风电变流器设计中,IGBT的散热设计非常关键,介绍了一种适用于风电变流器工程应用的IGBI损耗的理论计算方法,并建立了准确的数学模型。针对风电变流器应用环境的差异性以及不同类型散热器的固有热阻属性,通过flotherm仿真软件搭建普通散热器与热管散热器的仿真模型,仿真对比了不同散热器散热能力的差异。最后,通过实验验证了该设计方法的合理性和实用性,为风电变流器IGBT散热器与散热系统设计提供了重要的参考依据。

高热流密度电子元件中热管散热技术的进展

散热器的散热性能是影响电子元件使用寿命与安全性的重要因素,热管以其空间尺寸小、冷却能力高、无需消耗动力等优点在高热流密度元件的散热技术领域得到广泛应用。文中总结了热管散热器整体结构设计的创新尤其是热管的不同排布和组合,研究了热管元件性能的提高包括热管内部吸液芯的改进、复杂结构吸液芯的制造,分析了纳米流体工质的引入对换热效果的强化,介绍了散热器热性能分析和参数优化的相关方法。通过分析总结国内外研究成果,提出了新概念热管散热器的结构设计、纳米流体理论模型及复合吸液芯的加工制造等方面的发展趋势与展望。

高热流密度器件热控制实验研究

高热流密度热控制或高性能服务器的冷却处理方式已受到广泛关注,其CPU散热量持续增高导致了能量分布的不均匀.本文对计算机服务器CPU的耗能量、冷却效果等进行了实验研究。提出通过采用导热板扩大CPU散热面积,以及采用高导热相变设备,如新型热管式散热器来解决高热流密度器件能耗的处理办法.研究结果证实,对高热流密度器件依靠增大外界气流的速度来改善散热器的冷却性能并不明显,采用高效热管散热器强化芯片传热可满足大型计算机服务器CPU的冷却要求。

TOPAZ-Ⅱ空间电源系统辐射器改进研究

针对前苏联TOPAZ-Ⅱ反应堆系统所采用回路式辐射器存在单点失效的问题,采用热管式辐射器对其进行改进以提高系统安全性。根据系统废热排出的要求及冷却剂工作温度,选取高温钾热管,对结构材料及相关参数进行了设计,同时设计了辐射器的结构、热管的布置方式及铜翅片的参数。热管中心蒸汽区通过一维流动方程进行了求解,采用有限元方法分析了热管管壁与吸液芯结构的导热,采用有限差分法对翅片的辐射导热进行了计算。对热管与翅片组成的辐射单元与集流环进行了耦合计算,得出了辐射器设计工况下的稳态结果,对其进行了分析并与回路式辐射器进行了相应比较。计算结果表明,所设计热管式辐射器满足TOPAZ-Ⅱ正常运行情况下的废热排出要求,并具有较多裕度,同时热管式辐射器的安全性与等温性也优于回路式辐射器。

基于热辐射成像建模求解的管式炉炉管温度检测

准确在线检测管壁表面分布式温度是优化管式炉加热工艺的关键所在。以一台工业管式裂解炉为试验对象,结合辐射图像处理方法,开展了管式炉炉管表面温度可视化检测研究。采用基于Monte Carlo的DRESOR法求解具有复杂边界条件的管式炉辐射成像模型,实现了炉管辐射与火焰辐射、炉壁辐射的解耦计算,对炉管表面温度与热通量分布进行了在线监测,并研究了二者随工质流动方向的变化趋势。经过验证,温度测量误差小于2%,测量误差主要出现在最高和最低温区域。该项研究将有助于指导管式炉燃烧调整,改进加热工艺,提高炉管表面受热均匀性,延长炉管工作寿命。