Theoretical and Experimental Investigation of Flexural Vibration Transfer Properties of High-Pressure Periodic Pipe

According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oii pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. A11 the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high- pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.

Energy Transfer Mechanism and Probability Analysis of Submarine Pipe Laterally Impacted by Dropped Objects

Energy transfer ratio is the basic-factor affecting the level of pipe damage during the impact between dropped object and submarine pipe. For the purpose of studying energy transfer and damage mechanism of submarine pipe impacted by dropped objects, series of experiments are designed and carried out. The effective yield strength is deduced to make the quasi-static analysis more reliable, and the normal distribution of energy transfer ratio caused by lateral impact on pipes is presented by statistic analysis of experimental results based on the effective yield strength, which provides experimental and theoretical basis for the risk analysis of submarine pipe system impacted by dropped objects. Failure strains of pipe material are confirmed by comparing experimental results with finite element simulation. In addition, impact contact area and impact time are proved to be the major influence factors of energy transfer by sensitivity analysis of the finite element simulation.

Maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick

A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered in the proposed model.Maximum heat transfer capacity was also investigated experimentally. The model was validated by comparing with the experimental results. The maximum heat transfer capacity increases with the vapor core radius increasing. Compared with the inclination angle of0°, the maximum heat transfer capacity increases at the larger inclination angle, and the change with temperature is larger. The performance of heat pipe with triangular grooved wick is greatly influenced by gravity, so it is not recommended to be applied to the dish solar heat pipe receiver.

Analysis of Vibration of the Euler-Bernoulli Pipe Conveying Fluid by Dynamic Stiffness Method and Transfer Matrix

The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fluid, the element dynamic stiffness is established. The vibration characteristic of the single-span pipe is analyzed under two kinds of boundary conditions. The results compared with the literature, which has a good consistency. Based on this method, natural frequency and the critical speed of the two types of multi-span pipe are deserved. This paper shows that the dynamic stiffness method and transfer matrix is an effective method to deal with the vibration problem of pipe conveying fluid.

STUDIES ON HEAT TRANSFER OF FLUID OSCILLATED WITHIN PIPES

This paper is a brief summarization of research achievements about enhanced heat transfer of a fluid oscillated within pipes. Analytical solutions, numerical results and dimensional analyses are summarized and compared with experimental data in the paper. Also, the mechanism of enhanced heat transfer is discussed. It is considered that increase in the effective area of heat conduction and increase in temperature gradient are the main reasons of enhanced heat transfer.

Experimental Analysis of Heat Transfer Behavior inside Heat Pipe Integrated with Cooling Plates

This work used experimental methods to study heat transfer behavior inside a heat pipe and found that heat transfer behavior inside the heat pipe was changed due to its integration with cooling plates. This change caused the heat pipe to have copper-like heat transfer behavior. Experimental performances first built a CPU simulator with maximum heat power 300 W in accordance with the ASTM standard as heat source and measured temperature distribution by using infrared thermography and thermocouple thermometer. Observation of heat transfer behavior inside heat pipe influenced by its integration with cooling plates used color schlieren technique. A commercial CPU heat pipe cooler was also used as reference object in this work. Integration of the heat pipe with cooling plates causes the heat pipe to have the copper-like heat transfer behavior. The results indicate that rebuilding the bare heat pipe’s heat transfer behavior is the best solution for improving cooling efficiency of the heat pipe cooler.

Simulation of Heat Transfer in a Tubular Pipe Using Different Twisted Tape Inserts

This paper performs a simulation study of the heat transfer phenomena in a tubular U-loop pipe. We have investigated the enhancement of heat transfer with mass flow in a pipe without insert, with full length and short length twisted tape inserts. The length of the pipe is approximately 2436.80 mm long with 29 mm inner and 33 mm outer diameter respectively. A constant heat flux is taken which generated the boundary layer of the pipe close to the flowing fluid around the boundary. The simulations are considered for the stationary and the time dependent module for 35 seconds with different length of inserts. The comparisons are made among the results. We observed that the transfer of heat is enhanced significantly with the increase of the length of inserts inside the computational domain. We also found that, full length twisted tape inserts are more effective than comparing with the short length inserts and without insert.

飞秒激光选区微织构AlN超浸润平板热管

目的为了提升AlN基板的散热性能,研究嵌入式一体化AlN平板热管的激光加工方法。方法通过飞秒激光微织构技术结合热处理工艺制备出AlN亲疏水组合表面,并组装嵌入式一体化平板热管,测试其传热性能。通过三维表面轮廓仪、SEM、EDS和XPS分别分析表面的三维轮廓、形貌、元素含量和化学成分,研究表面亲、疏水的形成机理。结果楔形亲疏组合AlN平板热管的启动时间、启动温度均最低,相较于全超亲水样品,启动时间降低了14.9%,启动温度降低了6.0%。楔形亲疏组合热管的热阻最低,热流密度最高。相较于全亲水热管,热阻降低了33%,热流密度提升了2%。结论AlN陶瓷表面经过激光织构会产生AlOx(多价铝氧化物),具有较高的表面能,呈超亲水状态。热处理能使表面充分氧化,降低表面能,呈超疏水状态。嵌入一体化AlN平板热管的设计和无化学激光选区微织构方法,为电子陶瓷基板的散热提供了一种新思路。

脉动热管太阳能集热器传热性能实验研究

以真空玻璃管为载体、石蜡为相变储热材料、脉动热管和铜管为传热元件,对比分析了充液率φ=50.0%的脉动热管太阳能集热器与铜管太阳能集热器在相同辐照度下的集热性能。研究结果表明,当辐照度大于0 W/m^(2)时,脉动热管太阳能集热器相比于铜管太阳能集热器管壁温度提高了40℃;相较于铜管太阳能集热器,热源温度越高,脉动热管太阳能集热器吸热能力越强,传热效果越好;在相同的辐照度下,相比于铜管太阳能集热器,脉动热管太阳能集热器内的石蜡达到熔点的时间缩短了13%;脉动热管太阳能集热器输出的热量比铜管太阳能集热器高0.5 kJ,随着辐照度的增强,热量差值将会更大;脉动热管蒸发段和冷凝段壁面与其相接触的传热工质会形成一种准平衡态,蒸发段与冷凝段的传热能力呈反比关系,当蒸发段传热能力下降时,冷凝段传热能力上升,保证了集热器的稳定运行。

低频导波检测技术在输油场站应用的效果分析

本文主要是对低频导波检测技术原理和应用进行分析,进而选取本次最优开挖验证点,通过MsS长距离超声导波检测仪在姬塬外输总站管网腐蚀检测过程中的应用效果分析,判断其应用效果具有哪些局限性和优缺点,为后续输油场站常规检测工作提供参考依据。

波纹结构液氮脉动热管传热传质特性研究

低温热管换热器是天然气液化系统中的关键装置,液氮脉动热管作为其核心器件具有体积小、换热效率高等特性,可有效克服系统冻堵及设备紧凑等问题,然而开展相应实验难度较大,因此通过数值模拟方法研究其内部传热传质规律具有重要意义。首先,文章通过UDF(User-Defined Functions)编写自适应相变模型,研究了典型液氮脉动热管的传热传质特性。随后,在冷凝段优化设计了波纹结构,结合相态分布与轴线温度方差值,对比分析了充液率为50%情况三种液氮脉动热管传热传质特性,结2果表明5 mm波纹结构热管两侧方差值为51.49 K与99.22 K2,工质循环速率较快且轴线温度分布均匀。最后,研究了充液率分别为30%、50%与70%情况下5 mm波纹结构的脉动热管的传热性能。结合相态、温度及轴线温度分布分析得出充液率过高或过低均会导致热管内部产生液塞,充液率较高时,轴线温度均匀分布,热管充液率为70%时,综合性能最佳。

超深井控温钻井隔热涂层参数影响机制研究

为揭示隔热涂层对超深井井筒温度场的影响规律,针对隔热涂层与钻杆的导热特点,采用传热热阻形式计算钻杆的综合传热系数,构建了考虑钻杆内隔热涂层影响的超深井井筒–地层瞬态传热模型,并采用有限差分法对模型进行离散,利用高斯–赛德尔算法进行迭代求解。通过理论分析和现场数据验证了模型的准确性。研究发现,钻杆内隔热涂层的导热系数对井底循环温度影响显著,随着导热系数减小,井筒环空温度迅速降低,出口温度升高;隔热涂层的厚度和长度对井筒温度也有重要影响,隔热涂层厚度越大,井底循环温度越低。这些发现为超深井钻井过程中井筒温度的调控和隔热钻杆参数的优选提供了重要理论依据。

不同土质条件下土壤蓄热特性的数值模拟研究

选取严寒地区、寒冷地区、夏热冬冷地区典型地源热泵作为研究对象,建立地埋管及周围土壤的物理模型,根据不同地域的地质条件,为土壤区域设置不同的热物性参数及分层数,对整个蓄热季的地埋管及周围土壤的换热情况进行数值模拟,探究地质条件对地源热泵换热特性及土壤蓄热量的影响。结果表明,由于所选各地区土壤热物性参数及分层数不同,整个蓄热季后土壤蓄热量差异较大,严寒地区、寒冷地区、夏热冬冷地区土壤蓄热量分别为949.251 MJ、1 031.122 MJ和709.225 MJ。受土壤各层热物性参数差异影响,同一地区各层土壤的热量传递半径及升温速率也存在较大不同。粉质粘土层热量传递半径大,中粗砂与淤泥质粘土层温度提升快。此外,在整个蓄热季中,受土壤热容增大影响,蓄热效率呈现出下降趋势,在实际运行过程中应采用间歇蓄热,提升蓄热效率。

航天器用钾热管传热性能的敏感性分析和优化

碱金属热管在空间核电源系统中具有重要应用,是航天器辐射散热器的重要组件。文章研究钾热管对充液率、吸液芯层数、吸液芯丝网目数及热负载功率的敏感性,并对上述多参数耦合下钾热管传热性能进行优化。分析结果表明:钾热管温差随充液率和吸液芯丝网目数的增加而降低,随吸液芯层数和热负载功率的增加而升高,且钾热管的整体温度和蒸气流速随热负载功率的增加分别升高和降低。钾热管性能对吸液芯层数和热负载功率敏感,优化得到最优参数组合为充液率1.0时7层350目吸液芯和712.475 W的热负载功率。文章采用的分析和优化方法对热管式辐射散热器的工程应用设计具有工程参考价值。

长距离输调水工程大口径FRPM管道研发与工程安全保障技术

长距离输调水工程是中国新疆地区重要的基础生命线,其长久稳定运行对于促进经济平稳增长和保障居民供水安全至关重要。新疆位居大陆中心,属温带极端大陆性气候,其长距离输调水工程面临严峻的环境挑战。玻璃纤维增强塑料夹砂管(glass fiber reinforced plastic mortar pipes,FRPM)作为长距离输调水工程中重要的水工地下结构用材,凭借其优异的耐化学腐蚀、轻质高强、无二次污染、安装方便、综合造价低等诸多优良特性而被广泛应用于新疆地区。然而,传统FRPM管生成工艺在铺层设计与生产自动化程度方面存在一定局限,导致工程施工过程效率低下;同时,缺少统一的技术标准和设计规范也间接制约了其应用范围。此外,管道工程自动巡检技术与缺陷定量评价标准尚未统一,无法合理量化和准确评价整体工程质量。为此,依托北疆小洼槽供水工程,围绕长距离大口径FRPM管的管材铺层设计与制造工艺、工程设计、质量评定、自动巡检、运行监测与安全保障等关键技术,通过产学研用相结合,持续15年攻关,取得突破性创新成果:①引进吸收并创新了适合于长距离、高工作压力、以连续缠绕工艺为首选的FRPM管生产工艺,优化了大口径FRPM管材铺层设计方法,实现了供料—缠绕—固化—切割—检测全自动化控制,与国外同类产品标准相比,管道挠曲性能和轴向拉伸强度等提高了20%~50%;②提出了安全防护的工程和非工程措施,建立了长距离FRPM管不同缺陷类型危害性等级划分原则,创建了复杂地质条件下长距离FRPM管道工程安全评价理论与方法;③系统揭示了FRPM管质量缺陷产生机理,开发了FRPM管光固化片材局部修复工艺以及内衬聚乙烯(PE)的整体非开挖修复技术,提出了修复效果后评价方法,实现了对长距离FRPM管道工程运行安全的有效掌控。

竖直铯热管传热特性的实验和数值模拟

近年来,有关中温铯热管的研究较少,主要因为铯热管造价昂贵且铯金属化学性质活泼,开展实验难度较大,因此通过数值模拟方法对铯热管启动特性与内部相变等过程进行分析预测具有重要意义。首先,本文开展铯热管冷启动实验,并基于目前的热管模拟模型,利用UDF建立蒸发与冷凝的自适应模型,对比实验热管稳态壁温与数值模拟计算壁温,最大温差小于20K,且较好地呈现了热管末端的温度突降,证明了模型的准确性。其次,基于竖直铯热管变功率冷态启动实验,模拟获得铯热管启动过程中热管壁面温度及内部工质相态分布的演变过程;并利用壁面温度的平均差数值评价有效长度上的均温性。最后,通过模拟研究改变热管蒸发段长度(200mm和120mm)、加热功率(1028.2W和844.4W)及充液率(8.8%、12%和15%),对比分析其相态分布、温度分布及压力分布;综合热管有效工作长度、壁面均温性、蒸发段液相堆积与干烧现象,分析蒸发段长度与充液率的最佳配比,为热管的优化设计提供基础。

基于火积理论对热管传热效率最优化问题的讨论

本文基于火积理论研究了热管中的热传输效率的优化问题。本文首先对比了传统熵理论和火积理论在分析传热效率方面的应用,然后详细介绍了火积理论,包括其物理意义和作为工程优化函数的应用。通过COMSOL仿真实验,本文展示了火积理论在热管设计优化中的实际应用,验证了理论的正确性,并对比了温差和火积耗散率与热管外径、芯层厚度等多个参数的关系,为热管等传热模型研究及生产设计优化提供了新视角。

基于平板热管技术的电子器件热管理研究进展

随着电子器件不断趋于小型化和高度集成化发展,电子器件功率过高引发的散热问题亟待解决。平板热管由于具有均温性好、散热效率高等优势已为许多大功率电子元器件的散热问题提供了有效的热管理解决方案。但面对如今越来越多元化的散热需求,开发适应新型电子设备散热需求的高效平板热管仍是当前研究的热点。基于此,在对平板热管工作原理及结构特点进行阐述的基础上,对平板热管的传热性能、影响传热性能的因素(毛细芯结构、腔体厚度、工质、充液率、倾角和热源)、强化平板热管传热性能的措施(不同润湿性表面和支撑柱结构等)及其在小型化电子设备、IGBT晶体管、LED和电池组等电子器件散热应用等方面进行了系统性综述,指出研究不同毛细芯结构与腔体厚度下平板热管内部流动传热特性、散热性能强化的机制和综合优化方法,以及如何在不同电子器件热管理需求下设计出空间适应性强而散热性能高效的平板热管等仍是当前平板热管有待进一步突破的关键技术,将为平板热管在电子器件散热领域的进一步深入研究与优化提供一定参考。

内置多叶扭带的碳化硅换热管强化传热特性研究

为了研究碳化硅换热管的流动和传热特性,达到增强综合换热能力的目的。采用数值模拟方法对内置4种不同结构扭带的换热管进行分析,确定四叶扭带模型作为后续研究对象,对比了在4种自定义的节距和宽度两种结构参数下,不同入口风速工况的换热管的热力性能。结果表明:扭带宽度对换热管的换热能力相较于节距具有更显著的强化作用,四叶扭带节距为360 mm、宽度为45 mm时换热管的综合换热能力最强,为1.59,此时换热管的努塞尔数相较光管提升了244.37%。

高温钠热管启动传热振荡及热疲劳安全分析

高温热管的启动是复杂的相变及流动过程,若发生传热振荡将造成温度波动,进而影响热管堆运行安全。本文通过实验及仿真方法研究高温钠热管在启动过程中的传热振荡现象及热疲劳后果。在竖直工况中,不同输入热流密度将引起钠蒸发速率变化,呈现不同振荡特征;热流密度提升时振幅下降,周期缩短;振荡发生时,若输入功率骤降,波形将从锯齿状转变为梯形状;在水平工况中,传热振荡被明显抑制。热管在堆内发生传热振荡时,应力风险区为热管蒸发段内壁中部;异相振荡时相较同相振荡工况应力均值升高,振幅下降,疲劳损伤减轻;当安全因子K低于1.4时热管不存在疲劳失效风险,K达1.4以上后损伤逐渐显著;其中同相工况疲劳损伤最严重,K=1.6时管壁材料疲劳寿命已降低至3.29年。本研究对高温钠热管传热振荡的机理分析及完善热管可靠性评估具有重要意义。