Performance analyses of a novel finned parabolic trough receiver with inner tube for solar cascade heat collection

Designing highly-efficient parabolic trough receiver(PTR)contributes to promoting solar thermal utilization and alleviating energy crisis and environmental problems.A novel finned PTR with inner tube(FPTR-IT),which can provide different grades of thermal energy with two heat transfer fluids(oil and water),is designed to improve thermal efficiency.In this FPTR-IT,an inner tube and straight fins are employed to respectively lessen heat loss at upper and lower parts of the absorber.Based on the design,a numerical model is developed to investigate its performance.Comparisons with other PTRs indicate that the FPTR-IT can combine the advantages of PTR with inner tube and finned PTR and obtain the best performance.Moreover,performance evaluation under broad ranges of direct normal irradiances(300–1000 W/m^(2)),flow rates(50–250 L/min)and inlet temperatures(400–600 K)of oil as well as flow rates(3.6–10 L/min)and inlet temperatures(298.15–318.15 K)of water is investigated.Compared with conventional PTR,heat loss is reduced by 20.7%–63.2%and total efficiency is improved by 0.03%–4.27%.Furthermore,the proportions of heat gains for water and oil are located in 8.3%–73.9%and-12.0%–64.3%,while their temperature gains are located in 11.6–37.9 K and-1.2–19.6 K,respectively.Thus,the proposed FPTR-IT may have a promising application prospect in remote arid areas or islands to provide different grades of heat for electricity and freshwater production.

Pipe reduction of miniature inner grooved copper tubes through rotary swaging process

A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.

Viscous Inner and Outer Pressure Forming Method of Thin-walled Tube and Its Application

Aiming at overcoming the difficulties in integral forming of thin-walled tubes with complex shapes, a novel forming method by inner and outer pressure through viscous was proposed. In this method, by dividing large deformation of the part into inner and outer pressure forming deformations, the limit deformation of tube part can be increased by several times. Meanwhile, the principle of viscous inner and outer pressure forming was provided, and key problems during the forming process such as reduction of the wall-thickness and instability wrinkling were analyzed. Thereby, the complex curved surface super-alloy GH3044 thin-walled tube with varying diameter ratio of 1.35（the ratio between the maximum and minimum diameters of the part） can be integrally formed by this method. The experimental surface of the formed part is superior in quality and the wall-thickness distribution is uniform. The results show that the viscous inner and outer pressure forming can provide a new approach for integral forming of thin-walled tubes with complex shapes.

AN INNER-FEEDBACK-STYLE TRAVELING-WAVE TUBE OSCILLATOR

A new concept of inner-feedback-style traveling wave tube oscillator, which is based on a traveling-wave tube having a partial reflector located at near the junction between the slow-wave structure and the output coupler and a mechanical tuner connected to the input coupler, is proposed. Simulations by CHIPIC code show that the inner-feedback-style traveling wave tube oscillator having 100W of power, about 10% of electron efficiency and a tunable band of 73.35-73.91 GHz may be achieved. Compared with Backward Wave Oscillators (BWOs), the new devices have similar ability for tuning, and have much higher electron efficiency, suggesting much more potential as a Terahertz source.

Extended Anode Effect for Tube Inner Coating of Non-Conductive Ceramics by Pulsed Coaxial Magnetron Plasma

For uniform tube inner coating of non-conductive thin films, the double-ended coaxial magnetron pulsed plasma (DCMPP) method was investigated. In this study, coating of TiN and TiO2 was performed. It was clearly shown that the extended anode effect was strongly influenced by the electric resistance of the coated thin films on the inner surface of an insulator tube. Additionally, high frequency (100 kHz) was better for relatively high plasma density. On the other hand, in the case of titanium oxide deposition, negative ion productions drastically decrease the deposition rate and the shifting velocity of plasma main position for coated TiO2 films.

Influences of the inner diameter of the solid shielding tube on the characteristics of the radio-frequency cold atmospheric plasma jet

Active control of the local environment of the cold atmospheric plasma(CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surrounding cold air. In this paper, the solid shielding effects of the cylindrical quartz tubes with different inner diameters on the characteristics of the CAP jets driven by a radio-frequency(RF) power supply are studied experimentally. The experimental results show that the total length of the shielded plasma jet can be increased significantly by an appropriate combination of the quartz tube inner diameter and that of the plasma generator nozzle exit with other parameters being unchanged. This phenomenon may be qualitatively attributed to the loss of diffusion of the charged particles in the radial direction under different inner diameters of the quartz tubes. Compared with the plasma free jet, the plasma shielding jet is produced with optimized parameters including longer plasma jet length, higher concentrations of chemically reactive species, higher rotational, vibrational, and electron excitation temperatures when the inner diameters of the solid shielding tube and the generator nozzle exit are the same. A maximum plasma jet length of 52.0 cm is obtained in contrast to that of 5.0 cm of the plasma free jet in this study. The experimental results indicate that the solid shielding effect provides a new method for the active control of the local environment of the RF-CAP jet operating in an open atmosphere.

Response features of nonlinear circumferential guided wave on early damage in inner layer of a composite circular tube

A theoretical model to analyze the nonlinear circumferential guided wave(CGW) propagation in a composite circular tube(CCT) is established. The response features of nonlinear CGWs to early damage [denoted by variations in third-order elastic constants(TOECs)] in an inner layer of CCT are investigated. On the basis of the modal expansion approach, the second-harmonic field of primary CGW propagation can be assumed to be a linear sum of a series of double-frequency CGW(DFCGW) modes. The quantitative relationship of DFCGW mode versus the relative changes in the inner layer TOECs is then investigated. It is found that the changes in the inner layer TOECs of CCT will obviously affect the driving source of DFCGW mode and its modal expansion coefficient, which is intrinsically able to influence the efficiency of cumulative second-harmonic generation(SHG) by primary CGW propagation. Theoretical analyses and numerical simulations demonstrate that the second harmonic of primary CGW is monotonic and very sensitive to the changes in the inner layer TOECs of CCT, while the linear properties of primary CGW propagation almost remain unchanged. Our results provide a potential application for accurately characterizing the level of early damage in the inner layer of CCT through the efficiency of cumulative SHG by primary CGW propagation.

充分利用隧道窑热量同步焙烧煤矸石轻集料技术研究

主要介绍了充分利用隧道窑热量同步焙烧煤矸石轻集料技术及节能焙烧设备的研究情况,依据以内螺旋筒为特征结构的节能焙烧工作原理,研究、设计、试制了实验炉模拟设备,并以辽源市煤矸石为原料进行了相关焙烧试验,验证了其所形成的煤矸石轻集料焙烧新工艺。模拟实验表明,利用隧道窑热量(余热)同步焙烧煤矸石轻集料技术具有可行性。

基于内管移动的卧式管壳式相变储热器储热性能优化研究

相变储热技术能够实现对固态储放氢过程热量的回收和供给,实现固态储氢罐内的自热平衡,提高储放氢性能。研究针对卧式管壳式相变储热器,提出了一种新型的内管偏心放置绕中心轴线旋转的运动方式,采用Fluent数值模拟软件,基于动网格技术编写了用户自定义函数UDF,重点研究了内管偏心距离与旋转速度对储热性能的影响。结果表明:与传统中心内管静止布置相比,偏心内管的旋转运动能够显著提高储热性能,当偏心距离为9 mm,旋转速度为0.10 r/min时,储热时间达到最小值,储热时间减少了92.16%,时间平均储热速率是内管静止布置的11.51倍;当偏心距离为9 mm,旋转速度由0.30 r/min减少至0.10 r/min时,储热时间减少了13.57%;当旋转速度为0.10 r/min,偏心距离由3 mm增至9 mm时,储热时间减少了70.48%。该研究结果可为卧式管壳式相变储热器在储氢领域的性能优化研究提供新思路。

冷凝液汽提系统夹套管不锈钢内管开裂失效分析

某化工企业甲醇中心净化装置冷凝液汽提系统夹套管不锈钢内管发生开裂泄漏,通过宏观观察、化学成分分析、力学性能测试、金相分析、硬度测试、能谱分析和断口扫描电镜分析等手段对失效原因进行了分析。结果显示:夹套管不锈钢内管力学性能不符合标准要求,且内部凹坑与裂纹均在酸洗前已存在,为原始制造缺陷。

甲醇管式SOFC防积碳研究及结构设计

为了解决甲醇固体氧化物燃料电池(solid oxide fuel cell,SOFC)积碳问题,提出了多孔内管甲醇管式SOFC设计.部分甲醇可以通过多孔内管进入阳极参与反应,进而降低了阳极顶部甲醇浓度及CO分压,并提升该区域的温度,所以有效缓解该区域积碳活性过高的问题,最大积碳活性降低了99%以上.其次,多孔内管甲醇管式SOFC的阳极表面最大温差仅为49.15 K,比传统甲醇管式SOFC的最大温差210.2 K,下降了76.6%,降低了电池热应力.

内套GFRP管圆钢管混凝土组合柱的偏压力学性能分析

利用ABAQUS有限元软件建立了适用于内套GFRP管圆钢管混凝土组合柱的单向偏压模型,研究了影响该组合柱力学性能及失效模式的关键因素。结果表明:该组合柱的极限承载力随着偏心距的增大而降低,随着外置圆钢管和内套GFRP管壁厚的增加而提高。内套GFRP管壁厚对构件极限承载力的影响小于偏心距和外置圆钢管壁厚造成的影响。长径比对极限承载力的影响较小。基于影响系数法建立了适用于单向偏压构件的极限承载力计算方法,该计算方法可为相关工程提供参考。

基于液压内胎硫化机的硫化飞边原因分析及控制措施

基于液压内胎硫化机的结构特点,分析造成内胎硫化飞边问题的原因,并提出相应的控制措施。通过采取准确计算硫化机合模力、检验新模具质量、控制模具预热变形、加强模具清洗和存放管理工作、将硫化机的空心热板更换为加厚的实心热板及将导向机构由工字型滚轮/铁板导轨更换为直线滑轨/滑块等措施,大幅降低了内胎硫化飞边出现的频率,为内胎硫化飞边问题提供设备检修流程的理论依据。

锥形内翅片管传热性能数值模拟研究

针对传统内螺纹翅片管的翅片高度较低,对热边界层的扰动较弱,传热性能不高等问题,基于计算流体力学理论,利用Fluent仿真软件,在雷诺数为10000~18000时,通过对内螺纹翅片管和一种锥形内翅片管数值模拟结果进行比较发现,锥形内翅片管的传热性能远高于内螺纹翅片管。此外,对锥形内翅片管的齿条数、翅片间距以及翅片高度分别进行数值模拟发现,当齿条数N=45时,锥形内翅片管的Nu值较大,约是光管的2倍;当翅片间距越小时,Nu值越大;在L=0.6 mm时,努塞尔数取得较大值,约为光滑管的1.6~1.9倍;高度h=0.7 mm时,努塞尔数有较大值,约是光滑管的1.95~2.01倍。结果表明,齿条数越多,翅片间距越小以及翅片高度越高的锥形内翅片管具有良好的传热性能。这种翅片管具有传热面积显著增大、翅高显著提高以及可以更好地破环热边界层等优点。通过比较不同的结构参数下对应的翅片管的摩擦因数、努塞尔数和综合评价指标等值,以寻求锥形内翅片管最佳的结构参数。

盾构接收端内衬管片主要质量缺陷原因分析及处置措施

盾构法施工被广泛应用于城市轨道交通和输水隧洞工程中,盾构接收端工况复杂,在进行洞门封堵注浆时会导致接收端内衬管片错台、破损及渗漏水加剧,文章以珠江三角洲水资源配置工程某一区间左线为例,对该区间接收端最后20环管片出现的错台、破损、渗漏水等质量缺陷原因进行统计研究分析,分缺陷大小等不同情况提出完整有针对性的处置措施,为后续相关类似工程盾构接收端内衬管片主要质量缺陷原因分析及处置措施提供参考与借鉴。

内壁喷丸设备在锅炉行业中的应用研究

本文首先阐述了不锈钢管内壁进行喷丸强化处理必要性,然后就公司引进开发了两条不锈钢管内壁喷丸强化处理生产线设备的工艺规范、质量要求、设备选型、设备组成、工作流程及控制和注意事项进行分析。

内耳1.5T MRI钆造影对可疑梅尼埃病的诊断价值

目的1.5T MRI条件下经咽鼓管给药行内耳3D-FLAIR序列MRI扫描,探讨其对可疑梅尼埃病的诊断价值。方法选取2019年3月-2023年10月在我院就诊的可疑梅尼埃病患者38例做为研究对象,经咽鼓管注射钆双胺24小时后进行内耳MRI检查,分析前庭及耳蜗膜迷路积水情况。结果38例可疑梅尼埃患者中临床确诊梅尼埃病31例,伴发眩晕的突聋4例,前庭性偏头痛2例,良性阵发性位置性眩晕1例。31例确诊梅尼埃患者中内淋巴积水27例,无积水4例,其中27例内淋巴积水患者中合计有32耳积水,其中双耳积水5例,单耳积水22例,32耳积水中轻度积水12耳,重度积水20耳。非梅尼埃患者中内淋巴积水1例、为轻度积水,无积水6例。内耳1.5T MRI钆造影对梅尼埃病诊断的灵敏度为87.1%、特异度85.7%,ROC曲线下面积为0.864,对于临床诊断价值较高。结论经咽鼓管给药内耳1.5T MRI钆造影可清晰显示内耳膜迷路积水情况,对梅尼埃病的诊断是可行的。

一种埋地电缆管道内切割装置的研制

针对目前10kV及以上埋地电缆保护管的切割待解决的问题,从传统的切割工具、切割方式的基础上研制了一款电缆保护管内切割装置。本款埋地电缆管道内切割装置采用半自动环绕管内壁切割的方式,结合其装置前后两端的固定结构完成切割工作,内切割装置的使用能有效解决电缆保护管端面切割不整齐的问题,最大限度地发挥了保护管的功能,提高了埋地敷设的施工质量。

聚二甲基硅氧烷膜对中硼硅玻璃管制注射剂瓶质量特性的影响研究

目的:研究镀聚二甲基硅氧烷膜后对中硼硅玻璃管制注射剂瓶质量特性和质控方法操作的影响,包括外观、鉴别、物理性能、内表面耐水性和元素浸出量的影响。方法:采用3家企业的9批镀膜中硼硅玻璃管制注射剂瓶和对应的中硼硅玻璃管制注射剂瓶,评估聚二甲基硅氧烷膜后中硼硅玻璃管制注射剂瓶质量控制方法是否需要进行针对性修改,以及评估评估镀膜对瓶质量特性的影响。结果:镀膜对中硼硅玻璃管制注射剂瓶的外观、鉴别、物理性能没有影响,镀膜过程并不会损害中硼硅玻璃管制注射剂瓶的原有性能,也不会导致检验方法出现需要特别关注的注意事项;镀膜后的中硼硅玻璃管制注射剂瓶在内表面耐水性方面有所改善。镀膜前后砷、锑、铅、镉等有害元素的浸出量均低,说明镀膜过程并未增加这些有害元素的浸出风险。通过ICP-OES测定元素浸出量,多数金属元素也未发现明显变化。结论:镀聚二甲基硅氧烷膜后中硼硅玻璃管制注射剂瓶的外观、鉴别、物理性能和元素浸出量质控方法操作不需要做针对性改变,镀膜后内表面耐水性有改善,对其他质量特性项目没有显著不利影响。

General issues of FEM in backward ball spinning of thin-walled tubular part with longitudinal inner ribs

Backward ball spinning was applied for manufacturing thin-walled tubular parts with longitudinal inner ribs. Rigid-plastic finite element method(FEM) was used for simulating the backward ball spinning process in order to calculate the height of the inner ribs. With a view to guarantee a better simulation accuracy, it is essential to enhance and improve some general problems of FEM, such as generation of initial velocity field, choice of penalty factor, determination of boundary conditions, treatment of rigid region and description of convergence criteria. It is evident that whether the problems with respect to FEM are dealt with appropriately or not, they have a significant influence on the modeling accuracy and efficiency. By reasonable solving the general problems, rigid-plastic FEM can successfully simulate the height of the inner ribs and the calculated values are in good agreement with the measured values.