外热式真空管材退火炉的研制

介绍了外热式真空管材退火炉的技术性能、设备结构及特点。该设备研制成功对钛管、棒及线材工业具有重要的现实意义。     

卧式管材半连续真空退火炉

本文介绍了一台新研制的我国目前最长的半连续式钛、锆等管材真空退火炉,包括主要技术参数、结构、微机程序控制以及调试经验等。     

中频感应炉烘炉工艺对坩埚寿命影响因素分析

针对中频感应炉烘炉工艺对坩埚寿命的主要影响因素，进行了示例分析的讨论，总结了在工艺和执行中的4个要点，为中频感应炉的烘炉、保障坩埚寿命，提供了理论实践指导。     

可控硅中频静止变频电源国内外发展简述

可控硅中频静止变频电源(简称可控硅中频电源),在熔炼和加热各种钢材、有色金属,以及各种热处理工艺中,可直接代替中频机组,作为中频感应电炉的供电设备。由于它利用可控硅元件的静止开关特性,直接将工频50赫转变为1000、2500赫,或更高的中频频率,因此它与中频发电机组比较,具有很多优点,比如,无噪音、无振动、重量轻、造价低、可自动调频和效率高等。近年来,可控硅中频电源,在国内外发展很迅速。随着可控硅元件的性能进一步提高,在感应电炉中,将更加广泛地采用可控硅中频电源。     

活塞销冷挤压毛坯的中频感应加热退火

我厂活塞销的冷挤压毛坯原来是采用油炉来进行退火处理的。由于油炉退火耗油多、效率低,并有严重的空气污染和噪音污染。因此采用新的退火工艺而取代油炉退火是一个急需解决的问题。我厂从78年开始着手试验中频感应退火工艺,经过几年的研究和试验,中频感应加热退火从设备和工艺上来说已基本成熟。现将试验情况及结果介绍如下: 一、冷挤压毛坯中频感应加热退火工艺试验情况如下 1、试验设备:DGT-T-252型中频加热设备,电源系中频发电机组,频率2500赫兹,最大输出功率250瓩。 2、实验毛坯;共两种:1、材料15CrA、φ36×80热轧棒材车削成形。2、材料SCr2_1(系日本进口,相当我国15CrA )、冷拉棒材经冲剪下料为生产中所用CA10活塞销冷挤压毛坯。     

打倒“四人帮” 生产力得解放——新系列静止变频电源中频感应熔炼炉试制成功

可控硅自进入工业应用以来,随着我国工业的迅速发展,用于感应加热方面的可控硅变频技术也得到飞速的发展,它给中频加热技术带来了广阔的前景,也为中频感应熔炼提供了新的工艺装备。过去,我国中频感应熔炼是依赖于传统的中频发电机组,生产的中频感应熔炼炉大多是仿苏产品,效率低,结构落后,操作不便。     

铜合金管材感应退火的试验

随着我国社会主义建设事业的飞速发展、电力、化工、造船等部门对铜合金管材,特别是对冷凝管的需要量日趋增多。为了适应四个现代化的需要,提高铜合金管材的质量、扩大品种,各铜加工厂正准备对现有企业进行技术改造,拟逐步形成管材生产自动线。在这一系列技术问题中,退火工艺是关键技术之一。目前,国内管材退火的设备是采用通保护气体的辊底式电阻炉,因此在管材质量和品种上(特别     

中频感应炉结构选择及节电途径探讨

近年来,中频感应电炉因其清洁环保、稳定高效、成分可控等优势,从各大熔炼炉中脱颖而出,现已逐步成为我国铸造行业普遍采用的关键熔炼设备。而中频感应电炉结构的选择,一定程度上决定了产品质量、熔炼电耗和熔炼成本等。浅要分析了中频感应电炉结构选择方案,以及针对感应电炉的结构及感应熔炼工艺指出几条节电途径。     

管材种类和污垢对凝汽器传热性能的影响

用凝汽器热力计算中的分布计算公式,对电厂常用的黄铜管HSn70-1、钛管TA2、奥氏体不锈钢管304、317L,铁素体不锈钢管444、SEA-CURE(海优)进行了传热性能的计算,定量分析研究了管材的导热系数和污垢对凝汽器传热性能的影响。结果表明,尽管不同管材的导热系数相差数倍,常用管材凝汽器的总传热系数K差别一般不到6%,有污垢时差别进一步缩小;污垢热阻是控制热阻,0.015mm碳酸钙垢就占总热阻的50%以上,使K降低一半左右;管壁热阻占比最小,清洁时约为3%~11%,0.015mm碳酸钙垢时,约占总热阻的1.5%~6%。     

自行车三角车架半自动中频感应钎焊工艺的研究

本文介绍自行车前三角车架采用中频感应钎焊的工艺方法、试验设备、以及试验结果和所取得的经济效益。     

Simulation of cross-flow-induced vibration of tube bundle by surface vorticity method

A fluid-structure interaction model based on Surface Vorticity Method (SVM) was used to study flow-induced vibrations of tube bundles in medium space ratio. The flow-induced vibrations of four tubes in a rotated square and a staggered tube bundle in three-row and five-column arrangements were simulated in the high sub-critical Reynolds number (Re) range. The results on fluid forces, tube responses and vorticity maps were presented. The vorticity maps of the four rotated-square tubes changed dramatically when the rigid tubes were replaced by the flexible tubes. From the vorticity maps and vibration responses of the staggered tube bundle of different structural parameters, it was found that with the decrease of tube natural frequency, the maximal vibration response moved from the third row to the first. The results also showed that when more flexible tubes are used, the flow pattern changed drastically and the fluid-structure interaction imposed a dominant impact on the flow.     

Simulation of cross-flow-induced vibration of tube bundle by surface vorticity method

A fluid-structure interaction model based on Surface Vorticity Method (SVM) was used to study flow-induced vibrations of tube bundles in medium space ratio. The flow-induced vibrations of four tubes in a rotated square and a staggered tube bundle in three-row and five-column arrangements were simulated in the high sub-critical Reynolds number (Re) range. The results on fluid forces, tube responses and vorticity maps were presented. The vorticity maps of the four rotated-square tubes changed dramatically when the rigid tubes were replaced by the flexible tubes. From the vorticity maps and vibration responses of the staggered tube bundle of different structural parameters, it was found that with the decrease of tube natural frequency, the maximal vibration response moved from the third row to the first. The results also showed that when more flexible tubes are used, the flow pattern changed drastically and the fluid-structure interaction imposed a dominant impact on the flow.     

Thermal stresses in radiant tubes: A comparison between recuperative and regenerative systems

A comparison was made between thermal stresses occurring in radiant tubes used in regenerative and recuperative systems. It was found that higher temperatures close to the annealing temperatures lead to stress relieving. The only stresses occurring were due to the non-linear axial temperature gradients along the length of the radiant tube in a recuperative system, whereas the radiant tube in a regenerative system remained essentially stress free due to a comparatively linear axial temperature gradient.     

Long time investigation of the effect of fouling on the super‐heaters in a circulating fluidized biomass boiler

The present investigation involves measurements and theories on the mechanisms of the forming of deposit layers on super‐heater tubes in a biomass‐fired CFD boiler. The deposit layer thickness and the soot‐blowing frequency effect on the super‐heaters heat transfer are the main subject of the study that has been conducted over a 3‐year period. The measurements show a deposit growth rate on the super‐heaters of approximately 4 g m^?2 h^?1. The distribution of the deposit material varies significantly between the windward and the leeward side of the tubes, with the thickest layers on the windward side. Further down stream of the first super‐heater, the fouling problem on the super‐heater and re‐heater tubes are not so severe. A theoretical model shows that a deposit layer of 20 mm will decrease the heat transfer rate of the first super‐heater by nearly 40%. The soot‐blowing system shows a strong positive effect on the heat transfer rate of the super‐heater a few hours after a soot‐blowing sequence has been completed. However in the long run, the varied soot‐blowing frequency does not have a significant influence on the deposit layer growth rate. Copyright © 2006 John Wiley & Sons, Ltd.     

大容量燃气热水锅炉对流管束的振动分析和预防措施

针对一台58 MW燃气热水锅炉部分对流管束产生的开裂现象进行了深入的原因分析.对断口部分进行了宏观检查、金相组织分析和扫描电镜分析,对烟气冲刷对流管束时气柱的固有(驻波)频率、卡门涡流频率和水管固有振动频率分别进行了计算,并对该锅炉的对流管束进行了振动测试,得出了对流管束产生管子的共振会引发部分对流管脆性断裂的结论.并据此提出了一系列具体的预防和控制措施及建议,通过改变管子的固有频率解决此类问题的发生,为锅炉的安全稳定运行提供保障.     

Heat Transfer Enhancement in Shell-and-Tube Heat Exchangers Using Porous Media

A numerical simulation has been carried out to investigate the heat transfer enhancement in a shell-and-tube heat exchanger using a porous medium inside its shell and tubes, separately. A three-dimensional geometry with k-? turbulent model is used to predict the heat transfer and pressure drop characteristics of the flow. The effects of porosity and dimensions of these media on the heat exchanger's thermal performance and pressure drop are analyzed. Inside the shell, the entire tube bundle is wrapped by the porous medium, whereas inside the tubes the porous media are located in two different ways: (1) at the center of the tubes, and (2) attached to the inner wall of the tubes. The results showed that this method can improve the heat transfer at the expense of higher pressure drop. Evaluating the method showed that using porous media inside the shell, with particular dimension and porosity can increase the heat transfer rate better than pressure drop. Using this method inside the tubes leads to two diverse results: In the first configuration, pressure loss prevails over the heat transfer augmentation and it causes energy loss, whereas in the second configuration a great performance enhancement is observed.     

大型稀有金属板带真空退火炉加热控制系统

针对大型真空退火炉多温区加热温度精确度和均温性控制难点,研究了基于Fuzzy—PID的多温区加热模糊控制策略,研制了工控机IPC＋PLC＋欧陆3504＋KTY3S晶闸管调功构成真空退火炉加热高精度控制系统。系统投入稀有金属大型真空退火炉运行,在加热温度精确度和均温性控制上取得显著效果,具有典型的应用价值。     

Enhancement of condensation heat transfer by means of EHD condensate drainage

The problem of electrohydrodynamic (EHD) condensation enhancement has been studied very recently. The electric field is commonly generated in such case by means of rod and mesh electrodes. The EHD method is suitable for dielectric media used in refrigeration and heat pump devices. The strong positive EHD effect has been obtained so far for vertical and horizontal bare tubes. However it was found that this effect for horizontal integral-fin tubes, commonly used in heat exchangers, is negligible small. The mechanism of the EHD condensation enhancement is discussed in the paper and a novel arrangement of the tube-electrode system is proposed. It consists of a horizontal finned tube with a rod type electrode placed beneath the tube. The experimental investigations have been carried out for this tube-electrode arrangement using HCFC-123 as a working medium. The obtained results confirmed the expectations since the application of EHD method for the new tube-electrode configuration increased the heat transfer coefficient from 27% to 110%, depending on the electrode potential. A simple model of the EHD condensate drainage has been proposed for the new tube-electrode arrangement.     

Tubular graphene architectures at the macroscopic scale: fabrication and properties

Specific graphene architectures at the macroscopic scale are paramount for exploring new functions and practical uses of graphene. In this study, macroscopic, freestanding, and tubular graphene (TG) architectures were successfully fabricated through a versatile and robust process based on the annealing of cellulose acetate (CA) on Ni templates. These TG architectures can be obtained as woven tubes with diameters of approximately 50 μm; they possess high graphitic crystallinity, strong electrical conductivity, and favorable corrosion resistance. The effects of processing parameters, such as annealing temperature, annealing time, and amount of CA, on the graphene properties of these architectures were investigated and are discussed in this paper. The graphene properties were characterized through field emission scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, Raman spectroscopy, four-point probe resistivity, and electrochemical measurements.