Experimental studies of heat transfer during steam condensation on a vertical multirow on-line bundle of slightly inclined coil tubes with and without noncondensable gas in the bundle

We present the results obtained from experimental studies and generalization of experimental data on heat transfer intensity during full condensation of downward flow of saturated steam on the outer surface of a vertical multirow in-line bundle of slightly inclined coil tubes at a steam pressure of 0.2–2.0 MPa. Specific features relating to heat transfer that occurs during steam condensation on a vertical coil tubing in the presence of heavy noncondensable gas in the space between its tubes are revealed.     

立管冷凝强化传热研究的进展

立管冷凝强化传热技术是利用Gregorig效应在凹槽的顶端产生薄膜冷凝,并通过凹槽有效地排液,从而达到强化膜状冷凝换热的目的。为此,对波形曲面凹槽管、垂直余弦形沟槽管、V形纵槽管、垂直光管设置纵向金属丝、立式螺旋槽管和小螺旋角的内外螺旋三角翅片管在强化冷凝热方面研究的进展作了概述,并介绍了制备低表面能合金材料以实现稳定滴状冷凝的冷凝换热强化新技术。最后指出,立管冷凝强化传热技术在电站的立式加热器中应用,可以较大幅度地提高给水温度,实现节能增效。     

Heat transfer during natural circulation and laminary flow of liquid through vertical and inclined tubes

We present the results of an investigation of the effect the inclination angle has on heat transfer during natural circulation and a laminar flow of liquid through vertical and inclined heated tubes. It is revealed that the maximum heat transfer is reached at inclination angles (with respect to a vertical line) ranging from 15° to 45°.     

斜柱斜面输电铁塔基础的计算要点及施工技术

近年来,在西北750 kV超高压输电线路工程的开挖回填类基础中,在终端塔、转角塔基础中广泛应用了塔脚板垂直方向的斜柱斜面基础.此种基础立柱顶面与斜立柱棱线垂直,不再呈水平面.直地脚螺栓与立柱坡度一致,倾斜锚固于立柱钢筋混凝土中.介绍了此类新型铁塔基础的特点,并详述其异形立柱模板、不等长柱主筋、找正测量等计算要点及基础施工技术控制难点,可为广大技术人员提供参考方案.     

热非平衡效应下蒸发或冷凝剪切液膜流的非稳定性

热非平衡效应下的液体薄膜流在相变和剪切力耦合作用下,气液交界面处的边界条件更为复杂,在一定程度上影响着液膜流动的非稳定性。通过建立热非平衡效应和剪切力耦合作用的液膜流动控制模型,得到扰动增长率与热非平衡效应、相变强度、剪切力、雷诺数和倾角间的理论表达式,探讨了不同因素对流动非稳定性的影响规律。研究表明,界面蒸发状态所引起的扰动将加剧流动非稳定性,而冷凝状态减缓其非稳定性;热非平衡效应及其相变强度的影响在小雷诺数下较为明显,随雷诺数增加,其影响逐渐减弱。扰动增长率随倾角呈单峰曲线变化,垂直液膜处于最不稳定状态,而水平流液膜最有利于减小流动的非稳定性;正向剪切力使表面波非稳定性增强,反向剪切力使其非稳定性减弱。     

Modeling steam condensation from steam-air mixture in the inclined tubes of an air-cooled condenser

Specific features pertinent to the flow of steam-gas mixture are discussed as applied to the inclined tubes of air-cooled condensers used in steam turbine units, and the condensate film annular flow and “streamlet” models are analyzed. The calculated results are compared with the data obtained by other researchers. It is shown that with relatively small flow rates of steam-gas mixture typical for air-cooled condensers, the restoration of pressure along the channel may exceed the losses connected with hydraulic resistance. Data on the influence of cooling air temperature on the condensation process are also presented.     

Condensation heat transfer of pure steam and steam from gas–steam mixture in tubes of AES-2006 PHRS SG heat exchanger

Results of experimental determination of the average heat transfer coefficient upon condensation of pure steam α_c and steam from air–steam mixture α_as.m in tubes of a large-scale model of the emergency cooling heat exchanger in the system of passive heat removal through steam generators of AES-2006 project at Leningrad II NPP are presented. The model contained 16 parallel tubes with a diameter of 16 × 2 mm and a length of 2.9 m connected to the upper steam distributing and lower condensate gathering horizontal collectors; the distance between their axes was 2.28 m. The tube segments were vertical, horizontal, or inclined. The internal diameter of the collectors was 40 or 60 mm. The model was placed in the lower part of a tank with a height of 6.5 m and a volume of 5.85 m³ filled with boiling water at atmospheric pressure. The experimental parameters were as follows: pressure range 0.43–7.77 MPa, condensate Reynolds number Re_f = (0.87–9.3) × 10³, and average air volume fraction at the segment with air–steam mixture 0.18–0.85. The studies showed that nonuniformity of static pressure distribution along the steam-distributing collector strongly influences the reduction of α_c value (ejecting effect). The agreement between experimental and calculated according to statutory guidelines values of α_c for vertical tubes is achieved if the dynamic head of the steam flow at the input of the steam-distributing collector does not exceed 1 kPa. Equations for calculation of the diffusion heat transfer coefficient at steam condensation from the air–steam mixture α_as.m on the internal tube surface are proposed. In the considered conditions, air is completely displaced by steam flow from the upper to the lower part of the tubes. The boundary between these regions is characterized by an average reduced steam velocity through this cross section of 1.6 ± 0.4 m/s. Above the boundary cross section, it is recommended to calculate α_c. according to [1].     

Surface modifications of aligned carbon nanotube thin films by Argon‐ion sputtering

To use carbon nanotubes (CNTs) as anode material for the solid‐state thin‐film Li‐ion rechargeable battery, the tubes are preferred to be aligned perpendicular to a substrate and the CNT thin film to have a smooth surface. Using an Ar‐ion sputtering technique, we carried out the surface modifications of the CNT thin film prepared by the SiC surface decomposition method. In order to evaluate the surface modification, the surface and cross section of the modified CNT film were investigated by field‐emission scanning electron microscopy and atomic force microscopy. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Contrastive Observation of Solar Thermal and Photovoltaic Resource

Solar thermal and photovoltaic applications are the most widely used and the most successful way of commercial development in solar energy applications. Observation and assessment of solar thermal and photovoltaic resources are the basis and key of their large-scale development and utilization. Using the observational data carried out from Beijing southern suburbs observation station of China Meteorological Administration in summer of 2009, preliminary solar thermal and photovoltaic resources characteristics for different weather conditions, different angle and different directions are analyzed. The results show that: (1) In sunny, cloudy or rainy weather conditions, both of solar thermal and photovoltaic sensors daily irradiance have consistent change in trend. Solar thermal irradiance is larger than photovoltaic. Under sunny conditions, solar thermal global radiation has about 2.7% higher than the photovoltaic global radiation. Under cloudy weather conditions, solar thermal global radiation has about 3.9% higher than the photovoltaic. Under rainy weather conditions, solar thermal global radiation has about 20% higher than the photovoltaic. (2) For different inclined plane daily global radiation, southern latitude -15 °incline is the maximum and southern vertical surface is the minimum. The order from large to small is southern latitude-15 ° incline, southern latitude incline, southern latitude+15 °incline, horizontal surface and southern vertical surface. Southern latitude -15 °incline global radiation has about 41% higher than the southern vertical surface. (3) For different orientation vertical surface daily global radiation, southern vertical surface is the maximum and western vertical surface is the minimum, which eastern vertical surface is in the middle. Southern vertical surface global radiation has about 20% higher than the western vertical surface.     

火电厂锅炉管道金属内壁氧化膜的影响因素研究

研究给水加氧处理前后锅炉管壁金属氧化膜生成情况,以确定不同温度范围内金属氧化膜的主要影响因素。分析和比较了给水全挥发处理（AVT）工况和加氧处理（OT）工况下,省煤器和水冷壁管氧化膜的特点;通过试验台和现场研究数据,探讨了锅炉高温段氧化皮生成与剥离的成因。研究结果表明,纯水中加入的氧气使热力系统低温段（300 ℃以内）金属表面生成了具有保护作用的棕红色Fe₂O₃膜,这层 Fe₂O₃膜需要连续供氧维持其稳定性;锅炉高温段受热面中18铬系列奥氏体不锈钢氧化皮剥落原因较为复杂,温度和材料本身应是主要影响因素。     

连州发电厂1号凝汽器铜管点蚀原因分析

连州发电厂1号机组出现大量凝汽器铜管迅速腐蚀的现象。为查明腐蚀原因，对腐蚀产物和备品黄铜管内表面膜进行了成分分析和动态对比试验。从腐蚀产物的形貌和成分判断该腐蚀属于点蚀，通过备品黄铜管内表面膜成分分析和动态对比试验得出产生腐蚀的主要原因是铜管内存在残碳膜。最后对铜管点蚀的机理进行了探讨。     

动压支承力对立式屏蔽电泵的影响

本文就倾斜平面缝隙间的动压支承力对立式屏蔽电泵运行的影响以及如何确定平面缝隙间的动压支承力等问题作了较为详细的探讨与研究.对判断屏蔽电泵的止推轴承是否安全运行具有一定的指导意义.     

Specific features pertinent to calculation of a condenser with inclined tubes

Matters concerned with calculation of heat and mass transfer during steam condensation from steam-gas mixtures in a condenser with inclined tubes used in production of sulfate-cellulose for recovering heat and chemical agents are discussed.     

高温运行后T91钢过热器管蒸汽侧氧化膜微观结构与形成机理

对运行85 000h后的T91钢过热器管内壁氧化膜的组织结构和微区成分等特征进行了分析,并讨论其形成机理。分析表明,氧化膜与金属基体间存在一过渡区,过渡区内Cr元素被O氧化,Fe元素向外层扩散而流失,造成该区域Fe浓度下降而Cr浓度相对升高;氧化膜为双层结构,其分界面为原金属表面,外氧化层富含Fe元素而不含Cr元素,主要成分为Fe3O4,内氧化层则由(Fe,Cr)3O4组成。     

Mathematical simulation of the heating of a viscous liquid droplet spreading over a horizontally oriented cylindrical pipe

Liquid film generated during steam condensation in a bundle of horizontal tubes flows down under the effect of surface forces in the form of separate droplets and streams. A mathematical model for nonisothermal spreading of a viscous liquid droplet over a horizontal surface is developed, using which it is possible to determine the temperature field and shape of such liquid droplet.     

斜掏挖与直掏挖斜插角钢基础性能对比

为了对比斜掏挖基础和直掏挖斜插角钢基础,设计了4个单腿试验基础。从基础位移、地基土压力、钢筋应力分布及经济性方面对比了2种基础。试验表明,相同尺寸的斜掏挖和直掏挖斜插角钢基础,虽然其抗拔承载力大体相同,但基础受力分布不同。斜掏挖基础相比直掏挖斜插角钢基础具有优越性。     

火电厂凝汽器铜管硫酸亚铁成膜质量保证体系

针对传统硫酸亚铁成膜工艺中存在的问题，经过试验研究，摸索出一套系统科学的成膜质量保证体系，即将成膜的全吩为三个紧密联系的阶段：成膜系统设计和铜管表面预处理、成膜工艺条件控制及成膜后膜质评价，并提出了各阶段的控制指标。工业机组的实践表明，这一方法是行之有效的，     

Theoretical and experimental validation of evacuated tubes directly coupled with solar still

Experimental study of evacuated tubes coupled solar still in the climatic conditions of Mehsana, a region of North Gujarat, India during summer and winter climate conditions has been made. Experimental setup was made by authors. Fourteen double-walled hard borosilicate glass tubes have been used. Evacuated tubes were inclined at angle of 45° from horizontal. Outer tubes of evacuated tubes were transparent, inner tubes were coated with a selective coating of Al-Ni/Al compound for better solar radiation absorption and minimum emittance. It has been shown that evacuated tube attachments to the solar still increased the water temperature inside the solar still for increment in the generation of distillate output. Evacuated tubes coupled solar still is not only produce distilled water during sunshine hours, but also off-sunshine hours due to heat storage effect. For the validation of the experimental results, a theoretical model is proposed based on the fundamentals of heat and mass transfer equations for solar still glass cover, water in basin and basin bottom. Two main statistical parameters—root mean square error and mean bias error—were calculated to compare the results of experiments and theoretical analysis. Closed matching of the experimental and theoretical results has been found.     

切应力下液膜线性稳定性分析

沿倾斜壁面下降的薄液膜表面受气流剪切力的影响产生波动，液膜表面的波动特性和力平衡关系基于液膜表面的力平衡方程和边界条件，建立了在切应力作用下表征沿倾斜壁面下降液膜流动特性的O-S方程。结合切应力作用下液膜的流动状态，分析了表面波扰动在初发时刻的不稳定性，并着重描述引发不稳定性的各种物理原因。研究表明：表面张力和重力的横向分量为稳定性因素，重力的纵向分量为不稳定性因素。切应力对表面波的稳定性作用与气流方向和液膜的流动状态相关。     

凝汽器铜管腐蚀原因分析及处理

荆门热电厂4号机凝汽器铜管在大修检查中发现甲、乙、丙三侧水进口端100mm左右管段有不均匀的铜基体裸露腐蚀,部分铜管中部也发生沉积物下腐蚀。在运行1年后的临检中发现,在大修中更换的新铜管进口端又发生了相同的腐蚀。经过对材质、水质、运行方式等试验研究,调整硫酸亚铁成膜处理、循环水加药处理,在铜管表面形成了较好的保护膜,控制了铜管腐蚀。