旋膜式除氧器传热传质特点及性能试验

介绍了旋膜式除氧器的主要结构和工作原理。对其主要除氧元件起膜管进行了冷态试验研究,根据试验情况分析了其传热传质特点。介绍了在某厂进行的旋膜式除氧器性能试验的主要数据,并据此评价了这种除氧器的实际除氧效果。     

旋膜式除氧器在电厂的应用

讨论了淋水盘式除氧器的缺点,介绍了旋膜式除氧器的制做方法,分析了旋膜式除氧器的除氧机理,并对其改进效果做了评估。     

热力除氧技术研究及其发展

水中溶解氧的存在是导致锅炉及汽轮机通汽部分设备腐蚀发生的重要原因,也影响给水系统以及整个热力系统的运行安全。随着高参数大容量发电机组的发展,对给水品质的要求不断提高。除氧技术也伴随着热力系统对除氧要求的提高而不断发展。热力除氧过程中加热蒸汽与除氧水之间传热传质过程的强化是确保和提高热力除氧器除氧性能的关键,也是热力除氧器结构改进与优化的基本原则。     

浅析大气式热力除氧效果不稳定的原因及其对策

工业锅炉热力系统中氧化腐蚀极大地危害了锅炉的安全和寿命。针对目前工业锅炉水处理使用大气式热力除氧器存在除氧效果不稳定的原因介绍了部分节能型地解决此问题的对策，其意为既解决了除氧效果的问题，又推广了节能新技术。     

低位真空除氧与热力除氧器

一、前言 锅炉设备和以水为工质的热交换器的氧腐蚀问题已引起人们的重视。一些小型工业锅炉运行表明,由于未采取除氧措施,往往运行三至五年,有的只运行一至两午,锅炉内壁就出现较严重的氧腐蚀。如河南省新乡树脂厂一台6.5t/h锅炉,使用两年汽包点状腐蚀多处,每处面积约80cm~2,深6～7mm。另有很多锅炉水冷壁部位运行两三年就被腐蚀穿孔。在吸收低温余热的加热器中使用未除氧水对设备腐蚀也很严重。     

热力除氧系统的计算机控制

介绍了某炼油厂除氧系统计算机控制系统的结构组成、控制功能和特点,设计了耦合系统的模糊控制叙述了压力和水位的控制方案和控制软件,该系统投入运行以来,效果良好。     

不用水蒸气的大气式热力除氧

节能在国际上已被认为是继煤炭、石油、水力和核能之后的第五能源。我国制定了开发与节约并重的正确的能源政策。据统计,我国目前的能源利用率平均约为30％,约70％的能源在热功转换及其他过程中以各种形式损失掉,这其中有相当大部分是可以回收利用的。随着能源供需矛盾的加剧和节能工作的深入开展,高、中温位的余热大多得到利用,要想在节能方面取得进一步进展,只有开发利用低温余热。因此,低温热的利用越来越受到人们的重视。     

低位热力除氧器的技术优势

在锅炉给水处理工艺过程中,除氧是一个非常关键的一个环节。热力除氧技术是一种普遍采用的成熟技术,本文对比了高位除氧与低位除氧的优缺点指出了低位除氧器的低位、高效、低汽耗、自动化程度高的技术优势。     

An application of thermal microscopes to the measurement of thermal effusivity of films

The application of thermal microscopes to the measurement of local thermal properties has drawn considerable scientific interest. We report on the application of a thermal microscope to the measurement of thermal effusivity for films comprising alumina deposited on a substrate, which were fabricated by an electrophoretic deposition method. The measured data was analyzed to consider the undulations on the sample surface The thermal effusivity of these samples was approximately 1×10³ Js^?0.5m^?2K^?1; this value is smaller than that for dense alumina because the alumina grain makes contact with a point. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20227     

The effects of thermal non-equilibrium and inlet temperature on two-phase flow pressure drop type instabilities in an upflow boiling system

In this paper a theoretical model for the two-phase flow pressure drop type instabilities in an upflow boiling system is presented. The thermal non-equilibrium effect between the two phases is included assuming the enthalpy profile in the subcooled boiling region. The system of differential equations describing the single-phase and boiling regions of the system (drift-flux model) is solved using finite difference method for the steady state characteristics of the system over a wide range of operating conditions. Upon obtaining the steady state characteristics, the dynamic formulation of the pressure drop type oscillation is solved numerically. The modeling results are verified by the experimental findings. The effect of the thermal non-equilibrium on the steady state characteristics, stability boundaries and oscillation periods at different heat inputs and inlet temperatures are presented as being compared with the experimental measurements as well as the results obtained from the thermal equilibrium model.     

Review on effective thermal conductivity of bubble type porous media

多孔介质内部结构中发生的质量,动量,能量的传递是众多自然现象和生产,生活领域中发生的基本过程.有关多孔介质中的传热问题涉及许多科学领域,早就引起人们的广泛关注,研究人员也对其进行了长期的研究.等效导热系数方法即将多孔介质视为一种连续介质,将实际多孔介质中固体骨架与各种流体的传热模式(导热,对流,辐射)折合成一个综合的传热问题.此方法已成为研究多孔介质内部传热问题最常用的方法.最近一二十年,泡沫型多孔介质(如泡沫金属,泡沫碳等)的出现引起人们广泛的关注.本文针对此种新型多孔介质等效导热系数的研究做了综述,介绍了3种常用的研究方法,分别是实验测试法,理论推导法及数值模拟法,探讨了各种研究方法存在的问题.实验测试法准确性高,但每种传热模式对等效导热系数的影响很难确定,且成本高;理论推导法虽然物理意义明确,适用性广,但与实测结果有较大的偏差,且有些方法还需与实验相结合;数值模拟法建模较复杂,但模拟结果与实验数据较接近.     

电厂除氧器运行中抽汽量为零原因分析与改进

除氧器运行中抽汽量为零是国内是民厂较为普遍的一种现象。本文结合具体实例分析了除氧器运行中抽汽量为零的原因,定量计算了除氧器运行中抽汽量为零对机组运动经济性的影响,并提出了相应的改进措施。     

An Experimental Study of the Drag Force on a Cylinder Exposed to an Argon Thermal Plasma Cross Flow

Experimental data are presented concerning the drag force on a cylinder exposed to an argon plasma cross flow with temperatures about 10~4 K and velocities about 10~2m/s. Using a method of sweeping a cylindrical probe across an argon plasma jet, the total drag force on the cylinder can be measured as a function of the lateral distance of cylindrical probe with respect to the plasma-jet axis. Through the Abel inversion, the drag force for per unit of cylinder length and thus the drag coefficient of cylinder have been measured under plasma conditions and compared with the values obtained from the standard drag curve of the cylinder in an isothermal flow. Experimental results show that the measured drag forces are always less than their counterparts read from the standard drag curve with the same Reynolds numbers based on the oncoming plasma properties. The drag force on the cylinder exoposed to a thermal plasma flow is shown to be approximately proportional to the square root of cylinder diameter in the present experiment and it increases slightly with increasing surface temperature of the cylinder. It is also shown that applying a voltage between the drag probe and the anode of the plasma jet generator has little effect on the drag force of cylinder under the experimental conditions. The drag force on a cylinder with finite length exposed to an argon plasma with the axis parallel to the plasma jet is independent of ratio of cylinder length to its dismeter L/d for the cases when L/d≤1.     

Dropwise condensation heat transfer of steam on a polytethefluoroethylene film

bouctionThe higher heat tranSfer phae due todroPwise condensation as cOmPared with filIncondensation had bo inveshgated extensively by manyresearchers durin the past sixty years["n. Grea PrOgI'esshad been Inade in understanding the IneCanisms fordroPwise condensation pessP'q, However unscondensation mode had not been widely aPPlied toPIaedcal heat exchanger devices due tO the crucialProblem of han an effeChve method formanhaurin the bopwise condensation sbos.ReCetly, the successful aP…     

基于蒸汽喷射式热泵的火电厂除氧器乏汽回收系统热经济性分析

针对火电厂汽轮机回热系统中的工质损失和热损失,以某电厂600MW机组为例,对采用蒸汽喷射式热泵将除氧器乏汽回收到低压加热器中的节能技术进行研究,利用等效焓降法对各个节能方案的热经济性指标进行了计算,并对不同节能方案的热经济性进行了比较.结果表明:除氧器乏汽通过蒸汽喷射式热泵回收到5号低压加热器(方案4)的节能效果最显著,经济效益最好.与原方案相比,采用方案4,每发1度电平均可以节约标准煤0.3g,按机组年运行5 500h计算,每年可以节约标准煤990t.     

On the feasibility of colored glazed thermal solar collectors based on thin film interference filters

Glazed thermal solar collectors, typically equipped with black, optical selective absorber sheets, exhibit good energy conversion efficiency. However, the black color, and sometimes the visibility of tubes and corrugations of the metal sheets, limit the architectural integration into buildings. In order to overcome this drawback, interference filters are considered as a promising approach. Multilayered thin film stacks deposited on the cover glass can produce a colored reflection hiding the black absorber without a great loss of energy. These interference filters are designed and optimized by numerical simulation. Such coatings are deposited by vacuum processes (e.g. magnetron sputtering) and also via the SolGel method. Optical measurements, such as real-time laser-reflectometry and spectrophotometry, are suitable to determine film thicknesses and optical constants of individual layers, and to measure color coordinates and solar transmittance for the multilayer stacks. Advantages and disadvantages of the different coating processes are discussed.     

Recommendations for the market introduction of solar thermal power stations

Until 2010, solar thermal power stations based on parabolic trough concentrating collectors can become a competitive option on the world's electricity market, if the market extension of this mature technology is supported by a concerted, long-term programme capable of bundling the forces of industry, finance, insurance and politics. Technical improvements based on the experience of over ten years of successful operation, series production and economies of scale will lead to a further cost reduction of 50% and to electricity costs of 0.06 - 0.04 US$/kWh for hybrid steam cycles and hybrid combined cycles, respectively. Until 2010, a capacity of 7 GW will be installed, avoiding 16 million tons of carbon dioxide per year. The programme comprises an investment of 16 billion US$ and requires external funding of 6%.     

Theoretical analysis of the stability of vapor film in subcooled film boiling on a horizontal wire

Linear stability analysis of a thin vapor film in subcooled film boiling on a horizontal cylinder is reported. The effects of liquid inertia, vapor viscosity and compressibility, and heat transfer were taken into account. Theoretical predictions of the heat transfer coefficient at the neutral stability point were compared with experimental data at the minimum-heat-flux point that was obtained during rapid quenching of thin horizontal wires in water and ethanol. At high liquid subcooling, the experimental value was 60% of the theoretical prediction irrespective of the wire diameter and quenching liquid. This difference was considered to be due to the nonuniformity of the vapor film which was neglected in the theoretical analysis. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(4): 219–235, 1997