螺旋翅片管省煤器抗磨性能的研究及实验验证

具体分析了省煤器结构的设计方法,并进行了电厂实验.分析了翅片几何参数选取的不同对抗磨性能与换热的影响;此外,还研究交错排列情形下,横向节距的选取原则,以及不同的横向节距对每列翅片管磨损程度的差异.     

圆形翅片管换热器在余热回收中流动与传热特性

对一台用于烟气余热回收的圆形翅片管换热器进行结构分析,在实测数据的基础上,采用数值仿真模型对该换热器翅片间流体进行三维模拟研究,分析换热器的流场特性,包括翅片间气体流速、温度分布、压力损失、传热负荷等。结果表明在Re为8 300时,模拟的压差与理论计算基本吻合,且有翅片截面的烟气压力损失比不含翅片截面压力损失大7.7%,同时对不同高度的翅片对换热特性的影响做了模拟,为圆形翅片管换热器在余热回收的应用提供理论依据。     

螺旋翅片管束传热和阻力特性的试验研究

对13个不同翅片间距、翅片高度、横向管间距、纵向管间距的螺旋翅片管束换热器在不同雷诺数条件下的传热和阻力特性进行了试验研究,得出了翅片间距、翅片高度、横向管间距、纵向管间距及雷诺数与换热特性Nu和阻力特性Eu的准则关系式,并对准则关系式进行了分析.结果表明:随着横向管间距和翅片间距的增大,螺旋翅片管的传热得到强化,但随着纵向管间距和翅片高度的增加,螺旋翅片管的传热有所减弱;随着横向管间距、纵向管间距和翅片间距的增大,螺旋翅片管的阻力减少,但随着翅片高度的增加,螺旋翅片管的阻力增加.     

单向开缝翅片管换热器传热与阻力性能的数值模拟及试验研究

对一种单向开缝翅片管换热器进行了数值模拟及试验研究,分析了不同翅片间距及管径下单向开缝翅片管换热器的传热与阻力性能的变化规律。数值模拟和试验结果的对比表明,采用数值模拟方法研究单向开缝翅片管换热器的传热与阻力性能是可行的。     

管间距对开缝翅片管换热器传热与阻力特性的影响

为了获得管间距对开缝翅片管换热器传热与阻力特性的影响规律,对5种不同翅片管换热器进行了数值模拟研究,并进行了模化试验验证。结果表明:开缝翅片管束的传热和阻力特性与翅片侧气体的Re数有关,随着Re数增大,翅片侧Nu数增大,摩擦因子f逐渐减小;纵向间距S2对开缝翅片管换热器的综合流动传热性能的影响较大。数值模拟与试验结果偏差较小,采用数值模拟方法能够比较准确地分析开缝翅片管换热器的传热与阻力特性。     

H型翅片椭圆管低低温省煤器换热与阻力特性研究

为满足燃煤电站节能减排要求,不同型式的翅片管省煤器已广泛应用于新建或在役的电站锅炉中。椭圆管的流线型外形使椭圆管的传热与阻力性能以及防积灰和磨损性能比圆管更佳,为此,对适用于低低温省煤器的不同结构H型翅片椭圆管束的换热与阻力特性进行了模化试验,并与应用于燃煤电站锅炉省煤器的H型翅片圆管束性能进行了比较和分析。结果表明:H型翅片椭圆管束具有明显的优势,值得在低低温省煤器中推广应用。     

开缝布置方式对开缝翅片管换热器 传热与阻力特性的影响

为了获得开缝布置方式对开缝翅片管换热器传热与阻力特性的影响规律,对5种不同翅片管换热器进行了数值模拟研究,并进行了模化试验验证。结果表明：增加开缝会提高翅片管换热器的传热性能,但阻力也随之增加;与开缝位置相比,开缝数量对开缝翅片管换热器传热与阻力特性的影响更大;在Re=4800~7500日时,开缝翅片管换热器综合流动传热性能 随着Re数的增大而增大;在5种翅片中,开缝翅片的综合流动传热性能高于普通平直翅片;数值模拟与试验结果偏差较小,采用数值模拟方法能够比较准确地分析开缝翅片管换热器的传热与阻力特性。     

连续型与锯齿型螺旋翅片管翅片效率计算与分析

介绍了烟气换热领域常用的两类高频焊钢质螺旋翅片管.指出目前存在多种连续型与锯齿型高频焊螺旋翅片管翅片效率计算方法,不便于同类换热实验结果的相互比较.通过深入分析与计算比较,对连续型与锯齿型高频焊螺旋翅片管分别给出了建议的翅片效率计算方法,供相关的工程设计及实验研究选用.两种管型的翅片效率比较表明,锯齿翅片的翅片效率较高,提高的幅度随翅片高度增大而增大.     

带短肋翅片管的强化传热机理研究

同时对普通翅片管和带有两个短肋的翅片管在均匀流场中、不同雷诺数下进行了流场和传热的数值模拟,分析了带有短肋的翅片管强化传热的机理。结果表明,由于翅片上带有的短肋和短肋后面的开孔,减少了翅片管管后流动的死滞区,提高了局部地区流体的流速,增加了扰动,从而起到了强化传热的作用。取入口雷诺数为20000时,加装短肋后可使总传热量增加5.1%,平均表面传热系数增加23.56%。随着雷诺数的增加,总换热量增加,强化传热效果也增强。     

空冷散热器换热特性的数值研究

通过数值模拟的方法对椭圆翅片管和圆形翅片管进行了模拟,得出了在低速风情况下椭圆翅片管和圆形翅片管的流场分布情况,并经过流场分析和理论推导得出了椭圆翅片管散热效果要优于圆翅片管的结论;对9个不同长宽比的椭圆翅片管散热性能进行了对比研究得出了最佳长宽比的概念。     

Visual study of flow patterns during condensation inside a microfin tube with different tube inclinations

In this paper, flow patterns and their transitions for refrigerant R-134a condensing in a microfin tube are visually observed and analyzed. The microfin tube has been provided with different tube inclination angles of the direction of fluid flow from horizontal, α. The experiments were performed for seven different tube inclinations, α, in a range of − 90° to + 90° and refrigerant mass velocities in a range of 53 to 212 kg/m²s for each tube inclination angle during condensation of R-134a vapor. From analysis of acquired data, it was found that the tube inclination strongly influenced the vapor and condensate liquid distribution. Annular flow was the dominant flow pattern for vertical downward flow, α = − 90°. Annular flow, semi annular flow and stratified flow were observed for α = − 60°and − 30°. Annular flow, wavy-annular flow and stratified-wavy flow exist in sequence for horizontal tube. Annular flow and wavy-annular flow were observed for α = + 30°and + 60°. Annular flow, annular-wavy flow, churn flow and slug flow occurred for α = + 90°.     

锅炉受热面管屏飞灰磨损问题分析

本文依据实际设计经验和磨损机理提出了防止受热面管子磨损的方法,引用了管壁表面磨损量的计算公式,依据给出的理论公式,提出了电站锅炉在实际运行过程中影响磨损量的几点主要因素,并提出了减少磨损量的若干种方法。在本文的最后提出了锅炉受热面管屏防磨问题在电厂实际运行中的重要性。     

循环流化床锅炉在热电联产中的应用及运行中存在的问题

通过对循环流化床锅炉运行中存在的返料器工作异常和磨损方面问题的分析、处理，提出了循环流化床锅炉炉膛水冷壁管磨损机理和防磨措施，并针对国产循环流化床锅炉提出了几个预防磨损的值得注意的问题，对循环流化床锅炉在设计上改进和运行中加强管理起到一定的帮助。     

横掠不同型式光滑管束流动的热力学分析和比较

对横掠不同型式光滑管束的流动进行了热力学分析，在熵产分析的基础上对不同型式的光滑管比较了它们热力学性能的优劣，总结发现了一些规律性的结论，对于横掠光滑管束的优化设计具有重要的指导意义。     

三叶膨胀管换热器壳程强化传热的数值研究

三叶膨胀管是一种新型强化传热管,针对纵向流换热器特点,设计了三种不同管束结构参数的三叶膨胀管自支撑纵向流换热器。应用FLUENT软件及Realizable k-ε湍流模型,对三种不同结构参数的三叶膨胀管换热器壳程强化传热特性展开了数值模拟,并通过与实验数据的对比,验证了计算模型的可靠性。计算了不同壳程介质流速下,三叶膨胀管换热器壳程的换热系数与压降值,并获得了壳程流体流线以及相应的温度场、速度场和二次流分布图。结果发现,在壳程水流速一致的情况下,管束横向间距越大的三叶膨胀管换热器,壳程拥有更高的综合换热性能和更低的压降值,但相应地,换热系数也更低。流场分析显示,壳程流体流线呈现出三维纵向旋流形态,二次流的出现改变了速度场和温度场分布,二次流的强度随着管束横向间距的减小而增大。     

A study on the gas-solid particle flows in a needle-free drug delivery device

Different systems have been used over the years to deliver drug particles to the human skin for pharmaceutical effect. Research has been done to improve the performance and flexibility of these systems. In recent years a unique system called the transdermal drug delivery has been developed. Transdermal drug delivery opened a new door in the field of drug delivery as it is more flexible and offers better performance than the conventional systems. The principle of this system is to accelerate drug particles with a high speed gas flow. Among different transdermal drug delivery systems we will concentrate on the contour shock tube system in this paper. A contoured shock tube is consists of a rupture chamber, a shock tube and a supersonic nozzle section. The drug particles are retained between a set of bursting diaphragm. When the diaphragm is ruptured at a certain pressure, a high speed unsteady flow is initiated through the shock tube which accelerates the particles. Computational fluid dynamics is used to simulate and analyze the flow field. The DPM (discrete phase method) is used to model the particle flow. As an unsteady flow is initiated though the shock tube the drag correlation proposed by Igra et al is used other than the standard drag correlation. The particle velocities at different sections including the nozzle exit are investigated under different operating conditions. Static pressure histories in different sections in the shock tube are investigated to analyze the flow field. The important aspects of the gas and particle dynamics in the shock tube are discussed and analyzed in details.     

Forced convective boiling in horizontal tube bundles

Experimental studies of crossflow boiling on a horizontal tube at various in Mass fluxes, local flow qualities and geometric arrangements are investigated. Since abundant information is available for the boiling on a single tube in a pool but it is still not clear whether this information in ay be applicable to tubes in bundles, the present study is therefore performed on three different conditions, namely: (1) a heated tube in a channel; (2) a heated tube in a non-heated, in-line tube bundle; and (3) a heated tube in a heated, in-line tube bundle. The different heat transfer results between a single tube in a channel and a tube in a non-heated bundle, and between a non-heated bundle and a heated bundle are discussed in terms of the different flow field geometry and thermal environment respectively due to the presence of different structures and the heating conditions near the tube. A modified Chen's correlation is established to predict the heat transfer of a single tube in a channel or in a bundle. The correlation is also in good agreement with other data in the literature.     

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.     

Local resistance of fluid flow across sudden contraction in small channels

The pressure drop caused by flow area contraction in microchannels has been experimentally studied in this paper using the tiny gap pressure measurement method. The working fluid was deionized water at room temperature at near-atmospheric pressure. Three test sections with area ratios of 0.284 and 0.274 and at different tube diameter sizes were used. The experimental results show that the abrupt contraction coefficient K_c decreases with the Reynolds number increasing, and it is much higher than that of conventional tubes in laminar flow. The widely-applied correlation K_c=0.5(1−σ)^0.75 could not predict the contraction coefficient of turbulent flow in the micro tubes. The K_c decreases as the tube diameter increases. The transition from laminar to turbulent flow is not obvious when the diameter of the small tube is 0.32mm.