某电厂TP304不锈钢换热管裂纹分析

某电厂汽轮机汽封加热器的TP304换热管出现裂纹,对已泄漏的换热管取样分析,TP304不锈钢管的化学成分和力学性能都符合技术条件要求,有应力腐蚀倾向,裂纹附近有较大拉应力,裂口表面含有Cl离子和Na离子等腐蚀介质,TP304管是由于应力腐蚀引起的开裂。     

冷凝器铜翅片管泄漏原因分析

某冷水机组冷凝器在短时间使用后铜翅片管发生泄漏。通过现场的外观检查，并对管试样进行宏观、微观分析，以及对垢物的能谱和X射线衍射分析，结果表明：翅片管泄漏的原因是管内沉积物导致缝隙腐蚀引起的管材穿孔。     

TP347H不锈钢管表面裂纹的产生原因

在TP347H不锈钢大小头管生产过程中表面出现了环向裂纹;通过对钢管的化学成分、硬度、夹杂物、晶粒度、显微组织、裂纹处微观形貌和能谱微区成分等进行了分析,找出了裂纹产生的原因。结果表明:不锈钢管的表面裂纹是应力腐蚀裂纹;不锈钢管在成型过程中产生残余应力是裂纹产生的内因,在酸洗过程中带来的氯离子是裂纹产生的外因,晶界碳化铬的析出加剧了应力腐蚀开裂。     

制氧压缩机组中间冷却器不锈钢封头的开裂分析

通过无损检测、常规力学性能试验以及金相分析等手段对制氧压缩机组中间冷却器不锈钢封头的开裂失效进行分析。分析结果表明：该失效属于304不锈钢的应力腐蚀开裂。由于1级冷却器管的开裂泄漏而造成的高温氧气 含氯离子冷却水介质环境，封头一筒体对接环焊缝区域的残余应力以及封头一侧热影响区中的晶界碳化物析出是诱发应力腐蚀开裂的三个主要因素。     

换热器列管与管板焊接应力腐蚀裂纹的防治

对换热器列管与管板焊缝泄漏原因进行分析,提出控制产生腐蚀泄漏的相应措施,及检修过程中泄漏处理的方法。     

热电厂用凝汽器黄铜管的失效分析

通过对穿孔泄漏的凝汽器黄铜管进行化学成分分析 ,力学性能测试、金相检验及扫描电镜能谱分析。结果表明 ,黄铜管穿孔泄漏主要是由于在冷却水介质作用下产生点状脱锌腐蚀所致 ,并提出了改进措施     

蜡油加氢装置主汽提塔腐蚀泄漏原因分析及预防

某公司蜡油加氢装置主汽提塔在运行期间发生塔壁腐蚀穿孔泄漏,腐蚀穿孔部位为汽提塔进料段下方塔壁,为检查塔内腐蚀情况,研究腐蚀原因,对装置进行停工检修。对汽提塔进行检修后发现,腐蚀严重部位呈阶梯状分布,进料分布管腐蚀穿孔,汽提塔第9～11层塔盘和连接件均发生严重腐蚀,塔壁表面不平整,有大面积白色、绿色或褐色沉积物覆盖。使用晶相分析、物相分析等方法对腐蚀样本进行分析,并结合塔内物料、温度等参数,判断塔内发生的腐蚀类型为氯化铵垢下腐蚀和湿硫化氢腐蚀。采用修正工艺参数、腐蚀部位修复、内件材质升级等方法,可有效减少塔内腐蚀情况发生,保证装置安全生产。     

重整装置双相不锈钢换热器腐蚀泄漏原因分析

某石化企业重整装置再生循环干燥系统S22053双相钢换热器换热管发生泄漏，堵管率达到64%,导致换热器失效。通过对泄漏换热器宏观观察，并对取样采用化学成分分析、金相分析、腐蚀坑形貌观察、能谱分析等表征手段，结合壳程入口处再生气露点温度计算、温度场数值模拟进行失效分析。结果表明：重整装置双相不锈钢换热器的失效原因为壳程侧的盐酸腐蚀。产生盐酸腐蚀的主要原因是壳程介质中水蒸气含量大于1.1%和氯化物含量偏高，在操作工况具有水蒸气结露的条件，继而形成盐酸液滴。双相钢换热管在pH值小于5的盐酸中发生严重的选择性腐蚀，最终导致换热管腐蚀穿孔泄漏。     

热电厂用凝汽器黄铜管的失效分析

通过对穿孔泄漏的凝汽器黄铜管进行化学成分分析，力学性能测试，金相检测及扫描电镜能谱分析。结果表明，黄铜管穿孔泄漏主要是由于在冷却水介质作用下产生点状脱锌腐蚀所致，并提出了改进措施。     

余热锅炉腐蚀机理及影响因素分析

首先分析腐蚀形成机理,然后从高温腐蚀和低温腐蚀两个方面对余热锅炉腐蚀的影响因素进行分析,最后针对这些因素给出减轻腐蚀的实施方法:选择合理的排烟温度和烟风流速比减少低温腐蚀;管表面可采用多种方法来增强耐腐蚀性能;降低烟气循环系统中O2、S等有害成分的含量;改善水质、减少溶解氧与Fe3+离子的含量;清除管内壁的污垢和锈蚀,提高管子的传热效率;按照作业要求,对锅炉进行水压、检修等施工,以确保质量。     

A numerical study on the conjugate natural convection in a circular pipe containing water

In this paper, the effect of material property of pipe on the conjugate natural convection in a circular pipe containing water was investigated by solving the unsteady incompressible Navier-Stokes equations coupled with energy equations of the water and pipe. Natural convection and conduction of water inside the pipe was coupled with the conduction of the pipe whose bottom was subject to uniform heat source. From the present grid resolution and time-step independent solutions, it has been confirmed that the water temperature inside a PVC pipe was higher than that inside a steel pipe due to the smaller heat capacity of PVC and that the streamline patterns of the two cases were found to be opposite because the thermal diffusivity of steel (PVC) is larger (smaller) than that of water such that steel (PVC) pipe is heated faster (slower) than water. Furthermore, a quantitative comparison of heat flux to water was performed by examining the distributions of the heat flux along the inside walls of steel/PVC. The average temperature of water inside steel was found to be higher than that inside PVC at the initial stage of heating. On the other hand, PVC provided a larger heat flux to water when it reached a steady value.     

Numerical investigation on the melting of circular finned PCM system using CFD & full factorial design

Heat energy storage equipment has the advantages of highly efficient energy storage performance and constant temperature owing to its adoption of Phase change material (PCM); however, its shortcoming is that it takes longer to complete thermal energy storage due to its low thermal conductivity. New technologies are being developed to overcome such shortcomings, including technology that would improve the heat transfer. This study is aimed at analyzing the impact on the energy storage time of the PCM via the Design of experiments (DOE) method and with changes to the following variables: The number of installed fins; the employed material (thermal conductivity); and the temperature of the supplied warm water, all by relying on Computational fluid dynamics (CFD). The PCM system is in the shape of a long vertical cylinder, with circular fins. The number of installed circular fins was one or five, the material used in the pipe and circular fins was changed from iron to copper, and the temperature of the warm water was 309.15 or 313.15 K. The thermal conductivity of each material employed for the CFD was 80.2 or 401.0 W/m-K. The DOE analysis was also performed to check for any curvature effect by adding a center point. The PCM used in this study is n-Octadecane 99% (CH₃(CH₂)16CH₃) with its melting temperature being roughly 300.85 K. To sum up the conclusions of this study, the change in the number of installed circular fins and the temperature of supplied warm water have a substantial influence on the melting of the PCM. The change in the thermal conductivity of the pipe and circular fins has only a meager influence on the melting of the PCM. To reduce the melting time of the PCM most effectively, it is recommended to install as many circular fins as possible and to raise the temperature of the supplied warm water. This may be related to the fact that the melting of the PCM is influenced more by convection inside the PCM system rather than conduction.

     

Heat dissipation in high-power semiconductor lasers with heat pipe cooling system

This study focuses on the application of heat pipes in thermal management for high-power semiconductor lasers. The heat pipe cooling systems are used for heat dissipation in high-power semiconductor lasers. These systems are used instead of water cooling machines to realize a compact and lightweight laser module. The n-shaped heat pipe cooling system, which consists of eight 6 mm copper heat pipes with sintered powder wicks, can easily handle a heat load of up to 73 W from a single-laser unit. The fabricated U-shaped heat pipe cooling system, which consists of ten 12 mm copper heat pipes with sintered powder wicks, can easily handle a heat load of up to 300 W from five laser units. The optical power of the multi-laser module cooled by the U-shaped heat pipe cooling system reaches 210 W. These results indicate that high-power semiconductor lasers can be cooled using heat pipe cooling systems instead of water cooling machines.     

Experiments on thermal stratification in inlet nozzle of steam generator

Nuclear power plant components suffer pipe shedding, cracking, thermal fatigue, bending and supporting bracket breakage during their life span. Notably, the horizontal inlet nozzle of steam generator is prone to thermal stratification frequently due to its operational characteristics. As a result, PWRs in many countries including the U.S.A. suffered a lot of pipe cracks and leakages around the late 1970s, as the thermal stress inflicted by thermal stratification formed in the horizontal inlet nozzle of steam generator during transition (auxiliary feedwater injection) was not reflected on power plant design. Therefore, we classified the nuclear power plants in Korea into KSNP and Westinghouse-type(W) power plants (Kori # 1,2,3,4, Yeonggwang # 1,2 and Uljin # 1,2) and conducted an experiment on thermal stratification and thermal cycling in relation to the volume of auxiliary feedwater injected into the horizontal inlet nozzle of steam generator and hot water flowing back from steam generator. As a result, it was found out that KSNP was hardly prone to thermal stratification while thermal stratification occurred in the horizontal inlet nozzle of steam generator in Westinghouse-tvpe(W) power plants, necessitating a solution to address such a phenomenon.••     

Thermal analysis of heat pipe shell-fin structures with selective coatings under radiation

The purpose of this study is to investigate the thermal response of a heat pipe shell-fin structure that is selectively coated and is subject to uneven radiation from upper and lower sides. Such a structure would arise when fins are attached to opposing sides of the condenser or evaporator section of heat pipes to enhance the heat transfer performance. Typical examples include radiators for space applications and solar energy collectors for water heating. The temperature distribution in the circumferential direction of the heat pipe shell as well as that in the fin is examined via theoretical modeling and numerical analysis. The model accounts for the effects of selective coatings. Both steady-state and transient solution procedures are presented. Examination of the steady-state results justifies the use of a thermally-lumped formulation for the heat pipe shell region. The effect of fin width is investigated as a typical design variable. The fin efficiency and the collector efficiency are also presented as functions of heat pipe operating temperature and fin widith. The influence of the surface properties on the thermal performance of the heat pipe shell-fin structure are also examined.     

油加氢换热器腐蚀失效分析

某柴油加氢换热器发生腐蚀,为了找到腐蚀发生的原因,对腐蚀产物、油品、综合全面进行了分析,通过分析研究发现,该设备空放,引起点蚀严重,并且壳体下部冷凝水比上部要多得多,故壳体底部腐蚀比上部严重：另外,由于管材材质316不锈钢比壳体347不锈钢材质多含2．5％Mo,故管材比壳体抗点蚀性能大为改善,腐蚀轻。论文最后分析了设备继续运行可能存在的风险,并就此提出了一些建议。     

热管导热板当量导热系数研究

对用于高热流密度分布式点热源的散热的预埋热管铝基导热板进行了传热性能试验研究,结合模拟仿真,通过求解导热反问题的方法求得热管导热板的当量导热系数。研究结果表明,采用的热管导热板具有优良的热传导能力,当量导热系数随传输功率的增大而降低,当量导热系数范围为1 100～7 600 W/(m.K)。     

锅炉减温器构件开裂分析

本文对某锅炉减温器进出水管两个部位的开裂进行了检测分析,认为开裂的原因是进出水管与减温器集箱内部构件焊接形成近乎刚性的结构,因升温产生的膨胀受到约束,过大的温差应力导致产生过量的变形及开裂。     

139.7mm加重钻杆外螺纹接头断裂原因分析

为查明某井139.7 mm加重钻杆外螺纹接头的断裂原因,对断口进行了宏观和微观分析,对材料进行了化学成分分析、力学性能试验和金相分析,并进行了有限元分析等。结果表明:加重钻杆断裂属于腐蚀疲劳断裂;断裂主要原因是加重钻杆接头内径大于标准规定值,降低了加重钻杆外螺纹接头断裂扭矩和抗拉载荷,在疲劳载荷与腐蚀介质作用下,腐蚀疲劳裂纹首先在加重钻杆外螺纹接头危险截面部位螺纹牙底萌生,随后在载荷作用下裂纹不断扩展,进一步降低了接头的强度,最终发生了断裂事故。     

Measurement of velocity of sand-containing Oil–Water two-phase flow with super high water holdup in horizontal small pipe based on thermal tracers

When oil fields enter the last production period, the water holdup in the well is extremely high. Chemical flooding and horizontal well technology are often used to enhance oil recovery. These techniques result in a high downhole fluid viscosity and serious sand production, which leads to the failure of common velocity measurements because of sticking sand, and yields new logging difficulties. This paper presents a method of the velocity measurement of sand-containing oil–water two-phase flow in a super high water holdup pipe diameter based on thermal tracers. The measurement accuracy of the thermal tracer velocity method is related closely to parameters that affect its performance. Parameter optimization is required to improve the measurement accuracy. ANSYS Fluent was used for a numerical simulation of the heat-source shape and material, thermistor probe installation position and fluid heating power, and the method was verified experimentally. The optimal parameters of the thermal tracer flowmeter were obtained by numerical simulation, the heat source material was aluminum and the shape was rectangular. The thermistor probe was located 160–220 mm from the heat source, and the pulse heating power was 350 W. The experiment results show that the accuracy of the thermal tracer flowmeter was 4%, the repeatability was 2.6%, and the measurement accuracy of the flow velocity was unaffected by water holdup and sand.