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联合循环电厂的汽轮机不采用抽汽回热系统,为了减小厂房高度、便于布置,通常将汽轮机设计成侧向排汽或轴向排汽形式,凝汽器也相应布置在与汽轮机高度相同的地面位置上。侧向布置凝汽器中的汽相流动与传热物理模型、传热系数的确定方法以及管束布置要求与常用的下挂式凝汽器有较大差别。国内制造厂家没有开展相关设计制造工作,也无此类凝汽器的设计手段和制造经验。开展侧向布置凝汽器汽相流动与传热特性的研究和产品开发工作,具有一定的学术意义和工程应用价值。
通过对国外A公司侧向布置凝汽器汽相流动与传热特性的数值计算与分析,提出了侧向布置双流程凝汽器汽相流动与传热特性的因素;提出了结构优化方案,并验证了结构优化方案的通用性,对今后开展侧向布置凝汽器的研发具有一定的指导作用。 相似文献
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潍坊电厂330MW机组的凝汽器改造前存在着真空低和水质变差导致铜管泄漏趋势加重的现象,严重地影响了机组的经济性、安全性和带负荷能力。采用TEPEE两山峰形管束布置方式对凝汽器进行改造,利用数值模拟的方法计算了改造后凝汽器壳侧的汽相流动与传热特性,并用改造前后的性能试验结果进行了验证。模拟结果表明:改造后的TEPEE两山峰形管束布置方式有利于凝汽器壳侧蒸汽的流动与传热。性能试验结果表明:在设计冷却水进口温度、流量、凝汽器热负荷相同的条件下,改造后的凝汽器真空比改造前提高1.743kPa,端差下降4.63℃;凝汽器改造后,试验端差和修正后端差、修正后的凝汽器压力、循环水温升都达到设计指标。 相似文献
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大功率汽轮机凝汽器汽相流动与传热特性的数值分析 总被引:15,自引:9,他引:15
介绍凝汽器汽相流场与传热特性的数值计算方法及算例分析。该计算方法采用多孔介质模型,以分布阻力和分布质量汇分别模拟冷却管束区的蒸汽流动阻力和凝结效应,利用控制容积积分法及解压力耦合方程的半隐式方法数值求解控制方程组,得出汽相速度、温度、压力、空气浓度、传热系数及热负荷等重要参数的分布。经试验研究表明,该方法能较好地预测凝汽器的工作特性以及管束布置对汽相流场和传热特性的影响。图9参8。 相似文献
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双流程大型电站凝汽器的冷却水流径主要有上进下出和下进上出两种。利用自行开发的凝汽器工作性能数值模拟软件PPOC3.0模拟和分析了4台不同管束类型的双流程凝汽器在这两种不同冷却水流径情况下的热力性能。结果表明,对于从顶部进汽的大型电站凝汽器,采用上进下出的冷却水流径,可以减小凝汽器的汽阻和凝结水的过冷度,并且改善凝汽器水侧的水力特性。冷却水流径对凝汽器热负荷的影响与凝汽器具体的管束型式有关,将冷却水的第一流程安排在有抽气口和空冷区的管束部分,可以提高凝汽器的热负荷。 相似文献
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采用多孔介质物理概念对1台双流程凝汽器的汽相流动与传热特性进行了数值计算与分析,结果表明:在该冷凝器中存在着严重的不凝结性气体的积聚现象,从而导致了流动与传热特性的恶化。 相似文献
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改造前后凝汽器性能的数值模拟与分析 总被引:1,自引:0,他引:1
对某厂330 MW机组凝汽器改造前向心形管束布置和改造后TEPEE两山峰形管束布置的壳侧汽相流动与传热进行了数值模拟与比较.结果表明:改造前凝汽嚣结构设计不合理,上部管束得不到充分利用,导致凝汽器性能差;改造后TEPEE两山峰形管束布置使压降分布均匀,传热系数增大,更有利于凝汽器壳侧蒸汽的流动与传热.改造前后的性能试验结果表明:采用TEPEE两山峰形管束布置方式的凝汽器,其性能指标达到设计值,优于向心形管束布置方式;改造后凝汽器真空比改造前提高了1.743 kPa,端差下降4.63 K. 相似文献
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冷却水流速是影响凝汽器性能的主要因素之一,为了实现基于冷却水流速实际分布的凝汽器性能模拟,借鉴多孔介质的阻力源项加载思想提出了基于冷却管入口实体建模的凝汽器水侧流动计算模型,以某600MW火电机组的低压凝汽器为例,在设计工况下对该凝汽器水侧流动进行了数值模拟,获得了凝汽器水侧管束截面上的冷却水流速分布,并基于上述冷却水流速分布的模拟结果,分别数值计算了冷却水流速均匀分布和不均匀分布两种情况下凝汽器汽侧的蒸汽流动,获得了相应情况下的凝汽器性能。计算结果表明:对于本文研究的凝汽器,基于多孔介质模型和基于冷却管入口实体建模的凝汽器水侧流动模拟得到的管束截面上的冷却水流速分布在流动细节上存在差异;冷却水流速均匀分布和不均匀分布两种情况下获得的凝汽器性能有差异,凝汽器压力相差10.9Pa,总平均传热系数相差12.6W/(m2·K)。建议对于冷却水流速不均匀分布比较严重的情况,在研究凝汽器性能时考虑冷却水流速不均匀分布的影响。 相似文献
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火电站直接空冷凝汽器积灰是影响传热性能的重要因素,研究直接空冷凝汽器积灰对传热性能的影响规律并提出监测措施具有重要意义。通过分析汽轮机背压与汽轮机排汽量、冷却空气流量、凝汽器传热系数、凝汽器总传热面积以及环境温度之间的关系,得到了空冷凝汽器在维持汽轮机排汽量和冷却空气量不变时,汽轮机背压和传热系数之间的关系以及凝汽器积灰对汽轮机背压的影响。研究表明:凝汽器积灰会导致凝汽器传热系数降低,汽轮机背压升高,机组运行经济性下降。设计工况下,当蛇形翅片扁平管结构凝汽器积灰厚度达到1.2 mm时,汽轮机背压将增加50%左右。通过监测空冷机组运行过程中汽轮机背压的变化,可预报积灰的程度,为直接空冷凝汽器清洗提供一定的理论依据。 相似文献
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The effect of the cooling water flow path on the flow and heat transfer in a double tube-pass condenser for a 660 MW power plant unit was numerically investigated based on a porous medium model. The results were used to analyze the streamline, velocity, air mass fraction and heat transfer coefficient distributions. The simulations indicate that the cooling water flow path is important in large condensers. For the original tube arrangement, the heat transfer with the lower-upper cooling water flow path is better than that with the upper-lower cooling water flow path. The reason is that the steam cannot flow into the internal of upper tube bundle and the air fractions are higher in the upper tube bundle with the upper-lower cooling water flow path. An improvement tube arrangement was developed for the upper-lower cooling water flow path which reduced the back pressure by 0.47 kPa compared to the original scheme. Thus, the results show that the tube arrangements should differ for different cooling water flow paths and the condenser heat transfer can be improved for the upper-lower cooling water flow path by modifying the tube arrangement. 相似文献
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Gavin Henderson Wenzhong Zhou Shripad T. Revankar 《International Journal of Heat and Mass Transfer》2010,53(5-6):1156-1163
An experimental study of the tube bundle effect on heat removal capabilities in complete condensation mode of a passive condenser was performed. A full scale test section, with four condenser tubes, was designed and constructed to simulate operating conditions of a passive containment cooling system. For complete condensation analysis, pure steam was supplied to the test section and heat transfer properties were measured for pressure from 100 to 280 kPa. The condensation heat transfer results were similar to the findings from single tubes, except for a slightly higher condensate mass flux. This was determined to be a result of turbulent mixing in the secondary boiling water caused by the tube bundle. 相似文献
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《International Communications in Heat and Mass Transfer》2005,32(5):593-602
An experimental study is performed for the steam condensation in a vertical tube where steam is completely condensed. A condenser tube is submerged in a water pool where the heat from the condenser tube is removed through boiling heat transfer. The experiment data showed that the operating pressure is uniquely determined by inlet steam flow rate for the complete condensation. The condensation heat transfer rate increases and the condensation heat transfer coefficient decreases with the system pressure. For the condenser submerged in a saturated water pool, strong primary pressure dependency was observed on the condensation heat transfer. 相似文献
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Experimental Study of Condensation in a Shell and Tube Heat Exchanger in the Presence of a Noncondensable Gas 下载免费PDF全文
In this paper, an experimental study of the condensation of water vapor from a binary mixture of air and low‐grade steam has been depicted. The study is based upon diffusion heat transfer in the presence of high concentration of noncondensable gas. To simplify the study, experimental analysis is supported by empirical solutions. The experimental setup is custom designed for testing a new shell and tube type heat exchanger supplied by the manufacturer. Air–vapor mixture at 80 °C (max) and 20.2% relative humidity enters the heat exchanger at a mass flow rate of 480 kg/h and condenses 27 kg/h vapor using cooling water at an inlet temperature of 7 °C to 10 °C and mass flow rate of 3500 kg/h. By using the experimental data of constant inlet air mass fraction, mixture gas velocity, and different volumetric flow rate of the cold fluid, the local heat transfer coefficients are obtained. The main objective of this work is to establish an approximate value for surface area and overall heat transfer coefficient of a horizontal shell and tube condenser used in process space. Under designed working conditions, the condenser is found to work efficiently with 90% vapor condensation by mass. 相似文献