共查询到20条相似文献,搜索用时 125 毫秒
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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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电站汽轮机配备的凝汽器大多采用双流程,冷却水的流径有上进下出和下进上出之分。作者从凝汽器的基本和和水力特性分析着手,根据有关的特性参数在凝汽器内的分布规律,研究了不路径对凝汽器性能的影响。结果表明,采用上进下出的冷却水流径,可以有效地减小凝汽器内的汽阻和凝结水的过冷度,改善冷却水侧的压力分布,明显降低所需的循环水泵扬程和冷却水漏入汽侧的可能性。 相似文献
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在提高机组初参数条件受到一定限制的情况下,从设计、制造和运行环节如何保证凝汽器的安全运行来提高汽轮发电机组的经济性得到各方面的重视.在上述背景下,国内外竞相开展了凝汽器的最佳经济方案的研制工作.以某厂600MW汽轮机组为例,根据汽轮机的设计参数,选择不同的冷却倍率,冷却水流速以及流程数,从经济角度确定凝汽器的最佳运行方案,计算得出冷却倍率为70的双流程凝汽器为最佳设计方案.此外,还利用Matlab编程绘制了该凝汽器在不同冷却水量及不同冷却水进口温度下的特性曲线,并对几个典型工况曲线进行了分析,为凝汽器的运行,改造提供参考依据. 相似文献
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以清华大学研制的性能优良的仿生双连树形管束式凝汽器为范例,介绍了第一流程与第二流程冷却管等距布置型凝汽器的结构,并分析其流场和换热特性,继而提出第一流程冷却管大间距、第二流程冷却管小间距的疏密管束优化布置方案,并进一步优化循环水流程为上进下出,两方面提高凝汽器换热效果,推荐工程设计上优先选用循环水为上进下出的双流程不等距布管式凝汽器。 相似文献
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为了改变目前的两壳体或三壳体结构的凝汽器无法满足与超超临界600MW汽轮发电机组配套使用的现状,研制成了单壳体、单背压、双流程的凝汽器。介绍了以往600MW机组凝汽器和超超临界600MW凝汽器的区别及设计的过程。 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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Experimental investigation is conducted to study the performance of evaporative condensers/coolers. The analysis includes development of correlations for the external heat transfer coefficient and the system efficiency. The evaporative condenser includes two finned-tube heat exchangers. The system is designed to allow for operation of a single condenser, two condensers in parallel, and two condensers in series. The analysis is performed as a function of the water-to-air mass flow rate ratio (L/G) and the steam temperature. Also, comparison is made between the performance of the evaporative condenser and same device as an air-cooled condenser. Analysis of the collected data shows that the system efficiency increases at lower L/G ratios and higher steam temperatures. The system efficiency for various configurations for the evaporative condenser varies between 97% and 99%. Lower efficiencies are obtained for the air-cooled condenser, with values between 88% and 92%. The highest efficiency is found for the two condensers in series, followed by two condensers in parallel and then the single condenser. The parallel condenser configuration can handle a larger amount of inlet steam and can provide the required system efficiency and degree of subcooling. The correlation for the system efficiency gives a simple tool for preliminary system design. The correlation developed for the external heat transfer coefficient is found to be consistent with the available literature data. 相似文献
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电站冷端优化的目的是从成本与收益方面综合考虑,确保在机组整个寿命期内获得最大效益。汽轮机、凝汽器、冷却塔及相关系统的设置影响成本,不同汽轮机排汽面积、凝汽器换热面积、冷却塔面积对应着不同的年发电量,只有合适的设计背压才能确保机组在电站整个寿命期内效益最大化。本研究根据内陆某核电站的厂址条件,通过对汽轮机排汽面积的计算、凝汽器换热面积的选择、冷却塔及循环水系统的设计,对该核电站汽轮机进行选型,并对冷端进行全面优化设计,最后确定凝汽器的最佳设计背压及冷却塔面积,确保机组在计算寿命期内获得最佳效益,可供同类型电站设计参考。 相似文献
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A modified k–ε turbulence model for the simulation of two-phase flow and heat transfer in condensers
《International Journal of Heat and Mass Transfer》2007,50(9-10):1641-1648
A modified k–ε turbulence model is developed in this study to simulate the gas–liquid two-phase flow and heat transfer in steam surface condensers. A quasi-three-dimensional algorithm is used to simulate the fluid flow and heat transfer in steam surface condensers. The numerical method is based on the conservation equations of mass and momentum for both gas-phase and liquid-phase, and mass fraction conservation equation for non-condensable gases. The numerical simulation of an experimental steam surface condenser has been conducted using the proposed modified k–ε turbulence model. The results obtained from the proposed model agree well with the experimental results and the results also show an obvious improvement in the prediction accuracy comparing with previous results where a constant value for the turbulent viscosity was used. 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积聚现象,从而导致了流动与传热特性的恶化。对此提出了改进方案,即将抽气口处的挡板开口,从而将积聚的不凝结气体引出,通过数值计算证实该措施有效。 相似文献
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The effects of different closure correlations on numerical simulations of vapor-liquid two-phase flow and heat transfer in steam surface condensers are critically assessed in this study. A modified k-? turbulence model for two-phase flows is used in the simulation. The closure correlations are those for condensation vapor shear, interphase drag forces, non-condensable air, tube-side fluid flow, inundation, and hydraulic resistance due to the tube bundle. Numerical simulations of a steam surface condenser are carried out using different closure correlations, and the numerical results are compared with the experimental data. Recommendations are given for different closure correlations. 相似文献