【作者】 乔英杰；

【导师】 杨建国；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2010， 硕士

【摘要】 我国煤炭资源主要集中在北方地区，传统湿冷式凝汽器在北方地区的应用受到限制，直接空冷式凝汽器以其优异的节水性能补充了传统湿冷技术的不足，改变了以水定电的格局，在我国北方地区得到了广泛应用。蛇形翅片管是直接空冷凝汽器的核心换热元件。对其进行详细的换热流动分析，对直接空冷系统的设计以及运行都具有非常重要的意义。本文应用计算流体力学数值模拟的方法，在不同迎面风速，温度条件以及翅片结构下，对翅片管的流动特性和换热性能进行了深入分析，并得出了翅片管的压力降、阻力系数、换热量、换热系数、出口温度、翅片温度等随迎面风速变化的曲线，提出了努塞尔数N_u与雷诺数R_e之间的无因次关系式，所得到的结果可为我国电站空冷系统的设计和运行提供参考。建立了单排空冷翅片管和1000MW直接空冷凝汽器单元三维流动换热的物理数学模型，并进行了数值计算，分析了夏季TRL工况下，环境因素对凝汽器单元流动与换热特性的影响规律，以及相邻单元之间的相互影响。重点研究了在最不利条件，即夏季高温且有自然大风条件下，空冷凝汽器边缘迎风单元流动换热差的问题，并给出了解决的措施，提出一种新型导流布置方式。分析结果表明单纯改变裙板高度对缓解大风影响效果有限；新型导流布置方式有效地改善了最不利条件下空冷单元的运行情况。更多还原

【Abstract】 The application of traditional wet-cooled condensers are limited and directair-cooled condensers(DACC) are widely and increasingly used in northernChina, where the coal mine mainly distributes upon, but water is short anddominates the price of electricity power.The finned-tube is the key element of heat transfer of DACC. R_esearches onthe flow and heat transfer performance of DACC is of great importance in thedesign and operation of DACC. Under different windward velocity, the flow andheat transfer performances of the finned-tube have been calculated and analyzedbased on CFD(Computational Fluid Mechanics). The relationships betweenpressure drop, fractional coefficient, heat exchange capacity, convectioncoefficient, outlet temperature, finned-tube temperature and windward velocity,and also the dimensionless relationship between N_usselt number and R_enoldsnumber are presented. The results can provide a theoretical basis for the optimaldesign of DACC.Physical and mathematical models were established for the finned-tube andthe DACC’s unit, and upon which the rules of flow and heat transferperformances affected by environment under the TRL operating mode in summer ,and the influence of the adjoining units were studied. The worst operatingcondition of DACC that is the gale in summer was emphasized, and under thiscondition the problem of bad heat transfer performance of the units on the edgeof DACC was analyzed. Methods were given and also a new type of guide flowdevice was created to improve the problem. The results of the numericalsimulation show that the length of apron has limited benefit to the gale condition,but the new type of guide flow device improves the problem well.更多还原