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ABSTRACTThe natural draft cooling tower has been widely used in thermal power plants because of its stable operation, lower maintenance cost, and smaller environmental impact. Hundreds of natural draft cooling towers have been built in China, including different types and various capacities of conventional cooling towers, seawater cooling towers, flue gas injection cooling towers, cooling towers with water collecting device, dry cooling towers, and others. A wide range of investigation for natural draft cooling towers was carried out for the first time by the Electric Power Planning & Engineering Institute in 2013 in China. Based on the collected data and summarized information, the statistical results and conclusive opinions are analyzed. The development trend of natural draft cooling tower technology is also explored in this paper. The investigation results are expected to be a reference for designing and operating natural draft cooling towers in thermal power plants. 相似文献
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由于我国北方地区冬季气温较低,冷却塔普遍存在结冰问题,必须采取一定的防冻措施。通过FLUENT软件模拟分析得出进塔水温对塔内不同特征面水温的影响规律,并进一步模拟加装不同层数挡风板后冷却塔内流场的变化。计算结果表明:①当运行工况其它条件不变时,随着进塔水温的升高,塔内不同特征面最低水温升高;②加装一定层数挡风板能使填料下面空气温度场和进风口上沿面空气速度场分布逐渐趋于均匀,有利于防止塔内结冰;③选取进塔水温分别为17.80℃、21.95℃、26.77℃、30.04℃时,分别加装4、3、2、1层挡风板可有效防止塔内结冰。 相似文献
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基于CFD软件和自然通风湿式冷却塔相关理论,对喷淋区和雨区采用离散相模型计算,对填料区建立了基于Poppe理论的数值求解模型,并通过编译自定义源项函数,实现其在Fluent中的求解。在该模型基础上,分析了横向风速对冷却塔热力性能的影响;最新提出了在雨区加装改进的十字挡风墙的措施,并引入多孔跳跃模型实现其数值求解。计算结果表明:横向风对出塔水温影响很大,当风速为6 m/s时,出塔水温最高,比无风时高1.34℃;改进的十字挡风墙能有效提高冷却塔性能,最大能使出塔水温降低0.32℃,并且能明显降低水损失。 相似文献
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Adam Klimanek Ryszard A. Białecki Ziemowit Ostrowski 《Numerical Heat Transfer, Part A: Applications》2013,63(2):119-137
A 2-D axisymmetric model of multiphase heat, mass, and momentum transfer phenomena in natural draft cooling tower is developed using a CFD code Fluent. The fill of the tower is modeled as a porous medium. The energy and mass sources in this zone are evaluated solving a separate 1-D model of mass and heat exchange. The spatial dependence of the sources is accounted for by dividing the fill into a set of vertical channels. The CFD solver produces boundary conditions for each channel, while the model of the channel exports the heat and mass sources to the CFD solver. To accelerate the calculations, an original technique known as the proper orthogonal decomposition (POD) is applied. This approach produces a reduced dimensionality model resulting in significant time economy and accuracy loss lower than 2%. The Euler-Euler multiphase model is used in the rain zone. The simulation results have been validated against experimental data coming from field measurements of a large industrial installation. 相似文献
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ABSTRACTThe natural draft cooling tower with water-cooled collectors has advantages including pump lift saving, being a type of energy-saving tower, and being suitable for application in huge capacity nuclear power plants. The height of the rain zone is reduced due to the existence of water-cooled collectors under the fill, which leads to a change of the tower's performance. In this paper, a three-dimensional mathematical model of the thermal and aerodynamic field of the tower is established. The thermal and resistance characteristics of the tower have been studied by a numerical simulation method. The study results include: (1) Owing to the existence of water-cooled collectors, the resistance of the rain zone is decreased and the total resistance of the tower is also decreased; (2) as the height of the rain zone for the natural draft cooling tower with water-cooled collectors is lower, the air velocity distribution in the fill section is more uniform than that of the natural draft cooling tower; and (3) the cooling efficiency of the tower with water-cooled collectors is superior to that of the natural draft cooling tower. 相似文献
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A three-dimensional study using the standard k-? turbulence model to simulate airflow in and around a natural draft dry cooling tower (NDDCT) has been conducted using a general-purpose CFD code. This investigation considered the location and the porosity of windbreak walls' structure on the NDDCT thermal performance. In addition, the effect of the windbreak walls on the thermal performance of two NDDCTs with different capacities has been investigated. Two parameters have been used to show the effect of the windbreak walls on the NDDCT thermal performance. At the reference heat exchanger temperature, the thermal effectiveness parameter has been employed. At the reference rejected heat from the NDDCT, the change in the cooling tower approach parameter has been employed. The results in this paper show an improvement in the NDDCT thermal performance due to the introduction of windbreak walls. Moreover, optimizing the location of the windbreak walls has been shown to have a more significant effect on the NDDCT thermal performance than the porosity of the walls. In addition, the effect of the windbreak walls on the thermal performance is similar for the two NDDCT with different capacities. 相似文献
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在自然通风冷却塔热力计算中,出塔水温及干空气量迭代初值的选取非常重要。若选取的不合适,有可能造成迭代过程的出错。采用麦克尔模型分析了这些迭代初值的取值。最后给出了一套在冷却塔热力计算中迭代初值取值的方法。 相似文献
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This paper presents an experimental work that studies the performance of a counterflow cooling tower with expanded wire mesh packing. Due to complicated configuration of the expanded wire mesh packing surface, it is not possible to measure the temperature of the air in the intermediate section of the cooling tower, but only that of the exit air and water temperature. In the experimental study a new concept of psychrometric gun technique is used to measure dry/wet bulb temperature of air at intermediate points of tower packing. First, the paper elaborates on the effect of atmospheric conditions, water mass flow rate and inlet temperature on the variation of the thermodynamics properties of moist air inside the cooling tower and thermal performance characteristics. Second, exergy analysis is applied to study the cooling tower potential of performance using the psychrometric gun technique. An analytical model was compared with experimental data. 相似文献
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In this paper, the development of natural draft cooling towers diagnostics is presented. Diagnostic method is based on measurements of velocity and temperature fields of the airflow in the entire surface area of cooling tower and the raised phenomenological model of heat and mass transfer in a selected reference vertical segment of cooling tower. Velocity and temperature fields of the airflow were measured with the aid of a remote control mobile robot unit that was developed to enable measurements in an arbitrary measurement point above the spray zones over the entire cooling tower area. Topological structures of the humid air velocity profiles and temperature profiles above the spray zones were obtained at constant integral parameters of a power plant. Measurement results of temperature and mass flow characteristics of the air and water flows in a selected reference vertical segment of cooling tower are presented in the form of phenomenological dependence. Phenomenological dependence links local cooling tower efficiency, geometrical characteristics of spray elements, and air and water flow rates. In the concluding part, both methods are applied together on a selected segment of cooling tower, and local and integral cooling tower efficiency can be determined. 相似文献
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为了便于在设计过程中能够快速选择合适的冷却塔型式,以某实际电厂为例,对10000 m2自然通风冷却塔与冷却效果相近的9500 m2高位收水冷却塔的通风热力与阻力、节能、降噪、循环水系统运行模式及年运行费用等方面进行了综合技术经济比较,分析表明:高位收水冷却塔具有技术先进,节能减噪效果明显的优点,但施工运行难度大,投资高;自然通风冷却塔技术成熟,投资低,施工运行简单,管理方便,但节能减噪效果差.电厂可以根据自然通风冷却塔及高位收水冷却塔的优缺点选择适合其建设的冷却塔型式,对周边噪声控制较严的区域,可以选择高位收水冷却塔;为节省投资,其他区域可以选择自然通风冷却塔. 相似文献
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"烟塔合一"技术,即取消火电厂中的烟囱,将锅炉经除尘脱硫后排出的烟气,经自然通风冷却塔排放到大气中。用等效热降的方法分析了"烟塔合一"技术增设烟气余热换热器的节能效果,并以660 MW机组为例,进行了几种方案比较。定量计算结果得出的结论对指导发电厂采用"烟塔合一"技术烟气余热换热器的设计具有重要的意义。 相似文献
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横向风对湿式冷却塔热力特性影响数值研究 总被引:2,自引:0,他引:2
基于CFD软件和湿冷塔相关理论,建立了基于Poppe理论的填料区数值求解模型,对喷淋区和雨区采用离散相模型计算.模拟了横向风对冷却塔热力特性和飘水损失的影响;提出了沿塔周设置回流槽的措施,以减少飘水损失.结果表明:横向风对出塔水温影响很大;无风时,出塔水温最低,随着风速的增加,出塔水温先升高后降低,并且,随着环境温度、湿度的不同,在横向风速为5m/s~7m/s间取得极大值. 相似文献