自然通风湿式冷却塔加装挡风板优化设计

以湿冷机组自然通风冷却塔相关理论为基础,借助于CFD模拟软件,建立了火电机组湿式冷却塔的传热传质模型,主要的换热区域如填料、雨区和喷淋区采用离散相模型。由于冬季气温较低和塔内的换热不均,在冷却塔的填料下面、进风口处、基环面容易结冰,提出了在进风口处加装挡风板的方案,数值模拟分析结果显示,该方案改善了塔内温度场,有效的防止了塔内结冰。     

湿式冷却塔加装挡风板的数值研究

针对我国北方冬季湿式冷却塔运行时填料下表面、进风口以及基环面等处容易结冰的问题,在冷却塔的进风口处加装挡风板,建立了冷却塔内的传热传质模型,并采用CFD软件模拟和分析了在不同横向风速和不同环境温度下加装不同层数的挡风板时冷却塔的热力特性.结果表明：在风速小于4m/s时,塔内的迎风面空气温度较低,极易结冰;随着风速的增大,低温区逐渐向背风侧转移;当风速为8m/s,环境温度分别为-10℃、-17℃、-23℃时,分别在冷却塔内加装1层、3层和5层挡风板,能大大改善塔内温度场,有效防止塔内结冰.     

核电机组巨型冷却塔进风口高度优化的三维数值研究

针对目前核电机组采用的巨型冷却塔无实际工程应用的现状,采用Fluent软件建立其三维热力计算模型,研究侧风下巨型冷却塔在不同进风口高度下的冷却效果,分析冷却数等热力性能参数,考察了侧风对塔内流场对称性的影响。以提高供电量为最终目标,综合考虑侧风的影响,确定巨型塔最优的进风口高度值。     

环境侧风对300MW火电机组冷却塔影响的数值模拟

以300MW机组双曲线自然通风冷却塔为研究对象,采用Fluent软件对冷却塔进行了三维数值模拟,分析了变工况下环境侧风对冷却塔冷却性能的影响、环境侧风对冷却塔进风口速度场的影响。研究发现:随着侧风风速的增加,冷却温差先减小后增大,出塔水温先增大后减小;并且,环境侧风的存在会扰乱冷却塔进风口流场,其临界风速值为6m/s。     

湿式冷却塔进风口导流板参数优化及安装实践

冷却塔作为火电厂冷端系统中重要的冷却设备之一,其冷却性能直接影响电厂运行的安全稳定性和经济性,而环境侧风在很大程度上影响冷却塔的冷却性能,可以采取在冷却塔进风口处安装导流板的措施予以改善。针对某600MW机组的自然通风湿式冷却塔,采用CFD软件Fluent,对进风口处安装导流板的冷却塔进行数值模拟。模拟结果表明:导叶板能够增加塔内中心区域的空气上升速度和扰动,加强传热,改善冷却塔冷却性能。导叶板相对最佳的安装角度为20°,导叶板安装数量为80块,出塔水温可以降低1.2K。根据模拟结果对某冷却塔进行改造,通过对比同一塔技改前后出塔水温,发现出塔水温可降低1.6K以上,验证了模拟计算的正确性和该项技术的实用性。     

逆流湿式冷却塔内不锈钢填料热力性能的试验研究

逆流湿式冷却塔是工业生产中普遍使用的换热设备,填料热力性能优劣直接影响到冷却塔热力性能优劣。为研究不锈钢填料的热力性能,搭建了逆流湿式冷却塔实验台,对比分析了S波、人字波和V波三种不锈钢填料与S波PVC填料随进塔水温的热力性能变化规律,以及研究了S波不锈钢填料随淋水密度的热力性能,结果表明:不锈钢填料的热力性能比常用PVC填料好,S波、人字波和V波不锈钢填料与S波PVC填料的冷却塔进出水温差和总换热量均随进塔水温的增大而增大,而冷却塔的冷却效率随进塔水温的升高先增大后减小,进塔水温在37.5～38.5℃时,冷却塔的冷却效率达到最大;且S波不锈钢填料冷却塔进出水温差、冷却塔的冷却效率及总换热量随淋水密度的增大而减小。优化填料波纹形状以及材料均有助于提高冷却塔的热力性能。     

超低噪声冷却塔轴流风机的技术简析

一、冷却塔的特点冷却塔是工业冷却水循环利用设备,从节能和环境保护考虑,所采用的风机应能提供所需的进塔空气量,力争高的运行效率,以利节能,并控制运行时产生的噪声（指装在市区的塔）和水滴的飞溅损失。当今,噪声问题是市场竞争的焦点。为节省能耗,我们采取以下措施：图1不同风机只适用于不同系统否则会降低运行效率l、首先考虑提高运行效率,选用风机的性能参数应与冷却塔实际阻力特性一致或接近,为此需对冷却塔的通风阻力进行精确计算,根据塔的型式、结构和尺寸,包括淋水装置的横截面积、填料高度、进风口、导风装置、收水器…     

基于焓差理论的带填料逆流闭塔热力性能分析

为了分析不同风量和喷淋水量对填料逆流闭式冷却塔热力性能的影响,建立和验证了带填料逆流闭式冷却塔热质交换的数学模型,基于焓差理论对模型计算的结果进行分析。结果表明：加入填料相当于对盘管区进口的喷淋水进行预冷,降低了喷淋水的平均温度,使带填料闭式冷却塔的冷却性能优于纯盘管闭式冷却塔;风量的增加可以提高带填料逆流闭式冷却塔和纯盘管逆流闭式冷却塔的热力性能,两种塔的冷却性能随风量增加的提升速率相同;喷淋水量的增加对纯盘管逆流闭式冷却塔的热力性能的影响较小,却可以较大幅度提高带填料逆流闭式冷却塔的热力性能。     

基坑式成组冷却塔的选型布置与热流模拟研究

对于基坑式环境，在环境风与冷却塔风机抽力的作用下，冷却塔出风口排出的热空气易被冷却塔进风口再次吸入塔内，形成热风回流，导致冷却塔实际冷效低于设计值。以某会议会展工程为例，通过CFD热流模拟，在基坑式环境下对冷却塔进行合理选型，根据气流组织模拟确定冷却塔的布置位置、方向以及基础高度，保证冷却塔使用能效优良。     

湿式瘦高冷却塔淋水装置节能技术应用

主要叙述了一种基于FLUENT UDF方法设计湿式冷却塔淋水装置的节能技术,并介绍其应用于电厂冷却塔的情况。该节能技术的应用研究主要包括,环境侧风对超大型自然通风冷却塔热力性能的影响;塔群效应和塔群效应与环境侧风叠加等条件下,超大型逆流式自然通风冷却塔的热力计算方法;基于FLUENT UDF方法准确分析塔内每个区域的热力参数(喷头实际出流能力、填料实际淋水密度和对应区域的集水池平均水温)等工艺性能关键技术研究;冷却塔新材料(不同波形、不同片距)、新设备的研发制造;冷却塔环境保护关键技术研究等。     

Direct contact condensation in packed beds

A diffusion driven desalination process was recently described where a very effective direct contact condenser with a packed bed is used to condense water vapor out of an air/vapor mixture. A laboratory scale direct contact condenser has been fabricated as a twin tower structure with two stages, co-current and countercurrent. Experiments have been operated in each stage with respective saturated air inlet temperatures of 36, 40 and 43 °C. The temperature and humidity data have been collected at the inlet and exit of the packed bed for different water to air mass flow ratios that vary between 0 and 2.5. A one-dimensional model based on conservation principles has been developed, which predicts the variation of temperature, humidity, and condensation rate through the condenser stages. Agreement between the model and experiments is very good. It is observed that the countercurrent flow stage condensation effectiveness is significantly higher than that for the co-current stage. The condensation heat and mass transfer rates were found to decrease when water blockages occur within the packed bed. Using high-speed digital cinematography, it was observed that this problem can occur at any operating condition, and is dependent on the packing surface wetting characteristics. This observation is used to explain the requirement for two different empirical constants, depending on packing diameter, suggested by Onda for the air side mass transfer coefficient correlation.     

蛋白粉尾气余热回收喷淋塔的热工特性研究

大豆蛋白粉干燥工艺过程产生的高温尾气中蕴含着大量显热和潜热,而无填料、垂直逆流喷淋塔可以深度回收尾气中的余热。对此建立了喷淋塔的数值模型,并通过实验验证其准确性;应用所建模型,分析喷淋高度、入口水温、喷淋密度、尾气流速和尾气入口湿球温度对喷淋塔热回收性能的影响规律,进而获得了喷淋塔在实验工况范围内的换热效率曲线及经验关联式,为尾气喷淋热回收塔的优化设计与工程应用提供了分析工具。     

The effect of wind speed at the top of the tower on the performance and energy generated from _thermosyphon solar turbine

Energy generated from wind turbine depends to a great extent on the wind speed at its inlet. The use of thermosyphon solar tower is an attempt to increase the air velocity at inlet of the wind turbine and of course to increase its power. The wind speed in a certain location changes always with time and with the height above ground surface. In this work, the effect of wind speed at the top of the tower on the performance as well as on the energy generated from thermosyphon solar turbine was studied theoretically. One location in Egypt was chosen for this study. The calculations were achieved mainly with the solar turbine located at tower bottom. For the purpose of comparison, the energy generated from the solar turbine was compared with that generated from free wind turbine at tower height with the absence of solar tower. It was found that, the wind speed at the top of the tower results in a pressure drop which affects the performance of the thermosyphon solar turbine. This pressure drop increases with the rise in wind speed and will be zero only when the wind speed at the top of the tower reaches zero. It was found also that, there is an increase in friction losses through the tower and a decrease in both temperature difference between inlet and outlet of the tower and in heat losses from tower walls with the rise in wind speed in location. The inlet air velocity to the solar turbine and consequently its specific power were found to be increased with the increase in wind speed at the top of the tower. Therefore, the effect of wind speed at the top of the tower must be taken into account during thermosyphon solar tower calculations. By comparing the performance of solar turbine and the free wind turbine located at tower height with the absence of thermosyphon solar tower, it was found that the mean inlet air velocity to the solar turbine located at tower bottom and consequently its specific power are higher than these values for free wind turbine. The mean inlet air velocity to the solar turbine is found to be 117% of its value for a free wind turbine. The yearly specific energy generated from solar turbine is expected to be 157% of its value for free wind turbine.     

Thermodynamic study of wet cooling tower performance

An analytical model was developed to describe thermodynamically the water evaporation process inside a counter‐flow wet cooling tower, where the air stream is in direct contact with the falling water, based on the implementation of the energy and mass balance between air and water stream describing thus, the rate of change of air temperature, humidity ratio, water temperature and evaporated water mass along tower height. The reliability of model predictions was ensured by comparisons made with pertinent experimental data, which were obtained from the literature. The paper elaborated the effect of atmospheric conditions, water mass flow rate and water inlet temperature on the variation of the thermodynamic properties of moist air inside the cooling tower and on its thermal performance characteristics. The analysis of the theoretical results revealed that the thermal performance of the cooling tower is sensitive to the degree of saturation of inlet air. Hence, the cooling capacity of the cooling tower increases with decreasing inlet air wet bulb temperature whereas the overall water temperature fall is curtailed with increasing water to air mass ratio. The change of inlet water temperature does not affect seriously the thermal behaviour of the cooling tower. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental and thermal analysis of energy efficient novel design wet cooling towers

Waste heat is generally dissipated from process water to atmospheric air in cooling towers. In the present study, a novel design is used to extract more amount of heat without any additional energy input by incorporating secondary ambient air in an induced draft wet cooling tower. In addition, more fresh air is induced in the tower from the rain zone, which increases the effectiveness at any value of the water to air flow rate (L/G ratio). Moreover, tower characteristics, range, and evaporation loss were also increased due to the novel design. It is noteworthy that secondary fresh air increases effectiveness, heat rejection, and tower characteristics by 10.12%, 19.65%, and 26.11%, respectively, and decreases approach by 16.32% at 0.55 L/G ratio, 44°C inlet water temperature, 29.7°C dry bulb temperature, and 18.4°C inlet air wet bulb temperature.     

低温工况热源塔热泵系统应用试验分析

针对热源塔换热能力及热源塔联立热泵主机制热情况分别进行试验研究,并与风冷热泵的制热变化性能进行比较分析。结果表明,控制热源塔进口气液温差恒定的情况下,塔从空气中吸收的热量随环境温度的降低而增加,溶液中溶质的挥发对热源塔吸热量有重要影响;热源塔进口气液温差随环境自然变化的情况下,环境温度与蒸发温度的温差随环境温度的降低而减小,热源塔从空气中吸收的热量也随之减少。在低温工况下,虽然空气含湿量较少,但热源塔热泵系统相比于其他空气作为热源的热泵系统,在潜热换热方面有较大优势。     

基于焓差法分析自然通风冷却塔出口水温的影响因素

采用焓差法建立了自然通风冷却塔出口水温的热力计算模型,并把凝汽器和冷却塔作为一个整体综合研究和分析了冷却塔出口水温的各种影响因素及其影响规律．结果表明：冷却水量、填料断面风速、凝汽器蒸汽负荷以及环境空气的相对湿度均对冷却塔的进口和出口水温有明显影响,且上述因素对进口水温的影响大于对出口水温的影响．