Wind-induced responses of super-large cooling towers

Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.

Evaporative Cooling Applied in Thermal Power Plants:A Review of the State-ofthe-Art and Typical Case Studies

A review is conducted about the application of the evaporative cooling technology in thermal power plants.Different case studies are considered,namely,evaporative air conditioners,evaporative cooling in direct air-cooled systems,gas turbine inlet cooling,wet cooling towers,and hybrid cooling towers with a crosswind effect.Some effort is provided to describe the advantages related to direct evaporative cooling when it is applied in thermal power plants and illustrate the research gaps,which have not been filled yet.In particular,typical case studies are intentionally used to compare the cooling performances when direct evaporative cooling is implemented in different types of cooling towers,including the natural draft wet cooling tower(NDWCT)and the pre-cooled natural draft dry cooling tower(NDDCT).It is shown that the NDWCT provides the best cooling performance in terms of power station cooling,followed by the pre-cooled NDDCT,and the NDDCT;moreover,the evaporative pre-cooling is able to enhance the cooling performance of NDDCT.Besides,on a yearly basis,better NDDCT cooling performances can be obtained by means of a spray-based pre-cooling approach with respect to wet media pre-cooling.Therefore,the use of nozzle spray is suggested for improvement in the performance of indirect/direct air-cooling systems with controlled water consumption.

Study on Operating Characteristics of Power Plant with Dry and Wet Cooling Systems

The represent paper will study the performance of the power plant with the combination of dry and wet cooling systems in different operating conditions. A thermodynamic performance analysis of the steam cycle system was performed by means of a program code dedicated to power plant modeling in design operating condition. Then the off-design behavior was studied by varying not only the ambient temperature and relative humidity but also several parameters connected to the cooling performance, like the exhaust steam flow rate, the air cooling fan load and the number of operating cooling water pumps and cooling towers. The result is an optimum set of variables allowing the dry and wet cooling system be regulated in such a way that the maximum power is achieved and low water consumption.

自然通风湿式冷却塔节水方案的数值研究

为降低自然通风湿式冷却塔的耗水量,本文采用一种可用于回收其蒸发损失的空气冷凝器结构,并通过数值模拟方法对其节水特性展开研究。首先基于空气运动控制方程和水蒸气冷凝模型,建立了用于分析空气冷凝器节水特性的数学模型,其次分析了冷却空气流速、空气冷凝器的结构尺寸和材质等因素对该冷凝器节水特性的影响。研究结果表明:空气冷凝器的单位面积节水量随着冷却空气流速以及冷凝器宽度的增大而增大,但随着冷凝器长度和高度的增大而减小;空气冷凝器的材质和壁厚对其单位面积节水量没有显著影响,空气冷凝器可采用重量轻和成本低的薄壁PVC来加工制造。

低风阻流线型导风板对自然通风湿式冷却塔的性能影响

为改善冷却塔雨区流场结构,进一步增大通风量,在已有平板型导风板基础上,提出一种布置在雨区的低风阻流线型导风板。设计工况下,以常规冷却塔和在各高度布置平板型导风板的改造塔为参考对象,分析5种不同布置高度(1/6、1/3、1/2、2/3、5/6进风高度)下低风阻流线型导风板对整塔通风量、塔内流场结构和温度分布等参数的影响。结果表明:随着导风板布置高度的升高,塔内各区域的空气分配发生了变化,对内区填料换热产生了明显影响,使整塔冷却性能呈现出先提升后下降的趋势;在进风口高度2/3处布置流线型导风板时,通风量增量与填料区底部平均温度减量达到最优值,冷却塔性能改善效果最佳,此时相较于常规冷却塔,循环水温降相对增长2.65%,通风量相对增长2.78%。此外,相较于最佳布置高度的平板型导风板,采用低风阻流线型导风板改造后循环水温降相对增长1.2%。

基于定热负荷的自然通风湿式冷却塔防冻特性三维数值研究

针对湿式冷却塔(湿冷塔)冬季运行易出现填料底层、进风口上缘等位置易挂冰的实际问题,建立了基于定热负荷的自然通风湿冷塔三维数值模型,探究了湿冷塔在严寒天气不外加防冻装置运行时的防冻特性规律,分析了填料底层水温、通风量等关键参数的变化特征及影响因素。研究结果表明:环境温度越低,机组负荷对填料底层平均水温、最低水温的影响越大;填料底层水温偏差变化的主要因素是机组负荷、环境风速、配水方式,其中配水方式的影响幅度较大,机组负荷次之,环境风速影响较小;通风量与机组负荷呈正相关关系,与环境温度呈负相关关系;环境温度相同时,外圈配水下的通风量小于全塔配水;迎风侧内部较低处及背风侧外部的水温最低,冻结风险最大,湿冷塔冬季运行时,应着重在迎风侧和背风侧进行防冻装置布置。

填料蒸发预冷进风的机械通风空冷塔设计及其运行性能

为了解决机械通风空冷塔夏季机组出力不足,无法满足冷却需求的问题,设计了一种带有填料蒸发预冷进风的机械通风空冷塔,并利用Matlab编写计算程序,仿真研究了填料厚度、环境温度和环境湿度对所设计空冷塔运行性能的影响规律及其节能效果。研究表明:在环境温度为26℃,相对湿度为57%条件下,厚300 mm的CELdek7060填料蒸发预冷进风的预冷效果最好,空冷塔的排热率可提高20.57%;空冷塔的排热性能随环境温度升高而降低,且存在一个临界点温度为13.5℃,只有当环境温度高于此温度,填料蒸发预冷进风才可提升空冷塔的排热性能;在环境温度、相对湿度分别为35℃和57%时,填料蒸发预冷系统可使空冷塔的排热率提高96.96%,使出塔水温进一步降低2.80℃;在环境相对湿度为0%、环境温度为26℃时,填料蒸发预冷系统可使空冷塔的排热率提高81.14%,出塔水温进一步降低6.81℃。单塔每年节能收益约为13.84万元,具有良好的经济效益。

高位收水冷却塔噪声预测方法优化及噪声治理措施探讨

对湖北省某660 MW燃煤发电厂高位收水冷却塔进行了现场测试,根据测试结果对高位收水冷却塔噪声预测模型进行了优化和验证,并对高位收水冷却塔的噪声治理措施进行了探讨。结果表明,采用发声部位水平面声源优化模型计算得到的高位收水冷却塔噪声衰减规律与实测结果更加接近;虽然高位收水冷却塔附近地面噪声源强实测声级较常规冷却塔低约8 dB(A),但总体声功率级的改善效果并不能达到8 dB(A)的水平;同时,由于高位收水冷却塔声源位置较高,对围墙外某些特殊点位,高位收水冷却塔的噪声影响可能反而会略高于常规冷却塔;消声导流片及吸隔声屏障在应用于高位收水冷却塔降噪时需根据声源实际情况进行模型验证优化,而声源降噪措施可从改善水滴对收水斜板的冲击以及收水斜板本身振动噪声方面进一步研究。

北京某商业内区免费供冷系统选用分析与设计

随着国家“双碳”政策的实施,建设节能低碳、绿色生态、集约高效的建筑用能体系,具有重要的现实意义和深远的战略意义。基于北京通州一大型商业综合体项目,对进深较大且余热较大的内区,在冬季或室外气温较低的过渡季,从充分利用室外新风,以及冷却塔供冷两个方面,分析了免费制冷系统选用依据。在不增加耗热量的前提下,适当增大新风量,并解决好低温送风问题。优先利用新风系统为商业内区部分店铺实现免费供冷;对采用新风免费供冷的方法仍不能消除内区余热的店铺,采用冷却塔免费供冷系统。描述了冷却塔免费制冷的设计方法:主要参数选取、设备配置以及系统设计计算等过程,并提出系统设计中需要注意且容易忽视的自控要点。为同类项目免费制冷系统选用、设计提供借鉴参考。

国内首台1000 MW褐煤机组的脱硫废水零排放技术路线应用

目前废水的低温多效蒸发零排放工艺成为现今市场的主流。以国内首台1000 MW褐煤机组采用的低温多效闪蒸浓缩工艺为例,其零排放技术路线包括低温烟气余热利用、多效闪蒸浓缩、干湿空冷联合冷却等创新技术,实现了脱硫废水处理零排放。该技术运行电耗低,淡水回收率高,在保障相对较低的运行成本的同时,实现了脱硫废水的零排放。此外,该技术还首次引入干湿空冷联合冷却塔装置用来给三效零排放系统提供冷却水,实现了系统补水的自供应。

Experimental Study on Performance of a Closed Wet Cooling Tower for Air Wet-Bulb Temperature near 0°C

Closed wet cooling towers(CWCTs) are used widely because of their better water quality and smaller water consumption. However, the operating parameters shown in the technical documents are only for rated conditions in summer, not for any other conditions, especially in low air wet-bulb temperature areas such as those near 0℃. In addition, CWCTs often fail to achieve the designed cooling effect at low air wet-bulb temperatures. A experiment set of CWCT was built, and the performance of the CWCT at low air wet-bulb temperature near 0℃ was investigated. The impact of the operating parameters(air flow rate, cooling water flow rate, and spray water flow rate) on the heat and mass transfer performance of the CWCT was measured and analyzed. The results show the cooling performance of the CWCT at an air wet-bulb temperature 0℃, 2℃, and 4℃ is about 47%–63% of the rated operating condition;the optimal operating parameters of these conditions for the CWCT are just the same as those of the rated operating condition in summer. According to the experimental results, some operating advices are given.

A Novel Approach for Energy and Water Conservation by Using Silver-Carbon Quantum Dots Hybrid Nanofluids in Wet Cooling Towers Systems

This study presents the use of Silver-Carbon Quantum Dots(Ag-CQD)hybrid nanofluids,prepared by a facile wet chemical method,for heat transfer enhancement of wet cooling towers systems.The samples were characterized using different analyses,including FT-IR,XRD and TEM.After synthesizing the CQD,it was hybridized with silver nanoparticles and dispersed in water,using ultrasonic probe.The viscosity and density of the prepared nanofluid were investigated as a function of temperature and nanoparticles concentration,which demonstrated that there were no noticeable changes at lower particles concentration.Then,thermal conductivity and convective heat transfer coefficient were measured to evaluate the heat transfer enhancement of the nanofluid.At 45℃ and 0.5 wt%,the most significant thermal conductivity improvement compared to the base fluid was 24%;and 28%enhancement of the heat transfer coefficient was obtained at Reynolds number of 15529.The nanofluid performance was evaluated in a wet cooling tower for investigating the efficiency and water consumption rate.The results indicated that the efficiency of the cooling tower,by applying Ag-CQD nanofluid,enhanced from 23.72%to 28.23%;consequently,the amount of the consumed water decreased from 80.76 mL·min^(−1)to 69.67 mL·min^(−1).The results proved that the prepared nanofluid is a successful and promising candidate to enhance heat transfer.

A Novel Approach for Energy Efficiency Prediction of Various Natural Draft Wet Cooling Towers Using ANN

Cooling tower is crucial equipment in the cool-end system of power plant and the natural draft counter-flow wet cooling tower(NDWCT)gets wide application.The artificial neural network(ANN)technique is becoming an effective method for the thermal performance investigation of cooling towers.However,the neural network research on the energy efficiency performance of NDWCTs is not sufficient.In this paper,a novel approach was proposed to predict energy efficiency of various NDWCTs by using Back Propagation(BP)neural network:Firstly,based on 638 sets of field test data within 36 diverse NDWCTs in power plant,a three-layer BP neural network model with structure of 8-14-2 was developed.Then the cooling number and evaporation loss of water of different NDWCTs were predicted adopting the BP model.The results show that the established BP neural network has preferable prediction accuracy for the heat and mass transfer performance of NDWCT with various scales.The predicted cooling number and evaporative loss proportion of the testing cooling towers are in good agreement with experimental values with the mean relative error in the range of 2.11%–4.45%and 1.04%–4.52%,respectively.Furthermore,the energy efficiency of different NDWCTs can also be predicted by the proposed BP model with consideration of evaporation loss of water in cooling tower.At last,a novel method for energy efficiency prediction of various NDWCTs using the developed ANN model was proposed.The energy efficiency index(EEI)of different NDWCTs can be achieved readily without measuring the temperature as well as velocity of the outlet air.

自然通风湿式冷却塔节水方案的试验研究

由于塔内空气与循环冷却水间蒸发换热产生的水损,自然通风湿式冷却塔耗水是火电厂的主要用水量,因此研究自然通风湿式冷却塔节水方案,促进火电行业节水改造具有重要的社会与经济意义。本文通过搭建热态模型试验平台,研究了水冷型冷凝锥体、气冷型冷凝锥体和空气冷凝器三种节水方案的原理可行性。研究结果表明:三种节水方案均可回收自然通风湿式冷却塔的蒸发损失;增大冷凝体表面积可提高节水方案的节水特性;相比于冷凝锥体,空气冷凝器具有更大的冷凝面积,能够更有效地回收蒸发损失,故具有更广泛的工程应用价值。

干湿联合冷却塔的节水消雾性能研究

针对常规湿式冷却塔的冷却效果变差、耗水量变大而导致在空气温湿度较低时出现羽雾的问题,搭建了干湿联合的横流式冷却塔模型试验系统,对比研究了常规湿式冷却塔与干湿联合冷却塔的冷却效率与消雾效果,试验结果表明,与常规湿式冷却塔相比,干湿联合冷却塔的循环水温降提升近明显,消雾指数提高63%。同时考察了进风速度、环境温湿度等因素对干湿联合冷却塔节水消雾性能的影响,为干湿联合冷却塔的优化设计提供了理论依据。

填料非均匀布置耦合分区配水对湿式冷却塔热力性能的影响

以某300 MW火力发电机组的大型湿式冷却塔为研究对象,建立填料非均匀布置耦合分区配水的三维数值模型。填料内外区分别布置30 mm和26 mm S波填料,改变配水分区半径R_(1),重新分配配水内外区配水占比,研究不同工况下填料非均匀布置耦合分区配水对冷却塔热力性能的影响。结果表明:填料非均匀布置耦合分区配水可显著降低塔心区的高温,提高气水比。设计工况下,随着填料分区半径R_(2)和内区配水占比P的增大,冷却数和体积传热系数均先增大后减小。当R_(1)=15~35 m时降低P,而当R_(1)=40 m时增大P,均可提高湿式冷却塔整体热力性能。此时相对最佳的耦合布置方案为R_(1)=25 m、R_(2)=25 m和P=35%,与原始塔相比,冷却数和体积传热系数分别增大0.09和17.0 W/(m^(3)·K)。

声屏障及填料和配水协同优化对湿式冷却塔热力性能的影响

为了降低湿式冷却塔的雨区噪声,同时强化其换热和通风,基于三维数值计算研究了声屏障对填料和配水协同优化的湿式冷却塔热力性能的影响。研究发现,在研究工况下,声屏障和两区协同增效方案可均匀冷却塔内温度场、空气流速分布和水蒸气质量分数分布;两区协同增效方案可在一定程度上抵消声屏障对冷却塔换热性能的不利影响,使循环水温降和冷却数比原始塔分别平均增加了0.06℃和3.8%;虽然改造后全塔通风量有所减小,但空气动力场分布更为合理,更有利于冷却塔的换热。研究结果可为带有声屏障的两区协同增效冷却塔的设计提供参考。

Three-dimensional Numerical Study on Thermal Performance of a Super Large Natural Draft Cooling Tower of 220m Height

Based on the heat and mass transfer theory and the characteristics of general-purpose software FLUENT, a three-dimensional numerical simulation platform, composed of lots of user defined functions(UDF), has been developed to simulate the thermal performance of natural draft wet cooling towers(NDWCTs). After validation, this platform is used to analyse thermal performances of a 220m high super large cooling tower designed for inland nuclear plant under different operational conditions. Variations of outlet temperature of the cooling tower caused by changes of water flow rates, inlet water temperatures are investigated. Effects of optimization through non-uniform water distributions on outlet water temperature are discussed, and the influences on the flow field inside the cooling tower are analyzed in detail. It is found that the outlet water temperature will increase as the water flow rate increases, but the air flow rate will decrease. The outlet water temperature will decrease 0.095K and 0.205K, respectively, if two non-uniform water distribution approaches are applied.

利用地铁车站公共区排风的冷却塔对空调系统节能效果分析

根据地铁新排风井设置条件,设置地铁车站隐藏式冷却塔,将专用冷却塔放置在新排风井道之间,利用地铁车站公共区排风作为冷却塔进风;测试地铁车站公共区排风湿球温度和新风湿球温度,在夏季空调运行时,排风湿球温度比新风湿球温度低约2.0℃,在过渡季空调运行时低约1.0℃;实验测试不同因素对隐藏式冷却塔的散热影响,建立冷却塔线性回归模型,模拟并对比隐藏式冷却塔和常规冷却塔全年能耗,得到隐藏式冷却塔具有2.01%的节能率。

封闭式冷却塔供冷系统气象条件分析

在阐述封闭式冷却塔供冷技术原理及系统形式的基础上,探讨了封闭式冷却塔供冷与空气湿球温度的关系,分析了封闭式冷却塔供冷技术的节能效果。根据山东省某市全年8760h逐时实测气象数据,统计出了空气湿球温度在各区间出现的频率及累计频率,结果表明,一年中空气湿球温度小于等于10℃的时间达4208h。这对于全年运行的空调系统而言,节能潜力巨大。