(中英)(整理)内陆核电厂用水系统冷却塔空气动力特性数值模拟汇总

1、鼓风式机械通风冷却塔空气动力特性数值模拟研究 赵顺安、李红莉、毋飞翔(中国水利水电科学研究院，北京 100038)Numerical research on aerod yn amic characteristics of the forced draft mecha ni cal cooling towerZhao Shunar、 Li Hongli、 Wu Feixiang (Chi na In stitute of Water Resource and HydropowerResearch, Beijing 100038 ) 摘要： 鼓风式机械通风冷却塔常用于核电厂的重要厂用水系统，但相

2、关设计规范 并没有给出冷却塔的空气动力特性计算公式。本文采用 Flue nt 软件对鼓风式机械通风冷却塔的空气动力进行了数值模拟计算，对冷却塔的设计布置进行了优化， 分析总结给出了冷却塔阻力计算公式。结果表明，填料安装位置对鼓风式机械通 风冷却塔整塔阻力影响不大，但会影响填料断面风速分布均匀性，填料安装高度 越低，风速分布越均匀；出口收缩段的高度越高，整塔阻力越小，风速分布越均 匀；出口收缩段与水平的夹角越大，整塔阻力系数越小，但变化趋势不明显，收 缩角基本不影响填料断面风速分布均匀性。关键词：鼓风式冷却塔；塔型；阻力系数；风速均匀性Abstract: The forced draft mec

3、ha ni cal cooli ng tower is always used in a nu clear powerpla nt, while the releva nt desig n specificatio ns have not formula about the aerod yn amiccharacteristics of cooli ng tower. This paper uses FLUENT software to simulate and studythe aerod yn amic characteristics of the forced draft mecha n

4、i cal cooli ng tower, andoptimize the design of the cooling tower, and analysis to summarize the cooling towerresistance calculative formula. The results show that the height of the fill has little effectson the whole tower resista nce coefficie nt, but it in flue nces the wind velocity distributio

5、nuni formity of the fill sect ion, the lower the positi on is, the more un iform the wi nd velocitydistributio n is; the con verge nt secti on height is higher, the whole tower resistance issmaller and the wind velocity distribution is more uniform. The angle betwee n con verge ntsecti on and horiz

6、on is bigger, the whole tower resista nce is smaller, while this trend is notobvious, it does not affect the wind velocity distribution un iformity on the fill secti on.Keywords: the forced draft mecha ni cal cooli ng tower, tower shape, resistance coefficient,wind velocity distribution uniformity1

7、研究背景 内陆核电厂的重要厂用水的水量不大，但却影响核电厂的安全。鼓风式机械通风 冷却塔能较好地适应核电对安全性和抗震性能的要求而常被内陆核电厂采用。鼓风式机械通风冷却塔不仅在通风方式上有别于常规的抽风式机械通风冷却塔， 在塔型结构布置上也有明显差异。我国的相关设计规范和资料对鼓风式机械通风 冷却塔没有明确的设计计算方法15。为了解塔内气流特性并对塔型进行优化，需要通过相关的研究来确定其 空气动力特性。通过物理模型试验来研究冷却塔空气动力特性是一个十分有效的 手段，但是由于鼓风式机械通风冷却塔模型本身的复杂性及系统试验的塔型的变 化，使模型试验研究工作量和投资都很大。本文利用 Flue nt

8、软件建立鼓风式机械通风冷却塔空气动力计算的数学模型，经过 与试验结果对比验证，确定模型参数和网格数量。研究了不同塔型条件下塔内气 流分布及阻力特性，最终分析总结出了鼓风式机械通风冷却塔的阻力计算公式以 及塔型与配风均匀性的关系。阻力系数计算公式与试验结果相比偏差小于5%,可为设计提供参考。research backgro undThe water qua ntity of importa nt water system of inland nu clear power pla nt is not big,but it affects the security of nu clear power

9、 pla nt. The forced draft mecha ni cal cooli ngtower can satisfy the requireme nts of equipme nt security and earthquake resista nee,so it will be used more and more in inland nu clear power pla nt.The forced draft mecha ni cal cooli ng tower is not only differe nt from the conven ti onalinduced dra

10、ft mechanical cooling tower in ventilation way, but also has distinct differenee in tower shape and structure layout. Chin as releva nt desig n specificati ons andin formati on on the forced draft mecha ni cal cooli ng tower have no clear desig nmethod. For un dersta nding the airflow characteristic

11、s of the tower and optimiz ing thetower shape, its n ecessary to do some releva nt research to realize the aerod yn amiccharacteristics. Its a very effective way to establish a physical model to study the aerodyn amic characteristics of the cooli ng tower, however, due to the forced draft mecha nica

12、l cooli ng tower models complexity and variability, the workload of experime nt andinv estme nt is very big.This paper uses FLUENT software to build a mathematical model of the forced draftmecha ni cal cooli ng tower to study the tower aerod yn amic characteristics, and aftercompari ng with the expe

13、rime ntal results to determ ine the model parameters and gridnumber. It studies the airflow distribution and resistance characteristics in the con ditions of differe nt tower shapes, and an alysis to summarize the cooli ng tower resistance calculative formula and the relati on ship betwee n tower sh

14、ape and airflowdistributio n un iformity. The differe nce of computati onal resista nce coefficie nt andthe experimental results is less than 5%, it can provide a reference for design.2 数学模型及计算方法2.1 空气流场控制方程塔内外流场为等温、不可压流动，其控制方程包括连续方程、动量方程，并选用 k- &双方程湍流模式对方程进行封闭，各方程可写为统一形式：?（ p?）? （1）+? ?pVJ）=?r

15、（P+s ?式中：p为空气密度，kg/m;为空气流速，m/s。各控制方程的变量、扩散系数 项r与源 3 项 S如下表 1。表 1 控制方程中各变量代表参数押制 7 ft1if10D动hlFr洗 mM p r rwP+Adp页k+川 6G -芦r/+ Mm1其中生成项 Gk=yt(?ui?uj?ui;卩为空气分子粘性系数；p 为压力；卩为紊流粘性系 +)?xj?xi?xjk2，Cu为经验常数；ck口C分别为 k 和&的紊流数，由动能 k 和紊动耗散率&求出：卩 t=pCu普朗特数。&2 Mathematical models and calculative methods

16、2.1 Air flow gover ning equati onsThe tower flow field is isothermal and in compressible. Its gover ning equati ons in clude continuityequation, momentum equation, which can be closed with k twoequation turbulence model, theseequations can be written as a unified form:?(P?+? ?pV=?r?+S? ?t (1)Where:p

17、is air density, kg/m3; V is air velocity, m/s. All governing equations variable、diffusion coefficient termrand source term Sare shown as Table 1 below.Table 1,randvery gifverning equationGnvrmingcqn口门弋65/ContinmiA eLiuathin一TI-00Moneniuni cqudijonU -1%wTurhiikni energyk出+川 Ea-解DiMkipaLiin cqualiuncr

18、kGen erated item?ui?uj?uiGk=yt(+)?xj?xi?xj,卩 is viscosity coefficient of the airmolecules; p is pressure, Pa;卩 t is the turbulent viscosity coefficient, which is can becalculated by the turbulent kinetic energy k and dissipation rate : an empirical constant;2.2 边界条件卩 t=pCyk2 ,C 卩 is(Tk and(Tare turb

19、ulent Prandtl number of k and底部为固壁无滑移边界条件，四周及顶部采用压力出口边界条件，塔壳采用固壁 边界条件。进风口及塔的出口都设置成内部边界；填料区域设置成多孔介质边界 条件，并根据实测填料阻力系数设置各方向阻力系数；风机采用Flue nt 风扇边界条件，也可采用第一类边界条件。2.2 Boun dary con diti onsThe bottom of the computati onal doma in is solid wall boun dary con diti on with no-slip, all aroundand top is pressu

20、re outlet boun dary con diti ons, the tower shell is solid wall boundary condition. Theboundaries of the air inlet and outlet are defined as interior; the porous model is used to simulate thefill and according to the measured resistance coefficie nt to set the fill resista nce coefficie nt in eachdi

21、recti on; the FLUENT fan model is used to simulate the fan of the tower, first boundary conditioncan also be used.2.3 冷却塔阻力系数及风速分布均匀性计算鼓风式机械通风冷却塔，气流经由风机鼓入塔内，依次经过塔进风口，雨区、填 料等，并经由出口排入到大气中，气流经过各部分的阻力为该区域前后断面的全 压差，一般表示为阻力系数与填料断面平均气流速度头之积：?P=EpV( 2)232f 式中？P 为气流经过某区域前后断面的全压差(Pa);p为空气密度(kg/m )； Vf 为填料断面平均

22、风速(m/s)。填料断面处风速分布状况影响冷却塔的热力特性，一般将填料断面风速分布均匀 性作为一个设计指标，用风速分布均布系数表示：a=E(Vi/Vf1)2n (3)式中a为填料断面风速分布均布系数；Vi 为填料断面各点风速(m/s); n 为风速 统计点的个数。2.3 Computati onal methods of the cooli ng tower resista nee coefficie nt and wind velocity uniformityFor the forced draft mechanical cooling tower, airflow is blown in

23、to the tower by the fan, sequentiallythrough the tower iniet, rain zone, fill etc, and is discharged into the atmosphere through the outlet finally. The resista nce of each part is the pressure loss of the regi on, which is gen erally expressed asthe resista nce coefficie nt multiply the average flo

24、w velocity head: Vf ?P=E p(2) 2Where ?P is the pressure loss of the regio(Pa);pis air densitykg/m3); Vf is the average windvelocity of the fill section(m/s).Distributio n of wind velocity at the fill sect ion affects the thermod yn amic characteristics of the cooling tower, gen erally put the wind v

25、elocity distributio n uniformity of the fill section as a design index,it can be expressed with a velocity distributio n uni formity coefficie nt: 2a=E(Vi/Vf1)2n (3)Whereais the velocity distribution uniformity coefficient; Vi is the velocity at the measure point in thefill section(m/s); n is the ve

26、locity statistical points number.2.4 模型的验证对已具有试验结果的某抽风式机械通风冷却塔的空气动力特性模型试验作对比验 证计算，冷却塔如图 1 示，首先对冷却塔进行网格的敏感性分析，然后再将计算 结果进行对比分析。风机风机进口过渡段收水器配水装置填料支撑结构图 1 抽风式机械通风冷却塔模型试验布置示意图不同填料阻力条件下模型试验实测与计算结果对比如图2 所示，图中横坐标 LO/L为距其中一侧塔壁的相对距离， V/V 为相对风速，V 为测点风速，V 为测点风速的平均值。进风口气流流态作对比如图 3 所示，从图中可以看出，试验结果与数 值计算结果规律较为一致，吻

27、合良好。LO/LflIj?I9.0m, fandiameter is 6.0m. Air outletWater distributio n systemAir ini etFa nHCFig.4 The forced draft mecha ni cal cooli ng tower elevati on3.1 计算模型的建立及网格划分流体仿真计算域范围的选取影响计算的速度和精度，根据经验，当计算域到达一 定的大小时，塔内的流场就不再受计算域大小的限制。假定塔高为H，宽为 W，进风口高为 H1，经过试算分析，计算域进风口上下游宽度取为 3H1、宽度取为 4W、高度取为 2H 时再增大计算域范

28、围对计算影响不大。数值模拟计算与计算网格的划分密切相关，本文进行了网格相关性分析计算，结 果如图 56 所示。当网格数量达到 50 万时，塔内气流特性受网格数量的影响已 经很小，计算区域网格图如图 7 所示。5L0102030405060图 5 网格数量对冷却塔阻力系数影响罷53、去走殳境料斷面與速分布均布系数)CO 91020306508080_專棒0图 7 塔内及计算域网格示意图3.1 Establishme nt of calculative model and mesh gen erati onThe scale of fluid computati onal doma in affe

29、cts the calculative velocity and accuracy,based on experie nee, whe n computati onal doma in reaches to a certa in scale, flowfield in the tower is no Ion ger limited by computati onal doma in scale. Assume that thetower height is H, width is W, air in let height is H1, accordi ng to the results of

30、the trialcomputati on, it makes little differe nee to in crease the computatio nal doma in whe n thelen gth of upstream and dow nstream of air in let is 3H1, the width of the whole computational doma in is 4W and the height is 2H.Numerical simulation is closely related to grid partition, this paper

31、analysis gridcorrelation, the results are shown in Figure 5 and 6. It is known according to the twofigures that the grid number has little effect on air flow characteristics in the tower whe nthe gridind number 1 -1nu mber reachi ng 500000, computati onal doma in grid is show n as Fig.7.Fig 5 The in

32、 flue nee of grid nu mber on the cooli ng tower resista nee coefficient tion uni formity2 2 s_s_5 5o9 -P84UdIP6 qc5-* *4*a9斗J14豪2Jn4I020301050GO708090D r i d n uITl 旧 E ) r *Tit. G 亠 fit . II f J . ! iFig 7 The tower and computati onal doma in grid schematic diagram3.2 填料安装高度对冷却塔气流特性影响不同的淋水填料安装高度时，

33、冷却塔的阻力系数与填料断面风速分布计算结果如 图8 和图 9 所示，图中横坐标 HF/L 为填料底至进风口上沿距离与塔宽之比，结 果表明，填料安装高度对整塔阻力系数影响不大，但填料安装高度离塔进风口远 时，填料阻力较小者风速分布均匀性变差。图 8 填料安装高度对整塔阻力系数的影响3.2 The in flue nee of the fill in stallati on height on the cooli ng tower aerod yn amiccharacteristicsIn the conditions of different fill installation height,

34、 the computational results of coolingtower resista nee coefficie nt and fill secti on wind velocity distributio n are show n infigure 8 and figure 9, abscissa HF/L is the distance from fill bottom to top of the air in letdivides tower width, it turns out that the bottom height of the fill has little

35、 effect on thewhole tower resistance coefficient, but when fill installation height is higher, theo o0HFHF/ /的料阻力系数馆填料阻力系数刘0 2HF/L0.3填强阳填料阳力系散 30&填料阴力蕪故循o ooooo70.65.o o5.smaller the fill resistance coefficient is ,theworse the wind velocity distributionuniformity is.*Flllrr rvviilaix dfirivht i

36、t ISfiller r 4 ! wrf nrjieni Ikidil mi I he Eill、CUIIHIwind vekKit dzrihi山询律期塔出口收第簡疫吋冷虻塔 T 汛特性的序吶调整冷却塔出口收缩角度，冷却塔的阻力系数与填料断面风速分布计算结果如图 12 和 13所示,图中横坐标为收缩段与水平的夹角。 随着塔出口收缩角度的增加, 冷却塔阻力系数降低，但趋势不明显。填料断面风速分布均布系数基本不受塔出 口收缩角度的影响。 *-* wFV-TXBI nrffaci RII 15*f illtr rtvivlohc* c*ffii tni i v 30 filin arV-CHBI

37、*-rvet 11-；勺 0別IK fl_60 i-ni Ujtus塢料PIL力蠹融30h & is图 13 收缩角度对填料断面风速分布均匀性的影响3.4 The in flue nee of con verge ntan gle on the cooli ng tower airflowcharacteristics Adjusting the cooling tower outlet con verge nt an gle, the computatio nal results of cooli ng tower resistanee coefficie nt and fill s

38、ect ion wind velocity distributio n are shown in figure 12 andfigure 13, Abscissa is the angle between convergent section and horiz on. With the increase of tower outlet conv erge nt an gle, the cooli ng tower resista nce coefficie ntdecrease, but this trend is not obvious. Fill sect ion wind veloci

39、ty distributio n un iformitycoefficie nt is not affected by tower outlet conv erge nt an gle.55.050.015- 010.035.030,025.020.01520 2S 303510也缩段b狀晋的夬角）图 12 收缩角度对整塔阻力系数的影响*烏I:卡TEW点y.一拒二二.-均料殂力厳敌话JA HA1h&30o o8耳-The inlluencc cl convergent angle on th? 1H1 wetion wind velocity distnburion按式対不幅塔fit尺

40、寸怖计計站卑进廿好常总雄握側以卜冷則和|14机itUM塔出口帽益贰整HtiK的出口SHtiM为27*.如段柯对靑處为Z=0.943zf+3.28+(0.0327Zf)(式中 FfHF2.284-0.012Zf)+1.2()2 (4) LF0F0 为冷却塔出 口面积(卅)。Z为 填料阻力系数；Ff 为冷却塔淋水面积(卅)；3.5 Calculative formula of cooli ng tower resista nee coefficie ntIn the con diti on of summariz ing the results of differe nt tower shapes

41、 accordi ng toequati on (2), it can obtai n the cooli ng tower resista nee coefficie nt calculative formulawhich is from tower in let to outlet relative to the fill sect ion wi nd velocity. TheODO0&DooLlLL-hLS SB乐o5&nM-Kri94g432r-wulKy-unmn3x* Filler reslstjirice cc-ef flclent Is 15Filler re

42、sistance coefficient ii 30 Fillerresistwice c efficient i? 1*5FilLrr瘵15Tlllri trsisf3E；e eoeffici-Eti: ts RiFxLlfi lenst3QC-coeffieITEIitconv erge nt an gle is 27pthe conv erge nt sect ion relative height HC/L is 0.50.92 whe nfinishing the formula.Z=0.943Zf+3.28+(0.0327Z，0(lf2fHF2+821)2LF(WhereZf is

43、 the fill resistance coefficient;Ff is towers rain area (m2);F0 is outlet area(m2)b4 结论 本文对鼓风式机械冷却塔在不同填料安装高度、 不同收缩高度与角度等条件下的 塔的空气动力特性进行了数值模拟，结果表明，填料安装高度对冷却塔整塔阻力 系数影响不大，在填料阻力小时，安装高度高时均匀性变差；出口收缩段相对高 度越大，阻力越低，填料断面风速分布也越均匀，当其大于0.90 时所获的收益已经很小；出口收缩段与水平夹角增大时，冷却塔阻力系数降低，但趋势不明显， 填料断面风速分布均布系数基本不受塔出口收缩角度的影响。本文

44、还分析总结了 鼓风式冷却塔的阻力系数计算公式，计算方法经过类似模型试验对比，与试验结 果偏差在 5%之内，可供冷却塔设计计算参考。4 Con clusi onsThis paper establishes a nu merical model to study the aerod yn amic characteristics ofthe forced draft mechanical cooling tower in the conditions of different fill installationheights、differe nt con verge nt heights and

45、 an gles, it turns out that the bottom height ofthe fill has little effects on the whole tower resistance coefficient, but when fill installationheight is higher, the smaller the fill resistance coefficient is ,the worse the distributio n uniformity is; with the in crease of the tower outlet conv er

46、ge nt height, cooli ng tower resistance coefficie nt decrease, the fill sect ion velocity distributio n is more uniform, when HC/Lis greater than 0.90, the profit is not obvious; with the in crease of the tower outlet converge nt an gle, the cooli ng tower resista nce coefficie nt decrease, but this trend is notobvious, fill sect ion wi nd velocity distributio n un iformi