外文翻译---轴流管壳式换热器壳侧流体进出口分布挡板的理论研究.docx

外文翻译THEORETICAL INVESTIGATION OF FLUID DISTRIBUTOR INTHE INLET/ OUTLET REGION OF SHELL-SIDE OF SHELL-AND-TUBE HEAT EXCHANGER WITHLONGITUDINAL FLOWZEN G Wen-Liang1，2, HU Xian-ping1, DEN G Xian-h1(1. The Key Lab. of Enhanced Heat Transfer & Energy Conservation of the Ministry of Education , South China University of Technology , Guangzhou 510640 ,China ; 2. The Chemistry and Materials Department ,Hengyang Normal University , Hengyang 421001 ,China)Abstract:Presents the theoretical investigation of fluid distributor in the region of inlet/ outlet of shell-side of shell-and-tube heat exchanger with longitudinal flow in this paper . It is advanced the structural optimal mathematical model among the various structural parameters of shell-side of heat exchanger. The model provides reference and direction not only for experimental and numerical investigation of this problem, but also for the other process with fluid distribution.Key words: shell-and-tube heat exchanger; longitudinal flow ; fluid distribution ; structural optimization ; theoretical modelCLC Number : TQ051. 5 Document Code :A0 IntroductionBecause of such advantages as lower pressure drop of shell-side , larger logarithmic mean temperature difference (LMTD) , eliminating vibration of heat-transfer tubes , and better overall heat transfer performance , shell-and-tube heat exchangers with axial flow have become more popular in various are as of industrial process comparing with shell-and-tube heat exchangers with segment baffles. With the scale of industrial production devices become lager and larger , heat exchanger as a type of universal equipment in industrial process also need to satisfy the requirement of industrial process , and the heat transfer capability of heat exchanger became larger and larger . Because the length of tube of shell-and-tube heat exchanger is decided by processing technology condition, it is necessary to enlarge the diameter of shell-side in order to enlarge the heat transfer capability. With the increasing of diameter of heat exchanger and decreasing of the ratio of length and diameter ( L/ D) , shell-side fluid flow maldistribution became more badly and pressure drop of shell-side increased more quickly , it is not only reduce the overall heat transfer performance of heat exchanger but also induce vibration of heat-transfer tubes. These are proved by ZHOU Sen-quan1 , Chiou J . P 2 , Ulrich Mohr and Horst Gelbe3 . In order to make fluid flow homo-distribution, constructing a fluid flow distributor and setting it in the region of inlet or outlet of equipment have been carried out by S. S. Mousavi, K. Hooman4 and L. Maharaj , J . Pocock , B. K.Loveday 5 . But there is no any report of fluid flow distributor about the shell-side of shell-and-tube heat exchanger with axial flow, especially the large-scale and super-large scale heat exchanger . Setting fluid distributor also has advantage and disadvantage at the same time. On one hand shell-side fluid flow maldistribution can be improved quickly, on the other hand pressure drop of shell-side be increased quickly at same time. So it is very important to develop the theoretical, numerical, and experimental investigation of fluid flow distributor of shell-and-tube heat exchanger . The purpose of this research program is to optimize structural parameter of heat exchanger, to improve shell-side fluid flow maldistribution, toreduce shell-side -pressure drop , and to enhance overall heat transfer performance , by theoretical , numerical , and experimental investigation methods respectively. In this paper, it will introduce optimal mathematical model among the various structural parameters of heat exchanger by theoretical methods.1 Physical ModelThe overall shell-side structural drawing and the position of fluid flow distributor of shell-and-tube heat exchanger with axial flow are shown as Fig. 1 (a) . Fig. 1 (b) is the sketch map of shell-side flow distributor structure. In fact , it is easily to understand the fluid distributor structure as that is a specified punched ratio board punched many mini-ostioles on it from the Fig. 1 (b) . The purpose of theoretical investigation is to found a mathematical model which brings out the optimal punched ratio of distributor as a function of parameter of heat exchanger. The main aspects affecting the fluid flow distribution of shellside are shown as follows: (1) punched ratio of distributor ; (2) rows of crossing tubes ; (3) arrangement style of tubes ; (4) tube pitch ; (5) tube outer diameter .Fig. 1 Schematic drawing of shell side configuration of shell and tubeheat exchangers with axial flowIn order to express t he researched physical model more concisely, it is be treated as a rectangle heatexchanger with axial flow when we take into account the partial unit and its inlet and outlet only. Theheat exchanger is made up of 36 tubes specification of 25 mm 2. 5 mm 1 000 mm. The exterior dimension of heat exchanger is a cube wit h t he dimension of 360 mm 120 mm 1 000 mm. The elevation of heat exchanger is shown in Fig. 2 (a) . Arrangement styles and parameter of tubes is shown in Fig. 2(b) . 2 Mathematical ModelIn order to found the mathematical model in theoretical method, a theoretical analysis model must be built firstly as Fig. 3. The following assumptions and illumination are necessary for modeling fluid flowing through the inlet region and distributor. (1) Many mini-ostioles be punched in the fluid dist ributed baffle, and diameter of mini-ostioles is infinitesimal .(2) Punched ratio of distributed baffle is a continuous function with x coordinate.(3) Fluid flow in the x direction as shown in Fig. 3.(4) Fluid flow velocity through distributed baffle is uniform.Based above assumptions and next analysis , it is easy to deduce the velocity distribution of x direction and pressure drop of x direction , z direction ,and x-z direction respectively.2. 1 Velocity dist ribution of x coordinateMass balance Equation of t he infinitesimal is shown in Fig. 4 , and the differential Equation of x Fig. 4 Schematic Drawing of analyzed areadirection velocity is obtained as Equa. (1) : (1)Where A x and A z denote the area of x coordinate and z coordinate , respectively.And; (2)The boundary condition is: x = X wit h u( x) = 0 ,so t he integral of Equa. (2) can be expressed as follows : (3) (4)2. 2 Pressure drop of x coordinateThe energy balance Equation of t he infinitesimal area is shown in Fig. 4. It s differential Equation ofx direction pressure drop can be obtained as follow : (5) Where DH is hydraulic diameter of shell-side.The boundary condition is x = 0 wit h p ( x) = 0 , so t he integral of t he Equa. (5) can be expressed as : (6) (7)2. 3 Pressure drop of x2z directionAccording to distribution and local flow pressure drop of fluid flow from x direction turn to z direction , we can obtain it s local pressure drop Equation as follow : (8)2. 4 Pressure drop of z coordinateAccording to the generic Equation of local pressure drop of fluid , we can obtain it s local pressuredrop Equation of fluid flow through mini2ostioles of distributor baffle in z direction as follow : (9)Where A ( x) denote punched ratio as a f unction of independent variable x.2. 5 Homo-distribution EquationIt is well known that t he condition of homo-distribution of fluid flow through distributor baffle can be deduced by mechanical energy balance Equation from inlet to cross section of outlet . The basic homo-distribution Equation is shown as follow : (10) 2. 6 Analysis and solutionCombining Equa.(7) , (8) , (9) with Equa. (10) , it will obtain the following Equation : (11)When x = X ,t hen it can be deduced the pressure drop of boundary condition :, and Putting the pressure drop under x = X into Equa. (10) , then it can be deduced the following Equation : (12)Associating with Equa. (11) and Equa. (12), and simplifying expression , t hen it can be deduced the following Equation : (13)Under the ideal model, optimal punched ratio can be expressed as follow : (14)3 Mathematical Model of In-line-square Aligned Tube BundleFor the in-line-square aligned tube bundle of shell-side of shell-and-tube heat exchanger, we define as tube pitch , d as outer diameter , and L as installation distance. So tube rows of shell-side under in-line-square aligned can be expresses as ,: , and putting them into Equa. (4), then the velocity of x direction can be expressed as : (15)According to the Equa. (7), (8) , and (9) , the pressure drop of x direction , x-z direction , and z direction at in-line-square aligned condition of shell-side can also be written as Equa. (16), (17) and (18) ,respectively : (16)Where denotes local pressure drop coefficient of crossing a t ube at t he in-line-square aligned. (17) (18)Put ting Equa. (16) , (17) and (18) into Equa. (10), it can be deduced as follow. (19)When x = X , it can be deduced t he pressure drop of boundary condition as follow :, and And p ut ting t hem into Equa. (10) , then it can be deduced the following Equation : (20)Associating with Equa. (19) and Equa. (20), and simplifying expression , t hen it can be deduced following Equation : (21) Under the in-line-square aligned tube bundle of shell-side of shell-and-tube heat exchanger, optimal punched ratio of fluid dist ributor in the inlet or outlet region can be expressed as follow : (22)In Equa. (15) to Equa. (21), A z and A x can be expressed as follows : (23) (24) It define ,and denote the ratio of out diameter of tube to tube pitch , putting it and Equa. (23)and (24) into Equa. (22) ,it will be deduced follow Equation (25) From Equa. (25), it has been shown that the optimal punched ratio of fluid distributor related to many factors which can be classified into two aspect s. One aspect is struct ural parameter of heat exchanger of shell-side such as out-diameter of tube, tube pitch , rows of tube buddle , cut length of distributor, and tube arrangement style. The other aspect is operating characteristic such as Reynolds number which can changer local pressure drop coefficient.Although a mathematical model of shell-side fluid flow homo-distribution be found , and the model shows the relationship of optimal punched ratio to structural parameter of heat exchanger and operating characteristic , but its correctness need to be validated by numerical and experimental methods. Future investigation will go on in numerical and experimental methods respectively.4 ConclusionsThrough founding mathematical model and above analysis, it is concluded as following :(1) For the in-line-square aligned tube bundle of shell-side , main factors of fluid flow maidist -ribution are as such punched ratio of distributor , out-diameter of tube , tube pitch , rows of tube buddle , cut length of distributor , and tube arrangement style.(2) According to Equa. (25), it is easy to design a optimal fluid flow dist ributor .(3) The pressure drop of shell-side is cube of rows which fluid cross flowed. To decrease pressuredrop of shell-side must decrease rows of fluid cross flowed.References 1 Zhou Sen2Quan. The analysis of heat exchanger performance wit h temperature nonuniformity of inlet J . Gongcheng Rewuli Xue-bao , 1994 ,15 (4) :8211.2 Chiou J . P. . The effect of nonuniformity of inlet fluid temperature on t he t hermal performance of cross-flow heat exchanger C .Proc. of 7th international heat transfer conf . , 1982 :1792126. 3 Ulrich Mohr , Horst Gelbe. Velocity dist ribution and vibration excitation in tube bundle heat exchangersJ . Int . J . Thermal . Science. ,2000 ,39 (4) :4142421. 4 S. S. Mousavi , K. Hooman. Heat and fluid flow in ent rance region of a channel with staggered bafflesJ . Energy Conversion and Management ,2006 , 47 (18) :2 01122 019. 5 L. Maharaj , J . Pocock , B. K. Loveday. The effect of dist ributor configuration on the hydrodynamics of t he teetered bed separator轴流管壳式换热器壳侧流体进/ 出口分布挡板的理论研究曾文良1 ,2 , 胡显平1 , 邓先和1(1. 华南理工大学传热强化与过程节能教育部重点实验室, 广东广州510640 ;2. 衡阳师范学院化学与材料科学系, 湖南衡阳421001)摘要:大型、超大型壳程轴流管壳式换热器壳侧流体的流动分布不均严重影响着换热器的整体传热性能,而在壳侧入口和出口位置安装流体分布挡板是解决这一问题的方法之一. 文中从流体分布挡板的影响参数入手,从理论上推导了挡板的开孔率与各种结构参数之间的数学模型,并且推导出优化的挡板设计参数方程,为壳侧流体的实验研究与数值研究提供了参考与方向.关键词:管壳式换热器; 轴向流; 流体分布; 结构优化; 理论模型中图分类号: TQ051. 5 文献标识码:A0 介绍 由于这些优势，降低壳程，大对数平均温差（数平均温差）压力下降，消除了传热管的振动，更好的整体传热性能，轴向流管壳式换热器与部分挡板壳式换热器相比在各种工业生产中变得更加受欢迎。随着工业生产设备的规模变得越来越大，换热器作为一种工业生产通用设备，还需要满足工业生产过程的要求，以及换热器传热能力越来越大。由于对壳管式换热器管的长度是由加工工艺条件决定，有必要扩大壳端直径，以扩大传热能力。随着换热器的直径的增大和长径比的减小（L/D），壳程流体流动分布不均变得更难以控制和壳层的压力降增长的更快，这不仅降低了换热器整体传热性能，而且也引起了传热管的振动。这些都是被ZHOU Sen-quan ，Chiou J . P ，Ulrich Mohr and Hor st Gelbe证明的。为了使流体流动同源分布，S. S. Mousavi , K. Hooman and L. Maharaj , J . Pocock , B. K.Loveday已经构建了一个流体流动分布结构并将其设置在设备的进出口区域。但没有任何有关轴流管壳式换热器流体流动分布的报告，特别是大规模和超大规模换热器。设置流体流动分布器有优点也有缺点。一方面壳层流体流动分布不均可以迅速好转，另一方面壳层压降在同时可迅速提高。所以发展流体流动壳式换热器管区理论，数值和实验研究是非常重要的。这项研究计划的目的是优化换热器结构参数，以提高壳程流体流动分布的不均匀性，根本上减少壳层压降以及分别提高了理论，数值和实验研究方法，整体传热性能。在这篇文章中，将介绍各种换热器结构参数的优化数学模型的理论方法。 1 物理模型 整体壳程结构图和流体的壳管式换热器机智和轴流流分配器位置如图1（a）所示。图1(b) 是壳侧流分销结构图。事实上，流体分配器结构很容易理解的，从图1（b）上看，是一个指定的穿满许多小孔的穿孔板。该理论研究的目的是要找到一个数学模型，带出了最佳的分布比例作为换热器参数的函数。流体流动的影响壳区主要表现为以下方面：（1）冲压比分配器;（2）交叉管行;（3）安排式管;（4）管间距;（5）管外径。 管壳壳端配置与轴流式换热器示意图1为了表达研究的物理模型更简洁，当我们考虑到部分单位和其进口和出口唯一时，我们把它看作一个矩形热处理轴流换热器。该换热器管子是36毫米规格，尺寸为25 mm 2. 5 mm 1 000 mm。该换热器外观尺寸是维立方体360毫米 120毫米 1 000毫米。该换热器高程图2（a）所示，布置风格和管参数如图2（b）所示。2 数学模型为了找到了理论方法，数学模型理论分析模型，必须首先建立如图（3）所示。以下假设的建模和光照是通过进口和分配器区域流体流动必要的。（1）许多小孔是分布在流体挡板上，小孔直径是微不足道的。（2）分布式挡板打孔比率是一个连续x函数。（3）在x方向流体流量，如图所示