文献翻译-管壳式与板式水水换热器的比较分析

5 翻译 5.1 英文原文 Shell-and-tube and plate heat exchanger water Comparative Analysis Abstract: Through the closed cycle cooling water system in thewater water heat interchanger shaping, in detail elaborated the shell type and the disc heat interchanger structure performance technology economy compares, provides the reference for the water and water heat interchanger shaping. Keyword: Heat interchanger performance comparison From the domestic power plants have been built, for closed-cycle cooling water system of water heat exchanger two categories. is a shell and tube type heat exchangers, and the other is the plate heat exchanger. Shell heat exchanger is used in the form of heat exchanger in the plant design has been widely used, In some domestic units of the plant imports, the gas-steam combined cycle power plants and nuclear power plants are more used plate heat exchanger. Plate heat exchanger as a compact, light weight, high heat transfer efficiency, and the people are interested in growing. This paper shell - and-tube heat exchanger plate and two kinds of styles, and make selection suggestions 1. A plate and shell heat exchanger structure brief (1) Shell type heat interchanger Shell-and-tube heat exchanger is the former Marine Room, probation, cylinder, the water room and so on. Control the use of pumped - Bundle, which consists of around tube sheet, Baffled, the stick, distance control, Tube components. Stick with the management board, demolition of the plates using screw connection tube and tube sheet adopted inflation accelerating sealed welding. In the shell side entrance to the control of water on board-equipped to prevent the cooling water washed Tube. In order to reduce the load or to take control of the cylinder friction, with the control on the slide. Room for cleaning up the rubbish, sediment and the blockage of the tubes in the water around the room on the Cover of an inspection hole. To monitor water heat exchanger performance, in the cooling water side (except salt water side) and the cooling water side (of seawater) for the import and export are equipped with a temperature and pressure measurement, There is also supposed to exhaust and interfaces. (2) Plate heat exchanger plate heat exchanger consists of a set of parallel corrugated sheet metal components, Plates in the four corner have access hole, Clamping plate was in connection with an aspect of the fixed plate compactor and activities in the framework of plate and clamping bolts used to be clamping. Connecting with the board of the channel pore right, and with two heat exchange liquid external piping connected Heat plate compactor and activities flag at the top plate bearing beams below it from the bottom of the beams at the position. Plate heat itself is a specific shape surrounded by solid-tight gasket seal to prevent external leakage. and the two heat exchange liquid form by alternating current to flow through another pair of plate heat transfer between the channel. Plates of corrugated not only improves the fluid turbulence, and creating many points of contact to withstand normal operating pressure. Fluid flow, physical properties, the pressure and temperature differential decision of the plate number and size. 2 Heat interchangers design conditions Heat exchanger design of the plant from the start to meet the greatest contribution to the various load operating conditions to take dollars, and leave enough margin to ensure heat exchanger in the maximum load and maximum inlet temperature and the largest Fouling, in the repair cycle, it was to be given the task of cooling. Domestic imported 300 MW coal-fired units as an example. Cooling equipment requirements of the cooling water inlet temperature is less than 37.5 C, from the cooling equipment was heating up over the cooling water temperature is about 42.8 3 Shells types and disc heat interchanger comparison 3.1 Flows the heat transfer design comparison Shell-and-tube heat exchanger tube heat exchanger is an essential component, It tube in a fluid flowing through the tube and another providing heat transfer fluid between the surface. According to both the fluid nature of pipe materials, will be corrosive, low-quality water on the water pipe flow In addition to better water quality brine on the shell side of the tubes, such tubes only used seawater corrosion-resistant titanium tube. Meanwhile more convenient cleaning dirt diameter from the point of view of heat transfer fluid dynamics, given the use of the shell of small diameter tubes can be greater density on the surface, but most fluid in the tubes on the surface dirt layer deposition, In particular, the cooling tube poor water, silt and dirt and sea organisms exist, are likely to be formed on the wall of sediments, will enable heat transfer deterioration regular cleansing becomes necessary, tube cleaning restrictions smallest diameter of about 20 mm, Titanium Tube general, 25 mm, the right to the fluid, formed mainly by dirt wall temperature and velocity impact to be reasonable maintenance cycle, the water inside the tube velocity in two 1961 (as to allow pressure drop requirements). As general use seawater cooling water, the river, prone to causing scaling the shell - and-tube heat exchanger, Water should be equipped concentration of plastic ball cleaning device for cleaning. Plate heat exchanger in the cooling water and cooling water on both sides of the corrugated plate convection, using corrugated chevron Bellows, These corrugated plate heat transfer bias, that is adjacent to the heat plate with the same angle of inclination and direction of the bellows. Cross sectional area along the direction of flow is constant, but due to the changing direction of flow resulting flow shape change, which leads to turbulence. Heat general corrugated plate depth of 3-5 mm, the turbulent flow is about 0.1 1.0 to 1.4 ms Bellows thin plate thickness 0.61 mm and the adjacent cubicle to have many points of contact to withstand normal operating pressure adjacent to the boards opposite direction of the chevron trench, two grooves on the intersection point of contact formation, this can also eliminate vibration, and the promotion of the exchange of heat and turbulence at the same time, eliminate fatigue cracks as a result of the internal leakage. Chevron corrugated plate turbulent higher, high turbulence can play a full role in cleaning, can be particularly effective deposition dirt minimized, but corrugated board more points of contact, when liquid water quality poor, containing suspended solid particles, debris and weeds, etc., because of the narrow gap plate. So to the extent possible, ensure that all particles above 2 mm into the heat exchanger in the past, must strip, If the filter can effectively play a role, it is easy to plug. 3.2 Heat transfer coefficients comparison Shell heat exchanger tube, a horizontal fluid passing through the tube wall and pipe flow of a heat transfer fluid, mutual vertical cross-flow heat transfer coefficient is generally 10003000 w/ (m2.k). Plate heat exchanger, the cooling water side with the side of the cooling water flow uniformity turbulence, the two reverse fluid flow As the ripple effect caused turbulence, resulting in higher heat transfer rate, high resistance to pressure and high shear stress field. This will lead to inhibit heat transfer surface of the dirt formed. Heat transfer coefficient is generally 35005500 w/ (m2.k), which can save heat exchanger heat transfer area. 3. Ends difference comparison Shell-and-tube heat exchanger temperature difference (that is, the cooling water inlet temperature and the cooling water outlet temperature difference) 5 . Plate heat exchanger due to its structural characteristics can be done to the economy as low as 1 C temperature difference. 3.4 Cooling water volume comparison Shell-and-tube heat exchanger general cooling and water cooling water than a 1.22.5:1. Plate heat exchanger, as two kinds of media flow with the same high heat transfer efficiency, Therefore plate heat exchanger can greatly reduce the cooling water, the general cooling water and cooling water than a 0.81.1 : 1, thus reducing pipe valves and pumps installed operating costs 3.5 Installments overhauls comparison Plate heat exchanger is small in size, light weight characteristics, maintenance convenience, without lifting based maintenance facilities, Therefore, the installation occupies less. Plate heat exchanger including the artificial maintenance unit packs will be opened, using water guns and brush cleaning plates and gaskets, check plate gasket and, if necessary, replace the plate and gasket. Plate heat exchanger generally a time to clean, and whether or not the actual needs to be done. When the application of the river, poor water quality, such as cooling water, silt and dirt because of the existence, and the rapid growth of microorganisms have caused pollution and the surface plug danger. Overseas, the application of water for cooling water, cleaning high frequency, the average annual 3.3. Shell-and-tube heat exchanger tube bundle is composed of its own weight is larger volume, maintenance of the pumping required to stay out of control as long distance, it occupies more needed with the necessary lifting overhaul facilities. Shell-and-tube heat exchanger design life-expectancy of 30 years, overhaul cycle four years, when heat exchanger leaked, (probably tubes and tube plate of tube leakage or rupture caused by the leakage) can be used to plug the pipe recovery in a short period of time Minute performance, shell - and-tube heat exchanger allows the blocking of 7% margin. For pipe cleaning may need plastic ball cleaning device for the mechanical cleaning regularly. 4 Heat interchangers in domestic power plant movement situation My early commissioning of the 300 MW coal-fired units closed cooling water systems are chosen shell - and-tube heat exchanger water. running relatively well. In recent years, because of the continuous advancement of technology, design optimization, shell - and-tube exchangers covers water, Maintenance of large venues in the main shortcomings of the plant layout optimization more prominent, In some circulating water system for secondary cooling water circulation unit, taking into account the water cooling heat exchanger of the relatively good water quality, Impurities less pollution and the small screen structure of continuous improvement, closed cooling water systems also use plate heat exchanger. 5 Conclusion On shell - -tube and plate heat exchanger the comparison may come to the following conclusions : Plate heat exchanger for high heat transfer efficiency, small size, light in weight dismounting, when cooling water better, It is an ideal heat exchanger equipment. But for a large number of cooling water sediment and dirt, such as the presence of water, the filters can not effectively play its role it is easy to plug, resulting in frequent cleansing affect the safe operation of the unit. 译文： 管壳式与板式水水换热器的比较分析 摘要 ：通过闭式循环冷却水系统中水水换热器的选型，详细论述了管壳式与板式换热器的结构性能技术 经济 比较，为水水换热器的选型提供 参考 。 关键词 ：换热器 性能 比较 从国内已建发电厂来看，用于闭式循环冷却水系统的水水换热器有两类，一类是管壳热换器，另一类是板式换热器。管壳换热器是常用的换热器形式，在电厂设计中已得到了广泛的 应用 ，而在国内一些进口机组的电厂、燃气蒸汽联合循环电厂和核电站多有采用板式换热器。由于板式换热器紧凑、重量轻、高传热效率，人们对它的兴趣日益增长。本文针对管壳式及板式换热器二种型式进行比较，并提出选型参考意见。 1 管壳式及板式换热器结构简介 （ 1）管壳式换热器 管壳式换热器是由前水室、管束、筒体、后水室等组成。管束采用可抽式管束，它由前后管板、折流板、拉杆、定距管、换热管组成。拉杆与管板、拆流板采用丝扣连接，换热管与管板采用胀接加密封焊。在壳侧水入口处的管束上设置防冲板，以防止被冷却水直接冲刷换热管。为了减少管束装入或抽出筒体时的摩擦力，在管束上设有滑轨。为了检查清理室中垃圾、泥沙及管子的堵塞等，在前后水室端盖上设有检查孔。为了监视水水换热器的运行情况，在被冷却水侧（除盐水侧）及冷却水侧（海水侧）进出口都设置温度和压力测点，此外还设有排气和放水接口等。 （ 2）板式换热器 板式换热器是由一组波纹形的平行金属板构成的，在板片的 4个拐角处都有通道孔，板被夹紧在一个侧面附有连接管的固定板和活动压紧板的框架中，并用夹紧螺栓加以夹紧。这些连接管同板上的通道孔对中，并与热交换的两种液体的外部管路相连，传热板和活动压紧板悬挂在顶部承载梁的下面并由底部横梁使其对准定位。 传热板本身是有其有特定形状并被固紧的垫片密封，以防止外部泄漏，并把热交换的两种液体按逆流方式交替地流过另一对传热板之间的通道内。板片上的波纹不但提高流体的湍流程度，并且形成许多接触点，以承受正常的运行压力。流体的流量、物理性质，压降和温度差决定了板片的数目和尺寸。 2 换热器设计条件 换热器设计应满足电厂从起动到最大出力时各种负荷下的运行需要，并留有一定的裕量，保证换热器在最大负荷、最高进水温度和最大污垢热阻时，在规定的检修周期内，仍能完成给定的冷却任务。 以国产引进型 300 MW燃煤机组为例，各冷却设备要求冷却水进水温度不大于 37 5 ，从冷却设备出来被加热过的冷却水最高温度约为 42 8. 3 管壳式及板式换热器的比较 3 1 流动传热设计比较 管壳式换热器的管子是换热器的基本构件，它为在管内流过一种流体和穿越管外的另一种流体之间提供传热面。根据两侧流体的性质决定管子材料，将具有腐蚀性，水质差的海水放在管内流动，水质较好的除盐水放在管子外壳侧，这样管子只需采用耐海水腐蚀的钛管，同时清洗污垢较为方便，管径从传热流体力学角度考虑，在给定壳体内使用小直径管子，可以得到更大的表面密度，但大多数流体会在管子表面上沉积污垢层，尤其管内冷却水水质较差，泥沙和污物及海生物的存在，都可能会在管壁上形成沉积物，将传热恶化并使定期的清洗工作成为必要，管子清洗限制管径最小约为 20 mm，钛管一般采 25 mm，对给定的流体，污垢形成主要受管壁温度和流速的 影响 ，为得到合理的维修周期，管内侧水的流速应在 2 ms左右（视允许压降的要求） 。由于一般冷却水选用海水、河水等，较易引起结垢，对管壳式换热器，应根据水质含沙量情况需设置胶球清洗装置进行定期清洗。 板式换热器的冷却水和被冷却水在波纹板的两侧对流，波纹采用人字形波纹，这些传热板的波纹斜交，即在相邻的传热板上具有倾斜角相同而方向不同的波纹。沿流动方向横截面积是恒定的，但是由于流动方向不断变化致使流道形状改变，而引起湍流。一般传热板的波纹深度为 3 5 mm，湍流区流速约为 0.1 1.0 m s，波纹板很薄，厚度为 0 6 1 mm，相邻板间要有许多接触点，以承受正常的运行