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5 翻譯
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 0.6~1 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 1000~3000 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 3500~5500 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 1.2~2.5:1.
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 0.8~1.1 : 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.
譯文：
管殼式與板式水水換熱器的比較分析
摘要：通過閉式循環(huán)冷卻水系統(tǒng)中水水換熱器的選型，詳細論述了管殼式與板式換熱器的結構性能技術經(jīng)濟比較，為水水換熱器的選型提供參考。
關鍵詞：換熱器 性能 比較
? 從國內已建發(fā)電廠來看，用于閉式循環(huán)冷卻水系統(tǒng)的水水換熱器有兩類，一類是管殼熱換器，另一類是板式換熱器。管殼換熱器是常用的換熱器形式，在電廠設計中已得到了廣泛的應用，而在國內一些進口機組的電廠、燃氣蒸汽聯(lián)合循環(huán)電廠和核電站多有采用板式換熱器。由于板式換熱器緊湊、重量輕、高傳熱效率，人們對它的興趣日益增長。本文針對管殼式及板式換熱器二種型式進行比較，并提出選型參考意見。
1 管殼式及板式換熱器結構簡介
（1）管殼式換熱器
? 管殼式換熱器是由前水室、管束、筒體、后水室等組成。管束采用可抽式管束，它由前后管板、折流板、拉桿、定距管、換熱管組成。拉桿與管板、拆流板采用絲扣連接，換熱管與管板采用脹接加密封焊。在殼側水入口處的管束上設置防沖板，以防止被冷卻水直接沖刷換熱管。為了減少管束裝入或抽出筒體時的摩擦力，在管束上設有滑軌。為了檢查清理室中垃圾、泥沙及管子的堵塞等，在前后水室端蓋上設有檢查孔。為了監(jiān)視水水換熱器的運行情況，在被冷卻水側（除鹽水側）及冷卻水側（海水側）進出口都設置溫度和壓力測點，此外還設有排氣和放水接口等。
（2）板式換熱器 ?
板式換熱器是由一組波紋形的平行金屬板構成的，在板片的4個拐角處都有通道孔，板被夾緊在一個側面附有連接管的固定板和活動壓緊板的框架中，并用夾緊螺栓加以夾緊。這些連接管同板上的通道孔對中，并與熱交換的兩種液體的外部管路相連，傳熱板和活動壓緊板懸掛在頂部承載梁的下面并由底部橫梁使其對準定位。
傳熱板本身是有其有特定形狀并被固緊的墊片密封，以防止外部泄漏，并把熱交換的兩種液體按逆流方式交替地流過另一對傳熱板之間的通道內。板片上的波紋不但提高流體的湍流程度，并且形成許多接觸點，以承受正常的運行壓力。流體的流量、物理性質，壓降和溫度差決定了板片的數(shù)目和尺寸。
2 換熱器設計條件
換熱器設計應滿足電廠從起動到最大出力時各種負荷下的運行需要，并留有一定的裕量，保證換熱器在最大負荷、最高進水溫度和最大污垢熱阻時，在規(guī)定的檢修周期內，仍能完成給定的冷卻任務。
以國產(chǎn)引進型300 MW燃煤機組為例，各冷卻設備要求冷卻水進水溫度不大于37．5℃，從冷卻設備出來被加熱過的冷卻水最高溫度約為42．8℃.
3 管殼式及板式換熱器的比較
3．1流動傳熱設計比較
管殼式換熱器的管子是換熱器的基本構件，它為在管內流過一種流體和穿越管外的另一種流體之間提供傳熱面。根據(jù)兩側流體的性質決定管子材料，將具有腐蝕性，水質差的海水放在管內流動，水質較好的除鹽水放在管子外殼側，這樣管子只需采用耐海水腐蝕的鈦管，同時清洗污垢較為方便，管徑從傳熱流體力學角度考慮，在給定殼體內使用小直徑管子，可以得到更大的表面密度，但大多數(shù)流體會在管子表面上沉積污垢層，尤其管內冷卻水水質較差，泥沙和污物及海生物的存在，都可能會在管壁上形成沉積物，將傳熱惡化并使定期的清洗工作成為必要，管子清洗限制管徑最小約為20 mm，鈦管一般采Φ25 mm，對給定的流體，污垢形成主要受管壁溫度和流速的影響，為得到合理的維修周期，管內側水的流速應在2 m／s左右（視允許壓降的要求）。由于一般冷卻水選用海水、河水等，較易引起結垢，對管殼式換熱器，應根據(jù)水質含沙量情況需設置膠球清洗裝置進行定期清洗。
板式換熱器的冷卻水和被冷卻水在波紋板的兩側對流，波紋采用人字形波紋，這些傳熱板的波紋斜交，即在相鄰的傳熱板上具有傾斜角相同而方向不同的波紋。沿流動方向橫截面積是恒定的，但是由于流動方向不斷變化致使流道形狀改變，而引起湍流。一般傳熱板的波紋深度為3～5 mm，湍流區(qū)流速約為0.1～1.0 m／s，波紋板很薄，厚度為0．6～1 mm，相鄰板間要有許多接觸點，以承受正常的運行壓力，相鄰的板有相反方向的人字形溝槽，兩種溝槽的交叉點就形成接觸點，這樣還可消除振動，并且在促進湍流和熱交換的同時，消除了由于疲勞裂縫引起的內部泄漏。人字形波紋板湍流度較高，高湍流還能充分發(fā)揮清洗作用，可以特別有效的將沉積污垢減至最小，但是波紋板的接觸點較多，當液體水質差，含有懸浮的固體顆粒、雜物和水草等時，由于板間隙很窄，所以要盡可能地保證將所有2 mm以上顆粒在進入換熱器以前，都要過濾掉，假如濾網(wǎng)不能有效地發(fā)揮作用，就容易發(fā)生堵塞。
3．2 傳熱系數(shù)的比較
管殼體換熱器中，一種流體橫向掠過管子通過管壁與管內流動的另一種流體換熱，彼此垂直交叉流動，其傳熱系數(shù)一般為1000～3000 w／（m2．k）。 ?
板式換熱器中，冷卻水側與被冷卻水側流動均勻湍流，兩種流體逆向流動，由于波紋的作用引起湍流，從而產(chǎn)生高傳熱率，高阻力壓降以及高切應力場，這將導致抑制污垢在傳熱面上形成。其傳熱系數(shù)一般為3500～5500 w／（m2．k），由此，可節(jié)省換熱器的換熱面積。
3．3 端差比較
管殼式換熱器傳熱端差（即冷卻水進口溫度和被冷卻水出口溫度差）為5℃左右。板式換熱器由于它的結構特點可以經(jīng)濟地做到低至1℃的端差。
3．4 冷卻水量比較
管殼式換熱器一般冷卻水量和被冷卻水量之比為1．2～2．5∶1。
板式換熱器，由于2種介質流道基本相同且傳熱效率高，因此板式換熱器可大大降低冷卻水量，一般冷卻水量和被冷卻水量之比為0．8～1．1∶1，這樣可以降低管道閥門和泵的安裝運行費用。
3．5 安裝檢修的比較
板式換熱器具有體積小，重量輕的特點，檢修方便，不需設檢修起吊設施，故安裝占地較少。板式換熱器的人工維護包括將整機折開，用噴水槍和刷子清洗板和墊片，檢查板片和墊片，如有必要，更換板片和墊片。板式換熱器一般每年要清洗1次，并且無論是否實際需要都要做。當應用河水、海水等水質較差的冷卻水時，由于泥沙和污物的存在，以及微生物的快速生長有引起表面污染和堵塞的危險。在國外，應用河水作冷卻水時，清洗頻率很高，平均每年3．3次。
管殼式換熱器是由管束組成，自身重量體積都較大，在檢修抽管時需要留出管束一樣長的距離，故占地較多，還需配備必要的起吊檢修設施。管殼式換熱器的設計壽命一般為30年，大修周期4年，當換熱器發(fā)生泄漏時，（可能是管子與管板間的泄漏或是管子破裂引起的泄漏）可以采用堵管的辦法在短時間內恢復工作性能，管殼式換熱器允許有7％的堵管裕量。對于管內的清洗可以根據(jù)需要采用膠球清洗裝置進行定期的機械清洗。
4 換熱器在國內電廠的運行情況
我國早期投產(chǎn)的300 MW的燃煤機組閉式冷卻水系統(tǒng)大多選用管殼式水水換熱器，運行情況都比較好。近年來由于技術的不斷進步，設計優(yōu)化的需要，管殼式水水換器占地面積大、檢修場地大的缺點在主廠房布置優(yōu)化中更顯突出，在一些循環(huán)水系統(tǒng)為二次循環(huán)冷卻水的機組中，考慮到水水換熱器的冷卻水水質相對較好、雜質少、污染小以及濾網(wǎng)結構的不斷改進，閉式冷卻水系統(tǒng)中亦有選用板式換熱器。
5 結論
通過對管殼式及板式換熱器的比較，可以得出以下結論：板式換熱器傳熱器傳熱效率高、體積小、重量輕便于拆裝，當冷卻水水質較好時，它是一種比較理想的換熱器設備。但是對于冷卻水中有大量泥沙、污物、水草等存在時，濾網(wǎng)又不能有效地發(fā)揮作用，很容易使其堵塞，造成頻繁地清洗，影響機組的安全運行。