過程裝備與控制工程專業(yè)英語翻譯

1、Unit 19 Types of Heat ExchangersHeat exchangers are equipment primarily for transferring heat between hot and cold streams.They have separate passages for the two streams and operate continuously.The most versatile and widely used exchangers are the shell-and-tube types but various plate and other t

2、ypes are valuable and economically competitive or superior in some applications.These other types will be discussed briefly but most of the space following will be devoted to the shell-and-tube types primarily because of their importance but also because they are most completely documented in the li

3、terature.Thus they can be designed with a degree of confidence to fit into a process.The other types are largely proprietary and for the most part must be process designed by their manufacturers.Plate-and-Frame Exchangers Plate-and-frame exchangers are assemblies of pressed corrugated plates on a fr

4、ame. Gaskets in grooves around the periphery contain the fluids and direct the flows into and out of the spaces between the plates.Close spacing and the presence of the corrugations result in high coefficients on both sides several times those of shell-and­ tube equipment and fouling factors ar

5、e low.he accessibility of the heat exchange surface for cleaning makes them particularly suitable for fouling services and where a high degree of sanitation is required as in food and pharmaceutical processing.Operating pressures and temperatures are limited by the natures of the available gasketing

6、 materials with usual maxima of 300 psig and 400 F.Since plate-and-frame exchangers are made by comparatively few concerns most process design information about them is proprietary but may be made available to serious engineers.Friction factors and heat transfer coefficients vary with the plate spac

7、ing and the kinds of corrugations.Pumping costs per unit of heat transfer are said to be lower than for shell-and-tube equipment.1n stainless steel construction the plate-and-frame construction cot is 50%-70% that of the shell-and-tube.Spiral Heat Exchangers In spiral heat exchangers the hot fluid e

8、nters at the center of the spiral element and flows to the periphery; flow of the cold liquid is countercurrent entering at the periphery and leaving at the center.Heat transfer coefficients are high on both sides and there is no correction to the log mean temperature difference because of the true

9、countercurrent'action. These factors may lead to surface requirements 20% or so less than those of shell-and-tube exchangers. Spiral types generally may be superior with highly viscous fluids at moderate pressures.Compact (Plate-Fin) Exchangers Compact exchangers are used primarily for gas servi

10、ce.Typically they have surfaces of the order of 1200 m2 /m3 corrugation height 3.8-11.8 mm corrugation thickness 0.2-0.6 mm and fin density 230-700 fins/m.The large extended surface permits about four times the heat transfer rate per unit volume that can be achieved with shell-and-tube construction.

11、Units have been designed for pressiIres up to 80 atm or so.The close spacings militate against fouling service.Commercially compact exchangers are used in cryogenic services and also for heat recovery at high temperatures in connection with gas turbines.For mobile units as in motor vehicles compact

12、exchangers have the great merits of compactness and light weight.Any kind of arrangement of cross and countercurrent flows is feasibleand three or more different streams can be accommodated in the same equipment.Pressure drop heat transfer relations and other aspects of design are well documented.Ai

13、r Coolers In such equipment the process fluid flows through finned tubes and cooling air is blown across them with fans. The economics of application of air coolers favors services that allow 25-40 1" temperature difference between ambient air and process outlet.In the range above 10 Mbtu/l air

14、 coolers can be economically competítíve with watercoolers when water of adequate quality is available in su Hicient amountDouble-Pipe Exchangers This kind of exchanger consísts of a central pipe supported withín a larger one by packíng glands. The straight length is limited

15、 to a maximum of about 20 ft;otherwise the center pipe wi1l sag and cause poor distribution in the annulus.It is customary to operate with the high pressure high temperature high density and corrosive fluid in the inner pipe and the less demanding one in the annulus. The inner surface can be provide

16、 with scrapers as in dewaxing of oils or crystallization from solutions.External longitudinal fins in the annular space can be used to improve heat transfer with gases or viscous fluids.When greater heat transfer surfaces are needed several double-pipes can be stacked in any combination of series or

17、 parallel.Double-pipe exchangers have largely lost out to shell-and-tube units in recent years.They may be worth considering in these situations:1. When the shell-side coefficient is less than half that of the tube side;the annular side coeHicient can be made comparable to the tube side.2. Temperatu

18、re crosses that require multishell shell-and-tube units can be avoided by the inherent true countercurrent flow in double pipes.3. High pressures can be accommodated more economically in the annulus than they can in a larger diameter shell.4. At duties requiring only 100200 sqft of surface the doubl

19、e-pipe may be more economical even in comparison with off-the-shell unts.Shell-and-Tube Exchangers This type of exchangers will be discussed in the following section.(Selected from: Stanley M.WalasChemical Process Equiment Butterworth Publishers 1988.)Words and Expressions1.passage n.通道，通過2.versatil

20、e a.多用途的，通用的3.proprietary a.專利的，私有的4.corrugate v.成波紋狀，起波紋;corrugation n5.groove n.溝，槽6.coefficient n.系數(shù)7.gasket n.密封墊片8.foul v.弄臟，堵塞;fouling factor 污垢系數(shù)9.sanitation n.衛(wèi)生10.pharmaceutical a.制藥的；藥物的11.countercurrent n. ; a.逆流12.fin n.翅片;v.裝翅片13.militate v.妨礙，起作用14.cryogenic a.冷凍的，低溫的15.recovery n.恢復(fù)，回

21、收，再生16.gland n.填料蓋，密封套17.sag v.下垂，下沉18.annulus n.環(huán)狀空間; annular a環(huán)形的.19.dewax v.脫蠟20.crystallization n.結(jié)晶，結(jié)晶體21.stack n.堆積，煙囪22.inherent .內(nèi)在的，固有的23.accommodate v.調(diào)節(jié)，適度，容納Unit 19 換熱器的種類換熱器起初是為了在熱流和冷流中傳熱。對兩種冷熱流體一般有單獨的通道，一般是連續(xù)性操作。最通用的換熱器是殼管式換熱器。但是不同種類板式和其他形式是有價值的和經(jīng)濟競爭能力。雖然一些其他形式也被討論，但是接下來大部分都在討論殼管式的。起初是

22、因為它們的重要性也是應(yīng)為他們在文獻中由較完整的記載。因襲它們可以以一種適當(dāng)過程的準(zhǔn)確標(biāo)準(zhǔn)被設(shè)計。其他類型的基本上市帶有專利性的，并且多數(shù)必須有他們的制造廠來進行工藝設(shè)計。板框式換熱器 板框式換熱器是在一個結(jié)構(gòu)上壓緊波紋板的裝配體。圍在邊緣的夠槽中密封墊片含有液體，并且控制板間液體的流入與流出空間。緊密的縫隙和波紋的板框換熱器，在兩側(cè)的上部達到了管殼式換熱器的幾倍，而且板框式換熱器的污垢系數(shù)較小。換熱表面對于清掃的容易性德爾板框式換熱器特別適用于污垢設(shè)備，也適用于衛(wèi)生要求較高的行業(yè)，比如制藥和食品工業(yè)，受到可能的墊圈式的密封材料性能的影響，一般最高壓力值為300 psig，最高溫度為400 .。

23、由于較少氣液制造板框式換熱器，大多數(shù)關(guān)于板框式換熱器的工藝設(shè)計資料到有專利性，但也許提供給負(fù)責(zé)的工程師。摩擦飲食和熱傳遞系數(shù)碎著班的空間和波紋的種類變化。泵花費的每個熱傳遞單元比殼管式設(shè)備低。用純鋼制造板框式換熱器的費用是管殼式的5070%。螺旋型換熱器 在螺旋形換熱設(shè)備中，熱流進入螺旋單元的中心，并且流到邊緣。冷流體是逆流的。在邊緣進入并在中心位置流出。在兩邊熱傳遞系數(shù)較高。由于真正的逆流形式?jīng)]有原來形式的溫差，這些因素可能導(dǎo)致表面要求20%或更小的殼管式換熱器。螺線形式對于中等壓力的高粘性流體比較適合。翹片式換熱器 翹片式換熱器首先被應(yīng)用在油氣設(shè)備中。典型的翹片式換熱器在單位體積上有120

24、0平方米的表面積，翹片高度3.811.8 mm，翹片的厚度是0. 20. 6 mm,片的密度是230700片每米。在單位體積上翹片式換熱器是殼管式換熱器的4倍。翹片式換熱器的操作壓力設(shè)計為80atm。因為翹片式換熱器之間的間距小，所以不適合易堵塞的設(shè)備。從商業(yè)上說，翹片式換熱器適用于低溫設(shè)備，也是用于與汽輪機相關(guān)的高溫恢復(fù)設(shè)備。對于動力設(shè)備來說，比如在有發(fā)動機的交通工具中，翹片式換熱器有結(jié)構(gòu)緊湊和質(zhì)量輕的優(yōu)點。錯流和逆流的任何排列形式都是可行的，并且在同一設(shè)備中可以安排三種或三種以上的流束，壓力下降、熱交換關(guān)系的設(shè)計其他方面被很好的記載。空氣冷卻器 這種設(shè)備是指由流體流過翹片式的管道，并且有風(fēng)

25、扇冷卻的空氣通過管道。考慮空氣冷卻器的經(jīng)濟性，可以允許流體與周圍空氣和出口的溫差為2540 。蕩船熱效率超過每小時1千萬英熱時單位時，空氣冷卻器與水滿足要求且供應(yīng)量充足時，與水冷在經(jīng)濟上不分上下。 套管式換熱器 套管式換熱器是由一個尺寸比較大的和中間一個尺寸比較小的中央管通過塑料密封套連接而成。直線長度被限制在20 ft，否則中心管將下沉并且使環(huán)面的分配空間較小。一般情況，高溫、高壓、高密度和腐蝕性的液體放在內(nèi)管上，較小要求的液體被放在外側(cè)管子上。當(dāng)在處理石油脫蠟和液體結(jié)晶時，內(nèi)表面上應(yīng)該提供刮刀。在環(huán)狀的空間上，軸向翹片可以改善氣體和粘性流體的熱交換效率。假如應(yīng)用較大的熱交換表面。套管可以排

26、布堆積起來，也可以應(yīng)用平行方式。這些套管式換熱器已經(jīng)逐漸被管殼式換熱器所取代。在以下情況下，是值得考慮的。（1） 當(dāng)殼側(cè)系數(shù)比管側(cè)系數(shù)一樣小時，這時殼側(cè)系數(shù)可以與管側(cè)相比了（2） 我們可以在套管式換熱器中采用真正意義上的逆流來代替，因為溫度較高需要多個套管單元。（3） 在與大直徑殼體相比，我們的環(huán)裝空間是使用較高壓力來滿足經(jīng)濟性能（4） 而與開放式殼體換熱器相比，當(dāng)我們的換熱器表面僅僅是100 200 sqft時，我們套管式換熱器有較高的經(jīng)濟性殼管換熱器 這種換熱器將在以后幾章討論。Notes 本句可譯為：“其他類型基本上是帶有專利性的，并且多數(shù)必須由它們的制造廠進行工藝設(shè)計”。 本句可譯為：

27、“由于較少企業(yè)制造板框式換熱器，大多數(shù)關(guān)于板框式換熱器的工藝設(shè)計資料是帶有專利性的，但也許可以提供給負(fù)責(zé)任的工程師”?！癗 isavailable to M”，M可以得到N.句中的“concers”作企業(yè),財團解釋。 本句可譯為：“錯流和逆流的任何排列形式都是可行的，并且在同一設(shè)備中可以安排三種或多種流束”。 本句可譯為：“當(dāng)傳熱速率超過每小時1千萬英熱單位時，空氣冷卻器與水質(zhì)滿足要求且供應(yīng)量充足時水冷卻器在經(jīng)濟性上不相上下”。Exercises1. What type of heat exchangers is most widely used in industries?2. In wha

28、t situations may the double-pipe exchangers be used?3. Using thefollowing phrases to make English sentences:(1) be available to (2) be feasible (3) be competitive with (4) militate against (5) in connection with4. Put the following phrases into Chinese:122(1) Plate-and-frame exchangers (2) spiral he

29、at exchangers(3) plate-fin exchangers (4) air coolers(5) double-pipe exchangers (6) shell-and-tube exchangersReading Material 19Shell-and-Tube Heat ExchangersShell-and-tube exchangers are made up of a number of tubes in parallel and series through which one fluid travels and enclosed in a shell thro

30、ugh which the other fluid is conducted. The shell side is provided with a number of baffles to promote high velocities and largely more efficient cross flow on the outsides of the tubes. The versatility and widespread use of this equipment has given rise to the development of industrywide standards

31、of shich the most widely observed are the TEMA standards. A typical shell-and-tube exchanger is presented on Fig. 4. 3. Fig.4.3 Shell-and-tube exchanger I-Shelh; 2-Shell coveq; 3-Shell channel; 4-shell cover end flange; 5-Shell nozzle 6-Floating tuesheet; 7-Floating head; 8-Floating head flange; 9-C

32、hannel partition; 10-Stationary tubesheet; 11-Channel; 12-Channel cover; 13-Channel nozzle; 14-Tie rods and spacers; 15-Transverse baffles or supportplates; 16-Impingement baffle; 17-Vent connection; 18-Drain connection; 19-Testconnection; 20-Support saddles; 21-Lifting ring;Baffle pitch , or distan

33、ce between baffles, normally is 0. 21. 0 times the inside diameter of the shell. Both the heat transfer coefficient and the pressure drop depend on the baffle pitch, so that is selection is part of the optimization of the heat exchanger. The window of segmental baffles commonly is abort 25%, but it

34、also is a parameter in the thermal-hydraulic design of the equipment. In order to simplify external piping, exchangers mostly are built with even number of tube passes. Partitioning reduces the number of the tubes that can be accommodated in a shell of a given size. Square tube pitch in comparison w

35、ith triangular pitch accommodates fewer tubes but is preferable when the shell side must be cleaned by brushing.Two shell passes are obtained with a longitudinal baffle. More than two shell passes normally are not provided in a single shell, brt a 48 arrangement is thermally equivalent to two 24 she

36、lls in series, and higher combinations is obtainable with shell-and tube exchangers, in particular: Single phase, condensation or boiling can be accommodated in either the tubes or the shell, in vertical or horizontal positions. Pressure range and pressure drop are virtually unlimited, and can be ad

37、justed independently for the two fluids. Thermal stresses can be accommodated inexpensively. A great variety of materials of construction can be used and may be different for the shell and tubes. Extended surfaces for improved heat transfer can be used on either side. A great range of thermal capaci

38、ties is obtainable. The equipment is readily dismantled for cleaning or repair.Several considerations may influence which fluid goes on the tube side or the shell side.The tube side is preferable for the fluid that has the higher pressure, or the higher temperature or is more corrosive. The tube sid

39、e is less likely to leak expensive or hazardous fluids and is more easily cleaned. Both pressure drop and laminar heat transfer can be predicted more accurately for the tube side. Accordingly, when these factors are critical, the tube side should be selected for that fluid.Turbulent flow is obtained

40、 at lower Reynolds numbers on the shell side, so that the fluid with the lower mass flow preferably goes on that side. High Reynolds numbers are obtained by multipassing the tube side, but at a price.A substantial number of parameters is involved in the design of a shell-and tube heat exchanger for

41、specified thermal and hydraulic conditions and desired economics, including: tube diameter, thickness, length, number of passes, pitch, square or triangular; size of shell, number of shell baffles, baffle type, baffle windows, baffle spacing, and so on. For even a modest sized design program, it is

42、estimated that 40 separate logical designs may need to be made which lead to 240=1.10X1012 different paths through the logic. Since such a number is entirely too large for normal computer process, the problem must be simplified with some arbitrary decisions based on as much current practice as possible.(Selected from: Stanley M.Walas. Chemical Process EquiPment.Butterworth Publishers，1988.)Words and