熱能與動(dòng)力工程專業(yè)英語

1、Chapter 1 Introduction to Thermal Science第一章 熱科學(xué)基礎(chǔ)Acoustic flow meter 聲波流量計(jì)Corrugated fin 波狀散熱片Adiabatic 絕熱的Cross product 矢量積Aerodynamics 空氣動(dòng)力學(xué)Denominator 分母Affiliation 聯(lián)系Developed flow 充分發(fā)展流Airfoil 機(jī)翼，螺旋槳Diffusion 擴(kuò)散Alternative 替代燃料Doppler effect 多普勒效應(yīng)Anemometer 風(fēng)速計(jì)Double-pipe heat exchanger 套管式換熱器

2、Angular speed 角速度Dry saturated vapor 干飽和蒸汽Area density 表面密度Electrode 電極Baffle 擋板Electrolyte 電解，電解液Bifurcation 分形Electrostatic 靜電的Blackbody 黑體Emissivity 發(fā)射率Blade 漿葉，葉片Equilibrium 平衡Boiler 鍋爐Fluid mechanics 流體力學(xué)Boundary layer 邊界層Forced convection 強(qiáng)制對流Carnot Cycle 卡諾循環(huán)Free convection 自然對流Cartesian coor

3、dinates 笛卡爾坐標(biāo)系Friction loss 摩擦損失Celsius Degree 攝氏度Glass ceramic 微晶玻璃，玻璃陶瓷Compact heat exchanger 緊湊式換熱器Heat engine 熱機(jī)Composition 成分，合成物Heat pump 熱泵Compressed liquid 壓縮液體Hydrofoil 水翼Compressibility 可壓縮性，壓縮率Hypersonic speed 高超音速Condensation 凝結(jié)Infinitesimal 無窮小的Condenser 冷凝器Inflating/deflating 充氣/壓縮Cond

4、uction 導(dǎo)熱Internal combustion engine 內(nèi)燃機(jī)Control volume 控制體Isentropic 等熵的Convection 對流Isobaric 等壓的Coriolis-accelaration flowmeter 科氏加速流量計(jì)Isolated system 孤立體系的Isometric 等容的Rough-wall tube 粗糙管Isothermal 等溫的Saturation 飽和Kinematic viscosity 運(yùn)動(dòng)黏度Shear stress 剪切力、切應(yīng)力Laminar 層流Shell-and-tube heat exchanger管殼

5、式換熱器Manuscript 手稿，原稿Specific volume 比容Moisture 濕度，水分Steady 穩(wěn)態(tài)的，定常的Molecule (化學(xué))分子Stifling engine 斯特林機(jī)Molten polymer 熔融聚合物Strain rate 變形速度，應(yīng)變率Muti-disciplinary 多學(xué)科的Streamline 流線Newtonian Fluid 牛頓流體Strut 支撐，支柱Nominal temperature gradient 法向溫度梯度Subcooled liquid過冷液體Numerator （數(shù)學(xué)）分子Superheated vapor 過熱蒸汽

6、Parallel flow 平行流動(dòng)，并流Surrounding 環(huán)境，外界Pathline跡線Thermal conductivity 熱傳導(dǎo)率Phase change 相變Thermal efficiency 熱效率Plane flow 平面流，二元流Thermodynamics 熱力學(xué)Plate and flame heat exchanger 板式換熱器Torsional 扭力的，扭轉(zhuǎn)的Polymer solution 膠漿Trailing edge 機(jī)翼后緣、尾緣Proof 校樣Transmitter 傳送裝置、發(fā)送器Propeller 螺旋槳，推進(jìn)器Turbine meter 渦輪

7、流量計(jì)Pump泵Turbulent 湍流的Qulity 干度Ultrosonic 超聲波的Qusi-equilibrium 準(zhǔn)平衡、準(zhǔn)靜態(tài)Uniform flow 均勻劉Radiation 輻射Vacuum 真空Rankin Cycle 朗肯循環(huán)View factor 角系數(shù)Regenerative heat exchanger 蓄熱/再生式換熱器Viscous 黏性的Reservoir 水庫，蓄水池Cortex shedding 漩渦脫落Reversible 可逆的Water faucet 水龍頭，水嘴Rotameter 轉(zhuǎn)子流量計(jì) Bi Biot number 比澳數(shù)NPSH 汽蝕余量CF

8、D 計(jì)算流體力學(xué)NTU 傳熱單元數(shù)CHF 臨界熱流量Nu 努謝爾特?cái)?shù)COP 制冷系數(shù)PE 勢能Eu 歐拉數(shù)Pr 普朗特?cái)?shù)Fo 富立葉數(shù)Ra 瑞利數(shù)Fr 弗勞德數(shù)Re 雷諾數(shù)Gr 格拉曉夫數(shù)Sc 施密特?cái)?shù)KE 動(dòng)能St 斯坦頓數(shù) ， 斯特勞哈數(shù)LMTD對數(shù)平均溫差We 韋伯?dāng)?shù)1.1 Fundamental of Engineering Thermodynamics1.1 工程熱力學(xué)基礎(chǔ)Thermodynamics is a science in which the storage, transformation and transfer of energy are studied. Energy

9、 is stored as internal energy (associated with temperature), kinetic energy (du to motion), potential energy (due to elevation) and chemical energy (due to chemical composition); it is transformed from one of these forms to another; and it is transferred across a boundary as either heat or work.熱力學(xué)是

10、一門研究能量儲存、轉(zhuǎn)換及傳遞的科學(xué)。能量以內(nèi)能（與溫度有關(guān)）、動(dòng)能（由物體運(yùn)動(dòng)引起）、勢能（由高度引起）和化學(xué)能（與化學(xué)組成相關(guān)）的形式儲存。不同形式的能量可以相互轉(zhuǎn)化，而且能量在邊界上可以以熱和功的形式進(jìn)行傳遞。In thermodynamics, we will derive equations that relate the transformations and transfers of energy to properties such as temperature, pressure and density. Substances and their properties, thu

11、s, become very important in thermodynamics. Many of our equations will be based on experimental observations that have been organized into mathematical statements or laws, the first and second laws of thermodynamics are most widely used.在熱力學(xué)中，我們將推導(dǎo)有關(guān)能量轉(zhuǎn)化和傳遞與物性參數(shù)，如溫度、壓強(qiáng)及密度等關(guān)系間的方程。因此，在熱力學(xué)中，物質(zhì)及其性質(zhì)變得非常重

12、要。許多熱力學(xué)方程都是建立在實(shí)驗(yàn)觀察的基礎(chǔ)之上，而且這些實(shí)驗(yàn)觀察的結(jié)果已被整理成數(shù)學(xué)表達(dá)式或定律的形式。其中，熱力學(xué)第一定律和第二定律應(yīng)用最為廣泛。1.1.1 Thermodynamic system and control volume1.1.1 熱力系統(tǒng)和控制體A thermodynamic system is a fixed quantity of matter contained within some enclosure. The surface is usually an obvious one (like that surrounding the gas in the cylin

13、der). However, it may be an imagined boundary (like the deforming boundary of a certain amount of mass as it flows through a pump).熱力系統(tǒng)是一包圍在某一封閉邊界內(nèi)的具有固定質(zhì)量的物質(zhì)。系統(tǒng)邊界通常是比較明顯的（如氣缸內(nèi)氣體的固定邊界）。然而，系統(tǒng)邊界也可以是假想的（如一定質(zhì)量的流體流經(jīng)泵時(shí)不斷變形的邊界）。All matter and space external to a system is collectively called its surrounding

14、s. Thermodynamics is concerned with the interaction of a system and its surroundings, or one system interacting with another. A system interacts with its surroundings by transferring energy across its boundary. No material crosses the boundary of a system. If the system does not exchange energy with

15、 the surroundings, it is an isolated system.系統(tǒng)之外的所有物質(zhì)和空間統(tǒng)稱外界或環(huán)境。熱力學(xué)主要研究系統(tǒng)與外界或系統(tǒng)與系統(tǒng)之間的相互作用。系統(tǒng)通過在邊界上進(jìn)行能量傳遞，從而與外界進(jìn)行相互作用，但在邊界上沒有質(zhì)量交換。當(dāng)系統(tǒng)與外界間沒有能量交換時(shí)，這樣的系統(tǒng)稱為孤立系統(tǒng)。In many cases, an analysis is simplified if attention is focused on a particular volume in space into which, or from which, a substance flows. S

16、uch a volume is a control volume. A pump, a turbine, and an inflating or deflating balloon are examples of control volume. The surface that completely surrounds the control volume is called a control surface.在許多情況下，當(dāng)我們只關(guān)心空間中有物質(zhì)流進(jìn)或流出的某個(gè)特定體積時(shí)，分析可以得到簡化。這樣的特定體積稱為控制體。例如泵、透平、充氣或放氣的氣球都是控制體的例子。包含控制體的表面稱為控制表

17、面。Thus, we must choose, in a particular problem, whether a system is to be considered or whether a control volume is more useful. If there is mass flux across a boundary, then a control volume is required; otherwise, a system is identified.因此，對于具體的問題，我們必須確定是選取系統(tǒng)作為研究對象有利還是選取控制體作為研究對象有利。如果邊界上有質(zhì)量交換，則選取

18、控制體有利；反之，則應(yīng)選取系統(tǒng)作為研究對象。1.1.2 Equilibrium, process and cycle平衡、過程和循環(huán)When the temperature of a system is referred to, it is assumed that all points of the system have the same, or essentially the same temperature. When the properties are constant from point to point and when there is no tendency for ch

19、ange with time, a condition of thermodynamic equilibrium exists. If the temperature, say, is suddenly increased at some part of the system boundary, spontaneous redistribution is assumed to occur until all parts of the 教材1頁system are at the same temperature.對于某一參考系統(tǒng)，假設(shè)系統(tǒng)內(nèi)各點(diǎn)溫度完全相同。當(dāng)物質(zhì)內(nèi)部各點(diǎn)的特性參數(shù)均相同且不隨時(shí)

20、間變化時(shí)，則稱系統(tǒng)處于熱力學(xué)平衡狀態(tài)。當(dāng)系統(tǒng)邊界某部分的溫度突然上升時(shí)，則系統(tǒng)內(nèi)的溫度將自發(fā)地重新分布，直至處處相同。When a system changes from one equilibrium state to another, the path of successive sates through which the system passes is called process. If, in the passing one state to the next, the deviation from equilibrium is infinitesimal, a quasi-e

21、quilibrium process occurs, and each state in the process may be idealized as an equilibrium state. Quasi-equilibrium processes can approximate many processes, such as the compression and expansion of gases in an internal combustion engine, with no significant loss of accuracy. If the system goes fro

22、m one equilibrium state to another through a series of non-equilibrium states (as in combustion), a non-equilibrium process occurs.當(dāng)系統(tǒng)從一個(gè)平衡狀態(tài)轉(zhuǎn)變?yōu)榱硪粋€(gè)平衡狀態(tài)時(shí)，系統(tǒng)所經(jīng)歷的一系列由中間狀態(tài)組成的變化歷程稱為過程。若從一個(gè)狀態(tài)到達(dá)另一個(gè)狀態(tài)的過程中，始終無限小地偏離平衡態(tài)，則稱該過程為準(zhǔn)靜態(tài)過程，可以把其中任一個(gè)中間狀態(tài)看作為平衡狀態(tài)。準(zhǔn)靜態(tài)過程可近似視為許多過程的疊加結(jié)果，而不會(huì)顯著減小其精確性，例如氣體在內(nèi)燃機(jī)內(nèi)的壓縮和膨脹過程。如果系統(tǒng)經(jīng)歷一系列

23、不平衡狀態(tài)（如燃燒），從一個(gè)平衡狀態(tài)轉(zhuǎn)變?yōu)榱硪粋€(gè)平衡狀態(tài)，則其過程為非平衡過程。When a system in a given initial state experiences a series of process and returns to the initial state, the system goes a cycle. At the end of the cycle, the properties of the system have the same values they had at the beginning.當(dāng)系統(tǒng)從一個(gè)給定的初始狀態(tài)出發(fā)，經(jīng)歷一系列中間過程又回到其

24、初始狀態(tài)，則稱系統(tǒng)經(jīng)歷了一個(gè)循環(huán)。循環(huán)結(jié)束時(shí)，系統(tǒng)中的各參數(shù)又與初始參數(shù)相同。 The prefix iso- is attached to the names of any property that remain unchanged in a process. An isothermal process is one in which the temperature is held constant; in an iso-baric process, the pressure remains constant; an isometric process is a constant-volu

25、me process.在任一特性參數(shù)名稱前加上前綴iso-，表示該參數(shù)在整個(gè)過程保持不變。等溫（isothermal）過程中溫度保持不變；等壓（isobaric）過程中壓強(qiáng)恒定；等容（isometric）過程中體積保持不變。1.1.3 Vapor-liquid phase equilibrium in pure substance純物質(zhì)的氣-液相平衡Consider as a system 1 kg of water contained in the piston or cylinder arrangement shown in Fig.1-1(a). Suppose the piston a

26、nd weight maintain a pressure of 0.1MPa in the cylinder and that the initial temperature is 20. As heat is transferred to the water, the temperature increase appreciably, the specific volume increase slightly, and the pressure remains constant. When the temperature reaches 99.6, additional heat tran

27、sfer results in a change of phase, as indicated in Fig.1-1 (b). That is, some of the liquid becomes vapor, and during this process both the temperature and pressure remain constant, but the specific volume increases considerably. When the last drop of liquid has vaporized, further transfer of heat r

28、esults in an increase in both temperature and specific volume of the vapor, as shown in Fig.1-1(c).如圖1-1(a)所示，由活塞和氣缸組成的裝置中裝有1kg水。假定活塞和其上的重物使氣缸內(nèi)壓強(qiáng)維持在0.1Mpa，初始溫度20。當(dāng)有熱量開始傳遞給水時(shí)，缸內(nèi)水溫迅速上升，而比容略有增加，氣缸內(nèi)壓強(qiáng)保持恒定不變。當(dāng)水溫達(dá)到99.6時(shí)，如若再增加傳熱量，水將發(fā)生相變，如圖1-1(b)所示。也就是說，一部分水開始?xì)饣優(yōu)檎羝?，在此相變過程中，溫度和壓強(qiáng)始終保持不變，但比容卻有大幅度的增加。當(dāng)最后一滴液體被氣

29、化時(shí)，進(jìn)一步的加熱將使蒸汽溫度和比容均有所增加，如同1-1(c)所示。圖1-1 液體在常壓下的蒸發(fā)過程The term saturation temperature designates the temperature at which vaporization takes place at a given pressure. This pressure is called the saturation pressure for the given temperature. Thus, for water at 99.6, the saturation pressure is 0.1MPa,

30、and for water at 0.1MPa the saturation temperature is 99.6.在給定壓強(qiáng)下發(fā)生氣化的溫度稱為飽和溫度，壓強(qiáng)稱為給定溫度下的飽和壓強(qiáng)。因此，99.6水的飽和壓強(qiáng)是0.1MPa，0.1MPa水的飽和溫度為99.6。If a substance exists as liquid at the saturation temperature, it is called saturated liquid. If the temperature of the liquid is lower than the saturation temperature

31、 for the existing pressure, it is called either a subcooled liquid (implying that the temperature is lower 教材2頁than the saturation temperature for the given pressure) or a compressed liquid (implying that the pressure is greater than the saturation pressure for the given temperature).如果某一工質(zhì)為液態(tài)并處于其飽和

32、溫度和飽和壓強(qiáng)下，則稱該液體為飽和液體。如果液體溫度低于當(dāng)前壓強(qiáng)下的飽和溫度，則稱該液體為過冷液體（表明液體的當(dāng)前溫度低于給定壓強(qiáng)下的飽和溫度）或壓縮液體（表明液體的當(dāng)前壓強(qiáng)大于給定溫度下的飽和壓強(qiáng)）。 When a substance exists as part liquid and part vapor at the saturation temperature, its quality is defined as the ratio of the mass of vapor to the total mass. Thus, in Fig.1-1(b), if the mass of v

33、apor is 0.2 kg and the mass of liquid is 0.8 kg, the quality is 0.2 or 20%. Quality has meaning only when the substance is in a saturated state.若某一工質(zhì)在飽和溫度下以液、氣共存的形式存在，則稱蒸汽質(zhì)量與總質(zhì)量之比為干度。因此，如圖1-1(b)所示，若蒸汽質(zhì)量為0.2kg，液體質(zhì)量為0.8kg，則其干度為0.2或20%。干度只有在飽和狀態(tài)下才有意義。 If a substance exists as vapor at the saturation te

34、mperature, it is called saturation vapor (Some times the term dry saturation vapor is used to emphasize that the quality is 100%). When the vapor is at a temperature greater than the saturation temperature, it is said to exist as superheated vapor. The pressure and temperature of superheated vapor a

35、re independent properties, since the temperature may increase while the pressure remains constant. 若某一工質(zhì)處于飽和溫度下并以蒸汽形態(tài)存在，則稱該蒸汽為飽和蒸汽（有時(shí)稱為干飽和蒸汽，意在強(qiáng)調(diào)其干度為100%）。當(dāng)蒸汽溫度高于其飽和溫度時(shí)，則稱之為過熱蒸汽。過熱蒸汽的壓強(qiáng)和溫度是彼此獨(dú)立的，因?yàn)闇囟壬仙龝r(shí)，壓強(qiáng)可能保持不變。Let us plot on the temperature-value diagram of Fig.1-2 the constant-pressure line that

36、represents the states through which the water passes as it is heated from the initial state of 0.1 MPa and 20. Let state A represent the initial state, B the saturated-liquid state(99.6), and line AB the process in which the liquid is heated from the initial temperature to the saturation temperature

37、. Point C is the saturated-vapor state, and line BC is the constant-temperature process in which the change of phase from liquid to vapor occurs. Line CD represents the process in which the steam is superheated at constant pressure. Temperature and volume both increase during this process.在圖1-2所示的溫度

38、-比容圖上作等壓線，表示水由初壓0.1MPa、初溫20被加熱的過程。點(diǎn)A代表初始狀態(tài)，點(diǎn)B為飽和液態(tài)（99.6），線AB表示液體由初始溫度被加熱至飽和溫度所經(jīng)歷的過程。點(diǎn)C表示飽和蒸汽狀態(tài)，線BC表示等溫過程，即液體氣化轉(zhuǎn)變?yōu)檎羝倪^程。線CD表示在等壓條件下蒸汽被加熱至過熱的過程，在此過程中，溫度和比容均增大。圖1-2 溫度-比容曲線表1-1 一些物質(zhì)的臨界參數(shù)In a similar name, a constant pressure of 10 MPa is represented by line IJKL, for which the saturation temperature is

39、 311.1. At a pressure of 22.09MPa, represented by line MNO, we find, however, that there is no constant-temperature vaporization process. Instead, point N is a point of inflection with a zero slope. This point is called the critical point. At the critical point the saturated-liquid and saturated-vap

40、or states are identical. The temperature, pressure and specific volume at critical point are called the critical temperature, critical pressure and critical volume. The critical-point data for some substances are given in Table 1-1.類似地，線IJKL表示壓強(qiáng)為10MPa下的等壓線，相應(yīng)的飽和溫度為311.1。但是，在壓強(qiáng)為22.09MPa條件下（線MNO），不存在等

41、溫蒸發(fā)過程。相反，點(diǎn)N是個(gè)轉(zhuǎn)折點(diǎn)，在該點(diǎn)上，切線斜率為零，通常把N點(diǎn)稱為臨界點(diǎn)。在臨界點(diǎn)處，飽和液體和飽和氣體的狀態(tài)都是相同的。臨界點(diǎn)下的溫度、壓強(qiáng)和比容分別稱為臨界溫度、臨界壓強(qiáng)和臨界比容。一些工質(zhì)的臨界點(diǎn)數(shù)據(jù)如表1-1所示。1.1.4 The first law of thermodynamics The first law of the thermodynamics is commonly called the law of conservation of energy. 教材3頁In elementary physics courses, the study of conservati

42、on of energy emphasizes changes in kinetic and potential energy and their relationship to work. A more general form of conservation of energy includes the effects of heat transfer and internal energy changes. Other forms of energy could also be included, such as electrostatic, magnetic, strain and s

43、urface energy.1.1.4 熱力學(xué)第一定律通常把熱力學(xué)第一定律稱為能量守恒定律。在基礎(chǔ)物理課程中，能量守恒定律側(cè)重動(dòng)能、勢能的變化以及和功之間的相互關(guān)系。更為常見的能量守恒形式還包括傳熱效應(yīng)和內(nèi)能的變化。當(dāng)然，也包括其它形式的能，如靜電能、磁場能、應(yīng)變能和表面能。 Historically, the first law of thermodynamics was stated for a cycle: the net heat transfer is equal to the net work done for a system undergoing a cycle.歷史上，用熱力

44、學(xué)第一定律來描述循環(huán)過程：凈傳熱量等于循環(huán)過程中對系統(tǒng)所做的凈功。1.1.5 The second law of thermodynamicsThe second law of thermodynamics can be stated in a variety of ways. Here we present two: the Clausius statement and the Kelvin-Planck statement.1.1.5 熱力學(xué)第二定律熱力學(xué)第二定律有多種表述形式。在此列舉兩種：克勞修斯表述和凱爾文-普朗克表述。Clausius statementIt is impossib

45、le to construct a device that operates in a cycle and whose sole effect is transfer of heat from a cooler body to a hotter body.克勞修斯表述：制造一臺唯一功能是把熱量從低溫物體傳給高溫物體的循環(huán)設(shè)備是不可能的。圖1-3 第二定律的違背This statement relates to a refrigerator (or a heat pump). It states that it is impossible to construct a refrigerator

46、that transfers energy from a cooler body to a hotter body without the input of work; this violation is shown in Fig.1-3(a).以冰箱（或熱泵）為例，不可能制造一臺不用輸入功就能把熱量從低溫物體傳給高溫物體的冰箱，如圖1-3(a)所示。It is impossible to construct a device that operates in a cycle and produces no other effect than the production of work an

47、d the transfer of heat from a single body.凱爾文-普朗克表述：制造一臺從單一熱源吸熱和做功的循環(huán)設(shè)備是不可能的。In other words, it is impossible to construct a heat engine that extracts energy from reservoir, does work, and does not transfer heat to a low-temperature reservoir. This rules out any heat engine that is 100 percent effic

48、ient, like the one shown in Fig.1-3(b).換句話說，制造這樣一臺從某一熱源吸熱并對外做功，而沒有與低溫?zé)嵩催M(jìn)行換熱的熱機(jī)是不可能的。因此，該表述說明了不存在工作效率為100%的熱機(jī)，如圖1-3(b)所示。1.1.6 The Carnot Cycle The heat engine that operates most efficiently between a high-temperature reservoir and a low-temperature reservoir is the Carnot engine. This is an ideal en

49、gine that uses reversible process to form its cycle of operation; such a cycle is Carnot cycle. The Carnot engine is very useful, since its efficiency establishes the maximum possible efficiency of any real engine. If the efficiency of a real is significantly lower than the efficiency of Carnot engi

50、ne between the same temperature limits, then additional improvements may be possible.1.1.6 卡諾循環(huán)卡諾機(jī)是低溫?zé)嵩春透邷責(zé)嵩撮g運(yùn)行效率最高的熱機(jī)。卡諾機(jī)是一個(gè)理想熱機(jī)，利用多個(gè)可逆過程組成一循環(huán)過程，該循環(huán)稱為卡諾循環(huán)。卡諾機(jī)非常有用，因?yàn)樗倪\(yùn)行效率為任何實(shí)際熱機(jī)最大可能的效率。因此，如果一臺實(shí)際熱機(jī)的效率要遠(yuǎn)低于同樣條件下的卡諾機(jī)效率，則有可能對該熱機(jī)進(jìn)行一些改進(jìn)以提高其效率。圖1-4 卡諾循環(huán)The ideal Carnot cycle in Fig.1-4 is composed of four

51、 reversible processes: 1à2: Isothermal expansion: 2à3；Adiabatic reversible expansion:3à4；Isothermal compression：4à1；Adiabatic reversible compression. The efficiency of a Carnot cycle is教材4頁Note that the efficiency is increased by raising the temperature TH at which heat is added

52、or by decreasing the temperature TL at which heat is rejected.理想的卡諾循環(huán)包括四個(gè)可逆過程，如圖1-4所示：12等溫膨脹；23絕熱可逆膨脹；34等溫壓縮；41可逆絕熱壓縮?？ㄖZ循環(huán)的效率為 (1-1)注意，提高TH（提高吸熱溫度）或降低TL（降低放熱溫度）均可使循環(huán)效率提高。1.1.7 The Rankine cycleThe first class of power cycles that we consider are those utilized by the electric power generating indust

53、ry, namely, power cycles that operates in such a way that the working fluid changes phases from a liquid to vapor. The simplest vapor-power cycle is called the Rankine cycle, shown schematically in Fig.1-5(a). A major feature of such cycle is that the pump requires very little work to deliver high-p

54、ressure water to the boiler. A possible disadvantage is that the expansion process in the turbine usually enters the quality region, resulting in the formation of liquid droplets that may damage the turbine blades.1.1.7 朗肯循環(huán)我們所關(guān)心的第一類動(dòng)力循環(huán)為電力生產(chǎn)工業(yè)所采用的，也就是說，動(dòng)力循環(huán)按這樣的方式運(yùn)行：工質(zhì)發(fā)生相變，由液態(tài)變?yōu)闅鈶B(tài)。最簡單的蒸汽-動(dòng)力循環(huán)是朗肯循環(huán)，如

55、圖1-5(a)所示。朗肯循環(huán)的一個(gè)主要特征是泵耗費(fèi)很少的功就能把高壓水送入鍋爐。其可能的缺點(diǎn)為工質(zhì)在汽機(jī)內(nèi)膨脹做功后，通常進(jìn)入濕蒸汽區(qū)，形成可能損害汽輪機(jī)葉片的液滴。圖1-5 朗肯循環(huán)The Rankine cycle is an idealized cycle in which friction losses in each of the four components are neglected. The losses usually are quite small and will be neglected completely in initial analysis. The Rank

56、ine cycle is composed of the four ideal processes shown on the T-s diagram in Fig.1-5(b):1à2: Isentropic compression in a pump；2à3: Constant-pressure heat addition in a boiler; 3à4: Isentropic expansion in a turbine; 4à1: Constant pressure heat rejection in a condenser.朗肯循環(huán)是一個(gè)理想循

57、環(huán)，其忽略了四個(gè)過程中的摩擦損失。這些損失通常很小，在初始分析時(shí)可完全忽略。朗肯循環(huán)由四個(gè)理想過程組成，其T-s圖如圖1-5(b)所示：12為泵內(nèi)等熵壓縮過程；23為爐內(nèi)定壓吸熱過程；34為汽輪機(jī)內(nèi)等熵膨脹做功過程；41為凝汽器內(nèi)定壓放熱過程。 The pump is used to increase the pressure of the saturated liquid. Actually, states 1 and 2 are essentially the same, since the high-pressure lines are extremely close to the sa

58、turation curve; they are shown separated for illustration only. The boiler (also called a steam generator) and the condenser are heat exchangers that neither require nor produce any work.泵用于提高飽和液體的壓強(qiáng)。事實(shí)上，狀態(tài)1和狀態(tài)2幾乎完全一樣，因?yàn)橛?點(diǎn)開始的較高壓強(qiáng)下的吸熱過程線非常接近飽和曲線，圖中僅為了解釋說明的需要分別標(biāo)出。鍋爐（也稱蒸汽發(fā)生器）和凝汽器均為換熱器，它們既不需要功也不產(chǎn)生功。If we neglect kinetic energy and potential