熱能動力工程專業(yè)英語課件part

1、2022/9/6Specialized English for Thermal Energy and Power Engineering熱能動力工程專業(yè)英語 2022/9/61.1.2 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(屬性)

2、are constant from point to point and when there is no tendency for change with time, a condition of thermodynamic equilibrium exists. If the temperature, say, is suddenly increased at some part of the system boundary, spontaneous(自發(fā)的) redistribution is assumed to occur until all parts of the system

3、are at the same temperature.對于某一參考系統(tǒng)，假設(shè)系統(tǒng)內(nèi)各點溫度完全相同。當(dāng)物質(zhì)內(nèi)部各點的特性參數(shù)均相同且不隨時間變化時，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，則系統(tǒng)內(nèi)的溫度將自發(fā)地重新分布，直至處處相同。Assume :假定;以為;假設(shè)，suppose . If you assume that something is true, you imagine that it is true, sometimes wronglyEssentially: 基本上、大體上。mainly2022/9/61.1.2 Equilibrium, proces

4、s and cycle平衡、過程和循環(huán)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-equilibrium(準(zhǔn)平衡) process occurs, and each

5、 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 from one equilibrium state to another

6、through a series of non-equilibrium states (as in combustion), a non-equilibrium(非平衡) process occurs.當(dāng)系統(tǒng)從一個平衡狀態(tài)轉(zhuǎn)變?yōu)榱硪粋€平衡狀態(tài)時，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。若從一個狀態(tài)到達另一個狀態(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，而不會顯著減小其精確性，例如氣體在內(nèi)燃機內(nèi)的壓縮和膨脹過程。如果系統(tǒng)經(jīng)歷一系列不平衡狀態(tài)（如燃燒），從一個平衡狀態(tài)轉(zhuǎn)變?yōu)榱硪粋€平衡狀態(tài)，則

7、其過程為非平衡過程。Deviation: 背離、偏差；difference Error: 誤差(與真值之間)approximately: about,大約地Occur: happen,出現(xiàn)，發(fā)生2022/9/61.1.2 Equilibrium, process and cycle平衡、過程和循環(huán)When a system in a given initial（初始的） state experiences a series of process and returns to the initial state, the system goes a cycle. At the end of th

8、e cycle, the properties of the system have the same values they had at the beginning.當(dāng)系統(tǒng)從一個給定的初始狀態(tài)出發(fā)，經(jīng)歷一系列中間過程又回到其初始狀態(tài)，則稱系統(tǒng)經(jīng)歷了一個循環(huán)。循環(huán)結(jié)束時，系統(tǒng)中的各參數(shù)又與初始參數(shù)相同。Iso: 等溫（isothermal）過程中溫度保持不變；等壓（isobaric）過程中壓力恒定；等容（isometric）過程中體積保持不變, isotropic 各向同性的。在任一特性參數(shù)名稱前加上前綴iso-，表示該參數(shù)在整個過程保持不變。專業(yè)英語詞匯大部分都是用派生法構(gòu)成的，therm

9、o-：thermo-dynamics，thermo-electricalmicro- microscopy，microscope, micrometer 300個以上 auto- automation 260個以上:2022/9/61.1.3 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(活塞) or cylinder(圓筒) arrangement shown in Fig.1-1(a). Suppose

10、the piston and 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, addition

11、al heat transfer results in a change of phase, as indicated in Fig.1-1 (b). That is, some of the liquid es 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

12、 heat results in an increase in both temperature and specific volume of the vapor, as shown in Fig.1-1(c).Consider,Suppose構(gòu)成祈使句remains（keep + adj）2022/9/61.1.3 Vapor-liquid phase equilibrium in pure substance純物質(zhì)的氣-液相平衡如圖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)壓力維持在0.1Mpa，初始溫度20。當(dāng)有熱量開始傳遞給水時，缸內(nèi)水溫迅速上

13、升，而比容略有增加，氣缸內(nèi)壓力保持恒定不變。當(dāng)水溫達到99.6時，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，一部分水開始氣化變?yōu)檎羝?，在此相變過程中，溫度和壓力始終保持不變，但比容卻有大幅度的增加。當(dāng)最后一滴液體被氣化時，進一步的加熱將使蒸汽溫度和比容均有所增加，如圖1-1(c)所示。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)壓力維持在0.1Mpa，初始溫度20。當(dāng)有熱量開始傳遞給水時，缸內(nèi)水溫迅速上升，而比容略有增加，氣缸內(nèi)壓力保持恒定不變。當(dāng)水溫達到99.6時，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

14、，一部分水開始氣化變?yōu)檎羝?，在此相變過程中，溫度和壓力始終保持不變，但比容卻有大幅度的增加。當(dāng)最后一滴液體被氣化時，進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。 2022/9/61.1.3 Vapor-liquid phase equilibrium in pure substance純物質(zhì)的氣-液相平衡The term（術(shù)語、項） saturation temperature designates the temperature at which vaporization takes place at a given pressure. This pressure is

15、called the saturation pressure for the given temperature. Thus, for water at 99.6, the saturation pressure is 0.1MPa, and for water at 0.1MPa the saturation temperature is 99.6.在給定壓力下發(fā)生氣化的溫度稱為飽和溫度，壓力稱為給定溫度下的飽和壓力。因此，99.6水的飽和壓力是0.1MPa，0.1MPa水的飽和溫度為99.6。If a substance exists(存在) as liquid at the satura

16、tion temperature, it is called saturated liquid. If the temperature of the liquid is lower than the saturation temperature for the existing pressure, it is called either a subcooled liquid (implying that the temperature is lower than the saturation temperature for the given pressure) or a compressed

17、 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)并處于其飽和溫度和飽和壓力下，則稱該液體為飽和液體。如果液體溫度低于當(dāng)前壓力下的飽和溫度，則稱該液體為過冷液體（表明液體的當(dāng)前溫度低于給定壓力下的飽和溫度）或壓縮液體（表明液體的當(dāng)前壓力大于給定溫度下的飽和壓力）。Cesisus 攝氏度,Fahrenheit 華氏度Water freezes at 32 degrees Fahrenheit (32 F) or zero/n

18、ought degrees Celsius (0 C). 2022/9/61.1.3 Vapor-liquid phase equilibrium in pure substance純物質(zhì)的氣-液相平衡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

19、 vapor 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。2022/9/61.1.3 Vapor-liquid phase equilibrium in pu

20、re substance純物質(zhì)的氣-液相平衡If a substance exists as vapor at the saturation temperature, it is called saturation vapor (Some times the term dry saturation vapor is used to emphasize(強調(diào)) that the quality is 100%). When the vapor is at a temperature greater than the saturation temperature, it is said to ex

21、ist as superheated vapor. The pressure and temperature of superheated vapor are 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（有時稱為干飽和蒸汽，意在強調(diào)其干度為100%）。當(dāng)蒸汽溫度高于其飽和溫度時，則稱之為過熱蒸汽。過熱蒸汽的壓力和溫度是彼此獨立的，因為溫度上升時，壓力可能保持不變。2022/9/61.1

22、.3 Vapor-liquid phase equilibrium in pure substance純物質(zhì)的氣-液相平衡Let us plot on the temperature-value diagram of Fig.1-2 the constant-pressure line that 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,

23、 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. 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

24、CD represents(表示) the process in which the steam is superheated at constant pressure. Temperature and volume both increase during this process. Mpa- Megapascal 兆 106）Represent- indicate, refer to,-show,illustrate2022/9/61.1.3 Vapor-liquid phase equilibrium in pure substance純物質(zhì)的氣-液相平衡In a similar nam

25、e, a constant pressure of 10 MPa is represented by line IJKL, for which the saturation temperature is 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(轉(zhuǎn)折點) with a zero sl

26、ope(斜率). This point is called the critical point. At the critical point the saturated-liquid and saturated-vapor 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 f

27、or some substances are given in Table 1-1.2022/9/61.1.4 The first law of thermodynamics熱力學(xué)第一定律The first law of thermodynamics is commonly called the law of conservation of energy.In elementary physics courses, the study of conservation of energy emphasizes changes in kinetic and potential energy and

28、 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 surface energy.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)重動能、勢能的變化以及和功之間的相互

29、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.2022/9/61.1.5 The second law of thermodynamics熱力學(xué)第二定律The second law of thermodynamics ca

30、n be stated in a variety of ways. Here we present two: the Clausius statement and the Kelvin-Planck statement.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。Clausius statement(?)It is impossible to construct a device that operates in a cycle and whose sole effect is transfer of heat from a cooler body to

31、a hotter body.This statement relates to a refrigerator (or a heat pump). It states that it is impossible to construct a refrigerator 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

32、圖1-3(a)所示。2022/9/61.1.5 The second law of thermodynamics熱力學(xué)第二定律Kelvin-Planck statementIt is impossible to construct a device that operates in a cycle and produces no other effect than the production of work and 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

33、, it is impossible to construct a heat engine that extracts energy from reservoir(熱源), does work, and does not transfer heat to a low-temperature reservoir. This rules out any heat engine that is 100 percent efficient, 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行換熱的熱機是不可能的。因此，

34、該表述說明了不存在工作效率為100%的熱機，如圖1-3(b)所示。2022/9/61.1.6 The Carnot cycle卡諾循環(huán)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 engine that uses reversible process to form its cycle of operation; such a cyc

35、le 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 engine between the same temperature limits, then additional improvements may be

36、possible.卡諾機是低溫?zé)嵩春透邷責(zé)嵩撮g運行效率最高的熱機?？ㄖZ機是一個理想熱機，利用多個可逆過程組成一循環(huán)過程，該循環(huán)稱為卡諾循環(huán)?？ㄖZ機非常有用，因為它的運行效率為任何實際熱機最大可能的效率。因此，如果一臺實際熱機的效率要遠低于同樣條件下的卡諾機效率，則有可能對該熱機進行一些改進以提高其效率。2022/9/61.1.6 The Carnot cycle卡諾循環(huán)The ideal Carnot cycle in Fig.1-4 is composed of four reversible processes: 12: Isothermal expansion: 23；Adiabatic

37、 reversible expansion:34；Isothermal compression：41；Adiabatic reversible compression. The efficiency of a Carnot cycle is理想的卡諾循環(huán)包括四個可逆過程，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。卡諾循環(huán)的效率為Note that the efficiency is increased by raising the temperature TH at which heat is added or by decreasing the temp

38、erature TL at which heat is rejected.Compose- be composed ofcontain, consist priseinclude;2022/9/61.1.7 The Rankine cycle朗肯循環(huán)The first class of power cycles that we consider are those utilized by the electric power generating industry, namely, power cycles that operates in such a way that the workin

39、g fluid changes phases from a liquid to vapor. The simplest vapor-power cycle is called the Rankine cycle, shown schematically(示意地) in Fig.1-5(a). A major feature of such cycle is that the pump requires very little work to deliver high-pressure water to the boiler. A possible disadvantage is that th

40、e expansion process in the turbine usually enters the quality region, resulting in the formation of liquid droplets that may damage the turbine blades.我們所關(guān)心的第一類動力循環(huán)為電力生產(chǎn)工業(yè)所采用的，也就是說，動力循環(huán)按這樣的方式運行：工質(zhì)發(fā)生相變，由液態(tài)變?yōu)闅鈶B(tài)。最簡單的蒸汽-動力循環(huán)是朗肯循環(huán)，如圖1-5(a)所示。朗肯循環(huán)的一個主要特征是泵耗費很少的功就能把高壓水送入鍋爐。其可能的缺點為工質(zhì)在汽機內(nèi)膨脹做功后，通常進入濕蒸汽區(qū)，形成可能損

41、害汽輪機葉片的液滴。2022/9/61.1.7 The Rankine cycle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 Rankine cycle is composed of the four ideal process

42、es shown on the T-s diagram in Fig.1-5(b):12: Isentropic compression in a pump；23: Constant-pressure heat addition in a boiler; 34: Isentropic expansion in a turbine; 41: Constant pressure heat rejection in a condenser.朗肯循環(huán)是一個理想循環(huán)，其忽略了四個過程中的摩擦損失。這些損失通常很小，在初始分析時可完全忽略。朗肯循環(huán)由四個理想過程組成，其T-s圖如圖1-5(b)所示：12為

43、泵內(nèi)等熵壓縮過程；23為爐內(nèi)定壓吸熱過程；34為汽輪機內(nèi)等熵膨脹做功過程；41為凝汽器內(nèi)定壓放熱過程。2022/9/61.1.7 The Rankine cycle朗肯循環(huán)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 saturation curve; they are shown separa

44、ted 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力。事實上，狀態(tài)1和狀態(tài)2幾乎完全一樣，因為由2點開始的較高壓力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。2022/9/61.1.7 The Rankine cycle朗肯循環(huán)If we

45、 neglect kinetic energy and potential energy changes, the net work output is the area under the T-s diagram, represented by area 1-2-3-4-1 of Fig.1-5(b); this is true since the first law requires that Wout=Qnet. The heat transfer to the working substance is represented by area a-2-3-b-a. Thus, the t

46、hermal efficiency of the Rankine cycle is That is, the desired output divided by the energy input (the purchased energy). Obviously, the thermal efficiency can be improved by increasing the numerator or by decreasing the denominator(分母). This can be done by increasing the pump outlet pressure p2, in

47、creasing the boiler outlet temperature T3, or decreasing the turbine outlet pressure p4.denominator: 分母； numerator: 分子Water Screw(螺桿) Perpetual Motion2022/9/6Robert Fludds 1618 water screw perpetual motion machine from a 1660 wood engraving. This device is widely credited as the first recorded attempt