燃气专业外语翻译.docx

1、燃气专业外语翻译Thermodynamics is a science in which the storage, transformation, and transfer of energy are studied. Energy is stored as internal energy (associated with temperature), kinetic energy (due tomotion), potential energy (due to elevation) and chemical energy (due to chemical composition); it is

2、 transformed from one of these forms to another; and it is transferred across a boundary as either heat or work.热力学是一门研究能量储存、转换及传递的科学。能量以内能（与温度有关） 、动能（由物体运动引起）、势能（由高度引起） 和化学能（与化学组成相关） 的形式储存。 不同形式的能量可以相互转化， 而且能量在边界上可以以热和功的形式进行传递。In thermodynamics, we will derive equations that relate the transformati

3、ons and transfers of energyto properties such as temperature, pressure, and density. Substances and their properties, thus, 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 fir

4、st and secondlaws of thermodynamics are the most widely used.在热力学中，我们将推导有关能量转化和传递与物性参数，如温度、压强及密度等关系间的方程。因 此，在热力学中，物质及其性质变得非常重要。许多热力学方程都是建立在实验观察的基础之上，而 且这些实验观察的结果已被整理成数学表达式或定律的形式。 其中，热力学第一定律和第二定律应用最为广泛。1.1.1 Thermodynamic system and control volume 热力系统和控制体A thermodynamic system is a fixed quantity of

5、 matter contained within some enclosure. The surface is usually an obvious one (like that surrounding the gas in the cylinder). However, it may bean imagined boundary (like the deforming boundary of a certain amount of mass as it flows througha pump).气体的固定边界）。然而，系统边界也可以是假想的（如一定质量的流体流经泵时不断变形的边界） 。All

6、 matter and space external to a system is collectively called its surroundings. Thermodynamics is concerned with the interactions of a system and its surroundings, or one system interacting with another. A system interacts with its surroundings by transferring energy across its boundary. Nomaterial

7、crosses the boundary of a system. If the system does not exchange energy with the surroundings ，it is an isolated system.系统之外的所有物质和空间统称外界或环境。 热力学主要研究系统与外界或系统与系统之间的相互作用。系统通过在边界上进行能量传递，从而与外界进行相互作用，但在边界上没有质量交换。当系统与外界间没有能量交换时，这样的系统称为孤立系统。In many cases, an analysis is simplified if attention is focused o

8、n a particular volume in space into which, or from which, a substance flows. Such a volume is a control volume. A pump, a turbine, and an inflating or deflating balloon are examples of control volumes. The surface that completely surrounds the control volume is called a control surface.在许多情况下，当我们只关心

9、空间中有物质流进或流出的某个特定体积时，分析可以得到简化。这样的特定体积称为控制体。例如泵、透平、充气或放气的气球都是控制体的例子。包含控制体的表面称为控制表面。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 sy

10、stem is identified.因此，对于具体的问题， 我们必须确定是选取系统作为研究对象有利还是选取控制体作为研究对象有利。如果边界上有质量交换，则选取控制体有利；反之，则应选取系统作为研究对象。1.1.2 Equilibrium, process and cycleWhen 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 propert

11、ies are constant from point topoint 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 redistribution is assumed to occur until all parts of the system ar

12、e at thesame temperature.对于某一参考系统， 假设系统内各点温度完全相同。 当物质内部各点的特性参数均相同且不随时间变化时，则称系统处于热力学平衡状态。 当系统边界某部分的温度突然上升时， 则系统内的温度将自发地重新分布，直至处处相同。When a system changes from one equilibrium state to another, the path of successive states through which the system passes is called a process. If, in the passing from on

13、e state to the next,the deviation from equilibrium is infinitesimal, a quasi-equilibrium 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 c

14、ombustion engine, with no significant loss of accuracy. If the system goes from one equilibriumstate to another through a series of nonequilibrium states (as in combustion) , a nonequilibrium process occurs.当系统从一个平衡状态转变为另一个平衡状态时， 系统所经历的一系列由中间状态组成的变化历程称为过程。若从一个状态到达另一个状态的过程中， 始终无限小地偏离平衡态， 则称该过程为准静态过程，

15、可以把其中任一个中间状态看作为平衡状态。 准静态过程可近似视为许多过程的叠加结果， 而不会显著减小其精确性， 例如气体在内燃机内的压缩和膨胀过程。 如果系统经历一系列不平衡状态 （如燃烧），从一个平衡状态转变为另一个平衡状态，则其过程为非平衡过程。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.当系统从一个给定的初始状态出发， 经历一系列中间过程又回到其初始状态， 则称系统经历了一个循环。循环

16、结束时，系统中的各参数又与初始参数相同。The prefix iso-is attached to the name of any property that remains 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-volume process.在任一特性参数名称前

17、加上前缀 iso- ，表示该参数在整个过程保持不变。等温（ isothermal ）过程中温度保持不变；等压（ isobaric ）过程中压强恒定；等容（ isometric ）过程中体积保持不变。1.1.3 Vapor-liquid phase equilibrium in pure substance纯物质的气 -液相平衡Consider as a system 1 kg of water contained in the piston/ cylinder arrangement shown in Fig.1-1(a). Suppose that the piston and weight

18、 maintain a pressure of 0.1 MPa in the cylinder and thatthe initial temperature is 20 . As heat is transferred to the water, the temperature increases appreciably, the specific volume increases slightly, and the pressure remains constant. When the temperature reaches 99. 6 , additional heat transfer

19、 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 thetemperature and pressure remain constant, but the specific volume increases considerably. Whenthe last drop of liquid has vaporized, further transfer of heat results

20、in an increase in both temperature and specific volume of the vapor, as shown in fig.1-1(c).如图 1-1(a) 所示，由活塞和气缸组成的装置中装有 1kg 水。假定活塞和其上的重物使气缸内压强维持在 0.1Mpa ，初始温度 20 。当有热量开始传递给水时，缸内水温迅速上升，而比容略有增加，气缸也就是说，一部分水开始气化变为蒸汽，在此相变过程中，温度和压强始终保持不变，但比容却有大幅度的增加。当最后一滴液体被气化时，进一步的加热将使蒸汽温度和比容均有所增加，如同 1-1(c)所示。图 1-1 液体在常压

21、下的蒸发过程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, forwater at 99. 6 the saturation pressure is 0.1 MPa, and for water at 0.1 MPa the saturationtemper

22、ature is 99. 6 .在给定压强下发生气化的温度称为饱和温度， 压强称为给定温度下的饱和压强。 因此，99.6 水的饱和压强是 0.1MPa ， 0.1MPa 水的饱和温度为 99.6 。If a substance exists as liquid at the saturation temperature and pressure, it is called saturated liquid. If the temperature of the liquid is lower than the saturation temperature for the existing pre

23、ssure, it is called either a subcooled liquid (implying that the temperature is lower 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).如果某一工质为液态并处于其饱和温度和饱和压强下， 则称该液体为饱和液体。 如果液

24、体温度低于当前压强下的饱和温度， 则称该液体为过冷液体 （表明液体的当前温度低于给定压强下的饱和温度） 或压缩液体（表明液体的当前压强大于给定温度下的饱和压强） 。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 the vapor is 0. 2 kg

25、and the mass of the liquid is 0.8 kg, the quality is 0.2 or 20%. Quality has meaningonly when the substance is in a saturated state.1-1(b) 所示，若蒸汽质量为 0.2kg ，液体质量为 0.8kg ，则其干度为 0.2 或 20% 。干度只有在饱和状态下才有意义。If a substance exists as vapor at the saturation temperature, it is called saturated vapor. (Someti

26、mes the term dry saturated vapor is used to emphasize that the quality is 100%). When thevapor is at a temperature greater than the saturation temperature, it is said to exist as superheated vapor. The pressure and temperature of superheated vapor are independent properties, since the temperature ma

27、y increase while the pressure remains constant.若某一工质处于饱和温度下并以蒸汽形态存在， 则称该蒸汽为饱和蒸汽 （有时称为干饱和蒸汽， 意在强调其干度为 100% ）。当蒸汽温度高于其饱和温度时，则称之为过热蒸汽。过热蒸汽的压强和温度是彼此独立的，因为温度上升时，压强可能保持不变。Let us plot on the temperature-volume diagram of Fig.1-2 the constant-pressure line that represents the states through which the water

28、passes as it is heated from the initial state of 0.1MPaand 20 . Let state A represent the initial state, B the saturated-liquid state (99. 6 ), and line ABthe process in which the liquid is heated from the initial temperature to the saturation temperature. Point C is the saturated-vapor state, and l

29、ine BC is the constant-temperature process in which the change of phase from liquid to vapor occurs. Line CD represents in which the steam is superheated at constant pressure. Temperature and volume both increase during this process.在图 1-2 所示的温度 -比容图上作等压线，表示水由初压 0.1MPa 、初温 20 被加热的过程。点 A 代表初始状态，点 B 为

30、饱和液态（ 99.6 ），线 AB 表示液体由初始温度被加热至饱和温度所经历的过程。点 C 表示饱和蒸汽状态，线 BC 表示等温过程，即液体气化转变为蒸汽的过程。线 CD 表示在等压条件下蒸汽被加热至过热的过程，在此过程中，温度和比容均增大。图 1-2 温度-比容曲线In a similar manner, a constant pressure of 10MPa is represented by line IJKL , for which the saturation temperature is 311. 1 . At a pressure of 22.09MPa, represente

31、d by line MNO ，we find,however, that there is no constant-temperature vaporization process. Instead ，point N is a point ofinflection with a zero slope. This point is called the critical point. At the critical point the saturated-liquid and saturated-vapor states are identical. The temperature, press

32、ure, and specificvolume at the 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.类似地，线 IJKL 表示压强为 10MPa 下的等压线，相应的饱和温度为 311.1 。但是，在压强为22.09MPa 条件下（线 MNO ），不存在等温蒸发过程。相反，点 N 是个转折点，在该点上，切线斜率为零，通常把 N 点称为临界点。在临界点处，饱和液体和饱和气体的状态都是相同的。临界点下的温度、压强和比容分别称为临界温度、 临界压强和临界比容。 一些工质的临界点数据如表 1-1 所示。1.1.4 The first law of thermodynamicsThe first law of thermodynamics is commonly called t