制冷专业英语课件.ppt

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1、Part 1 Thermodynamics and Heat Transfer This unit introduces the basic and elementary knowledge of thermodynamics and heat transfer.After learning,you will be able to understand:lThe basic concepts and terminology in thermodynamics and heat transferlThe three ways of thermal transmissionlThe composi

2、tion of thermal systems lThe thermodynamic cycle principlereturn to contentsPart 1 Thermodynamics and Heat TransferText 1 Thermodynamic SystemText 2 General Characteristics of Heat TransferText 3 ConductionText 4 Convectionreturn to contentsText 1 Thermodynamic System lIn the thermal engineering,the

3、 studied objects normally are isolated from one another and then we try to analysis the change and interaction,the studied objects isolated is named thermodynamic system.1 lThe boundary of a system can be either real or imaginary,and either fixed or movable.If the gas in a cylinder is the studying o

4、bject,then it is the thermodynamic system.2lThere may be many objects in an engineering problem.The solution of a system is dependent on which objects are under consideration.In a thermodynamics system,we can do it either by placing an imaginary envelope around the objects under consideration or by

5、using an actual envelope if it exists.3contentsUnit 1New wordslFor example,when dealing with a gas in the cylinder where the boundaries are located on the outside of the cylinder,4 the system includes both the cylinder and its contained gas.On the other hand,when the boundaries are placed at the inn

6、er face of the cylinder,the system consists solely of the gas itself.So it is very important and essential for us to specify the boundaries of the system carefully.5lThe boundaries of a closed system may be either rigid or may expand or contract,6 but its mass will not change.When the energy crossin

7、g the boundaries of a closed system is zero,the system may be treated as an isolated system.lBased on the difference of the characteristic of the systems,the different systems are named.(1)When the boundaries of a system would not exchange with the surroundings,then can said that it is a closed syst

8、em.However,it may exchange energy in any form of heat or work with the surroundings.(2)Conversely,if there are any matter exchange between the system and the surroundings,then it is an open system.The quantity of the matter in an open system may be either variable or constant.The boundaries of an op

9、en system are so placed that their location does not change with time.Thus,the boundaries enclose a fixed volume,commonly known as the control volume.lSometimes a system may be a closed system at one moment and an open one the next.For example,consider we would study a cylinder of an internal combus

10、tion engine,when the valves close,the system is a closed system.And when either or both of the valves open,the system will become an open system.lIn most cases,a studied object would be a large and very complex system.We can break down it into a lot of component parts and analyze every component par

11、ts.Then the performance of the entire system can be determined by the summation of the performance of the individual component systems.7lFor example,consider the liquid-vapor part of a steam power plant as a total system.This closed system contains the steam generator,the steam turbine,the steam con

12、denser,the feed-water pumps,and the feed-water heaters.All of these units may be considered separately by throwing a boundary around them.Since a fluid enters and leaves each of these smaller systems,each one is an open system and must be analyzed.boundaryn.边界,分界线consideration n.体谅,考虑,需要考虑的事项,报酬cyli

13、nder n.圆筒,圆柱体,汽缸,柱面envelopen.信封,封袋,天包层,数包迹,生包膜imaginarya.假想的,想象的,虚构的Solely ad.独自地,单独地solutionn.解答,解决办法,溶解,溶液,解决方案be isolated from被与隔绝either or或（者）或（者）for example例如be dependent on依靠,依赖 New Words and ExpressionsText 2lTechnical Termsla steam power plant蒸汽发电厂lan internal combustion engine 内燃机lthe feed-

14、water heater给水加热器lthe feed-water pump(给水)泵lthe steam condenser蒸汽冷凝器lthe steam generator蒸汽发生器（锅炉）lthe steam turbine蒸汽轮机 Exercise(1)l Answer the following questions according to the text.(1)How do we usually do when studying a thermal engineering?(2)How can be the boundary of a system?(3)What is the s

15、olution of a system dependent on?(4)Based on the difference of the characteristic of the systems,how many the different systems are named?(5)How do we usually do when a studied object is a large and very complex system?(6)What is the boundary of a studying object?Exercise(2)lDecide whether the follo

16、wing statements is true or false according to the text.(1)In the thermal engineering,the studied objects normally are isolated from one another and then try to analysis the change and interaction.(2)The boundary of a system can be either real or imaginary,but it can not be either fixed or movable.(3

17、)In a thermodynamics system,we can solute it only by placing an imaginary envelope around the objects under consideration and not by using an actual envelope if it exists.(4)It is not very important and essential for us to specify the boundaries of the system carefully.(5)Then the performance of the

18、 entire system can be determined by the summation of the performance of the individual component systems.Exercise(3)lPut the following words into Chinese/English.(1)If the gas in a cylinder is the studying object,then it is the thermodynamic system.(2)研究缸内气体时，其（系统）边界在汽缸体外，系统则包含汽缸及缸内气体。以汽缸内表面为边界，系统则只

19、包括（缸内）气体。(3)In most cases,a studied object would be a large and very complex system.We can break down it into a lot of component parts and analyze every component parts.(4)因为当流体进入或离开这些小系统时，各部均为开口系统且需如此分析。Notes to the Text1.In the thermal engineering,the studied objects normally are isolated from one

20、 another and then we try to analysis the change and interaction,the studied objects isolated is named thermodynamic system.句中the studied objects normally are isolated from one another与we try to analysis the change and interaction相并列。在热力工程中，通常将研究对象分离出来再分析其变化及（与外界）的相互作用，该对象即热力系统。2.The boundary of a sy

21、stem can be either real or imaginary,and either fixed or movable.If the gas in a cylinder is the studying object,then it is the thermodynamic system.句中and either fixed or movable.是省略句。全句为and it can also be either fixed or movable.3.we can do it either by placing an imaginary envelope around the obje

22、cts under consideration or by using an actual envelope if it exists.eitheror结构，两个介词短语（by）相并列。Text 1l4.when dealing with a gas in the cylinder where the boundaries are located on the outside of the cylinder,分词短语做状语，全句为when we deal with 5.So it is very important and essential for us to specify the bou

23、ndaries of the system carefully.此句为it is for sb.to do sth.结构。6.The boundaries of a closed system may be either rigid or may expand or contract,是eitheroror句。7.Then the performance of the entire system can be determined by the summation of the performance of the individual component systems.可将之化整为零再逐件

24、分析。则全系统的性能取决于各分系统之统和。Text 2 General Characteristics of Heat TransferlWhen study the course of the heat transfer carefully，we can find that the heat or thermal energy is transferred from one region to another by three modes:conduction,convection and radiation.In fact，the heat transfer process is a co

25、mbining of two or three.1l在仔细研究热量传递的过程中，我们可以发现热量/能量由一个区域到另外一个时，通过三种方式进行传递：导热、对流和辐射。l事实上，热传递通常为（其中）两或者三种中的组合。contentsUnit 1New wordsl（1）Conduction is a process that the heat transfers from the parts of high temperature of the object to the low or from a warmer object to the cooler contacting with it.

26、2l导热即热量从物体的高温部向低温部或从热物体向与之接触的冷物体传递的过程。lTemperature is the driving force behind the heat transfer.The great the temperature difference,the greater the heat transfer rate is.And heat does not conduct at the same rate in different materials.l热传导的动力为温差。温差越大，传热率越高，并且不同物质的导热系数不同。lThe heat transfer in cond

27、uction can be explained as the energy actually traveling from one molecule to another.The second law of thermodynamics states that thermal transfer occurs in the direction of decreasing temperature.In solid opaque bodies,the significant heat transfer is thermal conductionl导热可以解释为能量在分子之间的传递。根据热力学第二定律

28、，热传递是发生在温度降低的方向。对于非透明固体而言，导热为其主要的热量传递方式。l（2）Thermal convection may occur from one location to another by means of current set up in a fluid medium.4 When heat is moved,it is normally transferred into some movable substance.The most common fluid mediums in convection process are air and water.l对流是借助于

29、流体形成的介质来实现热量由某一区域到另一区域的传递。当热量传递时，往往传低于某种可移动的物质中。空气和水是最常见的两种热传递流体媒介。lThermal convection involves energy transfer by eddy mixing and diffusion of the fluid in addition to conduction.Consider heat transfer to a fluid flowing inside a pipe，If the Reynolds number is sufficiently great,three different flo

30、w regions will exist.l除导热外，对流换热还借助于流体的涡旋洄流及流体碰撞混合过程予以实现。对于管内流动流体的传热，如果雷诺数足够大，则三种流动边界均会存在。lWhen fluid currents are produced by sources external to the heat transfer region,for example,a blower or pump,the solid-to-fluid heat transfer is termed forced convection.If the fluid flow is generated internal

31、ly by non-uniform densities caused by temperature variation,the heat transfer is termed free or natural convection.5l当流体产生于（源于）热传递区之外时，例如风机或泵，则固液之间的热传递成为强制对流。如果流体是由于系统内部温度变化所导致的流体密度不同而产生的，则该热传递成为自由或自然对流。l（3）In conduction and convection,heat transfer takes place through matter.For radiant heat transf

32、er,there is a change in energy form;from internal energy at the source to electromagnetic energy for transmission,then back to internal energy at the receiver.6l对于导热和对流，其热量传递需借助物质实现。对于辐射换热过程，其需要一个能量形式的转换，既热源的内容转换为电磁能来实现传递，然后于接收处转换为内能。lWhereas conduction and convection are affected primarily by tempe

33、rature difference and somewhat by temperature level,the heat transferred by radiation increase rapidly as the temperature increases.l导热和对流主要受温差和物体的不同温度水平的影响，而辐射换热直接随温度的升高而加强。lRadiation is the only type of heat transfer that can travel through a vacuum,such as space,because radiation is not dependent

34、 on matter as a medium of heat transfer.l辐射是唯一可以在真空，如太空，进行热传递的形式，因为其无需依靠某种物质作为介质进行传热。lThis is impossible with convection and conduction because they require some form of matter,like air or water,to be the transmitting medium.l而这对于对流换热和热传导是不可能发生的，因为他们需要诸如空气和水作为传热介质。New Words and Expressionsblower n.风

35、机，风扇,爱吹牛的人characteristica.特有的,典型的;n.特性,特征collision n.碰撞,冲突conduction n.传导contact n.接触,联系 vt.接触,联系convection n.传送,对流eddy n.旋转,漩涡v.(使)起漩涡elastic a.弹性的electromagnetic a.电磁的internally ad.在内,在中心 Text 2mediumn.媒体,方法,媒介 a.中间的,中等moleculen.化分子,些微non-uniform a.不一致的,不均匀的opaque n.不透明物 a.不透明的,不传热的,迟钝的primarily a

36、d.首先,起初,主要地,根本上radiationn.发（光、热）,辐射,放射（线）region n区域,地方,地区,领域,(大气)层temperature n.温度transmission n.播送,发射,传动,传送,传输,转播vacuum n.真空,真空吸尘器 a.(产生)真空的 vt.用真空variation n.变更,变化,变异,变种,音变奏,变调whereas conj.然而,反之,鉴于,尽管,但是a combining of结合by means of依靠contact with与联系，与接触takes place发生 Technical Termselastic collision弹

37、性碰撞flow region 流动区域temperature difference温差the fluid flow液体流动，液流the heat transfer region传热区the heat transfer传热the Reynolds number 雷诺数the second law of thermodynamics热力学第二定律 Text 2Exercise(1)Answer the following questions according to the text.(1)How many modes are there in the heat transfer？(2)What

38、is the heat conduction process?(3)What is the significant heat transfer mechanism in a solid opaque body?(4)What are the most common fluid mediums in convection process?(5)Which is the only type of the heat transfer that can travel through a vacuum?Exercise(2)Decide whether the following statements

39、is true or false according to the text.(1)The heat transfer process is not net.(2)Temperature different is the driving force behind the heat transfer.(3)Thermal convection can not occur from one location to another by means of current set up in a fluid medium.(4)For radiant heat transfer,there is no

40、t a change in energy form.(5)When fluid currents are produced by sources external to the heat transfer region,for example,a blower or pump,the solid-to-fluid heat transfer is termed forced convection.(6)This is possible with convection and conduction because they require some forms of matter,like ai

41、r or water,to be the transmitting medium.Exercise(3)Put the following words into Chinese/English.(1)Conduction is a process that the heat transfers from the parts of high temperature of the object to the low or from a warmer object to the cooler contacting with it.(2)根据热力学第二定律，热传递指向温度降低的方向。(3)Wherea

42、s conduction and convection are affected primarily by temperature difference and somewhat by temperature level,the heat transferred by radiation increase rapidly as the temperature increases.(4)辐射是唯一可以在真空（例如太空）进行的热传递（形式），因其可以不依赖（某种）物质进行传热。Notes to the Text1.When study the course of the heat transfer

43、 carefully，we can find that the heat or thermal energy is transferred from one region to another by three modes:句中that the heat or thermal energy is transferred from one region to another by three modes是宾语从句。仔细研究热量传递过程，我们可以发现热量通过三种方式进行传递：2.Conduction is a process that the heat transfers from the par

44、ts of high temperature of the object to the low or from a warmer object to the cooler contacting with it.句中the low是省略句，完全形式应为the parts of low temperature of the object。that the heat transfers from the parts of high temperature of the object to the low or from a warmer object to the cooler contacting

45、 with it是表语a process的定语从句，句中fromto为介词短语做状语。导热即热量从物体的高温部向低温部或从热物体向与之接触的冷物体传递的过程。3.In gases,conduction is a result of elastic collision of molecules.In liquids and electrically conducting solids,it is believed to be caused by longitudinal oscillations of the lattice structure.句中it is believed to be ca

46、used by longitudinal oscillations of the lattice structure.是it isto 结构，it是形式主语，to be caused（by longitudinal oscillations of the lattice structure.）是真实主语。Text 24.Thermal convection may occur from one location to another by means of current set up in a fluid medium.句中set up in a fluid medium.为分词短语，做cu

47、rrent的定语。其中的set是分词形式。对流是借助于流体介质形成的介质流来实现热量传递任务的。5.If the fluid flow is generated internally by non-uniform densities caused by temperature variation,the heat transfer is termed free or natural convection.caused by temperature variation是分词短语做定语。如果液流乃是由于系统内部由于温度变化所导致的密度不同导致，则该热传递过程成为自由（自然）对流。6.For rad

48、iant heat transfer,there is a change in energy form;from internal energy at the source to electromagnetic energy for transmission,then back to internal energy at the receiver.该句为省略句。from internal energy at the source to electromagnetic energy for transmission,then back to internal energy at the rece

49、iver.是fromto结构。而热辐射（过程的实现）有一能量形式的转换过程，即热源内能（先）转化为电磁能进行传递，再于接受处转化为内能形式。介词短语at the source，for transmission，at the receiver分别做三个energy的宾语。Text 2Text 3 ConductionlConduction is that the heat transfer through one or more substances from a region of high temperature to a region of low temperature by the e

50、xchange of energy between the molecules of the substance.1 In the process of transferring heat by conduction is based on the movement of the molecules,but no bodily displacement of the molecules occurs.However,the electron movement in a metal greatly assists in the heat transfer by conduction.l导热即分子