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1、.word.zl.ChapterChapter 1 1 IntroductionIntroduction toto ThermalThermal ScienceScience第一章热科学第一章热科学根底根底Acoustic flow meter 声波流量计Corrugated fin 波状散热片Adiabatic 绝热的Cross product 矢量积Aerodynamics 空气动力学Denominator 分母Affiliation 联系Developed flow 充分开展流Airfoil 机翼，螺旋桨Diffusion 扩散Alternative 替代燃料Doppler effect
2、 多普勒效应Anemometer 风速计Double-pipe heat exchanger 套管式换热器Angular speed 角速度Dry saturated vapor 干饱和蒸汽Area density 外表密度Electrode 电极Baffle 挡板Electrolyte 电解，电解液Bifurcation 分形Electrostatic 静电的Blackbody 黑体Emissivity 发射率Blade 浆叶，叶片Equilibrium 平衡Boiler 锅炉Fluid mechanics 流体力学Boundary layer 边界层Forced convection强制对
3、流Carnot Cycle 卡诺循环Free convection 自然对流Cartesian coordinates 笛卡尔坐标系Friction loss 摩擦损失Celsius Degree 摄氏度Glass ceramic 微晶玻璃，玻璃瓷pact heat exchanger 紧凑式换热器Heat engine 热机position 成分，合成物Heat pump 热泵pressed liquid 压缩液体Hydrofoil 水翼pressibility 可压缩性，压缩率Hypersonic speed 高超音速Condensation 凝结Infinitesimal 无穷小的Con
4、denser 冷凝器Inflating/deflating 充气/压缩Conduction 导热Internal bustion engine 燃机Control volume 控制体Isentropic 等熵的Convection 对流Isobaric 等压的Coriolis-accelaration flowmeter 科氏加速Isolated system 孤立体系的.word.zl.流量计Isometric 等容的Rough-wall tube 粗糙管Isothermal 等温的Saturation 饱和Kinematic viscosity 运动黏度Shear stress 剪切力、
5、切应力Laminar 层流Shell-and-tube heat exchanger管壳式换热器Manuscript 手稿，原稿Specific volume 比容Moisture 湿度，水分Steady 稳态的，定常的Molecule(化学)分子Stifling engine 斯特林机Molten polymer 熔融聚合物Strain rate 变形速度，应变率Muti-disciplinary 多学科的Streamline 流线Newtonian Fluid 牛顿流体Strut 支撑，支柱Nominal temperature gradient 法向温度梯度Subcooled liqui
6、d 过冷液体Numerator 数学分子Superheated vapor 过热蒸汽Parallel flow 平行流动，并流Surrounding 环境，外界Pathline 迹线Thermal conductivity 热传导率Phase change 相变Thermal efficiency 热效率Plane flow 平面流，二元流Thermodynamics 热力学Plate and flame heat exchanger板式换热器Torsional 扭力的，扭转的Polymer solution 胶浆Trailing edge 机翼后缘、尾缘Proof 校样Transmitter
7、 传送装置、发送器Propeller 螺旋桨，推进器Turbine meter 涡轮流量计Pump 泵Turbulent 湍流的Qulity 干度Ultrosonic 超声波的Qusi-equilibrium 准平衡、准静态Uniform flow 均匀Radiation 辐射Vacuum 真空Rankin Cycle 朗肯循环View factor 角系数Regenerative heat exchanger蓄热/再生式换热器Viscous 黏性的Reservoir 水库，蓄水池Cortex shedding 漩涡脱落Reversible 可逆的Water faucet 水龙头，水嘴.wor
8、d.zl.Rotameter 转子流量计Bi Biot number 比澳数NPSH 汽蚀余量CFD计算流体力学NTU 传热单元数CHF临界热流量Nu 努尔特数COP 制冷系数PE 势能Eu 欧拉数Pr 普朗特数Fo 富立叶数Ra 瑞利数Fr 弗劳德数Re 雷诺数Gr 格拉晓夫数Sc 施密特数KE 动能St斯坦顿数，斯特劳哈数LMTD 对数平均温差We 韦伯数1.11.1 FundamentalFundamental ofof EngineeringEngineering ThermodynamicsThermodynamics1.11.1 工程热力学根底工程热力学根底Thermodynami
9、cs is a science in which the storage,transformation and transfer ofenergy are studied.Energy is stored as internal energy(associated with temperature),kinetic energy(du to motion),potential energy(due to elevation)and chemical energy(due to chemical position);it is transformed from one of these form
10、s to another;and it istransferred 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展传递。In thermodynamics,we will derive equations that relate the transformations andtransfers of energy to properties such as tem
11、perature,pressure and density.Substancesand their properties,thus,bee very important in thermodynamics.Many of our equationswill be based on experimental observations that have been organized into mathematicalstatements or laws,the first and second laws of thermodynamics are most widely used.在热力学中，我
12、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程。因此，在热力学中，物质及其性质变得非常重要。多热力学.word.zl.程都是建立在实验观察的根底之上，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。1.1.11.1.1ThermodynamicThermodynamic systemsystem andand controlcontrol volumevolume1.1.11.1.1热力系统和控制体热力系统和控制体A thermodynamic system is a fixed quantity of matter c
13、ontained within someenclosure.The surface is usually an obvious one(like that surrounding the gas in thecylinder).However,it may be an imagined boundary(like the deforming boundary of acertain amount of mass as it flows through a pump).热力系统是一包围在某一封闭边界的具有固定质量的物质。系统边界通常是比较明显的如气缸气体的固定边界。然而，系统边界也可以是假想的如
14、一定质量的流体流经泵时不断变形的边界。All matter and space external to a system is collectively called its surroundings.Thermodynamics is concerned with the interaction of a system and its surroundings,orone system interacting with another.A system interacts with its surroundings bytransferring energy across its bound
15、ary.No material crosses the boundary of a system.Ifthe 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展能量传递，从而与外界进展相互作用，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 i
16、s focused on a particular volumein space into which,or from which,a substance flows.Such a volume is a controlvolume.A pump,a turbine,and an inflating or deflating balloon are examples of controlvolume.The surface that pletely surrounds the control volume is called a control surface.在多情况下，当我们只关心空间中有
17、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。包含控制体的外表称为控制外表。Thus,we must choose,in a particular problem,whether a system is to be considered.word.zl.or whether a control volume is more useful.If there is mass flux across a boundary,thena control volume is required;otherwise,a system
18、 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，那么选取控制体有利；反之，那么应选取系统作为研究对象。1.1.21.1.2Equilibrium,Equilibrium,processprocess andand cyclecycle平衡、过程和循环平衡、过程和循环When the temperature of a system is referred to,it is assumed that all points of thesystem have the same,or essentially
19、 the same temperature.When the properties areconstant from point to point and when there is no tendency for change with time,acondition of thermodynamic equilibrium exists.If the temperature,say,is suddenlyincreased at some part of the system boundary,spontaneous redistribution is assumed tooccur un
20、til all parts of the教材教材 1 1 页页system are at the same temperature.对于某一参考系统，假设系统各点温度完全一样。当物质部各点的特性参数均一样且不随时间变化时，那么称系统处于热力学平衡状态。当系统边界某局部的温度突然上升时，那么系统的温度将自发地重新分布，直至处处一样。When a system changes from one equilibrium state to another,the path ofsuccessive sates through which the system passes is called proc
21、ess.If,in the passing onestate to the next,the deviation from equilibrium is infinitesimal,a quasi-equilibriumprocess occurs,and each state in the process may be idealized as an equilibrium state.Quasi-equilibrium processes can approximate many processes,such as the pression andexpansion of gases in
22、 an internal bustion engine,with no significant loss of accuracy.Ifthe system goes from one equilibrium state to another through a series ofnon-equilibrium states(as in bustion),a non-equilibrium 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。假设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，那么称该过程为准静态
23、过程，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多过程的叠加结果，而不会显著减小其准确性，例如气体在燃机的压缩和膨胀过程。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，.word.zl.那么其过程为非平衡过程。When a system in a given initial state experiences a series of process and returns tothe initial state,the system goes a cycle.At the end of the cycle,the properties of thes
24、ystem 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，那么称系统经历了一个循环。循环完毕时，系统中的各参数又与初始参数一样。The prefix iso-is attached to the names of any property that remain unchanged in aprocess.An isothermal process is one in which the temperature is held constant;in aniso-baricpro
25、cess,thepressureremainsconstant;anisometricprocessisaconstant-volume process.在任一特性参数名称前加上前缀 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。1.1.31.1.3Vapor-liquidVapor-liquid phasephase equilibriumequilibrium in in purepure substancesubstance纯物质的气纯物质的气-液相平衡液相平衡Consid
26、er as a system 1 kg of water contained in the piston or cylinderarrangement shown in Fig.1-1(a).Suppose the piston and weight maintain a pressure of0.1MPa in the cylinder and that the initial temperature is 20.As heat is transferred tothe water,the temperature increase appreciably,the specific volum
27、e increase slightly,andthe pressure remains constant.When the temperature reaches 99.6,additional heattransfer results in a change of phase,as indicated in Fig.1-1(b).That is,some of theliquid bees vapor,and during this process both the temperature and pressure remainconstant,but the specific volume
28、 increases considerably.When the last drop of liquid hasvaporized,further transfer of heat results in an increase in both temperature and specificvolume 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压强维持在 0.1Mpa，初始温度 20。当有热量开场传递给水时，缸水温迅速上升，而比容略有增加，气缸压强保持恒定不变。当水温到达
29、 99.6时，如假设再增加传热量，水将发生相变，如图 1-1(b)所示。也就是说，一局部水开场气化变为蒸汽，在此相变过程中，温度.word.zl.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。图图 1-11-1 液体在常压下的蒸发过程液体在常压下的蒸发过程The term saturation temperature designates the temperature at which vaporizationtakes place at a given pressure.This pressure is
30、 called the saturation pressure for thegiven temperature.Thus,for water at 99.6,the saturation pressure is 0.1MPa,and forwater at 0.1MPa the saturation temperature 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 t
31、emperature,it is called saturatedliquid.If the temperature of the liquid is lower than the saturation temperature for theexisting pressure,it is called either a subcooled liquid(implying that the temperature islower教材教材 2 2 页页than the saturation temperature for the given pressure)or a pressed liquid
32、(implyingthat 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，那么称该液体为饱和液体。如果液体温度低于当前压强下的饱和温度，那么称该液体为过冷液体 说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 说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 q
33、uality is defined as the ratio of the mass of vapor to the total mass.Thus,inFig.1-1(b),if the mass of vapor is 0.2 kg and the mass of liquid is 0.8 kg,the quality is 0.2or 20%.Quality has meaning only when the substance is in a saturated state.假设某一工质在饱和温度下以液、气共存的形式存在，那么称蒸汽质量与总质量之比为干度。因此，如图 1-1(b)所示
34、，假设蒸汽质量为 0.2kg，液体质量为 0.8kg，那么其干度为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 saturationvapor(Some times the term dry saturation vapor is used to emphasize that the quality is.word.zl.100%).When the vapor is at a temperature greater than the satu
35、ration temperature,it issaid to exist as superheated vapor.The pressure and temperature of superheated vaporare independent properties,since the temperature may increase while the pressureremains constant.假设某一工质处于饱和温度下并以蒸汽形态存在，那么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，那么称之为过热蒸汽。过热蒸汽的压强和温度是彼此独
36、立的，因为温度上升时，压强可能保持不变。Let us plot on the temperature-value diagram of Fig.1-2 the constant-pressure linethat represents the states through which the water passes as it is heated from the initialstate of 0.1 MPa and 20.Let state A represent the initial state,B the saturated-liquidstate(99.6),and line A
37、B the process in which the liquid is heated from the initialtemperature to the saturation temperature.Point C is the saturated-vapor state,and lineBC is the constant-temperature process in which the change of phase from liquid tovapor occurs.Line CD represents the process in which the steam issuperh
38、eated at constant pressure.Temperature and volume both increase during thisprocess.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。图图 1-21-2 温度温度-比容曲线比容曲线表表 1-11-1 一些物
39、质的临界参数一些物质的临界参数In a similar name,a constant pressure of 10 MPa is represented by line IJKL,forwhich the saturation temperature is 311.1.At a pressure of 22.09MPa,represented byline MNO,we find,however,that there is no constant-temperature vaporization process.Instead,point N is a point of inflection
40、 with a zero slope.This point is called the criticalpoint.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 criticaltemperature,critical pressure and critical volume.The critical-point dat
41、a for some.word.zl.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一样的。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。1.1.41.1.4 TheThe firstfirst lawlaw ofof thermodynami
42、csthermodynamicsThe first law of the thermodynamics is monly called the law of conservation ofenergy.教材教材 3 3 页页In elementary physics courses,the study of conservation of energy emphasizeschanges in kinetic and potential energy and their relationship to work.A more generalform of conservation of ene
43、rgy includes the effects of heat transfer and internal energychanges.Other forms of energy could also be included,such as electrostatic,magnetic,strain and surface energy.1.1.41.1.4 热力学第一定律热力学第一定律通常把热力学第一定律称为能量守恒定律。在根底物理课程中，能量守恒定律侧重动能、势能的变化以及和功之间的相互关系。更为常见的能量守恒形式还包括传热效应和能的变化。当然，也包括其它形式的能，如静电能、磁场能、应变
44、能和外表能。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.历史上，用热力学第一定律来描述循环过程：净传热量等于循环过程中对系统所做的净功。1.1.51.1.5 TheThe secondsecond lawlaw ofof thermodynamicsthermodynamicsThe second law of thermodynamic
45、s can be stated in a variety of ways.Here wepresent two:the Clausius statement and the Kelvin-Planck statement.1.1.51.1.5 热力学第二定律热力学第二定律热力学第二定律有多种表述形式。在此列举两种：克劳修斯表述和凯尔文-普朗克表述。.word.zl.Clausius statementIt is impossible to construct a device that operates in a cycle and whose sole effectis transfer o
46、f heat from a cooler body to a hotter body.克劳修斯表述克劳修斯表述：制造一台唯一功能是把热量从低温物体传给高温物体的循环设备是不可能的。图图 1-31-3 第二定律的违背第二定律的违背This statement relates to a refrigerator(or a heat pump).It states that it isimpossible to construct a refrigerator that transfers energy from a cooler body to a hotterbody without the i
47、nput of work;this violation is shown in Fig.1-3(a).以冰箱或热泵为例，不可能制造一台不用输入功就能把热量从低温物体传给高温物体的冰箱，如图 1-3(a)所示。It is impossible to construct a device that operates in a cycle and produces no othereffect than the production of work and the transfer of heat from a single body.凯尔文凯尔文-普朗克表述普朗克表述：制造一台从单一热源吸热和做功
48、的循环设备是不可能的。In other words,it is impossible to construct a heat engine that extracts energy fromreservoir,does work,and does not transfer heat to a low-temperature reservoir.Thisrules out any heat engine that is 100 percent efficient,like the one shown in Fig.1-3(b).换句话说，制造这样一台从某一热源吸热并对外做功，而没有与低温热源进展
49、换热的热机是不可能的。因此，该表述说明了不存在工作效率为 100%的热机，如图 1-3(b)所示。1.1.61.1.6 TheThe CarnotCarnot CycleCycleThe heat engine that operates most efficiently between a high-temperature reservoir anda low-temperature reservoir is the Carnot engine.This is an ideal engine that usesreversible process to form its cycle of o
50、peration;such a cycle is Carnot cycle.The Carnotengine is very useful,since its efficiency establishes the maximum possible efficiency ofany real engine.If the efficiency of a real is significantly lower than the efficiency ofCarnot engine between the same temperature limits,then additional improvem