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1、学 时：30,授课班级：1014091/2,Specialized English for Chemical Engineering and Technology,授课教师：李 霞,联系电话：,After completing this unit,you should be able to:,Identify the application of thermodynamics.Discuss the nature of thermodynamics.State and describe briefly each of the three thermodynamic laws.Explain t
2、he mechanisms of heat flow:conduction,convection and radiation.,Unit 11 Chemical and Process Thermodynamics,Before committing(犯罪，投入时间/金钱等)a great deal of time and effort to the study of a subject,it is reasonable to ask the following two questions:what is it?What is it good for?Regarding thermodynam
3、ics,the second question is more easily answered,but an answer to the first is essential to an understanding of the subject.,译：在投入大量的时间和精力去研究一个学科时，有理由去问一下以下两个问题：该学科是什么？（研究）它有何用途？对于热力学而言，第二个问题比较容易回答，但回答第一个问题有必要对该学科较深入的理解。,Although it is doubtful that many experts or scholars would agree on a simple an
4、d precise definition of thermodynamics,necessity demands that a definition be attempted.However,this is best accomplished after the applications of thermodynamics have been discussed.,译：（尽管）许多专家或学者赞同热力学的简单而准确的定义的观点（看法）值得怀疑，但是还是有必要确定它的定义。然而，在讨论热力学的应用之后，就可以很容易完成其定义.,Applications of Thermodynamics Ther
5、e are two major applications of thermodynamics,both of which are important to chemical engineers:,译：热力学有两个主要的应用，两者对化学工程师都很重要。,()The calculation of heat and work effects associated with processes as well as the calculation of the maximum work obtainable from a process or the minimum work required to
6、drive a process.()The establishment of relationships among the variables describing systems at equilibrium.,译:（1）与过程相联系的热效应和功效应的计算，以及从过程得到的最大功或驱动过程所需的最小功的计算。（2）描述处于平衡的系统的各变量之间的关系的确定。,The first application is suggested（建议，提议；暗示；使联想到；启示）by the name thermodynamics,which implies heat in motion.Most of t
7、hese calculating can be made by the direct implementation of the first and second laws.,译：第一种应用由热力学这个名词可联想到，热力学表示运动中的热。直接利用第一和第二定律可完成许多（热效应和功效应的）计算。,Examples are calculating the work of compressing a gas,performing an energy balance on an entire process or a process unit,determining the minimum work
8、 of separating a mixture of ethanol and water or evaluating the efficiency of an ammonia synthesis plant.,译：例如：计算压缩气体的功，对一个完整过程或某一过程单元的进行能量衡算，确定分离乙醇和水混合物所需的最小功，或者评估一个氨合成工厂的效率。,The application of thermodynamics to a particular system results in the definition of useful properties and the establishmen
9、t of a network of relationships among the properties and other variables such as pressure,temperature,volume,and mol fraction.,译：热力学在特殊体系中的应用，引出了一些有用的函数的定义以及这些函数和其它变量（如压强、温度、体积和摩尔分数）关系网络的确定。,Actually,application 1 would not be possible unless a means exists for evaluating the necessary thermodynamic
10、 property changes required in implementing the first and second laws.The property changes are calculated from experimentally determined data via the established network of relationships.,译：实际上，在运用第一、第二定律时，除非用于评价必要的热力学函数变化的方法已经存在，否则热力学的第一种应用不可能实现。通过已经建立的关系网络，从实验确定的数据可以计算函数变化。,Additionally,the network
11、 of relationships among the variables of a system allows the calculation of values of variables which are either unknown or difficult to determine experimentally from variables which are either available or easier to measure.,译：除此之外，某一体系中变量的关系网络，可让那些未知的或者那些难以从变量（这些变量容易得到或较易测量）中实验确定的变量得以计算。,For examp
12、le,the heat of vaporizing a liquid can be calculated from measurements of the vapor pressure at several temperatures and densities of the liquid and vapor phases at several temperatures,and the maximum conversion obtainable in a chemical reaction at any temperature can be calculated from calorimetri
13、c measurements performed on the individual substances participating in the reaction.,译：例如，一种液体的汽化热，可以通过测量几个温度的蒸汽压和几个温度下液相和汽相的密度得以计算；某一化学反应中任一温度下的可得的最大转化率，可以通过参与该反应的各物质的热量法测量加以计算。,2.The Nature of Thermodynamics The laws of thermodynamics have an empirical or experimental basis,and in the delineation(
14、描述)of its applications the reliance upon（依赖，依靠）experimental measurement stands out（突出）.Thus,thermodynamics might be broadly defined as a means of extending our experimentally gained knowledge of a system or as a framework for viewing and correlating the behavior of the system.,译：热力学定律有着经验或实验基础，但是在描述
15、其应用时，依赖实验测量显得很明显。因此，热力学广义上可以定义为：拓展我们实验所得的体系知识的一种手段（方法），或定义为：观察和关联一个体系的行为的基本框架。,To understand thermodynamic,it is essential to keep an experimental perspective,for if we do not have a physical appreciation for the system or phenomenon studied,the methods of thermodynamics will have little meaning.We
16、should always ask the following questions:How is this particular variable measured?How,and form what type of data,is a particular property calculates?,译：为了理解热力学，拥有实验的观点很必要，因为，如果我们不能对研究的体系或现象做出物理上正确的评价，那么热力学的方法就无意义。我们应该要经常问问如下问题：怎样测量这一特殊的变量？怎样计算以及从哪一类的数据计算一个特殊的函数。,Because of its experimental foundati
17、on,thermodynamics deals with macroscopic properties,or properties of matter in bulk,as opposed to microscopic properties which are assigned to the atoms and,molecules constituting matter.Macroscopic properties are either directly measurable or calculable from directly measurable properties without r
18、esource to a specific theory.,译：由于热力学的实验基础，热力学讨论的是宏观函数或大量的物质的函数，而不是微观函数，微观函数涉及到的是组成物质的原子或分子。宏观函数要么可以直接测量，要么可以从直接测量的函数计算得到，而不需要借助于某一具体的理论。,Conversely,while microscopic properties are ultimately determined from experimental measurements,their authenticity depends on the validity of the particular theo
19、ry applied to their calculation.Herein(于此，此中)lies the power and authority of thermodynamics：Its results are independent of（与无关）theories of matter and are thus respected and confidently accepted.,译：相反，尽管微观函数最终是从实验测量得以确定，但是它们的真实性取决于用于它们计算时的特殊理论的有效性。热力学的权威性就在于此：它的结果与物质的理论无关，倍受尊敬，为大家大胆地接受。,In addition t
20、o the certitude（确信）accorded its results,thermodynamics enjoys a broad range of applicability.Thus,it forms an integral part of（的组成部分）the education of engineers and scientists in many disciplines;nevertheless,this panoramic(全景的，全貌的)scope is often unappreciated because each discipline focuses only on
21、the few applications specific to it.,译：除了与热力学结论一致的必然性以外，热力学有着广泛的应用性。因此，热力学形成了许多学科中的工程师和科学家的教育中不可分割的部分。尽管如此，因为每门科学都只局限于关于热力学方面的较少应用，所以其全貌常被低估。,Actually,any system which can exist in observable and reproducible equilibrium states is amenable to（服从的）the methods of thermodynamics.In addition to fluids,c
22、hemically reacting systems,and systems in phase equilibrium,which are of major interest to chemical engineers,thermodynamics has also been successfully applied to systems with surface effects,stressed solids,and substances subjected to(使遭受，使服从)gravitational,centrifugal,magnetic,and electric fields.,
23、译：实际上，在明显的（可观察到）可再现的平衡态中存在的任何体系，都服从于热力学方法。除了流体、化学反应系统和处于相平衡体系（化学工程师对这些十分感兴趣）之外，热力学也成功适用于有表面效应的系统、受压力的固体以及处于重力场、离心力场、磁场和电场的物质。,Through thermodynamics the potentials which define and determine equilibrium are identified and quantified.These potentials also determine the direction in which a system wil
24、l move as well as the final state it will reach but offer no information concerning the time required to attain the final state.,译：通过热力学，可以被确定用于定义和确定平衡的势能，并将之定量化。势能也可以确定一个体系移动的方向以及体系达到的终态，但是不能提供有关到达终态所需要的时间的信息。,Thus,time is not a thermodynamic variable,and the study of rates is outside the bounds（超出
25、的范围）or thermodynamics except in the limit as the system nears equilibrium.Here rate expressions should be thermodynamically consistent.,译：因此，时间不是热力学的变量，速率的研究已超出了热力学的范畴，除了体系接近平衡的极限情况以外。在这儿，速率的表达式应该在热力学上是连续的。,The experiments and observations on which the laws of thermodynamics are based are neither gr
26、and nor sophisticated.Also,the laws themselves are stated in rather pedestrian（平淡无奇的）language.Yet,from this apparently unimpressive beginning a grand structure has evolved which is a tribute to the inductive powers of the human mind.,译：热力学定律建立于实验和观测基础之上的，这些实验和观测既不庞大，又不复杂。此外，这些定律的本身是用相当普通的语言加以描述的。然而，
27、从这一明显的平淡的开始，发展成为一个很大的结构，这对人类思想的归纳能力做出了贡献。,This never fails to inspire awe in the thoughtful and serious student and has led Lewis and Randall to refer to thermodynamics as a cathedral（总教堂，权威）of science.The metaphor(隐喻，比喻)is well chosen for in addition to technical accomplishment and structural integ
28、rity one also sees beauty and grandeur(美丽和壮观）.,译：这在想象力丰富、严肃认真的学生中成功地激发了敬畏（inspire awe），这使得Lewis 和Randall 将热力学称为科学的总教堂。这个比喻选择很恰当，因为除了技术上的成功和结构的严密性，我们还可观察到美妙之处。,It is no small wonder(难怪，不足为奇)that the study of thermodynamics can be technically rewarding,intellectually stimulating,and,for some,a pleasur
29、able experience.,译：难怪人们说，热力学的研究在学术上是有意义的，智力上可以得到激发，同时，对一些人来说，是一种很好的经历。,3.The Thermodynamic Laws The First Law.The first law of thermodynamics is simply a statement of the conservation of energy.As shown in Fig 3-1,the sum of all the energy leaving a process must equal the sum of all the energy enter
30、ing,in the steady state.The laws of conservation of mass and energy are followed implicitly by engineers designing and operating processes of all kinds.,译：第一定律.热力学第一定律是能量守恒的简单的一种描述。如图3-1 所示，稳态时离开一个过程的所有能量的总和必须与所进入该过程的能量总和相等。工程师在设计和操作各种过程时绝对遵循质量和能量守恒定律。,Unfortunately,taken by itself(就其本身而言),the first
31、 law has led to much confusion when attempting to evaluate process efficiency.People talk of energy conservation being an important effort,but in fact,no effort is required to conserve energy it is naturally conserved.,译：不幸的是，就其本身而言，当试图评估过程的效率时，第一定律会引起混淆不清。人们认为能量守恒需要付出很大的努力，但是事实上，使能量守恒不需要花任何努力 能量本身就
32、是守恒的。,The conclusions which can be drawn from(从得到)the first law are limited because it does not distinguish among the various energy forms.Shaft work(轴功)introduced by a reflux pump will leave a column as heat to the condenser just as readily as(正如一样)will heat introduced at the reboiler.,译：因为第一定律没有区分
33、各种各样能量的形式，所以从第一定律所得到的结论是有限的。由往复泵引入的轴功会以热量流向冷凝器的形式离开蒸馏塔，与在再沸器引入的热一样容易。,Some engineers have fallen into the trap(陷入困境)of lumping all forms of energy together in attempting to determine process efficiency.This is obviously not justifiedthe various energy forms have different costs.,译：在试图确定过程的效率时，一些工程师总
34、掉入将各种形式的能量一起处理的陷阱。这种做法明显是不合理，因为各种能量形式有着不同的费用。,The Second Law.There are many different statements of the second law as applied to cycles in which heat is converted into work.At this point,a more general statement is desirable:The conversion of energy from one form to another always results in an over
35、all loss in quality.,译：第二定律:第二定律应用于热转变为功的循环，有多种不同的描述。至于这一点，一种更加普通的描述是需要的：从一种形式的能量到另一种形式的能量的转换，总是导致质量上总量的损失。,Another is:All systems tend to approach equilibrium(disorder).These statements point out the difficulty in expressing the second law.It cannot really be done satisfactorily without defining an
36、other term describing quality or disorder.,译：另一种描述为：所有系统都有接近平衡（无序）的趋势。这些表达方式指出了在表达第二定律时的困难之处。如果不定义另一个专门描述质量或无序的词语，第二定律的表达就不能令人满意。,That term is entropy(熵).This property of state quantifies the level of disorder in a fluid,body,or system.Absolute zero entropy is defined as the state of a pure,crystall
37、ine solid at absolute zero temperature.Each molecule is surrounded by identical molecules in a perfectly ordered structure at rest.,译：这个专用名词为熵。这个状态函数对流体、物质或系统中的无序程度进行了定量化。绝对零熵值定义绝对零度时纯净的、晶体固体的状态。每一个分子都由其他的以相当有序结构的相同的分子所包围。,Motion,randomness,contamination,uncertainty,all adds disorder and therefore c
38、ontribute to(贡献)entropy.Conversely,order is valuable,whether(无论)in the clarity of a gem stone,the purity of a chemical product,the cleanliness of a living space,or the freshness of air and water.,译：运动、随意、污染、不确定性，这一切都增加了混乱度，因此对熵做出了贡献。相反，不论是透明宝石，还是纯净化学产品，还是清洁的生活空间，还是新鲜的空气和水，（都是属于有序状态），有序是有价值的。,Order c
39、ommands a high price and can be creates only by applying work.Most of our work is expended in creating or restoring order in the home,the workplace,and environment.High entropy in the environment is one of externalized(具体化)costs of manufacturing.,译：有序需要付出很高的代价，只有通过做功才得以实现。我们很多工作都花费在家里、车间和环境中创造或恢复有序状
40、态。环境中较高的熵值是较高的生产费用的具体化表现。,The purpose of every productive process is to reduce entropy by separating mixtures into pure products,reducing uncertainty in our knowledge,or creating works of art from raw materials.,译：每一种生产过程的目的都是，利用将混合物分离为纯净物、减小我们知识的不确定性、或是从原料创造（works of art）艺术品以减小熵值。,In general,there
41、is a progression of decreasing entropy from feedstock(原料)to products.However,this is an uphill struggle(艰难的过程)inasmuch as(因为)the natural tendency is for entropy to increase as systems approach equilibrium.,译：总之，从将原料转变为产品的过程中，熵值不断减小。然而，（inasmuch as）因为随着系统接近平衡，熵的增加是自发的趋势，所以减少熵值是艰难的工作（struggle）,The dri
42、ving force for the decreasing in entropy required of production is a concomitant increase in entropy by a greater amount in the rest of the universe.Generally speaking,this increase is sustained within the same plant and is therefore responsible for the decrease in product entropy.,译：生产过程所需熵减的驱动力同时伴
43、随着宇宙其余部分熵的剧增。一般说来，这种熵的增加在同一工厂内不断持续下去，因此这种造成了产品熵的减小。,Whereas the entropy decrease resides in the conversion of feedstock unto products,the greater increase is indicated by the conversion of fuels,electricity,air,and water,into combustion products,wastewater,and waste heat.,译：反过来（whereas 而，却，其实，反过来），熵
44、减存在于原料向产品的转化过程。燃料、电、空气以及水向燃烧产品、废水和无用的热量的形式的转化可表示熵值的大大增加。,The bottom lines of fig.3-1 describe the second law,just as the middle line describes the first law.The total entropy of all streams leaving a process must always exceed that of all streams entering.If the entropy were to balance,as do the mas
45、s and energy,the process would be reversible,i.e.it could function as well to backward.,译：正象图3-1 中中间部分描述为第一定律一样，图中的底线部分描述了第二定律。离开一个过程的所有的物流的熵值的总和，总是超过进入该过程的物流的熵值的总和。如果熵达到平衡，象质量和能量达到平衡一样，那么该过程是可逆的，即该过程也会反向移动。,Reversible processes are only theoretically possible,requiring dynamic equilibrium to exist
46、continually they are not productive.Furthermore,if the inequality were reversed,i.e.if there were a not entropy decease,all the arrows would also be reversed and the process would be forced to run backward.,译：可逆过程只是在理论上是可能的，需要动力学平衡维持连续存在，因此可逆过程是不可产生的。而且，如果不平衡（过程）倒过来，即如果有净熵的减少，那么所有的箭头也要反向，该过程被迫反向进行。,
47、In essence,it is the entropy rise that drives the progress;It is the same driving force that makes water flow downhill(往下),heat flow from hot to cold,vessels leak,glass break,metals corrode(腐蚀).In short,all things approach equilibrium with their surroundings.,译：实质上，是熵增驱使该过程：是同一种驱动力使水向下流，热流从热物质流向冷物质，
48、使玻璃打碎，金属腐蚀。简而言之，所有事物都同它们周围的环境接近平衡。,The first law requires the conservation of energy and gives equal weight to all types of energy changes.While no process is immune to its authority,this law does not recognize the quality of energy nor does it explain why spontaneously occurring processes are never
49、 observed to spontaneously reverse themselves.,译：第一定律，需要能量守恒，所有形式能量变化有着相同的重要性。尽管所有过程都受第一定律权威性的影响，但是该定律不能区分能量的质量，也不能解释为什么观察不到自发发生的过程自发地使自身可逆。,The repeatedly confirmed observation that work may be completely converted into heat but that the reverse transformation never occurs quantitatively leads to t
50、he recognition that heat is a lower quality of energy.The second law with its origins deeply rooted in(扎根于)the study of the efficiency of heat engines recognizes the quality of energy.,译：功可以全部转化为热而反向转换从来不会定量发生，这种反复验证过的观测达成了这样的共识热是一种低质量的能量。第二定律，深深扎根于热发动机效率的研究，能分辨能量的质量。,Through this law the existence
