第一篇：化學工程與工藝專業(yè)英語作文2

Curriculum of chemical engineering

As chemical engineering knowledge developed, it was inserted into university courses and curricula.Before World WarⅠ, chemical engineering programs were distinguishable from chemistry programs in that they contained courses in engineering drawing, engineering thermodynamics, mechanics, and hydraulics taken from engineering departments.Shortly after World WarⅠthe first text in unit operations was published.Courses in this area became the core of chemical engineering teaching.By the mid-1930s, chemical engineering programs included courses in(1)stoichiometry(using material and energy conservation ideas to analyze chemical process steps),(2)chemical processes or “unit operations”,(3)chemical engineering laboratories “in which equipment was operated and tested”, and(4)chemical plant design(in which cost factors were combined with technical elements to arrive at preliminary plant designs).The student was still asked to take the core chemistry courses, including general, analytical, organic, and physical chemistry.However, in addition, he or she took courses in mechanical drawing, engineering mechanics, electric circuits, metallurgy, and thermo-dynamics with other engineers.Since World War Ⅱ chemical engineering has develop rapidly.As new disciplines have proven useful, they have been added to the curriculum.Chemical

engineering

thermodynamics

became generally formulated and taught by about 1945.By 1950, courses in applied chemical kinetics and chemical reactor design appeared.Process control appeared as an undergraduate course in about 1955, and digital computer use began to develop about 1960.The idea that the various unit operations depended on common mechanisms of heat, mass, and momentum transfer developed about 1960.Consequently, courses in transport phenomena assumed an important position as an underlying, unifying basis for chemical engineering education.New general disciplines that have emerged in the last two decades include environmental and safety engineering, biotechnology, and electronics manufacturing processing.There has been an enormous amount of development in all fields, much of it arising out of more powerful computing and applied mathematics capabilities.1.Science and Mathematics Courses Chemistry Chemical engineers continue to need background in organic, inorganic and physical chemistry, but also should introduced to the principles of instrumental analysis and biochemistry.· Valuable conceptual material should be strongly emphasized in organic chemistry including that associated with biochemical process.· Much of thermodynamic is more efficiently taught in chemical engineering, and physical chemistry should include the foundations of thermodynamic.Physics.Biology.· Biology has emerged from the classification stage, and modern molecular biology holds great promise for application.Future graduates will become involved with applying this knowledge at some time in their careers.· A special course is required on the functions and characteristics of living cells with some emphasis on genetic engineering as practiced with microorganisms.Materials Science.· Course work should include the effects of microstructure on physical, chemical, optical, magnetic and electronic properties of solids.· Fields of study should encompass ceramics, polymers, semiconductors, metals, and composites.Mathematics.Computer Instruction.· Although students should develop reasonable proficiency in programming, the main thrust should be that use of standard software including the merging of various programs to accomplish a given task.Major emphasis should be on how to analyze and solve problems with existing software including that for simulation to evaluate and check such software with thoroughness and precision.· Students should learn how to critically evaluate programs written by others.· All courses involving calculations should make extensive use of the computer and the latest software.Such activity should be more frequent as students progress in the curriculum.Adequate computer hardware and software must be freely available to the student through superior centralized facilities and/or individual PC’s.Development of professionally written software for chemical engineering should be encouraged.2.Chemical engineering courses Thermodynamics.· The important concepts of the courses should be emphasized;software should e developed to implement the concepts in treating a wide variety of complex, yet interesting, problems in a reasonable time.The value of analysis of units and dimensions in checking problems should continue to be emphasized.· Examples in thermodynamics should involve problems from a variety of industries so that the subject comes alive and its power in decision making is clearly emphasized.Kinetics, Catalysis, and Reactor Design and Analysis.· This course also needs a broad variety of real problems, not only design but also diagnostic and economic problems.Real problems involve real compounds and the chemistry related to them.· Existing software for algebraic and differential equation solving make simulation and design calculation on many reactor systems quite straightforward.· Shortcut estimating methods should be emphasized in addition to computer calculations.· The increased production of specialties make batch ad semibatch reactor more important, and scale-up of laboratory studies is an important technique in the fast-moving specialties business.3.Unit Operations The unit operations were conceived as an organized means for discussing the many kind of equipment-oriented physical processes required in the process industries.This approach continues to be valid.Over the years some portions have bee given separate status such as transport phenomena and separations while some equipment and related principles have not been included in the required courses, as is the case with polymer processing, an area in which all chemical engineers should have some knowledge.·Transport phenomena principles can be made more compelling by using problems form a wide range of industries that can be analyzed and solved using the principles taught.·Some efficiency may be gained by teaching several principles and procedures for developing specifications and selection the large number of equipment items normally purchased off-the-shelf or as standard design.·A great deal of time can be saved in addressing designed equipped such as fractionators and absorbers be emphasizing rigorous computer calculations and the simplest shortcut procedures.Most intermediate calculation procedures and graphical methods should be eliminated unless they have real conceptual value.Process Control.·This course should emphasize control strategy and precise measurement in addition to theory.·Some hands-on experience using current practices of computer control with industrial-type consoles should be encouraged.·Computer simulation of processes for demonstration of control principles and techniques can be most valuable, but contact with actual control devices should not be ignored.Chemical engineering laboratories.·Creative problem solving should be emphasized.·Reports should be written as briefly as possible;they should contain an executive summary with clearly drawn conclusions and brief observations and explanations with graphical rather than tabular representation of data.A great deal of such graphing can be done in the laboratory on computers with modern graphics capabilities.Detailed calculations should be included in an appendix.·Some part of the laboratory should be structured to relate to product development, Design/Economics ·In the design course in engineering, students learn the techniques of complex problem solving and decision making within a framework of economic analysis.The very nature of processes requires a system approach’ the ability to analyze a total system is one of the special attributes of chemical engineers that will continue to prove most sought after in a complex technological world.·Because of the greater diversity of interests and job opportunities, some consideration should be given to providing a variety of short design problem of greatest personal interest.·The design approach can be most valuable in diagnosing plant problems, and some practice in this interesting area should be provided.·Rigorous economic analysis and predictive efforts should be required in all decision processes.·Safety and environmental considerations should also be emphasized.·Modern simulation tools should be made available to the students.Other Engineering Courses.The electrical engineering courses should emphasize application of microprocessors, lasers, sensing devices, and control systems as well as the traditional areas of circuits and motors.The course should provide insight into the principles on which each subject is based.Remaining courses in engineering mechanics and engineering drawing should be considered for their relevance to current and future chemical engineering practice.4.Other courses Economics and Business courses.It is difficult to find a single course in economics or business departments that covers the various needs of engineers.The qualitative ability of engineers makes it possible to teach following topics in a single-semester course—in many cases in the Chemical Engineering Department: business economics, project economic analysis, economic theory, marketing and market studies, and national and global economics.Humanities and Social Science Courses.It is important to understand the origins of one’s own culture as well as that of others.Communication Course.Since improved communication skills require continuous attention, the following requirements may be useful: ·Oral presentations in at least one course each year.·Several literature surveys in the junior and senior years.·Introduce computer-based communication systems.Area of Specialization.The elective areas should be generous in hours to maximize freedom of choice.Each department will have to consider its own and its total university resources and strenghs as well as the quality and preparation of its students.The suggested areas are: ·Life sciences and applications ·Materials sciences and applications ·Catalysis and electrochemical science and applications ·Separations technology ·Computer applications technology ·Techniques of product development and marketing ·Polymer technology Each of these areas should be strongly career-oriented.The interest in a given area will depend on opportunities perceived by the students.

第二篇：化學工程與工藝專業(yè)英語

1.Although the use of chemicals dates back to the ancient civilizations, the evolution of what we know as the modern chemical industry started much more recently.It may be considered to have begun during the Industrial Revolution, about 1800, and developed to provide chemicals roe use by other industries.盡管化學品的使用可以追溯到古代文明時代，我們所謂的現(xiàn)代化學工業(yè)的發(fā)展卻是非常近代（才開始的）。可以認為它起源于工業(yè)革命其間，大約在1800年，并發(fā)展成為為其它工業(yè)部門提供化學原料的產(chǎn)業(yè).2.At the start of the twentieth century the emphasis on research on the applied aspects of chemistry in Germany had paid off handsomely, and by 1914 had resulted in the German chemical industry having 75% of the world market in chemicals.This was based on the discovery of new dyestuffs plus the development of both the contact process for sulphuric acid and the Haber process for ammonia.The later required a major technological breakthrough that of being able to carry out chemical reactions under conditions of very high pressure for the first time.20世紀初，德國花費大量資金用于實用化學方面的重點研究，到1914年，德國的化學工業(yè)在世界化學產(chǎn)品市場上占有75%的份額。這要歸因于新染料的發(fā)現(xiàn)以及硫酸的接觸法生產(chǎn)和氨的哈伯生產(chǎn)工藝的發(fā)展。而后者需要較大的技術突破使得化學反應第一次可以在非常高的壓力條件下進行。

3.At present, however, many intermediates to products produced, from raw materials like crude oil through(in some cases)many intermediates to products which may be used directly as consumer goods, or readily converted into them.The difficulty cones in deciding at which point in this sequence the particular operation ceases to be part of the chemical industry’s sphere of activities.然而現(xiàn)在有數(shù)千種化學產(chǎn)品被生產(chǎn)，從一些原料物質像用于制備許多的半成品的石油，到可以直接作為消費品或很容易轉化為消費品的商品。困難在于如何決定在一些特殊的生產(chǎn)過程中哪一個環(huán)節(jié)不再屬于化學工業(yè)的活動范疇.4.The chemical industry is concerned with converting raw materials, such as crude oil, firstly into chemical intermediates and then into a tremendous variety of other chemicals.These are then used to produce consumer products, which make our lives more comfortable or, in some cases such as pharmaceutical produces, help to maintain our well-being or even life itself.化學工業(yè)涉及到原材料的轉化，如石油 首先轉化為化學中間體，然后轉化為數(shù)量眾多的其它化學產(chǎn)品。這些產(chǎn)品再被用來生產(chǎn)消費品，這些消費品可以使我們的生活更為舒適或者作藥物維持人類的健康或生命。

5.The improvement in properties of modern synthetic fibers over the traditional clothing materials has been quite remarkable.在傳統(tǒng)的衣服面料上，現(xiàn)代合成纖維性質的改善也是非常顯著的。

6.In terms of shelter the contribution of modern synthetic polymers has been substantial.Plastics are tending to replace traditional building materials like wood because they are lighter, maintenance-free

講到住所方面現(xiàn)代合成高聚物的貢獻是巨大的。塑料正在取代像木材一類的傳統(tǒng)建筑材料，因為它們更輕，免維護

7.The classical role of the chemical engineer is to take the discoveries made by the chemist in the laboratory and develop them into money--making, commercial-scale chemical processes.化學工程師經(jīng)典的角色是把化學家在實驗室里的發(fā)現(xiàn)拿來并發(fā)展成為能賺錢的商業(yè)規(guī)模的化學過程。1

8.The chemical industry is a very high technology industry which takes full advantage of the latest advances in electronics and engineering.Computers are very widely used for all sorts of applications, from automatic control of chemical plants, to molecular modeling of structures of new compounds, to the control of analytical instruments in the laboratory.化學工業(yè)是高技術工業(yè)，它需要利用電子學和工程學的最新成果。計算機被廣泛應用，從化工廠的自動控制，到新化合物結構的分子模擬，再到實驗室分析儀器的控制。

9.Once the pilot plant is operational, performance and optimization data can be obtained in order to evaluate the process from an economic point of view.The profitability is assessed at each stage of the development of the process.If it appears that not enough money will be made to justify the capital investment, the project will be stopped.中試車間一旦開始運轉，就能獲得性能數(shù)據(jù)和選定最佳數(shù)值以便從經(jīng)濟學角度對流程進行評價。對生產(chǎn)過程的每一個階段可能獲得的利潤進行評定。如果結果顯示投入的資金不能有足夠的回報，這項計劃將被停止。

10.Based on the experience and data obtained in the laboratory and the pilot plant, a team of engineers is assembled to design the commercial plant.The chemical engineer’s job is to specify all process flow rates and conditions, equipment types and sizes, materials of construction, process configurations, control systems, safety systems, environmental protection systems, and other relevant specifications.根據(jù)在實驗室和中試車間獲得的經(jīng)驗和數(shù)據(jù)，一組工程師集中起來設計工業(yè)化的車間。化學工程師的職責就是詳細說明所有過程中的流速和條件，設備類型和尺寸，制造材料，流程構造，控制系統(tǒng)，環(huán)境保護系統(tǒng)以及其它相關技術參數(shù)。

11.The startup period can require a few days or a few moths, depending on the newness of the technology, the complexity of the process, and quality of the engineering that has gone into the design.Problems are frequently encountered that require equipment modifications.This is time consuming and expensive: just the lost production from a plant can amount to thousands of dollars per day.Indeed, there have been some plants that have never operated, because of unexpected problems with control, corrosion, or impurities, or because of economic problems.啟動階段需要幾天或幾個月，根據(jù)設計所涉及工藝技術的新穎、流程的復雜程度以及工程的質量而定。中間經(jīng)常會遇到要求設備完善的問題。這是耗時耗財?shù)碾A段：僅僅每天從車間出來的廢品會高達數(shù)千美金。確實，曾經(jīng)有些車間因為沒有預計到的問題如控制、腐蝕、雜質或因為經(jīng)濟方面的問題而從來沒有運轉過。

12.Chemical engineers study ways to reduce operating costs by saving energy, cutting raw material consumption, and reducing production of off-specification products that require reprocessing.They study ways to improve product quality and reduce environmental pollution of both air and water.化學工程師研究一些方法節(jié)省能源，降低原材料消耗、減少不合要求的需進行處理的產(chǎn)品的生產(chǎn)，以降低生產(chǎn)成本。他們還研究一些提高產(chǎn)品質量、減少空氣和水中環(huán)境污染的措施。

13.The marketing of many chemicals requires a considerable amount of interaction between engineers in the company producing the chemical and engineers in the company using the chemical.This interaction can take the form of advising on how to use a chemical or developing a new chemical in order to solve a specific problem of a customer.許多化工產(chǎn)品的市場開發(fā)需要制造化工產(chǎn)品公司的工程師與使用化工產(chǎn)品公司的工程師密切合作。這種合作所采取的方式可以是對如何使用一種化學產(chǎn)品提出建議，或者是生產(chǎn)出一種新的化學產(chǎn)品以解決客戶的某個特殊的困難。

14.The number and diversity of chemical compounds is remarkable: over ten million are now known.Even this vase number pales into insignificance when compared to the number of carbon compounds which is theoretically possible.化學物質的數(shù)量多得驚人，其差異很大：所知道的化學物質的數(shù)量就達上千萬種。如此的數(shù)量與理論上可能形成的含碳化合物的數(shù)量相比，相形見絀。

15.Since the term “inorganic chemical” covers compounds of all the elements other than carbon, the diversity of origins is not surprising.Some of the more important sources are metallic ores, and salt or brine.In all these cases at least two different elements are combine together chemically in the form of a stable compound.因為“無機化學品”這個詞涉及到的是除碳以外所有元素構成的化合物.其來源的多樣性并不很大。一些較重要的來源是金屬礦以及鹽和海水。在這些情況下，至少兩種不同的元素化合以一種穩(wěn)定的化合物在一起。

16.In contrast to inorganic chemicals which, as we have already seen,are derived pfom many different sources, the multitude of commercially important organic compounds are essentially derived from a single source.Nowadays in excess of 99% of all organic chemicals is obtained from crue oil and natural gas via petrochemical processes.相比于無機化學品來自于眾多不同的資源，商業(yè)上的一些重要的有機化合物基本上來源單一。如今，所有有機化合物的99%以上，可以通過石化工藝過程從原油和天然氣得到.17.The major route form biomass to chemicals is via fermentation processes.However these processes cannot utillize polysaccharides like cellulose and starch, and so the latter must first be subjected to acidic or enzymic hydrolysis to from the simpler sugars which are suitable starting materials.從碳水化合物得到化學物質的主要途徑是通過發(fā)酵過程。然而發(fā)酵過程不能利用多糖，因此，淀粉必須先受到酸性或酶水解反應，生成更簡單的糖類，是合適的起始原料。

18.Being esters, the use of lipids for chemicals production starts with hydrolysis.Although this can be either acid-or alkali-catalyzed, the latter is preferred since it is an irreversiblereaction, and under these conditions the process is known as saponification.類脂屬于脂類（物質），用于生產(chǎn)化學物質時，以水解反應開始，雖然水解反應可以用酸或堿催化，但堿催化效果更好，因為堿催化反應不可逆。堿性條件下的水解反應叫做皂化反應。

19.In effect he applied the ethics of industrial consultancy by which experience was transmitted “from plant to plant and from process to process in such a way which did not compromise the private or specific knowledge which contributed to a given plant’s profitability”.The concept of unit operations held that any chemical manufacturing process could be resolved into a coordinated series of operations such as pulverizing, drying, roasting, electrolyzing, and so on.他采用了工業(yè)顧問公司的理念，經(jīng)驗傳遞從一個車間到另一個車間，從一個過程到另一個過程。這種方式不包含限于某個給定工廠的利潤的私人的或特殊的知識。單元操作的概念使每一個化學制造過程都能分解為一系列的操作步驟，如研末、干燥、烤干、電解等等。

20.Chemical engineers of the future will be integrating a wider range of scales than any other branch of engineering.未來的化學工程師將比任何其他分支的工程師在更為寬廣的規(guī)模范圍緊密協(xié)作

21.Thus, future chemical and engineers will conceive and rigorously solve problems on a continuum of scales ranging from microscale.因此，未來的化學工程師們要準備好解決從微型的到巨型的規(guī)模范圍內(nèi)出現(xiàn)的問題。

22.Chemical engineers will become more heavily involved in product design as a complement to process design.化學工程師將越來越多地涉及到對過程設計進行補充的產(chǎn)品設計中。

23.Chemical engineers will be frequent participants in multidisciplinary research efforts.化學工程師將經(jīng)常性地介入到多學科領域的研究工程。

carbonate 碳酸鹽 spectrum 光譜 silica 二氧化硅epoxy 環(huán)氧樹脂 vinyl 乙烯基 acetate 醋酸鹽 pharmaceutical 藥物 polypropylene 聚丙烯 formaldehyde 甲醛 ammonium 銨基polyester 聚酯 the lion’s share 較大部分

reactant 反應物 distillation 蒸餾 nozzle 噴嘴 compressor 壓縮機 pilot-plant 中試裝置 specification 說明書 flow sheet 工藝流程圖

corrosion 腐蝕 sensor 傳感器 atrophy 退化，衰退 on-line 聯(lián)機 commission 投產(chǎn)，交工式運轉 covalent 共價的 isomerism 同分異構

froth flotation 泡沫浮選 borate 硼酸鹽（酯）fluoride 氟化物 amino 氨基的 hydrolysis 水解 nap h the ne 環(huán)烷烴 naphtha 揮發(fā)油

鈉 sodium 鉀 potassium 磷 phosphorus 氨 ammonia 聚合物 polymer 粘度 viscosity 聚乙烯 polyethylene 氯化物 chloride

烴 hydrocarbon 催化劑 catalyst 煉油廠 refinery 添加劑 additive 間歇的 batch 反應器 reactor 放大 scale-up 熱交換器 heat exchanger

創(chuàng)新 innovation 術語 terminology 閥 valve 梯度 gradient 組成 composition 雜質 impurity 模擬 simulate 氫氧化物 hydroxide 酯 ester 脂肪族的 aliphatic 不飽和的 unsaturated

芳香族的 aromatic 甲烷 methane 烯烴 olefin 烷烴 alkaneenzymic 酶 xylene 二甲苯

第三篇：《化學工程與工藝專業(yè)英語》翻譯

Unit 11 Chemical and Process

Thermodynamics

化工熱力學

在投入大量的時間和精力去研究一個學科時，有理由去問一下以下兩個問題：該學科是什 么？（研究）它有何用途？關于熱力學，雖然第二個問題更容易回答，但回答第一個問題有必要對該學科較深入的理解。（盡管）許多專家或學者贊同熱力學的簡單而準確的定義的觀點（看法）值得懷疑，但是還是有必要確定它的定義。然而，在討論熱力學的應用之后，就可以很容易完成其定義

1．熱力學的應用

熱力學有兩個主要的應用，兩者對化學工程師都很重要。

（1）與過程相聯(lián)系的熱效應和功效應的計算，以及從過程得到的最大功或驅動過程所需 的最小功的計算。

（2）描述處于平衡的系統(tǒng)的各變量之間的關系的確定。

第一種應用由熱力學這個名詞可聯(lián)想到，熱力學表示運動中的熱。直接利用第一和第二定 律可完成許多（熱效應和功效應的）計算。例如：計算壓縮氣體的功，對一個完整過程或某一過程單元的進行能量衡算，確定分離乙醇和水混合物所需的最小功，或者（evaluate）評估一個氨合成工廠的效率。熱力學在特殊體系中的應用，引出了一些有用的函數(shù)的定義以及這些函數(shù)和其它變量（如壓強、溫度、體積和摩爾分數(shù)）關系網(wǎng)絡的確定。實際上，在運用第一、第二定律時，除非用于評價必要的熱力學函數(shù)變化已經(jīng)存在，否則熱力學的第一種應用不可能實現(xiàn)。通過已經(jīng)建立的關系網(wǎng)絡，從實驗確定的數(shù)據(jù)可以計算函數(shù)變化。除此之外，某一體系中變量的關系網(wǎng)絡，可讓那些未知的或者那些難以從變量（這些變量容易得到或較易測量）中實驗確定的變量得以計算。例如，一種液體的汽化熱，可以通過測量幾個溫度的蒸汽壓和幾個溫度下液相和汽相的密度得以計算；某一化學反應中任一溫度下的可得的最大轉化率，可以通過參與該反應的各物質的熱量法測量加以計算。

2.熱力學的本質

熱力學定律有這經(jīng)驗的基礎或實驗基礎，但是在描述其應用時，依賴實驗測量顯得很明顯 化學工程與工藝專業(yè)英語第十一單元化工熱力學（stand out 突出）。因此，熱力學廣義上可以定義為：拓展我們實驗所得的體系知識的一種手段（方法），或定義為：觀察和關聯(lián)一個體系的行為的基本框架。為了理解熱力學，擁有實驗的觀點有必要，因為，如果我們不能對研究的體系或現(xiàn)象做出物理上正確的評價，那么熱力學的方法就無意義。我們應該要經(jīng)常問問如下問題：怎樣測量這一特殊的變量？怎樣計算以及從哪一類的數(shù)據(jù)計算一個特殊的函數(shù)。由于熱力學的實驗基礎，熱力學處理的是宏觀函數(shù)或大量的物質的函數(shù)，這與微觀的函數(shù)恰恰相反，微觀函數(shù)涉及到的是組成物質的原子或分子。宏觀函數(shù)要么可以直接測量，要么可以從直接測量的函數(shù)計算得到，而不需要借助于某一具體的理論。相反，盡管（while）微觀函數(shù)最終是從實驗測量得以確定，但是它們的真實性取決于用于它們計算時的特殊理論的有效性。因此，熱力學的權威性在于：它的結果與物質的理論無關，倍受尊敬，為大家大膽地接受。除了與熱力學結論一致的必然性以外，熱力學有著廣泛的應用性。因此，熱力學形成了許多學科中的工程師和科學家的教育中不可分割的部分。盡管如此，因為每門科學都只局限于（focus on）關于熱力學方面的較少應用，所以其全貌常被低估。實際上，在明顯的（可觀察到）可再現(xiàn)的平衡態(tài)中存在的任何體系，都服從與熱力學方法。除了流體、化學反應系統(tǒng)和處于相平衡（化學工程師對這些十分感興趣）之外，熱力學也成功適用于有表面效應的系統(tǒng)、受壓力的固體以及處于重力場、離心力場、磁場和電場的物質。通過熱力學，1

可以被確定用于定義和確定平衡的位能，并將之定量化。位能也可以確定一個體系移動的方向以及體系達到的終態(tài)，但是不能提供有關到達終態(tài)所需要的時間的信息。因此，時間不是熱力學的變量，速度的研究已超出了熱力學的范疇，或者除了體系接近平衡的極限以外，速率的研究屬于熱力學的范疇。在這兒，速率的表達式應該在熱力學上是連續(xù)的。

熱力學定律建立于實驗和觀測基礎之上的，這些實驗和觀測既不是最重要的，又不復雜。同時，這些定律的本身是用相當普通語言加以描述的。然而，從這一明顯的平淡的開始，發(fā)展成為一個很大的結構，這種結構對人類思想歸納力做出了貢獻。這在想象力豐富、嚴肅認真的學生中成功地激發(fā)了敬畏（inspire awe），這使得Lewis 和Randall 將熱力學視為科學的權威。因為除了技術上的成功和結構的嚴密性，這個比喻選擇很恰當，我們可觀察到美妙之處（和宏觀體）。因此，毫無疑問，熱力學的研究在學術上有價值的，智力上可以得到激發(fā)，同時，對一些人來說，是一種很好的經(jīng)歷。

3.熱力學定律

第一定律.熱力學第一定律是能量守恒的簡單的一種描述。如圖3-1 所示，穩(wěn)態(tài)時離開一個過程的所有能量的總和必須與所進入該過程的能量總和相等。工程師在設計和操作各種過程 時絕對遵循質量和能量守恒定律。所不幸的是，就其本身而言，當試圖評估過程的效率時，第化學工程與工藝專業(yè)英語第十一單元化工熱力學

一定律引起混淆不清。人們將能量守恒視為一種重要的努力成果，但是事實上，使能量守恒不需要花任何努力— — 能量本身就是守恒的。因為第一定律沒有區(qū)分各種各樣能量的形式，所以從第一定律所得到的結論是有限的。由往復泵引入的軸功會以熱量流向冷凝器的形式離開蒸餾塔，與在再沸器引入的熱一樣容易。在試圖確定過程的效率時，一些工程師總掉入將各種形式的能量一起處理的陷阱。這種做法明顯是不合理，因為各種能量形式有著不同的費用。第二定律第二定律應用于熱轉變?yōu)楣Φ难h(huán)，有多種不同的描述。至于這一點，一種更

加普通的描述是需要的：從一種形式的能量到另一種形式的能量的轉換，總是導致質量上總量的損失。另一種描述為：所有系統(tǒng)都有接近平衡（無序）的趨勢。這些表達方式指出了在表達第二定律時的困難之處。如果不定義另一個專門描述質量或無序的詞語，第二定律的表達就不能令人滿意。這個專用名詞為熵。這個狀態(tài)函數(shù)對流體、物質或系統(tǒng)中的無序程度進行了定量化。絕對零熵值定義絕對零度時純凈的、晶體固體的狀態(tài)。每一個分子都由其他的以相當有序結構的相同的分子所包圍。運動、隨意、污染、不確定性，這一切都增加了混亂度，因此對熵做出了貢獻。相反，不論是透明寶石，還是純凈化學產(chǎn)品，還是清潔的生活空間，還是新鮮的空氣和水，（都是屬于有序狀態(tài)），有序是有價值的。有序需要付出很高的代價，只有通過做功才得以實現(xiàn)。我們很多工作都花費在家里、車間和環(huán)境中創(chuàng)造或恢復有序狀態(tài)。環(huán)境中較高的熵值是較高的生產(chǎn)費用的具體化表現(xiàn)。每一種生產(chǎn)過程的目的都是，利用將混合物分離為純凈物、減小我們知識的不確定性、或是從原料創(chuàng)造（works of art）藝術品以減小熵值。總之，從將原料轉變?yōu)楫a(chǎn)品的過程中，熵值不斷減小。然而，（inasmuch as）因為隨著系統(tǒng)接近平衡，熵的增加是自發(fā)的趨勢，所以減少熵值是艱難的工作（struggle）。生產(chǎn)過程所需熵減的驅動力同時伴隨著宇宙其余部分熵的劇增。一般說來，這種熵的增加在同一工廠內(nèi)不斷持續(xù)下去，因此這種造成了產(chǎn)品熵的減小。反過來（whereas 而，卻，其實，反過來），熵減存在于原料向產(chǎn)品的轉化過程。燃料、電、空氣以及水向燃燒產(chǎn)品、廢水和無用的熱量的形式的轉化可表示熵值的大大增加。正象圖3-1 中中間部分描述為第一定律一樣，圖中的底線部分描述了第二定律。離開一個過程的所有的物流的熵值的總和，總是超過進入該過程的物流的熵值的總和。如果熵達到平衡，象質量和能量達到平衡一樣，那么該過

程是可逆的，即該過程也會反向移動。可逆過程只是在理論上是可能的，需要動力學平衡維持連續(xù)存在，因此可逆過程是不可產(chǎn)生的。而且，如果不化學工程與工藝專業(yè)英語第十一單元化工熱力學4平衡（過程）倒過來，即如果有凈熵的減少，那么所有的箭頭也要反向，該過程被迫反向進行。實質上，是熵增驅使該過程：是同一種驅動力使水向下流，熱流從熱物質流向冷物質，使玻璃打碎，金屬腐蝕。簡而言之，所有事物都同它們周圍的環(huán)境接近平衡。第一定律，需要能量守恒，所有形式能量變化有著相同的重要性。盡管所有過程都受第一定律權威性的影響，但是該定律不能區(qū)分能量的質量，也不能解釋為什么觀察不到自發(fā)發(fā)生的 過程自發(fā)地使自身可逆。功可以全部轉化為熱而反向轉換從來不會定量發(fā)生，這種反復驗證過的觀測達成了這樣的共識— — 熱是一種低質量的能量。第二定律，深深扎根于熱發(fā)動機效率的研究，能分辨能量的質量。通過這一定律，揭示了以前未認可的函數(shù)— — 熵的存在，可以看出，該函數(shù)確定了自發(fā)變化的方向。第二定律并沒有（in no way）減小第一定律的權威性；相反，第二定律拓展和加強了熱力學的權限。第三定律熱力學第三定律規(guī)定了熵的絕對零值，描述如下：對于那些處在絕對零度的完美晶體的變化來說，總的熵的變化為零。該定律使用絕對值來描述熵。

Unit 13 Unit Operations in Chemical

Engineering

化學工程中的單元操作

化學工程由不同順序的步驟組成，這些步驟的原理與被操作的物料以及該特殊體系的其他特征無關。在設計一個過程中，如果（研究）步驟得到認可，那么所用每一步驟可以分別進行研究。有些步驟為化學反應，而其他步驟為物理變化。化學工程的可變通性（versatility）源于將一復雜過程的分解為單個的物理步驟（叫做單元操作）和化學反應的實踐。化學工程中單元操作的概念基于這種哲學觀點：各種不同順序的步驟可以減少為簡單的操作或反應。不管所處理的物料如何，這些簡單的操作或反應基本原理（fundamentals）是相同的。這一原理，在美國化學工業(yè)發(fā)展期間先驅者來說是明顯的，首先由A.D.Lttle 于1915 年明確提出：任何化學過程，不管所進行的規(guī)模如何，均可分解為（be resolvedinto）一系列的相同的單元操作，如：粉碎、混合、加熱、烘烤、吸收、壓縮、沉淀、結晶、過濾、溶解、電解等等。這些基本單元操作（的數(shù)目）為數(shù)不多，任何特殊的過程中包含其中的幾種。化學工程的復雜性來自于條件（溫度、壓力等等）的多樣性，在這些條件下，單元操作以不同的過程進行，同時其復雜性來自于限制條件，如由反應物質的物化特征所規(guī)定的結構材料和設備的設計。最初列出的單元操作，引用的是上述的十二種操作，不是所有的操作都可視為單元操作。從那時起，確定了其他單元操作，過去確定的速度適中，但是近來速度加快。流體流動、傳熱、蒸餾、潤濕、氣體吸收、沉降、分粒、攪拌以及離心得到了認可。近年來，對新技術的不斷理解以及古老但很少使用的分離技術的采用，引起了分離、處理操作或生產(chǎn)過程步驟上的數(shù)量不斷增加，在多種操作中，這些操作步驟在使用時不要大的改變。這就是“單元操作”這個術語的基礎，此基礎為我們提供了一系列的技術。1.單元操作的分類

（1）流體流動流體流動所涉及到的是確定任何流體的從一位置到另一位置的流動或輸送的原理。（2）傳熱該單元操作涉及到（deal with）原理為：支配熱量和能量從一位置到另一位置的積累和傳遞。（3）蒸發(fā)這是傳熱中的一種特例，涉及到的是在溶液中揮發(fā)性溶劑從不揮發(fā)性的溶質（如鹽或其他任何物質）的揮發(fā)。（4）干燥在該操作中，揮發(fā)性的液體（通常是水）從固體物質中除去。（5）蒸餾蒸餾是這樣一個操作：因為液體混合物的蒸汽壓強的差別，利用沸騰可將其中的各組分加以分離。（6）吸收在該操作中，一種氣流經(jīng)過一種液體處理后，其中一種組分得以除去。（7）膜分離該操作涉及到液體或氣體中的一種溶質

通過半透膜向另一種流中的擴散（8）液-液萃取在該操作中，（液體）溶液中的一種溶質通過與該溶液相對不互溶的另一種液體溶劑相接觸而加以分離。（9）液-固浸取在該操作所涉及的是，用一種液體處理一種細小可分固體，該液體能溶解這種固體，從而除去該固體中所含的溶質。（10）結晶結晶涉及到的是，通過沉降方法將溶液中的溶質（如一種鹽）從該溶液中加以分離。（11）機械物理分離這些分離方法包括，利用物理方法分離固體、液體、或氣體。這些物理方法，如過濾、沉降、粒分，通常歸為分離單元操作。許多單元操作有著相同的基本原理、基本原則或機理。例如，擴散機理或質量傳遞發(fā)生于干燥、吸收、蒸餾和結晶中，傳熱存在于干燥、蒸餾、蒸發(fā)等等。

2.基本概念

因為單元操作是工程學的一個分支，所以它們同時建立在科學研究和實驗的基礎之上。在設計那些能夠制造、能組合、能操作、能維修的設備時，必須要將理論和實踐結合起來。下面四個概念是基本的（basic），形成了所有操作的計算的基礎。物料衡算如果物質既沒有被創(chuàng)造又沒有被消滅，除了在操作中物質停留和積累以外，那么進入某一操作的所有物料的總質量與離開該操作的所有物料的總質量相等。應用該原理，可以計算出化學反應的收率或工程操作的得率。在連續(xù)操作中，操作中通常沒有物料的積累，物料平衡簡單地由所有的進入的物料和所有的離開的物料組成，這種方式與會計所用方法相同。結果必須要達到平衡。只要（as long as）該反應是化學反應，而且不消滅或創(chuàng)造原子，那么將原子作為物料平衡的基礎是正確的，而且常常非常方便。可以整個工廠或某一單元的任何一部分進行物料衡算，這取決于所研究的問題。能量恒算相似地，要確定操作一操作所需的能量或維持所需的操作條件時，可以對任何工廠或單元操作進行能量衡算。該原理與物料衡算同樣重要，使用方式相同。重要的是記住，盡管能量可能會轉換為另一種等量形式，但是要把各種形式的所有的能量包括在內(nèi)。理想接觸（平衡級模型）無論（whenever）所處理的物料在具體條件（如溫度、壓強、化學組成或電勢條件）下接觸時間長短如何，這些物料都有接近一定的平衡條件的趨勢，該平衡由具體的條件確定。在多數(shù)情況下，達到平衡條件的速率如此之快或所需時間足夠長，以致每一次接觸都達到了平衡條件。這樣的接觸可視為一種平衡或一種平衡接觸。理想接觸數(shù)目的計算是理解這些單元操作時所需的重要的步驟，這些單元操作涉及到物料從一相到另一相的傳遞，如浸取、萃取、吸收和溶解。操作速率（傳遞速率模型）在大多數(shù)操作中，要么是因為時間不夠，要么是因為不需要平衡，因此達不到平衡，只要一達到平衡，就不會發(fā)生進一步變化，該過程就會停止，但是工程師們必須要使該過程繼續(xù)進行。由于這種原因，速率操作，例如能量傳遞速率、質量傳遞速率以及化學反應速率，是極其重要而有趣的。在所有的情況中，速率和方向決定于位能的差異或驅動力。速率通常可表示為，與除以阻力的壓降成正比。這種原理在電能中應用，與用于穩(wěn)定或直流電流的歐姆定律相似。用這種簡單的概念解決傳熱或傳質中的速率問題時，主要的困難是對阻力的估計，阻力一般是通過不同條件下許多傳遞速率的確定式（determination）的經(jīng)驗關聯(lián)式加以計算。速率直接地決定于壓降，間接地決定于阻力的這種基本概念，可以運用到任一速率操作，盡管對于特殊情況的速率可以不同的方式用特殊的系數(shù)來表達。

第四篇：化學工程與工藝專業(yè)英語Unit 3

第三單元化學工程師的典型活動

化學工程師的傳統(tǒng)角色是將化學家在實驗室所得發(fā)現(xiàn)轉化為可盈利的、工業(yè)規(guī)模的化工工藝。化學家通常只在試管和派式氧彈中進行一批恒溫的實驗，只有非常少量的反應物和產(chǎn)物（如100ml）。在恒溫浴的條件下，反應物被置于一個小型容器中。催化劑加入后，反應隨著時間進行。隨著時間的推進，以適當?shù)臅r間間隔取出樣品，以跟蹤了解反應物的消耗和產(chǎn)物的產(chǎn)出情況。

相比之下，化學工程師通常操作更大量的原材料和非常龐大且昂貴的設備。反應器能夠容納1000加侖到10000加侖，甚至更多。蒸餾塔高有100多英尺，直徑有10到30英尺。在一個化工廠里，對一個工藝流程裝置的資本投資可能會超過10000萬美元。

化學工程師的工作通常涉及將一個化學家設計的小型反應器和分離系統(tǒng)按比例放大為一個非常大的工廠。化學工程師必須與化學家密切工作，以完全理解工藝流程中涉及的化學反應，并且保證化學家得到設計、操作和優(yōu)化工藝流程所需的反應動力學數(shù)據(jù)和物理屬性數(shù)據(jù)。這就是為什么化學工程課程包含如此多化學課程的原因。

化學工程師也必須和機械工程師、電機工程師、土木工程師、冶金工程師密切工作，以設計和操作工廠里的物理設備，包括反應器、貯水池、蒸餾塔、熱交換器、泵、壓縮機、控制鍵和儀器設備等。管道通常是這個設備列表中的一個大的項目。一個典型化工廠給人印象最深刻的特征之一是鋪設于那里的大量的管子，在很多工廠它們確實有好幾百英里。這些管子負責工廠里工藝材料（氣體和液體）的進出。它們也輸送公共事業(yè)設備（蒸汽、冷卻水、空氣、氮氣和制冷劑）到過程裝備。

將化學實驗商業(yè)化，化學工程師的工作涉及開發(fā)、設計、建造、操作、銷售和研究。不同公司給這些功能的名稱是不同的，但是僅僅就是名稱不同而已。讓我們簡略描述一下每項功能吧。應該強調的是我們將要考慮的工作是典型和經(jīng)典的，但是這決不是化學工程師唯一做的事。化學工程師在數(shù)學、化學和物理方面有一個廣泛的背景。因此，他或她在工業(yè)、政府和學術界能夠并且確實有豐富的工作種類。

1.開發(fā)

開發(fā)是將一個實驗室規(guī)模的工藝流程轉化為一個商業(yè)規(guī)模的工藝流程所需的中間步驟。開發(fā)中所涉及的中試裝置可能會用到五加侖容量的反應器和直徑為3英寸的蒸餾塔。開發(fā)通常只是化工工藝商業(yè)化中的一個部分，因為擴大問題是一件非常難的事。從試管直接到10000加侖的反應器是一項棘手的嘗試，有時還是危險的。其中涉及的一些在外行看來不明顯的細微問題包括混合缺陷、徑向溫度梯度的增加和傳熱對產(chǎn)熱比率的減小。

化學工程師和化學家與其他工程師組成的團隊一起工作，來設計、建造和操作中試裝置。設計方面涉及設備尺寸、結構以及建造材料的確定。通常，中試裝置會被設計得非常靈活，以便在不同條件和構造中能夠進行評估。

一旦中試裝置可使用了，性能和優(yōu)化數(shù)據(jù)便可獲得，以從經(jīng)濟的角度評估這個工藝流程。在工藝流程開發(fā)的每個階段都會對收益性進行評估。如果盈利情況不足以說明資本投資的合理性，那么這個項目便會被終止。

中試裝置為建造材料、測量技術和工藝流程控制策略的評估提供了機會。在中試裝置中的實驗發(fā)現(xiàn)可被用來提高真實工廠的設計指標。

2.設計

基于從實驗室和中試裝置中所得的經(jīng)驗和數(shù)據(jù)，一個工程師組成的團隊會一起來設計這個商業(yè)設備。化學工程師的工作則是確定工藝流程的速度和條件、設備的類型和尺寸、建造材料、工藝流程的結構、控制系統(tǒng)、安全系統(tǒng)、環(huán)境保護系統(tǒng)以及其他相關的規(guī)格。這是一項巨大的責任。

設計階段是非常耗費資金的。一個典型的化工工藝可能需要5000到10000萬美元的資本投資。這真是一大筆資金！并且化學工程師需要做很多這種決定。當你發(fā)現(xiàn)你自己在那個位置的時候，你將會高興你盡你自己所能（當然也是我們所希望的）學習了，因此你能夠以可能的最好的工具和方法來解決這些問題。

設計過程的成果是很多的文件：

（1）工藝流程圖是以示意圖的形式展示所有設備，并且流程定名，條件確定（流量、溫

度、壓力、組成、粘度、濃度等。）。

（2）管道和裝設儀器圖是展示設備所有部分（包括尺寸、噴嘴位置、材料）的圖，包括

所有管道（包括尺寸、材料和閥門），所有裝設儀器（包括傳感器的位置和類型、控制閥和控制器），還有所有的安全系統(tǒng)（包括安全閥和安全隔膜的位置與尺寸、廢氣燃燒管路和安全操作條件）。

（3）設備規(guī)格表上有所有設備的精確尺寸、性能標準、建造材料、腐蝕裕度、操作溫度

和壓力、流量的最大最小值等。這些設備規(guī)格表會被送到設備制造廠進行報價，然后再制造。

3.建造

設備制造廠（賣主）制造好設備的單個零件后，零件會被運送到工廠所在地（有時是一件頗具挑戰(zhàn)性的后勤保障工作，尤其是對于蒸餾塔這樣的大型容器）。建設階段的工作是將所有零件組裝成一個完整的工廠。對于大型的設備和建筑（如控制室、進程分析實驗室和維修車間），首先要在地面上挖洞并且傾倒混凝土作為地基。

最初的準備工作完成后，設備的主要零件和上層鋼結構就建立了。熱交換器、泵、壓縮機、管道、儀表傳感器和自動控制閥安裝完畢。控制系統(tǒng)線路和管道溝通了控制室和設備。為發(fā)動機安裝電線、開關和變壓器，以驅動泵和壓縮機。加工設備安裝完后，接下來化學工程師就得檢查各部分是否合理連接，各零件是否正常運轉。

對很多工程師而言，這通常是一個令人激動和值得的時刻。你看到你的設想從紙張變?yōu)楝F(xiàn)實。鋼材和混凝土取代了設計圖和圖表。整個工廠是很多人多年工作的結晶。你最終站在了發(fā)射臺上，整個工廠將投入運轉或宣告失敗！揭示真相的時刻即將到來。

一旦檢查階段結束就開始運轉了。開動是工廠最初的投產(chǎn)。這是一個振奮人心的時刻，并且活動要持續(xù)一整天。對化學工程師而言，這是最好的學習地方之一。現(xiàn)在你發(fā)現(xiàn)你的設想和計算確實是多么好。參與中試裝置和設計工作的工程師通常是運轉工作組的一部分。

開動階段會持續(xù)幾天或幾個月，這取決于設計中技術的先進程度、工藝流程的復雜性和工程的質量。設備需要改良的問題經(jīng)常出現(xiàn)。這是耗時且昂貴的，工廠每天損失的產(chǎn)品折合成現(xiàn)金都有數(shù)千萬美元。實際上，一些工廠都沒有能夠運轉，因為控制、腐蝕或污染方面的一些意想不到的問題，或者因為資金的問題。

在開動階段，工程師通常需要輪流值班。在短期內(nèi)需要學習大量的東西。一旦工廠成功以它的額定性能運轉，便可移交操作或生產(chǎn)部門進行產(chǎn)品的日常生產(chǎn)。

4.生產(chǎn)

化學工程師在生產(chǎn)（在一些公司或者稱為操作或制作）中占據(jù)中心地位。工廠的技術服務團隊負責工廠高效、安全運行的技術部分。它們在工廠中進行容量和性能的測試以確定設備的瓶頸在何處，然后設計改良物和增建物以去除這些瓶頸。

化學工程師研究方法，節(jié)約能源、減少原材料消耗、減少需再生的不合格產(chǎn)品的生產(chǎn)，以減

少操作費用。他們研究方法以提高產(chǎn)品質量，并減少空氣和水源的污染。

除了在工廠提供技術服務外，很多工程師還是營運監(jiān)督者。這些監(jiān)督者負責工廠日常操作的方方面面，包括監(jiān)督全天以三班制運營的工廠的經(jīng)營者，監(jiān)督產(chǎn)品達到質量標準、在約定時間以約定數(shù)量提供產(chǎn)品、更新和維護設備備件的存貨清單、維持好工廠運營、確保安全技術規(guī)章被遵循、避免過多排放物進入當?shù)丨h(huán)境并且在當?shù)爻洚敼S的發(fā)言人。

5.技術銷售

很多化學工程師在技術銷售領域找到了一項刺激且賺錢的事業(yè)。和其他銷售職位一樣，他們的工作也涉及拜訪客戶，為客戶推薦特別的產(chǎn)品以滿足他們的需求以及確保訂單順利處理。銷售工程師是公司的代表，并且必須熟知公司的生產(chǎn)線。銷售工程師的銷售能力會大大影響公司的發(fā)展和收益。

很多化學制品的銷售需要公司中生產(chǎn)化學制品的工程師與使用化學制品的工程師之間的廣泛合作。這種合作的形式可以是，建議如何使用化學制品，或者研發(fā)新化學制品以解決客戶的具體問題。

當銷售工程師有問題不能自信處理時，他或她必須能夠得到專家的意見。化學工程師有時可能必須號召來自幾個公司的為解決同一問題而工作的研究者共同努力。

6.研究

化學工程師從事很多類型的研究。他們與化學家一起研發(fā)新型或改良的產(chǎn)品。他們研發(fā)新型和改良的工程方法（如更好的模擬化工工藝的計算機程序、更好的描述化學制品的特性的實驗室分析方法和新型反應器與分離系統(tǒng)）。它們以改良的傳感器進行聯(lián)機的物理屬性測量。他們研究供選擇的工藝流程的結構和設備。

你可能會看到研發(fā)工程師在實驗室或書桌旁解決問題。他們通常是由科學家和工程師組成的團隊中的一員。工藝流程和加工設備普通型方面的知識使得化學工程師對研究工作作出了特殊貢獻。化學工程師的日常活動有時可能與在同一團隊中的化學家或物理學家非常相像。

節(jié)選自“化工工藝分析，威廉著，出版社，1988年”

第五篇：化學工程與工藝專業(yè)英語Unit 12

Unit 12 what do we mean by transport

phenomena ?

Transport phenomena is the collective name given to the systematic and integrated study of three classical areas of engineering science :(i)energy or heat transport ,(ii)mass transport or diffusion ,and(iii)momentum transport or fluid dynamics.傳遞現(xiàn)象是工程科學三個典型領域系統(tǒng)性和綜合性研究的總稱：能量或熱量傳遞，質量傳遞或擴散，以及動量傳遞或流體力學。Ofcourse , heat and mass transport occur frequently in fluids , and for this reason some engineering educators prefer to includes these processes in their treatment of fluid mechanics.當然，熱量和質量傳遞在流體中經(jīng)常發(fā)生，正因如此一些工程教育家喜歡把這些過程包含在流體力學的范疇內(nèi)。Since transport phenomena also includes heat conduction and diffusion in solids , however , the subjectis actually ofwider scope than fluid mechanics.由于傳遞現(xiàn)象也包括固體中的熱傳導和擴散，因此，傳遞現(xiàn)象實際上比流體力學的領域更廣。It is also distinguished from fluid mechanics in that the study of transport phenomena make use of the similarities between the equations used to describe the processes of heat,mass,and momentum transport.傳遞現(xiàn)象的研究充分利用描述傳熱，傳質，動量傳遞過程的方程間的相似性，這也區(qū)別于流體力學。These analogies,as they are usually called, can often be related to similarities in the physical mechanisms whereby the transport takes place.這些類推(通常被這么叫)常常可以與傳遞現(xiàn)象發(fā)生的物理機制間的相似性關聯(lián)起來。As a consequence,an understanding of one transport process can readily lead to an understanding of other processes.因此，一個傳遞過程的理解能夠容易促使其他過程的理解。Moreover,ifthe differential equations and boundary conditions are the same,a solution need be obtained for only one of the processes since by changing the nomenclature that solution can be used to obtain the solution for any other transport process.而且，如果微分方程和邊界條件是一樣的，只需獲得一個傳遞過程的解決方案即可，因為通過改變名稱就可以用來獲得其他任何傳遞過程的解決方案。

It must be emphasized , however, that while there are similarities between the transport processes, there are also important differences , especially between the transport of momentum(a vector)and that of heat or mass(scalars).必須強調,雖然有相似之處,也有傳遞過程之間的差異,尤其重要的是運輸動量(矢量)和熱或質量(標量).Nevertheless , a systematic study of the similarities between the transport processes makes it easier to identify and understand the differences between them.然而,系統(tǒng)地研究了相似性傳遞過程之間的相似性,使它更容易識別和理解它們之間的差別。

1．How We Approach the Subject怎么研究傳遞過程？

In order to demonstrate the analogies between the transport processes , we will study each of the process in parallel-instead of studying momentum transport first , then energy transport , and finally mass transport.為了找出傳遞過程間的相似性，我們將同時研究每一種傳遞過程——取代先研究動量傳遞，再傳熱，最后傳質的方法。Besides promoting understanding , there is another pedagogical reason for not using the serial approach that is used in other textbooks : of the three processes, the concepts and equations involved in the study of momentum transport are the most difficult for the beginner to understand and to use.除了促進理解之外，對于不使用在其他教科書里用到的順序法還有另一個教學的原因：在三個過程中，包含在動量傳遞研究中的概念和方程對初學者來說是最難以理解并使用。Because it is impossible to cover heat and mass transport thoroughly without prior knowledge of momentum transport ,one is forced under the serial approach to take up the most difficult subject(momentum transport)first.因為在不具有有關動量傳遞的知識前提下一個人不可能完全理解傳熱和傳質，在順序法的情況下他就被迫先研究最難的課程即動量傳遞。On the other hand ,if the subjects are studied in parallel , momentum transport becomes more understandable by reference to the familiar subject of heat transport.另一方面，如果課程同時被研究，通過參照有關傳熱的熟悉課程動量傳遞就變得更好理解。Furthermore ,the parallel treatment makes it possible to study the simpler the physical processes that are occurring rather than the mathematical procedures and representations.而且，平行研究法可以先研究較為簡單的概念，再深入到較難和較抽象的概念。我們可以先強調所發(fā)生的物理過程而不是數(shù)學性步驟和描述。For example，we will study one-dimensional transport phenomena first because equations instead of partial requiring vector notation and we can often use ordinary differential equations instead of partial differential equations ,which are harder to solve.例如，我們將先研究一維傳遞現(xiàn)象，因為它在不要求矢量標注下就可以被解決，并且我們常常可以使用普通的微分方程代替難以解決的偏微分方程。This procedure is also justified by the fact that many of the practical problems of transport phenomena can be solved by one-dimensional models.加上傳遞現(xiàn)象的許多實際問題可以通過一維模型解決的這樣一個事實，這種處理做法也是合理的。

2.Why Should Engineers Study Transport Phenomena? 為什么工程師要研究傳遞現(xiàn)象？

Since the discipline of transport phenomena deals with certain laws of nature , some people classify it as a branch of engineering.因為傳遞現(xiàn)象這個學科牽扯到自然界定則，一些人就把它劃分為工程的一個分支。For this reason the engineer , who is concerned with the economical design and operation of plants and equipment , quite properly should ask how transport phenomena will be of value in practice.正因如此，對于那些關心工廠和設備設計和操作經(jīng)濟性的工程師而言，十分應該探知在實際中傳遞現(xiàn)象如何起到價值作用。There are two general types of answers to those questions.對于那些問題有兩種通用型答案。The first requires one to recognize that heat ,mass ,and momentum transport occur in many kinds of engineering , e.g., heat exchangers ,compressors ,nuclear and chemical reactors, humidifiers, air coolers ,driers , fractionaters , and absorbers.第一種要求大家認識到傳熱，傳質和動量傳遞發(fā)生在許多工程設備中，如熱交換器，壓縮機，核化反應器，增濕器，空氣冷卻器，干燥器，分離器和吸收器。These transport processes are also involved in the human body as well as in the complex processes whereby pollutants react and diffuse in the atmosphere.這些傳遞過程也發(fā)生在人體內(nèi)以及大氣中污染物反應和擴散的一些復雜過程中。It is important that engineers have an understanding of the physical laws governing these transport processes if they are to understand what is taking place in engineering equipment and to make wise decisions with regard to its economical operation.如果工程師要知道工程設備中正在發(fā)生什么并要做出能達到經(jīng)濟性操作的決策，對主導這些傳遞過程的物理定律有一個認識很重要。

The second answer is that engineers need to be able to use their understanding of natural laws to design process equipment in which these processes are occurring.第二種答案是工程師需要能夠運用自然定律的知識設計包含這些過程的工藝設備。To do so they must be able to predict rates of heat ,mass , or momentum transport.要做到這點，他們必須能夠預測傳熱，傳質，或動量傳遞速率。For example, consider a simple heat exchanger , i.e., a pipe used to heat a

fluid by maintaining its wall at a higher temperature than that of the fluid flowing through it.例如，考慮一個簡單的熱交換器，也就是一根管道——通過維持壁溫高于流經(jīng)管道的流體溫度來加熱流體。The rate at which heat passes from the wall of the pipe to the fluid depends upon a parameter , etc.熱量從管壁傳遞到流體的速率取決于傳熱系數(shù)，傳熱系數(shù)反過來取決于管的大小，流體流速，流體性質等。Traditionally heat-transfer coefficients are obtained after expensive and time-consuming laboratory or pilot-plant measurements and are correlated through the use of dimensionless empirical equations.傳統(tǒng)上傳熱系數(shù)是在耗費和耗時的實驗室或模范工廠的測量之后獲得并且通過使用一維經(jīng)驗方程關聯(lián)起來。Empirical equations are equations that fit the data over a certain range;they are not based upon theory and cannot be used accurately outside the range for which the data have heen taken.經(jīng)驗方程是適合一定數(shù)據(jù)范圍的方程，它們不是建立在理論基礎上而且在應用數(shù)據(jù)的范圍外不能被精確使用。

The less expensive and usually more reliable approach used in transport phenomena is to predict the heat-transfer coefficient from equations based on the laws of nature.使用在傳遞現(xiàn)象中比較不耗費和通常較為可靠的方法是從以自然定律為基礎的方程中預測傳熱系數(shù)。The predicted result would be obtained by a research engineer by solving some equations(often on a computer).預測的結果將由一個研究工程師通過解一些方程獲得（常常在電腦上）A design engineer would then use the equation for the heat-transfer coefficient obtained by the research engineer.設計工程師再使用由研究工程師獲得的關于傳熱系數(shù)的方程。

Keep in mind that the job of designing the heat exchanger would be essentially the same no matter how the heat-transfer coefficients were originally obtained.要記住無論傳熱系數(shù)是怎么得來的設計熱交換器的工作將基本上是一樣的。For this reason ,some courses in transport phenomena emphasize only the determination of the heat-transfer coefficient and leave the actual design procedure to a course in unit operations.正因如此，傳遞現(xiàn)象的一些課程只強調傳熱系數(shù)的決定而把真正的設計步驟留給單元操作中的一個課程。It is of cource a “practical “ matter to be able to obtain the parameters , i.e., the heat-transfer coefficients that are used in design , and for that reason a transport phenomena course can be considered an engineering course as well as one in science.當然，能獲得參數(shù)也就是設計中使用的傳熱系數(shù)是事實，并正因此，一個傳遞現(xiàn)象課程可被視為一個工程課程或一個科學課程。

In fact , there are some cases in which the design engineer might use the methods and equations of transport phenomena directly in the design of equipment.實際上，在設備設計中有一些情況下設計工程師可能直接使用傳遞現(xiàn)象的方法和方程。An example would be a tubular reactor ,which might be illustrated as a pipe ,e.g., the heat exchanger described earlier, with a homogeneous chemical reaction occurring in the fluid within.一種情況就是設計可以被稱為管道的管式反應器，如，前面所提過的熱交換器，在它里面的液相中發(fā)生著一個均相化學反應。The fluid enters with a certain concentration ofreactant and leaves the tube with a decreased concentration of reactant and an increased concentration of product.流體以一定濃度的反應物流進并以濃度降低的反應物和濃度增加的產(chǎn)物流出反應管。

If the reaction is exothermic , the reactor wall will usually be maintained at a low temperature in order to remove the heat generated by the chemical reaction.如果反應是放熱的，為了移除化學反應生成的熱量反應器壁通常維持在一個低的溫度。Therefore the temperature will

decrease with radial position , i.e.,with the distance from the centerline of the pipe.因此沿徑向方向也就是說隨離管道中心線距離的增大，溫度降低。Then , since the reaction rate increases with temperature , it will be higher at the center ,where the temperature is high , than at the wall , where the temperature is low.再者，因為反應速率隨溫度升高而增大，在溫度高的中心處的反應速率高于溫度低的管壁處的反應速率。Accordingly ,the products of the reaction will tend to accumulate at the centerline while the reactants accumulate near the wall of the reactor.結果，反應產(chǎn)物將傾向于在中心線處積累而反應物在靠近管壁處積累。Hence , concentration as well as temperature will vary both with radial position and with length.因此，沿徑向和橫向濃度和溫度都將改變。To design the reactor we would need to know ,at any given length , the mean concentration of product.為了設計反應器我們需要知道在任意給定的管長下產(chǎn)物的平均濃度。Since this mean concentration is obtained from the point values averaged over the cross section , we actually need to obtain the concentration at every point in the reactor , i.e., at every radial position and at every length.由于這個平均濃度是將整個反應器內(nèi)每個點的濃度平均起來得到的，實際上我們需要得到反應器內(nèi)每個點的濃度，也就是說，在每個徑向和橫向位置。But to calculate the concentration at every point we need to know the reaction rate at every point , and to calculate the rate at every point we need to know both the temperature and the concentration at every point!但是為了計算每個點的濃度我們需要知道每個點處的反應速率，而為了計算每個點處的速率我們需要知道溫度和濃度！Furthermore, to calculate the temperature we also need to know the rate and the velocity of the fluid at every point.而且，為了計算溫度我們也要知道每個點處的反應速率和速度。We will not go into the equations involved ,but obviously we have a complicated set of partial differential equations that must be solved by sophisticated procedures, usually on a computer.我們將不得到所包含的方程，但顯然有一組必須由精細繁瑣的步驟解決的復雜偏微分方程（通常在電腦上）。It should be apparent that we could not handle such a problem by the empirical design procedures used in unit operations courses for a heat exchanger.我們不能通過用于單元操作課程中關于熱交換器的經(jīng)驗設計步驟來解決這樣一個問題，應該是明顯的。Instead the theory and mathematical procedures of transport phenomena are essential ,unless one wishes to go go the expense and take the time to build pilot plants of increasing size and measure the conersion in each.然而傳遞現(xiàn)象的理論和數(shù)學步驟是必不可少的，除非一個人愿意花金錢和時間去建立規(guī)模不斷擴大的模范工廠并測出每一個工廠的產(chǎn)率。Even then the final scale-up is precarious and uncertain.即便最后的擴大規(guī)模是靠不住和不確定的。

Of course ,not all problems today can be solved by the methods of transport phenomena.當然，并非今天所有的問題都能通過傳遞現(xiàn)象的方法解決。However, with the development of the computer ,more and more problems are being solved by these methods.然而，隨著電腦科技的發(fā)展，越來越多的問題通過這些方法正被解決。If engineering students are to have an education that is not become obsolete , they must be prepared, through an understanding of the methods oftransport phenomena , to make use of the computations that will be made in the future.如果工程學學生要得到一個不過時的教育，他們必須通過理解傳遞現(xiàn)象的方法準備好去充分利用將在未來形成的計算機計算。Because of its great potential as well as its current usefulness , a course in transport phenomena may ultimately prove to be the most practical and useful course on a student’s undergraduate career.由于其極大的潛能及當前的實用性，在一個大學生的在校學習生涯中，傳遞現(xiàn)象這門課程或許最終證明是最實用和有用的課程。