流体力学与传热 Introduction

1、IntroductionBreathe in: O2Breathe out: CO20.1 Examples of Mass TransferRespiration: What do we breathe in? breathe out?0.1 Examples of Mass TransferBlood streamBlood VesselLungBlood stream with High conc. of CO2Blood stream with low conc. of CO2肺血流(CO2含量高)血流(CO2含量低)血液血管Other examples of mass transfe

2、r:A lump of sugar added to a cup of black coffee.Water evaporates from ponds to increase the humidity of the passing air stream.Perfume presents a pleasant fragrance which is imparted throughout the surrounding atmosphere.0.1 Examples of Mass Transfer传质的其他例子：把一小块糖放进一杯黑咖啡中。从水池中蒸发的水增加了气流的湿度。香水挥发到周围空气中

3、从而散发出宜人的香气。In industrial processes, A group of operations for separating the components of mixtures is based on the transfer of material from one homogeneous phase to another.工业过程: 分离均相混合物中各组分的各种单元操作以相际传质为基础.0.1 Examples of Mass Transfer0.2 Definition of Separation ProcessesAll natural processes tak

4、e place so as to increase the entropy, or randomness, of the universe.一切自发过程的发生均倾向于使宇宙的熵或混乱度增加 。The second law of thermodynamicsHow to separate a solution of salt and water? (Problem for producing fresh water from the sea.)Question:Answer0.2 Definition of Separation Processes怎样分离盐的水溶液?(海水淡化问题)思考：0.3

5、 分离过程的定义All three approaches are the reverse procedure of mixing, or “unmixing” , or separation processes.Supply heat and boil water offSupply refrigeration and freeze out pure icePump the water to a higher pressure and force it through a thin solid membrane that will let water through preferentiall

6、y to salt (reverse osmosis).0.2 Definition of Separation ProcessesAnswer:答案：加热，汽化水分加冷（供给冷量），使水结冰加压，用膜分离方法0.3 分离过程的定义所有的三种处理方法都是混合的相反程序, 或者叫 “非混合” , 又叫分离过程.Spontaneous processes: randomness Separation processes: randomness (supplying the equivalent of thermodynamic work to the mixture, reverse proced

7、ure of Spontaneous processes)0.2 Definition of Separation Processes自发过程:混乱度分离过程:混乱度Separation processes are those operations which transform a mixture of substances into two or more products which differ from each other in composition.What is separation processes0.2 Definition of Separation Processe

8、s分离过程定义: 将一混合物转变为组成互不相同的两种或几种产品的操作。0.3 General Separation processFeed stream(one or more)(different in composition, at least 2 streams)Product Stream1Separating agent（matter or energy）SeparationdeviceProduct Stream2(supplying thermodynamic work)0.4 一般分离过程分离装置进料最少二股(各股组成不同)产品流1分离剂(物质或能量)产品流2(一股或多股)Th

9、e separation is caused by the addition of a separating agent, that is matter or energy.Usually the separating agent will cause the formation of a second phase of matter.For homogeneous mixtures, by utilizing differences in some physical property such as vapor pressure, solubility or diffusivity, the

10、 components of mixtures are separated from one homogeneous phase to another.0.3 General Separation ProcessSummary:分离是由于分离剂的加入而引起的。分离剂即物质或者能量。通常，分离剂将会促使第二个物相的形成。均相物系的分离过程（相际传质）：1)通过形成第二个物相而产生一个两相物系；2)根据物系中不同组分间某种物性差异，例如蒸汽压、溶解度或者扩散能力等，使其中某个组分或某些组分从一相向另一相转移，从而达到分离的目的。0.4 一般分离过程Separation processes in m

11、anufacturing0.4 Importance and Variety of SeparationsSeparationReactionSeparationSeparationSeparationImpurity Raw MaterialsClean WaterEffluent WaterEffluent AirClean AirRecycleContaminant By-ProductsProductsRecycleRecycleContaminant Raw materials: 原材料; impurity: 杂质; effluent water: 废水; by-product: 副

12、产品; contaminant: 污染物About several-decades of Unit Operations of Separation ProcessesSeparation equipment accounts for 50 to 90% of the capital investment in large-scale petroleum and petrochemical processes centered around chemical reactions.Often separation itself can be the main function of an ent

13、ire process: sugar refining; natural gas refining; manufacture of oxygen and nitrogen from air.0.4 Importance and Variety of SeparationsFood processing: dehydration, removal of toxic or objectionable components, beverage extracts; separation of fermentation broths and many other details of pharmaceu

14、tical manufacture.Separation of fissionable 235U Uranium from the more abundant 238U.Desalination of seawater.0.4 Importance and Variety of Separations0.4 Importance and Variety of SeparationsWater and air pollution , municipal refuse (solid wastes) present separation problems of immense social impo

15、rtance.0.5 Categorizations of Separation ProcessesMechanical separation processesSeparation processes with chemical reactionDiffusional separation processes 1) Equilibration processes 2) Rate-governed processes (membrane separations)0.5 分离过程的分类机械分离（非均相物系分离）反应分离扩散分离过程1)平衡过程（相际传质）2)速率控制过程（膜分离等）0.6 Technological and Use Maturities of ProcessesDistillationAbsorptionExtractionAzeotropic DistillationIon Exchan