化工热力学(国际班)课件 Ch1 Thermodynamics

1、化工热力学CHEMICAL ENGINEERING THERMODYNAMICSGiven by Office : Room 4-317, Chem. Eng. Lab, West Campus Tel :84986170 Email: Chemical Engineering Institute,School of Chemical Engineering热-thermal energy力-mechanical energy THERMODYNAMICS is a subject on energy and energy conversionThermodynamics- 是关于热能转化为机

2、械能的学问.HEATPOWERHeating is almost one of the oldest phenomenon recognized and used by human The birth of THERMODYNAMICSreHistoryThe first time you go through it, you dont understand it at all.The second time you go through it, you think you understand it, except for one or two small point.The third t

3、ime you go through it, you know you dont understand it ,but you are so used to it, it doesnt bother you any more. Amold sommerfield :Thermodynamics is a funny subject.Thermodynamicsis a funny subject.The description of the thermoengine The principals and the efficienciesThe 1st and 2nd law of thermo

4、dynamics The mathematical deductions applicable to all branches of science Engineering Thermodynamics Chemical Thermodynamics Statistical Thermodynamics Chemical Engineering Thermodynamics Molecular Thermodynamics Chem. Eng. ThermodynamicsChemical Reaction Eng.Transport PhenomenaKey Chem. Eng. Sci.C

5、HEMICAL ENGINEERING THERMODYNAMICSThe 1st and 2nd law Thermodynamic properties of fluidsThe thermo-cycle, refrigeration cycle, heat pumpSolution thermodynamicsPhase and chemical equilibria Thermodynamic analysis of chemical plant Syllabus The PurposeTeaching RequirementContentsThe evaluation The Pur

6、poseTo have a better understanding on general principles of thermodynamicsTo master the principles of energy conversion, the 1st and 2nd law of thermodynamics, and make reasonable and best usage of energy.Get a sound knowledge of calculating the PVT behavior and thermodynamic properties for real sta

7、te of chemical processes.To master the basic principles of phase and chemical equilibrium, do equilibrium calculations and solve practical problems for chemical processing.Thermodynamicsis often characterized as adifficult subject.why?New concepts Strict mathematical deductionsComplex systems Indeed

8、, if ones approach is to memorize every equation developed in the course, the subject will be very difficult. to understand the concepts and develop the ability to apply the basic principles in a systematic way.So, try to adopt a fundamental approach:WorkThermodynamics The student who takes this app

9、roach will find that the subjectis really quite easy.is really quite easy !work to understand the conceptsThis way pleaseand develop the ability to apply the basic principles in a systematic way.Teaching RequirementsPreview the contents for each classAttend to class punctually, actively, and serious

10、ly.The failure rule of the “three times absence”Master basic concepts and principles and develop the ability to apply the principles in a systematic wayMaster the methods and techniques of thermodynamic calculationsFinish home works (DIY is strongly encouraged)The scores Total marks 100 Terminal Exa

11、m 80%Home works 20%Text Book 于志家 李香琴 兰忠Chemical Engineering Thermodynamic 高等教育双语教学推荐教材化学工业出版社，2014References Chapter 1 Introduction绪论1.1 The Scope of Chemical Engineering ThermodynamicsThe development of chemical engineering thermodynamics.The utility of fire in the ancient time The development of s

12、team engine in the 18th centuryChemistry thermodynamicsChemical Engineering Thermodynamics, Dodge, 1944Thermodynamics in chemical and petrol-chemical industryThermodynamics in newly developed area: fine chem., pharmacy, environment Our ancestors invented a kind of decorating lamp, the “走马灯”, and als

13、o the ancient rockets。古代火箭飞龙出水 走马灯The industry revolution in England in 1760s.Thomas Newcomen (纽科门), an English Engineer is one of the inventor of steam engine which was developed as the Watt Engine. The Watt Engine (In 1784) The 1st applicable steam engine in the World The statue of Watt1912年4月15日凌

14、晨2点，“泰坦尼克号”沉入海底。 Roles in processes design and developmentFine reliable data for the design of chemical processMake thermodynamic analysis for chemical processesPromote the production of desired chemicals with improved quality.Minimize energy consumption and the production cost, make best usage of e

15、nergy. A practical chemical engineer must get a sound knowledge of thermodynamics1.2 System and Surroundingsthe materials or a region under study is called the system, and all of the rest are its surroundings. Isolated system: there is neither material nor energy transferred across the boundary betw

16、een the system and its surroundings.Closed system: there is only energy transferred across the boundary between the system and its surroundings, but without any material or mass transferOpen system: there are both material and energy transferred across the boundary between the system and its surroun

17、dings. 1.3The Chemical State and Fluid PropertiesMassComposition (mole or mass fraction for each chemical species)Phase (solid, liquid, gas)Form (crystalline modificationapplied only to solid)Temperature.Pressure.The equilibrium stateIt does not vary with time.The system is uniform (there are no int

18、ernal temperature, pressure, velocity, or concentration gradients), or is composed of uniform subsystems.All the flows of heat, mass or work between the system and its surroundings are zero.The net rate of each chemical reaction is zero.1.4 The First Law of ThermodynamicsEnergy: The capacity of a bo

19、dy for doing work . The general measurement of matter motion. Mechanical energy (机械能): Potential energy, kinetic energyInternal energy (内能)Electrical energy (电能)Chemical energy (化学能)Atomic energy (原子能)To study the energy change is very important to chemical engineering Mechanical Energy: The kinetic

20、 energy Potential energyThe roller coasterInternal Energy URefers to the energy of the ceaseless moving molecules.Does not include the macroscopic position and movement焓EnthalpyH = U + PV函数的组合Joules ExperimentsEnergy can be neither created nor destroyed. The total quantity of energy is constant. Whe

21、n energy disappears in one form, it appears simultaneously in other forms.-the 1st law of thermodynamics for controlled mass system. The Law of Nature!doing work with heat1.4.1 Energy balances for non-flow processes of closed systems1.4.2 Energy balances for flow processes of open systems1.4.3 Energ

22、y balances for steady flow processes 1.4.1 Energy Balances for Non-Flow processes of Closed Systems闭系非流动过程的能量平衡For control mass system: Where is the difference operator. The signs for Q and W were set to be positive if the energy transports are from surroundings to system.For controlled mass systems

23、,For finite changes：-the 1st law of thermodynamics for controlled mass system. Then:1.4.2 Energy balances for flow processes of open systems 开系流动过程的能量平衡 For controlled mass system:The EB eqns for controlled volume system can be set up with the help of the concept of controlled massA typical controll

24、ed volume system:At time 0: the unit mass of feed with internal energy of U1, specific vol of feed V1 is forced by P1, the, then: x1=V1/A1. The work done to force the unit mass of reactant into the controlled volume is : w1=P1A1x1=P1V1Total internal energy: U1+E1At time t: w2=-P2V2Total internal ene

25、rgy: U2+E2E1E2The work necessary for fluid flowThe Flow Work PV滔滔后浪推前浪正所谓：名词解释WF滚滚长江东逝水Then :If potential and kinetic energy are considered:Expressed the eqn based on flow rate:For multi-streams:-The energy balance equation for open flowing systems flow into (the controlled volume)flow out ofmi, Qi,

26、 Wi+-redW/dt=0; without power supply，dQ/dt=0; potential and kinetic energy are negligible：For liquid water：Solution:EX1.1p81.4.3 Energy balances for steady flow processes 稳流过程的能量平衡If the process is a continuous process operated at steady state:The accumulating rate of mass and energy within the boun

27、dary is zero.Mass flow rate of each stream is constantThe heat and work flow rate of the process are constantEnergy balance equation for steady flow process 稳流过程的能量平衡方程flow into (the controlled volume)flow out ofmi, Qi, Wi+-Based on per unit mass fluid:reEx. Solution :dW/dt=2kW, T1=95, m=3.5kg/s, dQ

28、/dt=-698kW, z1=0, z2=15m, T2=?Ek is negligible small.CPm=4.208kJ/(kg.K) (95)Home Work1.3, 1.6, 1.91.5 The Second Law of ThermodynamicsThe 1st law illustrate the conservation of energy, but no restriction is given. Heat and work are 2 kinds of energy, 1 J 0f heat and 1 J of work means the same by the

29、 1st law. But in fact they are different in quality.Not all the kind of energy is available for use.If one decreases the temperature of sea water in the whole world by 1K, were there any worry about energy shortage?If a process or a phenomenon can occur, how about the process direction ?The 2nd law

30、of thermodynamics纽科门(Newcomen，Thomas)英国工程师.蒸汽机发明人之一。Carnot French Engineer 1.5.1 The upper limit for the conversion of heat into workStatement of the Second Law 热力学第二定律There are deferent statements. The most common accepted statements are:1）On heat flow direction （Rudolf Clausius 1850）:Heat cannot b

31、e transferred solely from one temperature level to a higher one.热量不能自动地从低温物体转移到高温物体去。 Re 2）On the thermal cycle (Kelvin 1851):No apparatus can operate in such a way that its only effect is to convert heat (absorbed by the system) completely to work (done by the system). -第二类永动机不可能造成。 3）The mathemati

32、cal statement :No process is possible for which the total entropy decreases-孤立体系的熵不可能减少。5.2 Heat Engines and Carnot theoremRe Carnot EngineThe Carnod Cycle on PV gragh ( AB): isothermal expansion at T1(B C)： adiabatic expansion(C D): isothermal compression(D A)： adiabatic compressionRe For the cycle

33、：W = -（Q1+Q2 ）= W1+W2+W3+W4 For the 2 adiabatic processes (bc and da), we have ：So ：The thermal efficiency of the engine： The thermal efficiency of reversible engine is a function of two reservoir temperatures only. T, . The actual efficiency is much less！The Carnot theorem:Any engine cannot get a h

34、igher thermal efficiency than reversible engine if it operates between the same high temperature and low temperature reservoirs. the 2nd LawAll the reversible engines that work between the same high temperature and low temperature reservoirs get the same thermal efficiencies.Deduced from Carnot theo

35、rem, we have:The thermal efficiency of a Carnot engine depends only on the temperature levels and not upon the working substance of the engineEx. 1.3 (p12)A power plant, W=800MW, TH=585K, TC=298K, =0.7max. Qc=?Solution:For a reversible engine working on an ideal gas:1.5.2 The entropy SEntropy熵For an

36、 arbitrary cycle：The sum of the ratio of absorbed heat over the temperature for an arbitrary reversible cycle is 0. We design an arbitrary reversible cycle ABA. The circular integration can be expressed by ： is a function of the initial and terminal state of the system, and unrelated with details of

37、 the process-the State Function Clousius defined it: Entropy, S :The concept is very important As important as energyMore important than energy 熵From the microscopic viewpoint, entropy S measures the disorder of the system molecules.1.5.3 Mathematical statement of the second law热力学第二定律用于闭系The Carnot theorem： Any engine cannot get a higher thermal efficiency than reversible engine if it operates between the same high temperature and low temperature reservoirs. For irreversible