Technology & Engineering
Thermodynamics of Gases
The thermodynamics of gases is the study of the behavior of gases in relation to temperature, pressure, and volume. It encompasses principles such as Boyle's law, Charles's law, and the ideal gas law, which describe the relationships between these variables. Understanding the thermodynamics of gases is crucial in various engineering applications, including the design of engines, refrigeration systems, and industrial processes.
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8 Key excerpts on "Thermodynamics of Gases"
- Allan D. Kraus, James R. Welty, Abdul Aziz(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
2 Thermodynamics: Preliminary Concepts and Definitions Chapter Objectives • To briefly introduce the subject of thermodynamics. • To provide precise definitions of some of the working terms used in a study of thermodynamics. • To consider the dimensions and units that pertain to thermodynamics. • To examine density and its related properties. • To define pressure and consider how it is measured. • To define temperature and to present the zeroth law of thermodynamics. • To outline a problem-solving methodology. 2.1 The Study of Thermodynamics When most people think about thermodynamics, they think about the transfer of energy and the utilization of such energy transfer for the useful production of work. This often leads many engineering students in fields such as computer science and electrical or civil engineering to wonder why this particular subject is relevant to them. In reality, thermody-namics deals with much more than the study of heat or energy transfer and the development of work. Indeed, it deals with virtually all aspects of our lives, from the combustion pro-cesses that run our automobiles and produce our electric power in power plants to the refrigeration cycles that cool our beer, from the cryogenic pumping of liquids and gases in space to the distillation processes used to produce the gasoline that runs our automobiles. Thermodynamics is important to electrical engineers so that they can better understand that the limiting factor in the microminiaturization of electronic components is the rejec-tion of heat. It is important to civil engineers because a knowledge of thermal expansion and thermal stresses is requisite to the design of structures and to the computer scien-tists who need to thoroughly understand the systems that they are trying to model and develop.
eBook - PDF- Kaufui Vincent Wong(Author)
- 2011(Publication Date)
- CRC Press(Publisher)
1 -1 1 Concepts, Definitions, and the Laws of Thermodynamics 1.1 Introduction Thermodynamics .is.the.science.of.energy . .The.topics.covered.will.be.about.energy.and. the.relationships.among.the.properties.of.matter . Thermodynamics.is.an.energy.science.that.is.a.key.to.the.design.of.important.and. interesting.energy.systems . .These.systems.include.automotive.engines,.heat.pumps,.air-planes,. rockets,. space. stations,. power. stations,. gas. turbines,. fuel. cells,. air. condition-ers,.artificial.kidneys,.firefighting.equipment,.chemical.refineries,.lasers,.refrigerators,. cryogenic. systems,. solar. heating. systems,. computers,. and. energy-efficient. buildings . . Thermodynamics.is.the.foundation.of.the.design.of.engineering.systems . The.existence.of.energy.can.be.deduced.from.the.physical.effects.of.energy.transfer . . For.instance,.the.hoisting.of.a.weight.increases.the.energy.of.the.weight . .This.could.be. accomplished.by.the.flow.of.electricity.through.a.motor,.or.the.flow.of.steam.through.a. turbine. .Quantitative.relations.do.exist.between.the.amount.of.electricity.or.steam.used. and.the.amount.of.weight.raised.through.a.given.elevation . .The.study.of.these.relation-ships.is.part.of.thermodynamics . A.system.may.be.investigated.from.either.a.microscopic.or.a.macroscopic.point.of. view. .In.the.microscopic.viewpoint,.the.position.and.velocity.of.the.molecules.forming. the.system.are.specified.in.detail . .The.behavior.of.the.system.is.the.sum.of.the.behavior. of.each.molecule . .Such.a.study.is.known.as.statistical.thermodynamics . .From.the.mac-roscopic.viewpoint,.we.are.concerned.with.the.gross.or.average.effects.of.many.mol-ecules. .We.can.feel.these.effects.and.measurements.can.be.made.by.instruments . .We.can. measure.the.system.or.parts.of.the.system,.the.dimensions.of.which.are.large.compared. to.the.distance.between.molecules . .In.this.book,.we.use.this.macroscopic.viewpoint .
eBook - PDFStatistical and Thermal Physics
An Introduction
- Michael J.R. Hoch(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
131 C H A P T E R 7 Application of Thermodynamics to Gases: The Maxwell Relations 7.1 INTRODUCTION Inpreviouschapters,ithasbeenshownthatthermodynamicsprovidesa phenomenologicaldescriptionofprocessesforsystemsmadeupofmany particles.Themethodsofthermodynamicsallowustoestablishrelation-shipsbetweenvariouspropertiesofasystemsothatmeasurementofone property permits other properties to be deduced without further mea-surement. Use is often made of the fundamental relation that combines thefirstandsecondlawsofthermodynamics.Forfluids,thishastheform T S E P V d d d = + (Equation3.18).Togetherwiththeequationofstateand theheatcapacity C V asafunctionoftemperature,thefundamentalrelation permitsawiderangeofprocessestobeanalyzed.Forsolidsandliquids, it is often convenient to use the isothermal compressibility κ , defined in Equation2.53,andtheisobaricthermalexpansioncoefficient β ,definedin Equation2.52,inplaceofaformalequationofstate.Fromtimetotime,it maybeconvenienttousetheadiabaticequationthatprovidesarelation-shipbetweentwothermodynamicvariablesforanadiabaticprocess,such as PV r =constantforanidealgas.Forafluid,theequationofstateprovides 132 ◾ Statistical and Thermal Physics: An Introduction arelationshipbetweenthethreethermodynamicvariables, P , V ,and T .The stateofasystemmaybespecifiedwithanytwoofthesevariables.Because theinternalenergy E andtheentropy S arestatefunctions,thesetwoquan-titiesmayalsobeusedtospecifythestateofasystem. In Section 3.13 of Chapter 3, we introduced three thermodynamic potentialsthatinvolvecombinationsofthefivevariables E , S , P , V ,and T . Inthesespecialfunctions, T and S occurtogether,asdo P and V .Thecon-jugatepairs PV and TS ,whichareproductsofintensiveandextensivevari-ables,havedimensionsenergy.Thethermodynamicpotentialsaredefined asfollowsforasinglecomponentsystemsuchasapuregas: Enthalpy, H = E + PV ; (7.1) Helmholtzpotential, F = E − TS ; (7.2) Gibbspotential, G = E − TS + PV .
eBook - PDF- Murry L. Salby(Author)
- 2012(Publication Date)
- Cambridge University Press(Publisher)
CHAPTER TWO Thermodynamics of Gases The link between the circulation and transfers of energy from the Earth’s surface is thermodynamics. Thermodynamics deals with internal transformations of the energy of a system and exchanges of energy between that system and its environment. Here, we develop the principles of thermodynamics for a discrete system, namely an air parcel moving through the circulation. In Chap. 10, these principles are generalized to a continuum of such systems, which represents the atmosphere as a whole. 2.1 THERMODYNAMIC CONCEPTS A thermodynamic system refers to a specified collection of matter (Fig. 2.1). Such a system is said to be “closed” if no mass is exchanged with its surroundings. Otherwise it is “open.” The air parcel that will serve as our system is, in principle, closed. In practice, however, mass can be exchanged with the surroundings through entrainment and mixing across the system’s boundary, which is referred to as the control surface . In addition, trace constituents such as water vapor can be absorbed through diffusion across the control surface. Above the planetary boundary layer, such exchanges are slow compared with other processes that influence an air parcel. The system may therefore be treated as closed. The thermodynamic state of a system is defined by the various properties char-acterizing it. In a strict sense, all of those properties must be specified to define the system’s thermodynamic state. However, that requirement is simplified for many applications, as is discussed next. 74 2.1 Thermodynamic concepts 75 dS dn Control Surface Mean Boundary Expanded Boundary z = p T m Z m Z Figure 2.1 A specified collection of matter defining an infinitesimal air parcel. The system’s thermodynamic state is characterized by the extensive proper-ties m and Z and by the intensive properties p , T , and z . 2.1.1 Thermodynamic properties Two types of properties characterize the state of a system.
eBook - PDFSuperstrings and Other Things
A Guide to Physics, Second Edition
- Carlos Calle(Author)
- 2009(Publication Date)
- CRC Press(Publisher)
177 11 The Laws of Thermodynamics THE FOUR LAWS OF THERMODYNAMICS Why does time seem to flow in only one direction? Can the flow of time be reversed? The directionality of time is still a puzzle because all the laws of physics except one are applicable if time were to be reversed. As we shall see in this chapter, the second law of thermodynamics is the exception. The flow of time seems to arise from the second law. There are four laws of thermodynamics: the second law was discovered first; the first was the second; the third was the third, but it probably is not a law of thermodynamics after all; and the zeroth law was an afterthought. We shall occupy ourselves in this chapter with the study of these laws. THE IDEAL GAS LAW The study of thermodynamics is intimately connected with the study of the behavior of gases. The reason is that gases, being much simpler, are better understood than liquids and solids. An ideal gas is any gas in which the cohesive forces between molecules are negligible and the collisions between molecules are perfectly elastic; that is, both momentum and kinetic energy are conserved. Many real gases behave as ideal gases at temperatures well above their boiling points and at low pressures. The English scientist Robert Boyle, the 14th child of the Earl of Cork, was an infant prodigy. At the age of eight he spoke Greek and Latin and at 14 traveled to Italy to study the works of Galileo. He returned to England in 1645 to find his father dead and himself wealthy. In 1654, he became a member of the “Invisible College,” which later became the Royal Society, where he met Newton, Halley, and Hooke. In 1662, while experimenting with gases, he was able to show that if a fixed amount of a gas was kept at a constant temperature, the pressure and the volume of the gas follow a simple mathematical relationship.
eBook - PDF- Marc J. Assael, William A. Wakeham, Anthony R. H. Goodwin, Stefan Will, Michael Stamatoudis(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
1 1 Chapter Definitions and the 1 st Law of Thermodynamics 1.1 INTRODUCTION The subjects of thermodynamics, statistical mechanics, kinetic theory, and transport phenomena are almost universal within university courses in physical and biological sciences, and engineering. The intensity with which these topics are studied as well as the balance between them varies considerably by disci-pline. However, to some extent the development and, indeed, ultimate practice of these disciplines requires thermodynamics as a foundation. It is, therefore, rather more than unfortunate that for many studying courses in one or more of these topics thermodynamics present a very great challenge. It is often argued by students that the topics are particularly diffi cult and abstract with a large amount of complicated mathematics and rather few practical examples that arise in everyday life. Probably for this reason surveys of students reveal that most strive simply to learn enough to pass the requisite examination but do not attempt serious understanding. However, our lives use and require energy, its conversion in a variety of forms, and understanding these processes is intimately connected to thermodynamics and transport phenomena; the latter is not the main subject of this work. For example, whether a particular proposed new source of energy or a new product is genuinely renewable and/or carbon neutral depends greatly on a global energy balance, on the processes of its production, and its interaction with the environment. This analysis is necessarily based on the laws of thermodynamics, which makes it even more important now for all scientists and engineers to have a full appreciation of these subjects as they seek to grapple with increasingly complex and interconnected problems. This book sets out to provide answers to some of the questions that under-graduate students and new researchers raise about thermodynamics and sta-tistical mechanics.
eBook - PDF- J. Edward Pope(Author)
- 1996(Publication Date)
- Gulf Professional Publishing(Publisher)
61 Brayton Cycle: A Gas Turbine Cycle ............................... 62 Otto Cycle: A Power Cycle .............................................. 63 Diesel Cycle: Another Power Cycle ................................. 63 Gas Power Cycles with Regeneration .............................. 64 51 52 Rules of Thumb for Mechanical Engineers THERMODYNAMIC ESSENTIALS Thermodynamics is the subject of engineering that pre- dicts how much energy can be extracted from a working fluid and the various ways of achieving it. Examples of such areas of engineering interest are steam power plants that gen- erate electricity, internal combustion engines that power au- tomobiles, jet engines that power airplanes, and diesel lo- comotives that pull freight. The working fluid that is the medium of such energy transfer may be either steam or gases generated by fuel-air mixtures. Phases of a Pure Substance The process of energy transfer from one form to anoth- er is dependent on the properties of the fluid medium and phases of this substance. While we are aware of basically three phases of any substance, namely solid, liquid, and gaseous, for the purposes of thermodynamic analysis we must define several other intermediate phases. They are: 9 Solid: The material in solid state does not take the shape of the container that holds it. 9 Subcooled liquid: The liquid at a condition below its boiling point is called subcooled because addition of a little more heat will not cause evaporation. 9 Saturated liquid: The state of liquid at which addition of any extra heat will cause it to vaporize. 9 Saturated vapor: The state of vapor that is at the verge of condensing back to liquid state. An example is steam at 212~ and standard atmospheric pressure. 9 Liquid vapor mix: The state at which both liquid and vapor may coexist at the same temperature and pres- sure.
eBook - PDFThermo and Fluid Dynamics
Recent Advances
- Dritan Hoxha(Author)
- 2019(Publication Date)
- Arcler Press(Publisher)
Naturally, this is a difficult apparatus to produce. But it will be useful to get a grip on the basics of gas We can adjust the pressure applied on the inside by the piston, by changing the weight of the piston as shown below (Figure 3.8). Theory of Thermodynamics 45 Figure 3.8. A thermodynamic system composed by a piston, a cylinder, some gas inside the cylinder and the surroundings outside the cylinder. In a cylinder – piston system: Movable piston implies constant pressure. Historically the relations among the temperature pressure and volume of a gas were established in 17th century by different scientists. Now we remember the relations by the names of these scientists. We will investigate three gas laws here, at constant temperature, at constant pressure, and at constant volume. Pressure-volume relation of a gas sample at constant temperature is established nearly at the same time by the English physicist Boyle and French scientist Mariotte. Now we name the relation as Boyle-Mariotte law. 3.12. BOYLE-MARIOTTE LAW Pressure – volume relation of a gas sample at constant temperature. Changing volume and pressure of a gas sample at constant temperature is called isothermal process. “Isothermal” means happening at “constant temperature.” When a fixed amount of gas is compressed, decreasing its volume, we expect its pressure to increase. You can easily observe this effect by trying to squeeze the air in a syringe with its nozzle closed. Pushing the piston will require more and more force as the volume of the air trapped inside decreases. But this “syringe experiment” is not a good example for isothermal process. As the air in the syringe is compressed, not only the pressure but also the temperature increases. To overcome this difficulty and keep the temperature constant we must work carefully (Figure 3.9). Thermo and Fluid Dynamics: Recent Advances 46 Figure 3.9. Demonstration of an isothermal process. To achieve isothermal process we can make such an arrangement.
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