Technical ThermodynamicsChapter 1 Introduction

Egon P. Hassel, University Rostock, Germany, Inst Technical Thermodynamics

October 25, 2010

In Italy

Technical Thermodynamics

Egon P Hassel• www.egonsthermosite.eu • University Rostock, Germany 1

Chapter 1: Introduction

Section 1.1: Introduction, some nomenclature, fundamental terms

Technical thermodynamics and Engineering thermodynamics are the same and mean thermodynamics for mechanical engineering. And that is mostly an energy related thermodynamics in contrast to chemical thermodynamics. As with each new theory one would like to introduce firstly some new terms and definitions in order to work with these later on, e.g. the terms “system”, “state”, “state variable”, “equilibrium” and “process”. Further we should define and quantify things like “energy”, “entropy”, “work”, “heat”, “temperature”, “pressure”, “ideal gas” and “gas thermometer” early on so that students are able to solve problems in exercises on an early stage. At the end of this chapter the extremely important concept of the balances are explained in very detail. To make things easy I invented a simple example with the “apple balance” and I will explain the “money account balance” anyone knows from everyday life. And it should already be mentioned here, that the basics of thermodynamics are firstly the “balances” and secondly the “material properties”. The former can be and will be derived from the laws of physics and the latter enter the theory of classical and engineering thermodynamics from measurements or from statistical physics. So they are introduced into the theory of classical and engineering thermodynamics like axioms.

Section 1.2: Preliminary notes

With the nomenclature there might be some small inconsistencies within the script and with the translation from German to English nomenclature. I apologize for this inconvenience. The possible differences are shown in the following four figures.

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Technical Thermodynamics

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Section 1.3: Further reading

There are numerous very excellent books on the market that you can easily find for yourself. However, be sure to get a book about engineering thermodynamics aka technical thermodynamics because e.g. chemical thermodynamics or thermodynamics of physics differs very much to engineering thermodynamics in nomenclature and in scope. Here are some good books as examples:

• Technische Thermodynamik and Technical Thermodynamics, A. Leipertz, in Deutsch und Englisch, German and English, to order at Lehrstuhl für Technische Thermodynamik, Universität Erlangen-Nürnberg, Germany. • Moran, Shapiro, fundamentals of engineering thermodynamics, excellent book with many numerical explicit and modern examples.•  VanWylen, Sonntag, fundamentals of classical thermodynamics, former international standard book.•  Schaums series.• And many more ...

Section 1.4: Examples of applications of engineering thermodynamics

Technical thermodynamics plays an important role in e.g.:

• Combustion engines• Gas-Turbines, Steam-Turbines, • Pumps and compressors• Fossil/nuclear-fueled power plants• Propulsions for planes and rockets• Combustion systems• Cooling process, gas separation and liquefaction• Heating, ventilation, air conditioner, HVAC• Vapor compression and absorption in refrigerators

Technical Thermodynamics

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• Heat pumps• Cooling of electronic components• Alternative energy systems• Fuel cells• Thermoelectronic devices• Magneto-hydrodynamic gadgets• Solar-powered heaters, refrigerators and powerplants• Geothermal systems•• And much more ….

In the next figure we see a very nice example of the importance of thermodynamics (and heat transfer), shown are the basic components of a gas turbine engine which has the purpose to generate as much thrust as possible.

From the left side we see an air flow into the turbine, it is compressed, mixed with fuel in the combustion chambers, the hot and high pressured exhaust gases

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drive the turbine, which is mechanically coupled to the compressor, and the exhaust gases leave the turbine on the right hand side delivering the thrust. The limitation of the thermal efficiency today are given by the maximum temperature the first rows of the turbine blades can stand.

Section 1.5: The five eʼs of thermodynamics

Thermodynamics has to do with or is the science of the 5 eʻs (five-e):

Energy: energy conversion, transformation, storage.

Entropy: only with entropy we can understand equilibrium, the time arrow, and thermal efficiency.

Exergy: is the (technical) availability of work.

Economy: the products an engineer creates must be sold.

Environment: to minimize the effect of the (industrial) # # techniques on environment is crucial for survival.

Thermodynamics is the basis of the science of heat energy, energy transport and transformation of one form of energy into another. The topics below belong to thermodynamics

• Atmospheric thermodynamic• Air-conditioning of buildings

Technical Thermodynamics

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• Many aspects of biological systems• Irreversible thermodynamics (= non-equilibrium thermodynamics)• Technical thermodynamics• Statistical thermodynamics• Classical thermodynamics

The “Technical Thermodynamics” aka “Engineering Thermodynamics” is a branch of “Classical thermodynamics'' in contrast to “Statistical Thermodynamics”. Classical thermodynamics deals with systems in (thermodynamical) equilibrium and these always include a great number of atoms and molecules (in the order of 1023 molecules). And additionally material is treated as continuum. To say it in other words, in technical thermodynamics exist no molecules, all matter is continuous.

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