User talk:Mre env

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Thermodynamics and statistical physics

Hi Mre env. I've put this explanation together with sources that can be read online. Physicists and engineers are looking at the behavior of matter at different scales. A very good explanation of this is given in this introduction by Kerson Huang.^[1] Pages 3 and 4 talk about the thermodynamic limit. The concepts of thermodynamics don't work at atomic scale systems, only for large collections of matter. But the basic physics at that scale is what leads to the large scale effects studied with thermodynamics. Chapters 5 and 6 of this book give a good introduction to the derivation of thermodynamics.

A physics major will take a class in "Thermodynamics and Statistical Mechanics" with a text like Concepts in Thermal Physics.^[2] This has large doses of of the kinetic theory of gases and statistical mechanics as you can see in the table of contents. They are learning the physics from which the laws of thermodynamics are derived. But there is a limit to what can be calculated at this scale. I was an astrophysicist and it works very well for stars. See stellar structure and this lovely diagram showing energy transfer in stars, highly dependent on stellar mass.

An engineering major will take a class in "Engineering Thermodynamics" with a text like Fundamentals of Engineering Thermodynamics.^[3] See that table of contents. This is the approach needed to be able to work with most materials, figuring out how to get heat out of computer processor chips and handling heat in nuclear power plants. An engineering curriculum is focused on the types of physics that support practical applications in the macroscopic world. There isn't any need in the curriculum to have students learn about what is happening on the atomic and molecular level when they do thermodynamics. The text does say in chapter 6, page 283, 6.1.3. Entropy and Probability:

"The macroscopic concepts of engineering thermodynamics introduced thus far, including energy and entropy, rest on operational definitions whose validity is shown directly or indirectly through experimentation. Still insights concerning energy and entropy can result from considering the microstucture of matter. This brings in the use of probability and the notion of disorder."

To get a full description of the basic physics behind thermodynamics you will need to refer to physics textbooks.

Bejan has made an extraordinary claim, that an optimization process in thermodynamics is THE basic law of physics. That will need extraordinary proof. Like the laws of thermodynamics it will have to be derivable from more basic areas of physics. It does happen that a senior scientist will have an insight that they persist in incorrectly carrying beyond their area of expertise. I think it happens less often in engineering. But I may have an idealized view of engineers. My engineer father sent me off to physics class with his slide rule.

Looking at the physics of this has been fun. I am reminded of being back in graduate school dealing with deriving the relations of thermodynamics using 6N dimensional phase spaces where N is the number of particles in a system. And I learned new things. Since I studied thermodynamics the concept of phonons has become important in thermal conductivity in non-metals. Phonons act like a Bose gas and can establish thermal equilibrium and conduct heat like a gas of particles.^[4] The underlying physics is explained by Gang Chen, a professor of power engineering at MIT.^[5]

References

^ Kerson Huang (2009). Introduction to Statistical Physics (2nd ed.). CRC Press. pp. 1–4. ISBN 978-1-4398-7813-2.
^ Stephen Blundell; Katherine M. Blundell (2010). Concepts in Thermal Physics. OUP Oxford. ISBN 978-0-19-956209-1.
^ Michael J. Moran; Howard N. Shapiro; Daisie D. Boettner; Margaret B. Bailey (2010). Fundamentals of Engineering Thermodynamics. John Wiley & Sons. ISBN 978-0-470-49590-2.
^ Chandler, David L. (8 July 2010). "Explained: Phonons. When trying to control the way heat moves through solids, it is often useful to think of it as a flow of particles". Massachusetts Institute of Technology.
^ Gang Chen (2005). Nanoscale Energy Transport and Conversion: A Parallel Treatment of Electrons, Molecules, Phonons, and Photons. Oxford University Press. ISBN 978-0-19-977468-5.

Hope this helps explain things. Best regards. StarryGrandma (talk) 21:20, 17 January 2018 (UTC)[reply]

StarryGrandma thanks for your time and thoughtfulness. I definitely look into it. Best regards. Mre env (talk) 23:09, 18 January 2018 (UTC)[reply]

[1] Kerson Huang (2009). Introduction to Statistical Physics (2nd ed.). CRC Press. pp. 1–4. ISBN 978-1-4398-7813-2.

[2] Stephen Blundell; Katherine M. Blundell (2010). Concepts in Thermal Physics. OUP Oxford. ISBN 978-0-19-956209-1.

[3] Michael J. Moran; Howard N. Shapiro; Daisie D. Boettner; Margaret B. Bailey (2010). Fundamentals of Engineering Thermodynamics. John Wiley & Sons. ISBN 978-0-470-49590-2.

[4] Chandler, David L. (8 July 2010). "Explained: Phonons. When trying to control the way heat moves through solids, it is often useful to think of it as a flow of particles". Massachusetts Institute of Technology.

[5] Gang Chen (2005). Nanoscale Energy Transport and Conversion: A Parallel Treatment of Electrons, Molecules, Phonons, and Photons. Oxford University Press. ISBN 978-0-19-977468-5.

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