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Wed 29 Aug, 2012 10:51 am
August 28, 2012

Thermodynamics — the branch of physics dealing with heat and its relation to other forms of energy — is profound stuff.

Rooted in the engineering realities of engines and air conditioners, it also rises above these day-to-day realities to embrace heady, universal principles in complexity, order, chaos and organization. Thermodynamics touches everything that really matters in human life, including — most famously — the nature of time. It is profound and slippery.

Some of this slipperiness showed up in responses to my physics and cities posts for the NPR Cities project. Some folks got angry with me because they claimed the second law is only relevent to closed systems. Some of the criticism comes from a misreading of what "closed" means in thermodynamics.

Thermodynamically "closed" systems exchange no matter with their surroundings. Energy transfer however is just fine for closed systems (No energy transfer means an "adiabatic" system). Other folks missed the point that the second law can still be applied to systems that are not closed and systems that are not in equilibrium. This makes sense because the second law would not be so profound if it only applied to things like an isolated thermos of coffee floating in space. In part, it's all about what you call the system and what you call the environment.

But I am no uber-meister of thermodynamics either. That PhD thing I got helps, but I too have to go back, re-read the basics and then build up to the relevant literature on the subject I am studying. (This is true of all scientific work; you are always reviewing the basics.)

Anyhow, I did (and continue to do) a lot of re-reading of my favorite thermo texts and I wanted to pass one of shortest ones of these along. It's called "The Laws of Thermodynamics" by Peter Atkins and is part of the Very Short Introduction books from Oxford. There are only a few basic equations stated for clarity and no math manipulations to follow. I highly recommend it.

Here is an example of Atkins ability to shift from discussion of the precise meaning of work and energy to a broader point:

"A final point is that the molecular interpretation of heat and work elucidates one aspect of the rise of civilization. Fire preceded the harnessing of fuels to achieve work. The heat of fire — the tumbling of out of energy as the chaotic motion of atoms — is easily contrived for the tumbling is unconstrained. Work is energy tamed, and requires greater sophistication to contrive. Thus humanity stumbled easily on to fire but needed millennia to arrive at the sophistication of the steam engine, the internal combustion engine and the jet engine."

Good stuff.

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raprap

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Wed 29 Aug, 2012 06:00 pm
BS about the closed system thing. As an Energy Engineer (Chemical and nuclear) thermodynamics is higly applicable to open systems. Additional terms to consider enthalpy, free energy, process work, energy balance--and the application to continuous operations and reaction kinetics leads to some really beautiful differential equations.

As a rule though thermodynmics breaks down to two isms;
1) You can't get something for nothing;
2) You won't break even.

Rap
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