Mechanical Engineering

# Thermodynamics: redefine work and heat

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I'm a retired engineer with a different approach to thermodynamics.

Suppose we redefine some terms in thermodynamics based on the following statements:

1. All energy has two components: work energy and heat energy

2. Work is the change in work energy which is equal to the energy available to do work.

3 Heat is the change in heat energy which is equal to the energy unavailable to do work.

4 Work can create heat but heat can not create work.

Next is to establish a common sense sign convention:

(-) = energy removed or energy released

(+) = energy added or energy absorbed

First law of thermodynamics

Change in energy HOT (-) + COLD (+) = zero

Energy release from the hot container is absorbed by the cold container

Second law of thermodynamics

Change in work energy released by HOT (-) is greater than the change work energy added to COLD (+)

Change in heat energy released by HOT (-) is less than the change heat energy added to COLD (+)

Another example of this is the constant enthalpy process. (throttling)

During this process the available energy to do work is converted to energy unavailable to work (heat).

If interested in this approach please read my free book titled "Weber's Thermodynamics Notes"

www.wrenchtime.com/booksarticles/bookthermodynamics.html

Fred

www.wrenchtime.com

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• 7 months later...

+1 from me.

Take the combustion engine as an example, a lot of energy is 'lost' as heat (meaning there is no power gain and the energy dissipates into the atmosphere and radiator). Same can be said for friction, I despise inefficiency.

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• 4 years later...

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• 1 month later...

Thanks for the book buddy, much appreciated.

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• 1 year later...

I don't agree following your statement about thermodynamic especially number four. I ever feel heat can be better works. If I can't reach deadline , my boss will angry and he shout loudly. But I don't care anymore and laugh loudly too. Jokes man but if it annoying so much I' sorry.

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