Examples of systems which cannot receive work adiabatically?

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A system that cannot receive work adiabatically is in thermodynamic equilibrium, as stated by Hatsopoulos and Keenan. An example is a piston with an ideal gas in thermal equilibrium with an infinite reservoir. When constant pressure work is applied, the gas cools, leading to irreversible heat flow from the reservoir into the cylinder. Conversely, expansion work causes heat to flow out, demonstrating that work on the system results in irreversible heat transfer. This irreversibility highlights the relationship between work, heat flow, and thermodynamic equilibrium.
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In Principles of General Thermodynamics, Hatsopoulus and Keenan (p 442) make the following claim:
if a system is in such a state that it cannot receive work adiabatically, it is in equilibrium.
What, however, would be some physical examples of such a system?
 
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A piston with ideal gas as a working fluid in thermal equilibrium with an infinite reservoir. If you do constant pressure compression work on the piston, the gas gets colder, so there's an irreversible flow of heat into the cylinder from the reservoir. The opposite is true if you do expansion work. Either way, doing work on the system results in heat flow in/out of the system in an irreversible manner. The irreversibility is the key to understanding this claim. Remember that thermodynamic equilibrium is a state of maximum entropy.
 
For simple comparison, I think the same thought process can be followed as a block slides down a hill, - for block down hill, simple starting PE of mgh to final max KE 0.5mv^2 - comparing PE1 to max KE2 would result in finding the work friction did through the process. efficiency is just 100*KE2/PE1. If a mousetrap car travels along a flat surface, a starting PE of 0.5 k th^2 can be measured and maximum velocity of the car can also be measured. If energy efficiency is defined by...

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