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VincentG wrote: ↑Sun Jun 23, 2024 5:09 am It draws an important distinction between closed cycle and open cycle mass flow type systems.

OK, so how is that relevant to this discussion?

According to your citation:

Note that work is entropy‐free, and no entropy is transferred with work.

No entropy involved when "internal energy" goes out from the system as "work".

So I still don't see any relevance in bringing entropy into the picture. No entropy is involved when converting "heat energy" into work, or "internal energy" leaving the system as work.

Tom now you must be trolling me. You brought turbines into a discussion about piston engines. I am simply trying to point out the differences.

Heat rejection is the only way that the entropy of a fixed mass can be  decreased.

Entropy Balance for a Closed System 
A closed system includes no mass flow across its boundaries, and the entropy change is  simply the difference between the initial and final entropies of the system.  
The entropy change of a closed system is due to the entropy transfer accompanying heat  transfer and the entropy generation within the system boundaries: 

It seems that the flow of heat is the primary way energy is transferred, unless there is a mass flow(like your turbines).

Take note of the charge pressures in those turbine systems and associated expansion ratios. They are far and above what a Stirling engine experiences.

Entropy is used to draw the lines of constant entropy onto a PV diagram. They are also call adiabatic with work lines.

VincentG wrote: ↑Mon Jun 24, 2024 4:51 am Tom now you must be trolling me. You brought turbines into a discussion about piston engines. I am simply trying to point out the differences.

Heat rejection is the only way that the entropy of a fixed mass can be  decreased.

Entropy Balance for a Closed System 
A closed system includes no mass flow across its boundaries, and the entropy change is  simply the difference between the initial and final entropies of the system.  
The entropy change of a closed system is due to the entropy transfer accompanying heat  transfer and the entropy generation within the system boundaries: 

It seems that the flow of heat is the primary way energy is transferred, unless there is a mass flow(like your turbines).

Take note of the charge pressures in those turbine systems and associated expansion ratios. They are far and above what a Stirling engine experiences.

You didn't mention turbines or explain your reason for posting or what point you were trying to make. You deliberately and repeatedly brought my attention to this entropy issue, apparently considering it to be of some great importance, so I took the time to try and understand why. That is hardly "trolling". Trying to understand someone who is insisting on your giving attention to something is not "trolling".

You seem to be misunderstanding "entropy" as if it somehow limits or controls heat conversion into work. It doesn't. If "heat" or the "internal energy" of a gas is converted to external work it's completely irrelevant if "entropy" goes up or down.

Anyway, thanks for clarifying why you think entropy is an issue here. I don't.

A gas expanding and doing work is an accepted scientific. principle regardless if that work is driving a piston or driving a turbine or the system is "open" or "closed". Work is work and heat converted to work one way or the other is still heat converted to work whether it's an expansion engine with a piston or an expansion turbine.

Entropy, even if such a thing actually existed, has nothing to do with it.

You didn't mention turbines or explain your reason for posting or what point you were trying to make. You deliberately and repeatedly brought my attention to this entropy issue, apparently considering it to be of some great importance, so I took the time to try and understand why. That is hardly "trolling". Trying to understand someone who is insisting on your giving attention to something is not "trolling".

My apologies it seemed like an obvious counter point to me.

You are overlooking the "note" I've already pointed out.

Your quote says:

"The entropy change of a closed system is due to the entropy transfer accompanying heat transfer "

And:

"Note that work is entropy‐free, and no entropy is transferred with work."

If your "internal energy" goes out as heat, that will, according to your source, result in a change in entropy.

If on the other hand, your "internal energy" goes out as work that will not result in a change in entropy.

There is nothing there to suggest that internal energy cannot go out as work. Nothing saying there must be an entropy change, therefore internal energy going out as work is impossible.

You seem to be misinterpreting, or reading something into that reference that just isn't there.