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Re: [Phys-L] Carnot (?) efficiency of non-Carnot cycles

On 03/05/2015 10:14 AM, Carl Mungan wrote:
"For an ideal regenerator, it contributes
nothing to the energy budget and entropy budget when summed
over a cycle. Whatever it takes it gives back over the
course of a cycle."

:-)

That's very clever.

I agree, a Stirling engine has some professional-grade
cleverness in it.

I can see indeed that we could undo in the isochoric
depressurization what we did in the isochoric pressurization step, at least
for an ideal device.

Right. Every step in one of those legs has a mirror
image in the other leg.

Now what is such a device

Try this:
https://www.av8n.com/physics/thermo/classical.html#sec-stirling

Obviously that's very new and very drafty. I don't expect
students to follow it, but I reckon the folks on this list
may get some value from it. Right now it's little more
than an outline, but it hits the main points.

Questions and suggestions are welcome.

I looked at the various animations and other references
that people suggested. Some of them are in the double-
or-nothing category: If you /already/ completely understand
the Stirling cycle, you can look at the animation and say
yeah, that's about right ... whereas if you don't already
understand, you will never figure out from the animation
what's important and what's not. Such things have next
to zero pedagogical value.

Others are even worse: For example, the wikipedia diagram
could charitably be called misleading, if not outright
wrong. It is unclever in several of the ways that a
proper Stirling engine is clever.

why don't intro textbooks mention it given that this seems a
pretty essential part of non-Carnot cycles?

Gaaaack! Don't ask me to explain those books!!!

Thermodynamics is never going to be easy, but the way
it's taught makes it muuuuuch harder.

One small part of an explanation: They guys that write
those books don't hang out on this list. I've gotten
a lot smarter about thermo (and other things) based on
discussions here.