Re: [Phys-L] Stirling engine efficiency

[Diego Saravia <dsa@unsa.edu.ar>]

  >    For starters, the

> regenerator returns to its initial state at the completion of each
> cycle, so it cannot possibly be a source or sink of energy or
> entropy.


You can have a system cycling and generating entropy, sending it to the
outside. Energy in = energy out, Entropy in < Entropy Out

I think that's the case with a non reversible regenerator



> So we don't care whether it's inside or outside the boundary of
> "the system".

I agree.



> The efficiency of an ideal Stirling engine is (Thot - Tcold) / Thot.

what is an ideal strirling engine?

if ideal = reversible, and you have al Energy in and out at the same
temperature, thats ok, (for that you need a regenerator)

to have a carnot machine all heat must enter and leave at the same
temperature.

so if you have heat sources at diferent temperatures you need more than one
carnot cycle, or another kind of cycle.

or if you have a device (better if reversible) attached to any cicle, that
lets all the heat go inside at the same temp, and the heat out the same,
you are nearer
to a carnot heat machine.

Usually you have machines with one source of heat  at one temperature. In
that case you can aproximate all cycles to a carnot one, using devices that
do that job.

You can put that devices inside your mental system boundaries or not, but
the physics will be the same.


http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node66.html


The laws of thermodynamics do not permit any greater efficiency.
> There is nothing intrinsic to the Stirling cycle that limits it to
> any lower efficiency.
>
> > From an engineering point of view, in a wide range of practical
> situations, if you care about high efficiency, you can do better
> with an almost-ideal Stirling-cycle engine than with an almost-
> ideal Carnot-cycle engine.  The Stirling engine is difficult to
> build and difficult to analyze, but finesse and effort are rewarded.
> In contrast, there's not much you can do to remedy the nonidealities
> of a real-world engine that tries to follow a Carnot cycle.
>
> Certain "modern PER-based" textbooks get this completely wrong.  I
> take responsibility for what *I* say;  I am not responsible for what
> other people say.  Please do not shoot the messenger.
>
> For details, see
>   https://www.av8n.com/physics/thermo/classical.html#sec-stirling
>
> _______________________________________________
> Forum for Physics Educators
> Phys-l@www.phys-l.org
> http://www.phys-l.org/mailman/listinfo/phys-l



-- 
Diego Saravia
Diego.Saravia@gmail.com
NO FUNCIONA->dsa@unsa.edu.ar

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