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

[Herbert Schulz <herbs@wideopenwest.com>]

> On Mar 3, 2015, at 11:05 AM, John Denker <jsd@av8n.com> wrote:
>
> On 03/03/2015 09:56 AM, Carl Mungan wrote:
> > I'm a bit confused about efficiency. For a Carnot cycle, we have two
> > isothermal steps and two adiabatic steps. The efficiency is then found to
> > be 1 - Tcold/Thot.
> >
> > Okay but what about a non-Carnot but still reversible cycle
>
> The efficiency of any reversible heat engine is
> the same:  1 - Tcold/Thot.                  [1]
>
> If it's reversible, entropy is conserved, and
> that's all you need to prove equation [1].
>
> The "Carnot cycle" is an easy-to-analyze example,
> but not the only example, not by a long shot.
>
> Note that any cycle can be approximated as closely
> as you wish by a sum over Carnot cycles.  Think 
> of tiling the area on the indicator diagram (PV
> diagram).

Howdy,

I always thought that you could prove that a true Carnot Engine, whose efficiency is indeed given by 1 - T(cold)/T(hot), is the most efficient engine that can exist running between those two extremes of temperature. ALL OTHER Engines running between those temperature extremes are LESS EFFICIENT.

Good Luck,

Herb Schulz
(herbs at wideopenwest dot com)