Subject:
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Re: Gray VS. Black Metroliner Nose
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Newsgroups:
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lugnet.trains
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Date:
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Thu, 1 Nov 2001 14:24:37 GMT
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Viewed:
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822 times
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In lugnet.trains, James Powell writes:
> > It can never convert as high a percentage of input energy to
> > work as an engine operating at higher temperatures (this is a basic fact of
> > Carnot cycle engines you cannot escape unless you can repeal the laws of
> > thermodynamics),
>
>
> I'd take serious challenge to that statement.
You can challenge it all you want. But you're not arguing with ME, you're
arguing with thermodynamics. (unless you can show I've misapplied it)
> The best steam only power plants
> are in the 45-47% range of effiency (input to output). Mind you,
> they DON"T MOVE!...
and I bet their operating temperature differential is higher, too, being
stationary. That's the only way they can get more theoretical efficiency.
Again, read up on Carnot cycle theory if you want to argue the point. Your
theoretical maximum efficiency is upper bound by this ratio
(operating - ambient)/ambient
if I am remembering right.
Rudolf Diesel knew that. He also knew of gas engine operating temperatures,
and that's why he went with a cycle that injected fuel AFTER compression...
so he could get higher operating temperatures.
> At 6%, fuel costs were lower than that of a diesel...mostly because coal costs
> less per BTU than diesel fuel...
Today. But shifting technology on what may be a temporary differential may
not be prudent, unless you are sure it's going to remain the same or move in
the favorable direction.
++Lar
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Message has 2 Replies:
 | | Re: Gray VS. Black Metroliner Nose
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| (...) I'm not, since that can lead to ratios greater than one which is wrong. It's (operating - ambient)/operating which means run in colder climates (absolute zero is ideal if you can find it... hence heat engines can be quite efficient in shaded (...) (23 years ago, 1-Nov-01, to lugnet.trains)
| | | Re: Gray VS. Black Metroliner Nose
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| (...) I can ask, but I believe the info was 1050F x3 reheat stages, and 47.5% overall. Yes, they are all governed by Carnot cycle (diesel and steam both...) (...) Yep. So did Stirling, who had it even better, since his cycle with regenerator is (...) (23 years ago, 2-Nov-01, to lugnet.trains)
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Message is in Reply To:
| | Re: Gray VS. Black Metroliner Nose
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| (...) I'd take serious challenge to that statement. The best steam only power plants are in the 45-47% range of effiency (input to output). Mind you, they DON"T MOVE!... When done correctly, steam has a cycle effiency of ~12% on the rails (I can get (...) (23 years ago, 1-Nov-01, to lugnet.trains)
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