Stirling engines in series to increase efficiency?

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james_1077
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Joined: Mon Jul 03, 2006 12:10 pm
First Name: James
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Stirling engines in series to increase efficiency?

Post by james_1077 »

Theoretically, could you put a series of Stirlings together to extract
the most mechanical energy possible from a heat source?

My thinking is to have a heat source heating the primary Stirling like
normal, then instead of air-cooling the cool side, cool that with a
water source that would act as the hot side for the second, smaller
Stirling in the series. From there, the water source that cools the
second Stirling would heat the third, and so on and so forth, such
that by the time you reach the end of the chain, you've extracted far
more mechanical energy along the way than by with one Stirling on its own.

The potential problem I see is the system reaching a sort of Delta-T
equilibrium, where all the shared water coolers/heaters reach roughly
the same temperature as the heat moves through the system on its way
to the final Stirling. I'm not sure if creating a significant Delta-T
at the final Stirling would be sufficient to keep the entire system
moving.

Has a similar system been attempted/been put into place on a large scale?
stan.hornbaker
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Joined: Thu Jun 20, 2002 6:01 pm
First Name: William S.
Last Name: Hornbaker

Stirling engines in series to increase efficiency?

Post by stan.hornbaker »

The Stirling efficiency, at best, is the efficiency of a Carnot engine.
This is expressed as: [1 - (T"/T')]X100% where T" is the absolute temperature of the cold side and T' is the absolute temperature of the hot side. This is usually about 15% or less with waste heat temperatures. When applied to engines in series it quickly degenerates to nothing.
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