I'll avoid the general discussion which has, i agree, taken a
different path than originally.

> Your original statement was only about using "waste heat" from the exhaus=
t.
> it seemed the point was to put this free power to use. =A0That by itself =
makes
> sense,

Yes.

> although you can't use that power to cause a net reduction in the
> overall heat transferred from the vehicle to the environment.

Agree. Almost ;-).

>=A0You can make
> something colder than ambient, but something else will end up getting hot=
ter
> and in the steady state transferring the same total heat flow to the
> environment.

Yes. But it's hard not to feel the VM (Vuilleumier machines) isn't
cheating when you first meet it.

Heat energy flows from hot to ambient via a "regenerator" -
essentially a thermal store.

By waving two dead fish or, more usually, cylindrical objects that fit
reasonably well but with NO pressurisation or sealing, in enlarged
"passages" between hot & ambient and between ambient and cold, you get
a net cooling of the cold end. The energy required comes from the
energy flow from hot to ambient.

Dh is a displacer that slides between hot and ambient.
Dc is a displacer that slides between ambient and cold.

When Dh moves towards A gas flows A>H and system pressure rises and
temperature of all spaces with gas in rise. Phasing is arranged such
that Dc is located in cold endat that stage so this pressure and
temperature rise has minimal effect on cold end. it DOS affect the
ambient space so heat energy flows out of ambient space to true
ambient.

When Dh move into hot end system pressure falls, spaces are cooled.
Cold end is arranged to NOT have Dc in it so cold end cools and
extracts heat from cold load. Both displacers are at ambient end so
ambient volume is minimised so system tends not to "suck" heat energy
back from external ambient at this state.

Slide displacers to and from and heat energy flows from hot to ambient
AND from cold to ambient.

Electrical engineers need not build the crankshaft and flywheel
monster of my reference pages.
A wholly sealed unit with two magnetically driven (and possibly
airspring bounce action coupled) magnetically suspended displacers
would give a very mechanically minimalist solution. You MAY be able to
build a very small degree of "heat engine" actio into the movement of
the hot displacer so the whole system then ran on hot to ambient
temperature differential.

There is no compression - power is required to drive gas through the
regenerators and for any non idealities in moving the displacers.
Overall I'd expect that Watts of input could control hundreds of Watts
of heat flow.

Whatever ;-)


    Russell

--=20
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