On Tue, 19 Oct 2010, RussellMc wrote:

> > A steam-jet evacuator would do what you describe.
> > Compressed-air a possible steam substitute.
>=20
> I mentioned air and water eductors at the end.
> I thought about adding, but didn't,  that I wasn't yet desperate enough t=
o
> use steam :-).
>=20
> I did some reading up on them a few days as part of my thinking. The ones
> used in steam locomotives are especially ingenious, originally using boil=
er
> steam in a multistage arrangement  which, when the latent heat of
> vaporisation is made use of, allows pressures higher than that in the boi=
ler
> to be produced and then used to inject water into the same boiler. Still
> more ingenious was the subsequent of low pressure waste steam for the sam=
e
> purpose so that boiler water injection is achieved at no loss of usable
>  energy. That is in Wikipedia - probably under steam ejectors.
>=20

Simpler still: fill a sturdy chamber with steam to drive out the air (air=20
gets vented via non-return valve to outside), then cool the steam to form=20
water and a partial vacuum. Connect the steam chamber via a non-return=20
valve to your vacuum chamber (before you begin the cycle) and hey presto=20
reduced pressure in the vacuum chamber. Adjust ratio of size of steam=20
chamber to vacuum chamber to increase efficiency. Maybe add salt to water=20
in steam chamber to increase boiling point and so help water condence at=20
lower pressure.

Maybe you could build a device that simply attaches to a standard pressure=
=20
cooker. Then you just get the guys at the destination to source you a=20
standard pressure cooker (to your spec) and a camping stove :-)

Regards
Sergio Masci
--=20
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