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Ideal Gas Law help please - Page 2

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Posted by Ahem A Rivet's Shot on December 31, 2010, 1:28 pm
On Thu, 30 Dec 2010 16:14:03 -0600

    This is true - but what I was thinking about was the
displacement/pressure available from the expansion of liquid water as it
changes temperature. If the volume is held constant the pressure change can
be very high, but if expansion is allowed at constant pressure the volume
change will be small. If phase changes are involved it all gets more
complicated - get out the tables.

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Posted by Morris Dovey on December 31, 2010, 5:47 pm
On 12/31/2010 7:28 AM, Ahem A Rivet's Shot wrote:

<fixed typo>

I'm still scratching my head, and I think you're right - which is why
the books are on order.

The challenge appears to be allowing (and controlling) the expansion in
such a way that the water remains fluid, and leveraging the high
pressure / low expansion efficiently in the neighborhood of the critical

It seems like it should be possible - and there may be some interesting
solar possibilities if it can be done...

Morris Dovey

Posted by daestrom on January 1, 2011, 7:43 pm
 On 12/31/2010 12:47 PM, Morris Dovey wrote:

If you let it expand enough to change phase, then you can *really* boost
the power output.  Expanding steam and 'compressing' only liquid water
yields a lot of net work. :-)

Problem is, it's been done to death.  That's a steam engine pure and
simple (expand steam in a cylinder/turbine, 'compress' water in a


Posted by Morris Dovey on January 1, 2011, 8:47 pm
 On 1/1/2011 1:43 PM, daestrom wrote:

Ok. I think that's easily managed. I suppose I shouldn't be surprised
that this part of the pump project now appears headed almost directly
toward a scaled-up and slightly-modified version of Sno's "pop-pop" engine.

Then so be it. The way it's shaping up, the "compression" mechanism will
probably be a a pump output column/standpipe arrangement.

I don't particularly mind that it's been done to death. If I could find
a combined engine/pump design that could be driven with solar heat and
that could be built in a third world bicycle shop for under US$00, I
could skip this entire exercise and remain blissfully ignorant.

I've probably become over-sensitized, but every news report telling
about crisis conditions in just about any underdeveloped area seems to
point to non-availability of water as at least a primary factor - and
it's not that there isn't any, it's simply in the wrong place - and the
folks with the problems lack the means to get it.

"Steam Tables (English Units)" by Keyes et al arrived yesterday
afternoon, and I've been immersed in the appendix a good part of the
time since. I'm in the process of turning "The Fundamental Equation"
(Helmholtz free energy) into a trio of C subfunctions - and, as usual, I
can say that I now know even /more/ that I don't understand. :)

Kinda hoping that Wark's "Thermodynamics" shows up soon to help me
better understand what I'm attempting...

Morris Dovey

Posted by sno on January 1, 2011, 9:52 pm
 On 1/1/2011 3:47 PM, Morris Dovey wrote:

You have my permission to call it the "dovey-sno pop pop pump" <grin>

have fun....sno

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