On 9/18/2010 10:38 AM, Morris Dovey wrote:
> My understanding is that above ~373°C the physical properties of the
> liquid and vapor phases are identical and that, in fact, any discussion
> of 'liquid' and/or 'vapor' is meaningless. Can anyone verify and/or
> improve my understanding?
Many thanks for doing both of those things.
> And, most important of all, if my pipe contains some volume /V/ of
> water, does anyone know how to calculate pressure /P/ as a function of
> temperature /T/ so I can think about using something less expensive than
> unobtanium?
I received a number of good references - many more thanks!
I found a photo of a "critical point tube" (as dow described) at
www.oberlin.edu/physics/catalog/demonstrations/thermo/criticalpoint.html
and when I e-mailed received a response indicating that the tube I saw
in the photo had been purchased from Welch Scientific (now
Sargent-Welch) back in the 1930's...
Vapor pressure can be approximated via the Antoine equation which can be
found in Wikipedia. For anyone who might be interested, I used it to
plot pressures from 0°C to 373.946°C and the plot can be seen (until I
clean house again) at
http://www.iedu.com/DeSoto/Misc/H2O_VP.png
It does appear that there may be significant advantage to operating in
the temperature range just below the critical point.
--
Morris Dovey
http://www.iedu.com/DeSoto/
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> liquid and vapor phases are identical and that, in fact, any discussion
> of 'liquid' and/or 'vapor' is meaningless. Can anyone verify and/or
> improve my understanding?