replying to Jon Danniken, Ron Henderson wrote:
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7 years ago
replying to Jon Danniken, Ron Henderson wrote:
You're missing the point that the boiling point of water is not absolute but varies with the pressure it is subjected to. At lower pressures, below 1atm, it boils at less than 212F (100C) and at higher pressures it boils at a higher pressure such as in Jon's pressure cooker. See
The "boiling point" is the temperature at which the liquid's vapor pressure equals the pressure of the air (or steam) above it, allowing bubbles that form at hot spots to expand against the surrounding pressure. Unlike the freezing point it is in no sense a constant, but varies with imposed conditions.
In mile-high Denver water boils at ~202F/94C. Room-temperature water will boil in a vacuum chamber. In a PWR-type nuclear power plant the primary coolant water remains liquid at 600F and 2250PSI. If it accidentally boils it becomes a less effective neutron moderator and automatically decreases the rates of fission and heat production.
--jsw
...while dramatically increasing fear and screaming in the local population.
In Chernobyl's graphite-moderated RBMK design the rates -increase- without water. This is the resulting melted core of Reactor 4 in the basement:
Despite the destruction and dangers they kept the three other reactors at the site operating for many years.
--jsw
STP - Standard Temperature and Pressure. Jack with pressure and the temperature specs change.
Take the pressure off water e.g. vacuum and you can boil it. In the reverse pressure up the water and it can't boil. e.g. no steam. Release the pressure and zap, almost instant 100% steam. Sometimes dangerously.
Mart> reply> It is impossible to heat water above it's boiling point. At that point it
That was a carbon pile moderator not a water moderator. The carbon caught on fire and there it went. Cascading, melting and more and more.
Mart>> >>
This is a practical application of the energy stored in hot water under pressure:
--jsw
"Jim Wilkins" on Fri, 10 Jun 2016 21:38:14
-0400 typed in rec.crafts.metalworking the following:
Something about still needing the electrical production, as I recall.
-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."
Actually, you're half correct. You cannot heat water above the boiling point. But the boiling point of any material is also subject to the pressure upon it. Carbon dioxide goes from solid to gas in atmosphere, because its boiling point at that pressure is below the melting point. If you want to heat water above the boiling point, you just have to be able to contain the pressure. The Steam Institute has a booklet with tables, that as temp goes up, pressure goes up, until the critical point, after which there is apparently no difference between liquid water and gaseous water.
22.064 MPa (218 atm). As the substance approaches critical temperature, the properties of its gas and liquid phases converge, resulting in only one phase at the critical point: a homogeneous supercritical fluid."tschus pyotr
-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."
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