Keith Hughes wrote in news:46f575f5$0$512$815e3792
@news.qwest.net:

Actually, do a search on "triple point" and look at the phase diagram
for water. That gives a good graphical depiction of the
pressure/temperature/phase relationships.



http://invsee.asu.edu/ed/phase/phasefeat.htm

Larry
--

On 2007-09-22 16:07:27 -0400, Keith Hughes said:

Actually, do a search on "triple point" and look at the phase diagram
for water. That gives a good graphical depiction of the
pressure/temperature/phase relationships.

That just shows the phase vs temperature, not the energy required to
get the substance to pass that critical temperature.

See
http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances
and search for "Enthalpy change of phase transitions" for some
explanation of the heat energy required to change phases, with a
diagram for zinc. (Thanks, Brian, for reminding me of the term I
couldn't remember.)

And also think a bit: If the difference between 32 and 33 were so
easily crossed, you wouldn't see so much ice in your drink so long.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's new pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI pages: http://homepage.mac.com/jerelull/BVI/

Jere Lull wrote:
On 2007-09-22 16:07:27 -0400, Keith Hughes said:

Actually, do a search on "triple point" and look at the phase diagram
for water. That gives a good graphical depiction of the
pressure/temperature/phase relationships.

That just shows the phase vs temperature, not the energy required to get
the substance to pass that critical temperature.

No, it shows the phase for temperature *versus* pressure, not the same
thing at all. And the point was to clarify the temperature/pressure
relationship.

See
http://en.wikipedia.org/wiki/Thermodynamic_databases_for_pure_substances
and search for "Enthalpy change of phase transitions" for some
explanation of the heat energy required to change phases, with a diagram
for zinc. (Thanks, Brian, for reminding me of the term I couldn't
remember.)

And also think a bit: If the difference between 32 and 33 were so easily
crossed, you wouldn't see so much ice in your drink so long.

Saying the difference between "32 and 33" is misleading (or a
misunderstanding of the process). Actually, it's the difference between
Ice at 32° and Water at 32°. All the energy (enthalpy) change is used
in the phase transition (latent heat of fusion, or evaporation in the
case of distillation), and not change in temperature. Additional heat
input will raise the temperature of the water (or steam in the case of
distillation - i.e. 100°C water [at standard pressure] evaporates to
100°C steam, at the moment of phase change, and additional heat input -
and pressure - are required to raise the steam temperature further).

Keith Hughes

On Fri, 21 Sep 2007 17:35:02 -0500, Brian Whatcott
wrote:

The boiling point of water at the top of a sealed 40 ft column of
water is near ambient.
So, it doesn't take much heat to boil the brackish water, and have it
pass to the fresh column where it is slightly cooled to hold the near
vacuum conditions at the boiling level.

Fraid not. It takes the same ammount of heat to boil water as at 212F.
Approximately 1175 BTU/lb. You might save a little not heating the
water all the wqy to 212.

On Sat, 22 Sep 2007 20:48:22 GMT, (Richard
Casady) wrote:

On Fri, 21 Sep 2007 17:35:02 -0500, Brian Whatcott
wrote:

The boiling point of water at the top of a sealed 40 ft column of
water is near ambient.
So, it doesn't take much heat to boil the brackish water, and have it
pass to the fresh column where it is slightly cooled to hold the near
vacuum conditions at the boiling level.

Fraid not. It takes the same ammount of heat to boil water as at 212F.
Approximately 1175 BTU/lb. You might save a little not heating the
water all the wqy to 212.


When you contradict me, it is always better to check your facts.
I do.

Brian Whatcott Altus OK

"Brian Whatcott" wrote in message
...

You've heard all about distilling water, and you've heard all about
reverse osmosis, but you haven't heard about low-cost, low energy
stills: they are brand new.

Briefly:
Take one forty ft vertical tube filled with saline.
Take one forty ft vertical tube filled with fresh water.
Connect them with a little engineering help - at the top.

The boiling point of water at sea level pressure is about 100 deg C

The boiling point of water at the top of a sealed 40 ft column of
water is near ambient.
So, it doesn't take much heat to boil the brackish water, and have it
pass to the fresh column where it is slightly cooled to hold the near
vacuum conditions at the boiling level.

[An engineering effort of a U of Utah group I think]

Brian Whatcott Altus OK


Lame suggestion and unworkable on most boats. Ya gotta think outta the
box, man.

However, there is another way. I thought it up all by my lonesome. All
you need is a reverse osmosis membrane. You put it into a chamber that
is vented to atmosphere on the inside and to the ocean on the outside of
the membrane. You lower it into the ocean to a depth of only 500 feet
and the pressure of the water is enough to push fresh water through the
membrane into the chamber. When it gets full you haul it up and empty in
into your tanks. Reverse osmosis without any energy used to get it.
Ain't Wilbur brilliant?

Wilbur Hubbard

Dear Wilbur Hubbard:

"Wilbur Hubbard" wrote in
message
anews.com...
....
Lame suggestion and unworkable on most boats. Ya
gotta think outta the box, man.

However, there is another way. I thought it up all by
my lonesome. All you need is a reverse osmosis
membrane. You put it into a chamber that is vented
to atmosphere on the inside and to the ocean on the
outside of the membrane. You lower it into the
ocean to a depth of only 500 feet and the pressure
of the water is enough to push fresh water through the membrane
into the chamber. When it gets full you
haul it up and empty in into your tanks. Reverse
osmosis without any energy used to get it. Ain't Wilbur
brilliant?

You are still displacing that much water... not a small feat.

David A. Smith

On Sat, 22 Sep 2007 17:51:56 -0400, "Wilbur Hubbard"
wrote:

When it gets full you haul it up and empty in
into your tanks. Reverse osmosis without any energy used to get it.
Ain't Wilbur brilliant?
You haul it up without using any energy to do it? Absolutely not/ It
will take a foot pound for each pound for each foot you haul it.
No your basis for perpetual motion will not work. And is the opposite
of brilliant.

Casady

Richard Casady brought forth on stone tablets:
On Sat, 22 Sep 2007 17:51:56 -0400, "Wilbur Hubbard"
wrote:


When it gets full you haul it up and empty in
into your tanks. Reverse osmosis without any energy used to get it.
Ain't Wilbur brilliant?

You haul it up without using any energy to do it? Absolutely not/ It
will take a foot pound for each pound for each foot you haul it.
No your basis for perpetual motion will not work. And is the opposite
of brilliant.

Casady

Well, not quite. The harvested fresh water is actually buoyant in the
sea water. Hauling up the water is energy free. Hauling up the
container and the rope is not, however.

With suitable flotation, the container could be made neutral-buoyant,
and so hauling it up could be free also, Finally, if the rope were HD
polyethylene or something else with about 1.0 density, the rope could be
free to hoist too. It would be necessary to attach a weight greater
than the weight of water to be harvested to the container in order to
get it to sink. This weight would then be disconnected/abandoned before
hoisting the recovered water. From an energy standpoint, the investment
would be that necessary to cover the friction in the hauling apparatus,
and the the invested energy content of the abandoned weight (steel:
high, concrete: medium, rock: free).

Venting the container to the surface would be impractical. Evacuate it
instead.

With Wilbur, one must be careful to not discard the wheat with the chaff...

bob
s/v Eolian
Seattle

On Tue, 02 Oct 2007 09:59:46 -0700, RW Salnick
wrote:

Richard Casady brought forth on stone tablets:
On Sat, 22 Sep 2007 17:51:56 -0400, "Wilbur Hubbard"
wrote:


When it gets full you haul it up and empty in
into your tanks. Reverse osmosis without any energy used to get it.
Ain't Wilbur brilliant?

You haul it up without using any energy to do it? Absolutely not/ It
will take a foot pound for each pound for each foot you haul it.
No your basis for perpetual motion will not work. And is the opposite
of brilliant.

Casady

Well, not quite. The harvested fresh water is actually buoyant in the
sea water. Hauling up the water is energy free. Hauling up the
container and the rope is not, however.

With suitable flotation, the container could be made neutral-buoyant,
and so hauling it up could be free also, Finally, if the rope were HD
polyethylene or something else with about 1.0 density, the rope could be
free to hoist too. It would be necessary to attach a weight greater
than the weight of water to be harvested to the container in order to
get it to sink. This weight would then be disconnected/abandoned before
hoisting the recovered water. From an energy standpoint, the investment
would be that necessary to cover the friction in the hauling apparatus,
and the the invested energy content of the abandoned weight (steel:
high, concrete: medium, rock: free).

Venting the container to the surface would be impractical. Evacuate it
instead.

With Wilbur, one must be careful to not discard the wheat with the chaff...

bob
s/v Eolian
Seattle


And how much of the time are you sailing in 500 ft deep water, which
was the original specification?

Bruce in Bangkok
(brucepaigeATgmailDOTcom)