Potable Water - The Third Way.
 

On Sep 30, 9:13 am, "jim.isbell" wrote:
... The salt water will boil
earlier because of the salt content. ...

http://en.wikipedia.org/wiki/Boiling-point_elevation

-- Tom.

Potable Water - The Third Way.
 

On Sat, 29 Sep 2007 19:44:35 -0700, Keith Hughes
wrote:

Vic Smith wrote:
On Sat, 29 Sep 2007 17:43:02 -0500, Brian Whatcott
wrote:

On Sat, 29 Sep 2007 20:40:57 GMT, (Richard
Casady) wrote:


There is a reverse osmosis watermaker intended for liferaft use, with
a hand pump, and RO takes hundreds of psi. That is what you want, if
you actually need high pressure.

Casady

I looked up an example
The Katadyn Survivor 35 hand pumped was formerly
called the PUR Survivor 35 RO.
At 30 strokes/minute for 1.2 gall/hr - it costs $1500.

Calorie expenditure by the survivor(s) could be a problem here.

Oh yeah, right. Now you want to survive also. Geez, what next? :-)

The strokes for this RO unit can probably be performed by devising a
simple hydraulic pump to move gears, cams, and levers.
The pump cylinder itself would probably need an inverted U tube with
legs perhaps 32' or 33' long.
An initial vacuum might be applied to the top of the U-tube by using a
fitting that can be connected to the PUR Survivor 35 RO.
Once the water starts flowing through the vane at one end of the U
tube, and the vane shaft is turning the gears, cams and levers will be
clacking way, running that PUR unit on auto, good as gold.
After that it's all gravy until you have to change the membrane.
In the meantime you can spend your time fishing until rescued.

Sounds like perpetual motion to me, but I'm having a hard time
envisioning what you're describing above.

Sorry, it was all said jokingly, but appears to be a poor joke.
I just went in a circle from the perpetual U-tube distiller to that
concept being employed to perpetually pump a purchased RO unit.
I never intended to make sense, except maybe to say it's time to go
fishing.

--Vic

Potable Water - The Third Way.
 

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

Potable Water - The Third Way.
 

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

Potable Water - The Third Way.
 

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)

Potable Water - The Third Way.
 

Potable Water - The Third Way.
 

On Wed, 03 Oct 2007 08:13:20 -0700, RW Salnick
wrote:

brought forth on stone tablets:
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)

500 feet? That's only 83 fathoms. My sailing area is Puget Sound, much
of which is 150 fathoms or more. Why? Is Thailand in a skinny water zone?

bob
s/v Eolian
Seattle

From Singapore north through either the Gulf of Thailand or up the
west coats of Malaysia or most of the western part of Indonesia 150
ft. of water would be deep water. Wilbur's invention isn;t going to
work very well over here.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)

Potable Water - The Third Way.
 

In article ,
says...
On Sat, 22 Sep 2007 10:55:52 -0500, Brian Whatcott
wrote stuff
and I replied:

But what is the cheap source of getting the vacuum? I figured there
had to be a vacuum, although it was not said. But how do you get it?

Well no, he obviously hadn't figured that out. Nor can anybody figure
out what is going to hold a column of water 40 ft high as was stated in
the original post. The tubes may be 40 feet but the column of water will
be considerably less. How much less will depend on how much energy is
heating on the hot side and how much energy is cooling on the cool side.
The total amount of energy needed is not going to be any different than
any other distilling method.
Unless you have the free or cheap sources of cooling and heating at
specific temperatures this isn't going to work any better either.

-jim

SNIP

Simply put a one-way (out only) valve at the top where the two tubes
are joined. Pump water up both tubes to about 3" from the top,
displacing the air in the tubes. That will only require about
16 PSI from the pumps.

The major problem would seem to be that vigorous boiling is going
to carry over salt and contaminants from the boiling salt water unless
the tubes are large or there is some sort of debubbler on the
salt water side.

For heating and cooling, I suppose that you could use the sunny and
shady sides of a sailboat mast.

Mark Borgerson

Potable Water - The Third Way.
 

In article ,
says...


jim wrote:

"jim.isbell" wrote:
Ah well, another great idea skuppered by dat old devil science :-)

Bruce in Bangkok
(brucepaigeATgmailDOTcom)
A 32' column of water is a continuous vacuum pump.

This is just plain wrong. As a *unit of measure* 32 feet of water
column equals about 13.9 psi. Meaning, if you pumped a 40' column up to
a 39' height with water, equalized the headspace to atmospheric pressure
(assuming 14.7psia), sealed it, then allowed gravity to *drain* the
water column to a height of 2', the resulting pressure in the headspace
will be about 0.8psia. Now you also have 33' of empty evacuated column.

As long as you put
water (salt water) into the column it will pull down and keep a vacuum
in the top of the column.

Sorry, this makes no sense. Putting water in does not cause it to "pull
down". Yes, you have supply makeup water to maintain column height lost
to evaporation.

The fresh water distills off the top of the
sal****er column then migrates

Yes, and this "migration" is simple diffusion. *And* you have (in the
example above) 33' of column it has to diffuse through on the seawater
side, and however many feet of column on the freshwater side it has to
traverse prior to condensation. If both columns (fresh and sea) are
referenced to the same height, then the evacuated column height on both
sides will be the same, and that diffusion path will be up to 66'. That
does not happen quickly.

How do you get 33' as 1/2 of the diffusion path. I think there will be
about 33 feet of water in the column on each side---to provide the
weigth that pulls the pressure down. That would leave only about
7 feet of water vapor path on each side of the column.

I'm not sure that 'diffusion' is the proper term for the motion
of the water vapor. After all, the heat engine is providing
water vapor on one side and condensing it on the other---so there
is a net mass flow and probably a small pressure differential to
move the vapor.

Still (pun intended), you need a lot of heat to provide the energy
to evaporate the water or it will soon cool to the point where
its vapor pressure is reduced and the process slows drastically.
The fact that the water 'boils' near room temperature does not
reduce the amount of heat required to change the water from
liquid to vapor.

As has been discussed, the simple idea does not address the problems
of salt buildup in the seawater side, or the addition of dissolved
gasses to the vacuum part of the loop.

With a large enough (or double) sal****er tube you might get a
convection cell going with the cold, saltier water sinking and
pulling up warmer seawater to the top.

You could solve the dissolved gas problem by periodically pumping
both tubes up enough to displace the accumulated gases.

Now the project is getting complex enough that an RO system
starts to look attractive!


Mark Borgerson

Potable Water - The Third Way.
 

In article . com,
says...
I give up. My Masters degree in Physics is of no value here. My
Bachelors degree in Math is of no value here. My 20 years with the
university (retired) means nothing. Someone with an opinion (however
false) instead of facts of physical science, seems to be more able to
swing the belief of the uninformed.

I will try to explain it again.

The vacuum will hold the column of water in the tube.

Dont believe it?
Test this statement, take a simple soda straw stick in in a glass of
water put your finger over the end and lift it out. The 8" column of
water stays in the straw because of the vacuum in the top of the
straw. Now remove your finger and the water drops out. So, it
doesn't TAKE a 32' column of water, but that is the tallest column of
water that will be suspended, a simple law of physics.

Thats why a lift pump like the old rocker handle pitcher pumps have to
be replaced with either submerged or Jet pumps in deeper wells. A
lesser column WILL work however. At the top is a vacuum. If its 32
feet, thats the greatest vacuum you can create. There is salt water
on one side and fresh water on the other. The salt water will boil
earlier because of the salt content.

Now test that statement.
Put a pot on the stove and then before it comes to a boil add salt.
Voila, it begins to boil.


BZZZZT!!! FALSE!!!


Salt water DOES NOT boil at a lower temperature than fresh water. It
boils at a higher temperature. When you add salt to heated water,
it appears to boil because the water is superheated near the bottom of
the pan and the salt crystals provide "nuclei" that start the boiling
process. You can easily verify this by starting with two pans
of water, one salty and one fresh and heating them to their respective
boiling points and measuring the temperature. More explicit
instructions, aimed at middle school students are at:

http://aquarius.nasa.gov/pdfs/prop_fresh_sea.pdf


snip


Mark Borgerson






SNIP