On Sep 21, 10:15 pm, Andrew Erickson
wrote:
In article ,



Larry wrote:
Brian Whatcott wrote in
:

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

My deepest apologies to the engineers who may be rolling under their
desks, crushing their pocket protectors. It took me a while to stop
chortling. I nearly lost my Chinese dinner!

Psst...Brian....40'? What about the lake above 40', it's 400' deep and
above 40' ASL. It hasn't boiled away in millions of years from all that
pressure and lack of pressure.

Ummm...there is quite a difference between atmospheric pressure at 40'
ASL and a (near) vacuum. Presumably the connection at the top is
airtight and made with as little air as possible entering the tubes, and
presumably also the bottoms of the tubes open and submerged in some sort
of a vented container At sea level, atmospheric pressure will only
support somewhere in the vicinity of 40 feet of water, so the top of the
tubes will be approaching a vacuum. (This is why wells water wells
deeper than 35 or so feet require a pump in the well, rather than at the
top.)

I see no reason why this wouldn't work, at least to some degree,
although I do wonder how using a still of any sort differs from
distillation. I also wonder how easy it would be to make an effective
vertical solar collector on a boat that doesn't need constant climbing
about to fiddle and adjust.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot

hmmm, I wonder what the rate would be? One could assume that you do
not have to put in any heat to increase the temp so any heat input
would simply go into latent heat of water vapor. You would hav o
maybe use solar to heat the salt water side and cool the fresh water
side by immersing it in the ocean. Then the max rate would simply be
power in (whatever the heat from the sun would be in watts/m2 times
the area of your collector) which is Joules/sec which is roughly 4
calories/sec. Somebody look up the latent heat of water (I dont have
my handbook handy) and then you have grams/sec of fresh water (maximum
rate).