Jere Lull wrote:
On 2007-10-08 18:17:58 -0400, Mark Borgerson said:

snip

Though I consider this whole discussion impractical,

I don't know that I'd call the *discussion* impractical; the device
certainly. Kind of the point of the discussion.

I haven't seen
anyone mention that the fresh-water side will be drawn down fairly
regularly. And, of course, the sea water side will be replenished from
time to time.

Suck hard enough on the fresh-water side and you get even better
"vacuum" at the top. (Dissolved gasses are likely to be a problem,
though.) Cool the fresh-water side and water vapor will condense there
-- the whole point of the exercise.

Thinking only momentarily on a problem that I have little interest in...
if the fresh-water side is evacuated to the point that the salt-water
side is slightly below the top, every once in a while (or perhaps
often), the fresh-water side will be empty and only the
previously-dissolved gasses evacuated.

The required evacuation pumps and one-way valves sound like the problem
at the moment.

The whole exercise was to get a passive system. If you're going to add
a vacuum pump, then you just provide continuous evacuation on the
freshwater side, using a demister that drains into the freshwater pool,
to separate the water vapor from the non-condensables. But if you
accept the need for a pump, why use this rather byzantine approach at all?


Keith Hughes