Potable Water - The Third Way.
 

On Sun, 23 Sep 2007 18:10:09 GMT, Brian Whatcott
wrote stuff

and I replied:

You are a rude and arrogant prick


On Sun, 23 Sep 2007 21:57:56 +0800, OldNick
wrote:
...
Then how do you keep the freshwater tube so cool? It has to be a _lot_
cooler, not so?


I'm probably going to regret responding, but I will anyway, with a
question:

What is the difference in temperature between steam and water,
both at the boiling temperature of water, whatever it may be?

Cooler means lower temperature, right?

OK you can now answer your own question.
I hope.

Brian W

Human bevaviour: Bestiality with a brain

Potable Water - The Third Way.
 

On Mon, 24 Sep 2007 09:38:16 +0800, OldNick
wrote stuff
and I replied:

and snickering, snide and childish as well

You are the sort of cliqueish dolt that spoils useful NGs like this.

If you have KF'd me, you simply prove your weak, childish nature.

It's shame. You do actually seem to have a lot of knowledge. IT's a
pity you have to use it to sneer and brag rather thatn help those
"lesser" than you


On Sun, 23 Sep 2007 18:10:09 GMT, Brian Whatcott
wrote stuff

and I replied:

You are a rude and arrogant prick


On Sun, 23 Sep 2007 21:57:56 +0800, OldNick
wrote:
...
Then how do you keep the freshwater tube so cool? It has to be a _lot_
cooler, not so?


I'm probably going to regret responding, but I will anyway, with a
question:

What is the difference in temperature between steam and water,
both at the boiling temperature of water, whatever it may be?

Cooler means lower temperature, right?

OK you can now answer your own question.
I hope.

Brian W

Human bevaviour: Bestiality with a brain

Human bevaviour: Bestiality with a brain

Potable Water - The Third Way.
 

On Sep 22, 11:12 am, "Roger Long" wrote:
There's another neat way you can demonstrate this with minimal equipment.

Take a tight fitting jar and get the water boiling vigerously in it with the
cap on loose enough to let the steam out. When it is full of dense steam
and about 1/3 boiling water, remove instantly from heat and tighten cap.

When everything is cooled to room temperature, put an ice cube against the
jar and the water will start to boil. The ice condenses the water vapor
further, reducing the pressure to the point where the water will boil at
room temperature.

I've seen it done and it looks like the ice cube is boiling the water.

My father won a science fair doing this back in the 1930's.

--
Roger Long

http://www.metacafe.com/watch/414997/boiling_using_ice/

Joe

Potable Water - The Third Way.
 

On Sep 25, 8:54 am, OldNick wrote:
On Mon, 24 Sep 2007 09:38:16 +0800, OldNick
wrote stuff
and I replied:

and snickering, snide and childish as well

You are the sort of cliqueish dolt that spoils useful
NGs like this.

.... "Go away" ...

If you have KF'd me, you simply prove your weak,
childish nature.

.... "Stay and argue with me" ...

It's shame. You do actually seem to have a lot
of knowledge. IT's a pity you have to use it to
sneer and brag rather thatn help those
"lesser" than you

.... "I will smear **** on you, if you don't argue with me" ...

Human bevaviour: Bestiality with a brain

Human bevaviour: Bestiality with a brain

How is it that you complain about other's behavior, yet you form not
one response but *two*, that show exactly the behavior your signature
talks about.

Is that signature line a complaint, an acknowledgement, or a promise?
Be good to know. Because it seems like we have a choice.

David A. Smith

Potable Water - The Third Way.
 

On Sep 22, 10:39 pm, OldNick wrote:
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?


Gravity.

Potable Water - The Third Way.
 

On Thu, 27 Sep 2007 13:54:13 -0000, "jim.isbell"
wrote:

On Sep 22, 10:39 pm, OldNick wrote:
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?


Gravity.


Wishful thinking. Where are you going to get the feedwater containing
no noncondensible gasses in solution? In all real distillation plants
a continuosly operating vacuum pump is required to maintain vacuum and
prevent the condensers from filling with noncondensible gasses. There
is no way you are going to eliminate the vacuum pumps with any kind of
inverted tube arrangement.

For reasonable efficiency real distillation plants are multi-stage,
where the latent heat of condensation from one stage is used to boil
feedwater in the next stage, with up to 5 stages being used in larger
plants (in the days before reverse osmosis made them uneconomical by
comparison). Sucessive stages operate at lower pressures, and
corresponding lower temperatures. The 1100 or so BTU required to boil
one pound of water can thus boil up to 5 pounds of water instead.

You still need enough thermal gradient to get the heat to flow through
all those heat exchangers. By using low thermal differentials between
the hot and cold ends you either reduce capacity to a pittance or
require huge and expensive heat exchangers, in either case not
competitive. TANSTAAFL.

Potable Water - The Third Way.
 

On Thu, 27 Sep 2007 21:25:39 GMT, Glen Walpert
wrote:

On Thu, 27 Sep 2007 13:54:13 -0000, "jim.isbell"
wrote:

On Sep 22, 10:39 pm, OldNick wrote:
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?


Gravity.


Wishful thinking. Where are you going to get the feedwater containing
no noncondensible gasses in solution? In all real distillation plants
a continuosly operating vacuum pump is required to maintain vacuum and
prevent the condensers from filling with noncondensible gasses. There
is no way you are going to eliminate the vacuum pumps with any kind of
inverted tube arrangement.

For reasonable efficiency real distillation plants are multi-stage,
where the latent heat of condensation from one stage is used to boil
feedwater in the next stage, with up to 5 stages being used in larger
plants (in the days before reverse osmosis made them uneconomical by
comparison). Sucessive stages operate at lower pressures, and
corresponding lower temperatures. The 1100 or so BTU required to boil
one pound of water can thus boil up to 5 pounds of water instead.

You still need enough thermal gradient to get the heat to flow through
all those heat exchangers. By using low thermal differentials between
the hot and cold ends you either reduce capacity to a pittance or
require huge and expensive heat exchangers, in either case not
competitive. TANSTAAFL.


Ah well, another great idea skuppered by dat old devil science :-)

Bruce in Bangkok
(brucepaigeATgmailDOTcom)

Potable Water - The Third Way.
 

Dear Glen Walpert:

"Glen Walpert" wrote in message
...
On Thu, 27 Sep 2007 13:54:13 -0000, "jim.isbell"
wrote:

On Sep 22, 10:39 pm, OldNick wrote:
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?


Gravity.

Wishful thinking. Where are you going to get the
feedwater containing no noncondensible gasses in
solution? In all real distillation plants a continuosly
operating vacuum pump is required to maintain
vacuum and prevent the condensers from filling with
noncondensible gasses. There is no way you are
going to eliminate the vacuum pumps with any kind of
inverted tube arrangement.

But they don't have to be large, and they don't even have to run
continuously (just frequently). There are also going to be
controls...

You could even run it without a vacuum pump until it shut itself
down, drop and purge the gas bubble, then "forklift" your pipes
back up.

And do it at less than the melting point of plastic (should that
be important).

For reasonable efficiency real distillation plants
are multi-stage, where the latent heat of
condensation from one stage is used to boil
feedwater in the next stage, with up to 5 stages
being used in larger plants (in the days before
reverse osmosis made them uneconomical by
comparison).

Scaling is real problem too...

Sucessive stages operate at lower pressures, and
corresponding lower temperatures. The 1100 or
so BTU required to boil one pound of water can
thus boil up to 5 pounds of water instead.

You still need enough thermal gradient to get the
heat to flow through all those heat exchangers.
By using low thermal differentials between the hot
and cold ends you either reduce capacity to a
pittance or require huge and expensive heat
exchangers, in either case not competitive.
TANSTAAFL.

.... a characteristic article ...
http://www.hcn.org/servlets/hcn.Arti...ticle_id=17136
This was not proposed to be a source of free energy, violate the
second law of thermodynamics, or poke fingers in anyone's eyes.

I think it was something that someone could do fairly cheaply, to
get drinkable water from salt water. In other words "a graduate
or undergraduate college project".

I just wonder if you get any improvement in what is left in the
brine, vs. what also evaporates at the lower temperatures...

David A. Smith

Potable Water - The Third Way.
 

On Thu, 27 Sep 2007 18:06:47 -0700, "N:dlzc D:aol T:com \(dlzc\)"
wrote:

Dear Glen Walpert:

"Glen Walpert" wrote in message
.. .
On Thu, 27 Sep 2007 13:54:13 -0000, "jim.isbell"
wrote:

On Sep 22, 10:39 pm, OldNick wrote:
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?


Gravity.

Wishful thinking. Where are you going to get the
feedwater containing no noncondensible gasses in
solution? In all real distillation plants a continuosly
operating vacuum pump is required to maintain
vacuum and prevent the condensers from filling with
noncondensible gasses. There is no way you are
going to eliminate the vacuum pumps with any kind of
inverted tube arrangement.

But they don't have to be large, and they don't even have to run
continuously (just frequently). There are also going to be
controls...

The vacuum pumps need to be sized to the load, and it is not a
foregone conclusion that a larger pump running intermittently would be
more efficient than a smaller one running continuosly. Consider also
that the vacuum pump cannot pump out just the noncondensible gasses,
it must pump out the gas mix in the condenser which will be mostly
water vapor - the pumping rate establishes the percentage
noncondensible gasses in the condenser, amd the optimum rate needs to
be established as part of a distillation plant design.

You could even run it without a vacuum pump until it shut itself
down, drop and purge the gas bubble, then "forklift" your pipes
back up.

Does this use less energy per gallon produced?

And do it at less than the melting point of plastic (should that
be important).

For reasonable efficiency real distillation plants
are multi-stage, where the latent heat of
condensation from one stage is used to boil
feedwater in the next stage, with up to 5 stages
being used in larger plants (in the days before
reverse osmosis made them uneconomical by
comparison).

Scaling is real problem too...

True, but one which can be solved by limiting brine concentration and
with chemical treatment and/or periodic cleaning.

Sucessive stages operate at lower pressures, and
corresponding lower temperatures. The 1100 or
so BTU required to boil one pound of water can
thus boil up to 5 pounds of water instead.

You still need enough thermal gradient to get the
heat to flow through all those heat exchangers.
By using low thermal differentials between the hot
and cold ends you either reduce capacity to a
pittance or require huge and expensive heat
exchangers, in either case not competitive.
TANSTAAFL.

... a characteristic article ...
http://www.hcn.org/servlets/hcn.Arti...ticle_id=17136
This was not proposed to be a source of free energy, violate the
second law of thermodynamics, or poke fingers in anyone's eyes.

As usual with this sort of article there are no meaningful numbers
included, perhaps because a complete design analysis has not been
done.

I think it was something that someone could do fairly cheaply, to
get drinkable water from salt water. In other words "a graduate
or undergraduate college project".

Doing an analysis of this approach would be a good student exercise.
Not much point building one without doing the anylysis first - a
complete engineering analysis including the selection or design of all
heat exchangers, mist eliminators, pumps, piping etc., including both
performance and cost calculations. It is always cheaper to optimize a
pencil and paper or computer model than hardware, especially for
something so well understood as heat transfer and fluid flow.

I just wonder if you get any improvement in what is left in the
brine, vs. what also evaporates at the lower temperatures...

David A. Smith

I doubt if that would be much of a factor. What contaminants would be
in the feedwater which would evaporate less compared to water as
boiling point is reduced by low pressure?

The biggest issue with distillate quality is carryover; a fine mist of
unevaporated water droplets are inevitably produced by boiling
regardless of temperature, and while most of these can be separated
out, some always make it through to the condenser. This is a big
issue where biological contamination exists in the feedwater,
requiring chlorination of the distillate to make it potable. It might
be possible to eliminate this factor by eliminating the boiling of
bulk liquid, and instead evaporating from a thin film of water flowing
over the heat exchanger surfaces, but I doubt if it would be cost
effective. Perhaps it would be another good student exercise.

Potable Water - The Third Way.
 

Dear Glen Walpert:

On Sep 28, 7:09 am, Glen Walpert wrote:
On Thu, 27 Sep 2007 18:06:47 -0700, "N:dlzc D:aol T:com \(dlzc\)"
....
Gravity.

Wishful thinking. Where are you going to get the
feedwater containing no noncondensible gasses in
solution? In all real distillation plants a continuosly
operating vacuum pump is required to maintain
vacuum and prevent the condensers from filling with
noncondensible gasses. There is no way you are
going to eliminate the vacuum pumps with any kind of
inverted tube arrangement.

But they don't have to be large, and they don't
even have to run continuously (just frequently).
There are also going to be controls...

The vacuum pumps need to be sized to the load,
and it is not a foregone conclusion that a larger
pump running intermittently would be more efficient
than a smaller one running continuosly. Consider
also that the vacuum pump cannot pump out just
the noncondensible gasses, it must pump out the
gas mix in the condenser which will be mostly
water vapor -

So you can get some condensate here, but it will likely have "vacuum
pump oil" in it...

the pumping rate establishes the percentage
noncondensible gasses in the condenser, amd
the optimum rate needs to be established as part
of a distillation plant design.

You could even run it without a vacuum pump
until it shut itself down, drop and purge the gas
bubble, then "forklift" your pipes back up.

Does this use less energy per gallon produced?

Available on a desert island. Simple block and tackle would do.
Since the (de)compression rate is likely low, and the condensation
production rate is necessarily low, if you were not using animal
power, it could be *more* efficient. But you still have to supply or
waste a good deal of heat.

....
For reasonable efficiency real distillation plants
are multi-stage, where the latent heat of
condensation from one stage is used to boil
feedwater in the next stage, with up to 5 stages
being used in larger plants (in the days before
reverse osmosis made them uneconomical by
comparison).

Scaling is real problem too...

True, but one which can be solved by limiting brine
concentration and with chemical treatment and/or
periodic cleaning.

In the case of the marine vacuum distillation unit, they simply have a
constant flow of brine. Probably need to have a "tube within a tube"
to refresh the fluid near the boiling interface.

Sucessive stages operate at lower pressures, and
corresponding lower temperatures. The 1100 or
so BTU required to boil one pound of water can
thus boil up to 5 pounds of water instead.

You still need enough thermal gradient to get the
heat to flow through all those heat exchangers.
By using low thermal differentials between the hot
and cold ends you either reduce capacity to a
pittance or require huge and expensive heat
exchangers, in either case not competitive.
TANSTAAFL.

... a characteristic article ...
http://www.hcn.org/servlets/hcn.Arti...ticle_id=17136
This was not proposed to be a source of free
energy, violate the second law of thermodynamics,
or poke fingers in anyone's eyes.

As usual with this sort of article there are no
meaningful numbers included, perhaps because
a complete design analysis has not been
done.

More than likely omitted because:
- the reporter's eyes were glazing over, or
- they are working on a patent (since you can probably even patent
cheese now).

I think it was something that someone could do
fairly cheaply, to get drinkable water from salt
water. In other words "a graduate or
undergraduate college project".

Doing an analysis of this approach would be a
good student exercise. Not much point building
one without doing the anylysis first - a complete
engineering analysis including the selection or
design of all heat exchangers, mist eliminators,
pumps, piping etc., including both performance
and cost calculations. It is always cheaper to
optimize a pencil and paper or computer model
than hardware, especially for something so well
understood as heat transfer and fluid flow.

I just wonder if you get any improvement in
what is left in the brine, vs. what also
evaporates at the lower temperatures...

I doubt if that would be much of a factor. What
contaminants would be in the feedwater which
would evaporate less compared to water as
boiling point is reduced by low pressure?

Water does get involved in some azeotropes (some alcohols), so
depression of boiling point would not help there. And
thermodynamically, if one of the things you were trying to remove
became a solid at high vacuum (NaOH maybe?) it might help.

The biggest issue with distillate quality is
carryover; a fine mist of unevaporated water
droplets are inevitably produced by boiling
regardless of temperature, and while most
of these can be separated out, some always
make it through to the condenser. This is a
big issue where biological contamination
exists in the feedwater,

Such as natural brines...

requiring chlorination of the distillate to
make it potable. It might be possible to
eliminate this factor by eliminating the
boiling of bulk liquid, and instead
evaporating from a thin film of water flowing
over the heat exchanger surfaces, but I
doubt if it would be cost effective. Perhaps
it would be another good student exercise.

I wonder if the increased viscosity of droplets at lower temperature
would assist in more efficient removal?

Thanks for the discussion...

David A. Smith