| Topic: |
Science > Physics |
| User: |
"Externet" |
| Date: |
02 Feb 2005 06:06:06 PM |
| Object: |
How to distill water with bottles ?... |
Hi.
One 2L PET beverage bottle painted flat black exposed to sun, =BE filled
with 50~60=BAC warm seawater.
Another clear, empty 2L PET beverage bottle, upside down, coupled neck
to neck to the one mentioned above.
The necks coupler has a collection channel and an aquarium hose to
evacuate condensate running down the inside walls of the upper bottle.
The top bottle is kept at ~25=BAC ambient temperature under shade.
No venting holes at any bottle (are they needed?) other than the hose
itself.
Why it does not work?
A solar still desalinator does work well in a different enclosure on
the same principle and thermal conditions.
[Very easy to try by yourself]
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| User: "CWatters" |
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| Title: Re: How to distill water with bottles ?... |
03 Feb 2005 09:48:55 AM |
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"Externet" <externet@inorbit.com> wrote in message
news:1107388538.663578.148770@z14g2000cwz.googlegroups.com...
Why it does not work?
Probably not enough convection currents to transport the humid air from the
hot bottle to the cold one. Probably due to the narrow necks.
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| User: "Franz Heymann" |
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| Title: Re: How to distill water with bottles ?... |
04 Feb 2005 04:17:01 PM |
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"Externet" <externet@inorbit.com> wrote in message
news:1107388538.663578.148770@z14g2000cwz.googlegroups.com...
Hi.
One 2L PET beverage bottle painted flat black exposed to sun, ¾ filled
with 50~60ºC warm seawater.
Another clear, empty 2L PET beverage bottle, upside down, coupled neck
to neck to the one mentioned above.
The necks coupler has a collection channel and an aquarium hose to
evacuate condensate running down the inside walls of the upper bottle.
The top bottle is kept at ~25ºC ambient temperature under shade.
No venting holes at any bottle (are they needed?) other than the hose
itself.
Why it does not work?
For the same reason as that which makes it take weeks for a bottle
full of water standing in the sun with its top off to evaporate dry.
If your scheme worked, bird baths in the garden would be an
impossibility.
Franz
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| User: "Franz Heymann" |
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| Title: Re: How to distill water with bottles ?... |
04 Feb 2005 04:50:11 PM |
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"Franz Heymann" <notfranz.heymann@btopenworld.com> wrote in message
news:cu0s8t$cid$4@hercules.btinternet.com...
"Externet" <externet@inorbit.com> wrote in message
news:1107388538.663578.148770@z14g2000cwz.googlegroups.com...
Hi.
One 2L PET beverage bottle painted flat black exposed to sun, ¾
filled
with 50~60ºC warm seawater.
Another clear, empty 2L PET beverage bottle, upside down, coupled
neck
to neck to the one mentioned above.
The necks coupler has a collection channel and an aquarium hose to
evacuate condensate running down the inside walls of the upper
bottle.
The top bottle is kept at ~25ºC ambient temperature under shade.
No venting holes at any bottle (are they needed?) other than the
hose
itself.
Why it does not work?
My apologies for the incorrect attribution marks. Mycontribution
stared here :-
For the same reason as that which makes it take weeks for a bottle
full of water standing in the sun with its top off to evaporate
dry.
If your scheme worked, bird baths in the garden would be an
impossibility.
Franz
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| User: "Mark Fergerson" |
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| Title: Re: How to distill water with bottles ?... |
03 Feb 2005 12:36:50 PM |
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Externet wrote:
Hi.
One 2L PET beverage bottle painted flat black exposed to sun, ¾ filled
with 50~60ºC warm seawater.
Another clear, empty 2L PET beverage bottle, upside down, coupled neck
to neck to the one mentioned above.
Why is it upside down?
The necks coupler has a collection channel and an aquarium hose to
evacuate condensate running down the inside walls of the upper bottle.
Where is the condensate supposed to evacuate to? What temperature is
that place at?
The top bottle is kept at ~25ºC ambient temperature under shade.
No venting holes at any bottle (are they needed?) other than the hose
itself.
No, venting is bad.
Why it does not work?
Because the system is actually vented, and there's an insufficient
temperature differential for distillation to occur. Who designed the
fool thing?
Either that, or you're not waiting long enough.
A solar still desalinator does work well in a different enclosure on
the same principle and thermal conditions.
[Very easy to try by yourself]
Try connecting them directly neck-to-neck with duct tape, with no
additional plumbing. Set them both level:
_____________ ____________
| \ / |
| \ / |
| \____/ |
| ____ |
| / \~~~~~~~~~~~~~~|
| / \ saltwater |
|_____________/ \____________|
Put the saltwater bottle in full sun, shade the other. Wait. The salt
water will concentrate to brine, and the water it lost by evaporation
will condense in the other bottle because it's cooler.
This is how the British SAS (and other similar services) distill
drinking water from urine.
Mark L. Fergerson
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| User: "CWatters" |
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| Title: Re: How to distill water with bottles ?... |
03 Feb 2005 03:20:04 PM |
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"Mark Fergerson" <nunya@biz.ness> wrote in message
news:XauMd.6277$6u.3186@fed1read02...
Because the system is actually vented, and there's an insufficient
temperature differential for distillation to occur.
If his bottles are connected together by narrow necks I'm sure it's just a
lack of air flow between the two. The Humid air isn't getting from the hot
bottle into the cold one so it can't condense there.
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| User: "Mark Fergerson" |
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| Title: Re: How to distill water with bottles ?... |
04 Feb 2005 11:51:29 AM |
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CWatters wrote:
"Mark Fergerson" <nunya@biz.ness> wrote in message
news:XauMd.6277$6u.3186@fed1read02...
Because the system is actually vented, and there's an insufficient
temperature differential for distillation to occur.
If his bottles are connected together by narrow necks I'm sure it's just a
lack of air flow between the two. The Humid air isn't getting from the hot
bottle into the cold one so it can't condense there.
Could be. The SAS doesn't issue empty 2L soda bottles. Still, even
with the restricted necks 2Ls have, there'll be _some_ flow; it'll just
take longer.
Mark L. Fergerson
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| User: "Externet" |
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| Title: Re: How to distill water with bottles ?... |
06 Feb 2005 06:35:33 PM |
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Thanks for your interest, Mark.
The bottle intended to collect distillate is upside down for no
particular reason, they could be both horizontal, coupled neck to neck,
with the one containing seawater/undrinkable water to a level that
willl not spill into the empty one.
The intention is to create a nearly zero cost gadget to provide some
drinking water re-using PET soda bottles at the third/fourth world.
The condensate is either to be harvested at the 'empty' bottle in
batches or to be drained with an aquarium hose to a shaded 25=BAC
(ambient) storage reservoir.
Nobody has designed the thing. Tests and attempts have been done in
several ways, there is no condensation running on the inside walls of
the 'empty' shaded bottle, no matter how long the wait, with or without
the venting/collecting aquarium hose.
It has also been observed as a single upright bottle, the bottom half
painted flat black containing seawater, with barely a condensation
forming at the upper half, but not really running down the walls;
either capped or vented at any waiting times.
The ascii graphic does not show properly. Is it to be understood as the
suggested contraption being just horizontal ?
A flat tilted glass panel covering a shallow box does produce a
reasonable amount of condensate (~2L/m=B2=B7day), running to a collecting
trough with same thermal conditions described under same sun, but
presents difficulty in implementing in remote areas due to logistics,
materials, fragility, assembly and cost.
(And works without the benefit of the shade at the condensation side)
Miguel
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| User: "CWatters" |
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| Title: Re: How to distill water with bottles ?... |
07 Feb 2005 11:02:51 AM |
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"Externet" <externet@inorbit.com> wrote in message
news:1107736533.800591.188560@c13g2000cwb.googlegroups.com...
Nobody has designed the thing. Tests and attempts have been done in
several ways, there is no condensation running on the inside walls of
the 'empty' shaded bottle, no matter how long the wait, with or without
the venting/collecting aquarium hose.
The production rate will depend on how much water vapour you can move from
the hot side to the cold side. No movement = no output. I think you need to
cut the bottles in some imaginative way to encourage convection (air
circulation) between the two sections. They still need to be reasonably well
sealed together - no venting to the outside - you don't want to loose the
vapour created in the hot side just move it from the hot part to the cold
part.
You will also need to keep the cold side cold enough. Shade may not be
enough. As water vapour condenses it releases energy. Roughly the same
energy that was needed to create it! So it tends to warm up the cold side.
I'm convinced the narrow necks are the real problem. If there is any
convection air flow the narrow neck will mix the warm wet air with the cold
dry air trying to go back the other way.
Perhaps you can cut and join bottles with tape to make a vertical loop. Warm
one vertical side and cool the other. Get the air going round the loop.
A flat tilted glass panel covering a shallow box does produce a
reasonable amount of condensate (~2L/m²·day),
eg..
http://www.rotaryzone2324.org/cwip/ftp/PeriUrban%20Development%20Project-LowCostSanitation.doc
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| User: "Mark Fergerson" |
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| Title: Re: How to distill water with bottles ?... |
07 Feb 2005 02:29:52 PM |
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Externet wrote:
Thanks for your interest, Mark.
I appreciate minimalist demonstrations of physical principles, even
when they have practical applications. ;>)
The bottle intended to collect distillate is upside down for no
particular reason, they could be both horizontal, coupled neck to neck,
with the one containing seawater/undrinkable water to a level that
willl not spill into the empty one.
That's what my illustration was intended to, um, illustrate.
The intention is to create a nearly zero cost gadget to provide some
drinking water re-using PET soda bottles at the third/fourth world.
The condensate is either to be harvested at the 'empty' bottle in
batches or to be drained with an aquarium hose to a shaded 25ºC
(ambient) storage reservoir.
OK. The system ought to be sealed to keep the moist air from
condensing its water out somewhere it can't be collected or would take
longer to collect than if simply allowed to collect in the reservoir by
itself.
One wonders how many empty 2L PET bottles and aquarium plumbing
is/are available in the intended "market".
Nobody has designed the thing. Tests and attempts have been done in
several ways, there is no condensation running on the inside walls of
the 'empty' shaded bottle, no matter how long the wait, with or without
the venting/collecting aquarium hose.
Ah, OK. I mentioned the SAS version to illustrate that somebody has
done minimum-tech research and gotten usable results.
I still have trouble believing that the restricted necks of 2L
bottles makes that much difference; I'll have to grab a couple and see.
I live in well-insolated PHX AZ USA, but it's "winter" just now (in
quotes because low temps are in the 50F range) so it'll take a little
longer than in summer.
It has also been observed as a single upright bottle, the bottom half
painted flat black containing seawater, with barely a condensation
forming at the upper half, but not really running down the walls;
either capped or vented at any waiting times.
Temperature difference is crucial. Water vapor really likes to
condense on surfaces colder than it is.
The ascii graphic does not show properly. Is it to be understood as the
suggested contraption being just horizontal ?
Yep.
A flat tilted glass panel covering a shallow box does produce a
reasonable amount of condensate (~2L/m²·day), running to a collecting
trough with same thermal conditions described under same sun, but
presents difficulty in implementing in remote areas due to logistics,
materials, fragility, assembly and cost.
Yep.
(And works without the benefit of the shade at the condensation side)
That's because heat builds up under the glass (Greenhouse Effect)
which stays cooler than the volume beneath it.
Mark L. Fergerson
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| User: "Externet" |
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| Title: Re: How to distill water with bottles ?... |
07 Feb 2005 10:39:54 PM |
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Thanks again, Mark.
Your interesting suggestions/comments :
..."OK. The system ought to be sealed to keep the moist air from
condensing its water out somewhere it can't be collected or would take
longer to collect than if simply allowed to collect in the reservoir by
itself"...
From observations, some vapors do flow out (by venturi) from the hot
bottle to its vented neck. There is no vapor flow towards a condenser
if sealed. The flat panel distiller works aparently by the condensing
surface-to-evaporating surface close proximity.
If this bottle contraption ever works, the trick has to be allow
transportation of the vapor towards a condensing surface where the
condensate is immediately drained to a reservoir, venting the air that
has already lost most of its humidity. Like a water vapor distillation
column in a laboratory, where steam flows due to energetic boiling.
..."One wonders how many empty 2L PET bottles and aquarium
plumbing is/are available in the intended "market"...
This has no commercial interest. By trying to use zero cost materials
available to the 'consumer', there is no way to profit, it is open to
the needy.
Several dozen of these contraptions yielding hopefully 100cc/day each
on a backyard is no problem in remote locations.
..."I live in well-insolated PHX AZ USA, but it's "winter" just now
(in quotes because low temps are in the 50F range) so it'll take a
little longer than in summer"...
A colder condensation side may also produce about the same temperature
differential as in summer. The water will be less warm, but the
condensing more effective.
..."That's because heat builds up under the glass (Greenhouse
Effect) which stays cooler than the volume beneath it"...
The same greenhouse effect happens in bottles.
If you happen at some point to give it a try with pre-heated water in a
PET bottle instead of waiting for summer climate, and this thread fades
in time, I would appreciate any comments to: externet @ inorbit . com
I was unable to open your link provided.
This link below sometimes works, shows a contraption claimed to work:
http://www.eurovinil.it/english/difesa/defence.htm
Miguel
California
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| User: "CWatters" |
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| Title: Re: How to distill water with bottles ?... |
08 Feb 2005 03:33:00 AM |
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Not sure if this ASCI art will work but this is what I would try...
__________
| |
| ______ |
| | | |
| | | |
| | | |
| | | |
| |______| |
| ___ |
|____| |_|
The dirty water goes in the shallow try bottom left.
Heat the waters and left hand vertical tube.
Cool the right hand side.
Collect clean water in smaller container on right hand side.
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| User: "Externet" |
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| Title: Re: How to distill water with bottles ?... |
10 Feb 2005 04:09:32 PM |
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Hi.
Just to attach a more functional link about a similar contraption...
http://www.speedplastics.co.uk/solarstill.html
Miguel
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| User: "CWatters" |
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| Title: Re: How to distill water with bottles ?... |
11 Feb 2005 03:49:36 PM |
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"Externet" <externet@inorbit.com> wrote in message
news:1108073372.323107.141340@l41g2000cwc.googlegroups.com...
Hi.
Just to attach a more functional link about a similar contraption...
http://www.speedplastics.co.uk/solarstill.html
Interesting photo. I guess that dome is double walled? I couldn't work out
how it would remain inflated but yet open at the bottom.
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