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Old 10-05-2011, 10:52 AM
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Default Evaporative cooling



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I ran across this while looking at other links. On one hand it sounds like it will work. On the other hand I have my doubts.

I don't have two pots. Is anyone interested in giving this a try and recording the inner temperature?

http://www.shtfplan.com/emergency-pr...ation_09252011


"SHTF Survival: Clay Pot Refrigeration
by Tess Pennington

Have you ever wondered what our ancestors did without refrigeration? How were they able to prevent their food from spoiling? Some of our ancient civilizations did in fact have refrigeration and used simple items they had on hand to create it.

The zeer, or clay pot refrigeration keeps food cool (icy cold) without electricity by using evaporative cooling. Essentially, a porous outer earthenware pot, lined with wet sand, contains an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed. The evaporation of the outer liquid draws heat from the inner pot."
Old 10-05-2011, 11:30 AM
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I am guessing they are using "icy cold" as a subjective term rather than truth.
I have however used evaporative cooling combined with convection to cool a room down by 15° but it failed as the humidity went up. Maybe in a dry enough and cold enough environment you could achieve icy cold but mid summer I'm betting cool to the touch is the best that can be achieved small scale.
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Old 10-05-2011, 09:58 PM
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I lived in kenya, east africa when I was a kid... parents were missionaries. We had one of these pots that we used to keep drinking water cool. Basically an unglazed pot filled with water on a metal stand to maximize surface area.

In kenya with almost no humidity it worked great, it was not "ice cold" but it was not something you would want to dump down your pants. I remember taking a shower, putting on my clothes without drying off and walking 200 yards to my room arriving completely dry.

It does not work so well with humidity. I tried it here in Arkansas and it got maybe 10 degrees cooler than ambient temperature.

Another thing to consider though is that if you take the average of the hottest it generally gets and the coldest it gets in your area it is about that temperature all year round if you dig down 6 feet or so. Here that comes out to about 65 degrees. If you bury a bunch of thermal mass (like 55-gallon drums of water) then pump it through a radiator with a fan you can make a cheap geothermal cooler. I am actually planning on doing this in a couple of weeks... going to take a while to dig a big hole.
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Old 10-07-2011, 07:54 PM
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It does work, I tried it out here in Okla. this summer. The best result was on a 101 F day with 16% humidity. The temp inside the pot was 72 F. At 20% humidity the temp was in the mid 80s.

Would work well in a very dry climate.
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Old 10-09-2011, 03:43 AM
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Saw this on one of the "learn me" channels.
It was one of the things that encouraged me to learn more about Heat.

The sand creates a "heat vacuum" so the interior pot loses heat.

What's really outstanding is that our ancient parents figured this out.
I'm beginning to think that they were a heck of a lot smarter than we are.

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Old 10-09-2011, 04:49 AM
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Quote:
Originally Posted by DaveMc View Post
Saw this on one of the "learn me" channels.
It was one of the things that encouraged me to learn more about Heat.

The sand creates a "heat vacuum" so the interior pot loses heat.

What's really outstanding is that our ancient parents figured this out.
I'm beginning to think that they were a heck of a lot smarter than we are.
Oh yeah, no doubt about it.
Most tech is either rediscovered, batteries are an example, or improperly attributed to, like the blast furnace.
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Old 10-09-2011, 06:28 AM
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Quote:
Originally Posted by bhoult View Post
I lived in kenya, east africa when I was a kid... parents were missionaries. We had one of these pots that we used to keep drinking water cool. Basically an unglazed pot filled with water on a metal stand to maximize surface area.

In kenya with almost no humidity it worked great, it was not "ice cold" but it was not something you would want to dump down your pants. I remember taking a shower, putting on my clothes without drying off and walking 200 yards to my room arriving completely dry.

It does not work so well with humidity. I tried it here in Arkansas and it got maybe 10 degrees cooler than ambient temperature.

Another thing to consider though is that if you take the average of the hottest it generally gets and the coldest it gets in your area it is about that temperature all year round if you dig down 6 feet or so. Here that comes out to about 65 degrees. If you bury a bunch of thermal mass (like 55-gallon drums of water) then pump it through a radiator with a fan you can make a cheap geothermal cooler. I am actually planning on doing this in a couple of weeks... going to take a while to dig a big hole.
Never thought about barrels. I have an old cistern outside the back door that could be fitted with a coil of copper or other pliable tubing and the water circulated through it. May give it a thought or two.
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Old 10-09-2011, 09:21 AM
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Quote:
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Never thought about barrels. I have an old cistern outside the back door that could be fitted with a coil of copper or other pliable tubing and the water circulated through it. May give it a thought or two.
My pit is now about three feet deep after two days of digging (couple of hours each day). When I get done I will bury probably four 55-gallon drums or the equivalent. I already have a couple of radiators off of old cars.

I will report the end result on my blog (minimlaintentions.com) hopefully in a few weeks... or whenever I manage to get it done. I have high hopes for this one, AC is the primary thing keeping me on the electrical grid.
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Old 10-10-2011, 05:02 AM
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Flowing water is generally 55 degrees. Toss your stuff in a bucket, tie a rope to it and toss it in a river. That will keep it cool.
Old 10-10-2011, 05:25 AM
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Quote:
Originally Posted by REM View Post
I ran across this while looking at other links. On one hand it sounds like it will work. On the other hand I have my doubts.

I don't have two pots. Is anyone interested in giving this a try and recording the inner temperature?

http://www.shtfplan.com/emergency-pr...ation_09252011


"SHTF Survival: Clay Pot Refrigeration
by Tess Pennington

Have you ever wondered what our ancestors did without refrigeration? How were they able to prevent their food from spoiling? Some of our ancient civilizations did in fact have refrigeration and used simple items they had on hand to create it.

The zeer, or clay pot refrigeration keeps food cool (icy cold) without electricity by using evaporative cooling. Essentially, a porous outer earthenware pot, lined with wet sand, contains an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed. The evaporation of the outer liquid draws heat from the inner pot."
If you live in a dry climate, it's also worth looking into a Coolgardie safe.
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Old 02-12-2012, 11:43 PM
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I just completed an experiment with a homemade "Zeer Pot".

with just a little airflow around the pot and moderate humidity in the air I got 6 to 7 degrees cooling from the pot. With lower humidity and a breeze around the pot I got 9-11 degrees of cooling.

My video about the build and trials:
Old 02-13-2012, 09:41 AM
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Thanks CC!

I'd about given up on the idea due to the high humidity. Even though it doesn't work as well as it might in a drier climate those precious degrees are worthy of working on.
Old 02-15-2012, 12:41 AM
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evaporation cooling is how an air conditioner works or how you cool your body.

evaporation is a cooling effect

research heat exchange hot to cold
Old 02-16-2012, 10:19 AM
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I made one here in East Texas. It made a few degrees difference, but its too humid in the piney woods, even in the driest summer on record. Might work better in desert climates.
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Old 02-16-2012, 03:17 PM
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Kind of off topic,but in Afghanistan we obviously had no way to refrigerate our stuff. So we would take old socks and hang them from the posts and put bottles of water in them. Then you pour water on the sock and make sure it stays damp. It actually would get pretty cold right near the end of the day. Id guess around 50-60 degrees. This was in 130-140 degree weather so it could possibly get alot colder here.
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Old 02-18-2012, 02:47 PM
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We tossed our cantenes for desert water bags made of canvas. Cool drinking water in 120 + degree heat as long as you kept the outside wet/damp.
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Old 02-22-2012, 11:36 PM
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Quote:
Originally Posted by REM View Post
Thanks CC!

I'd about given up on the idea due to the high humidity. Even though it doesn't work as well as it might in a drier climate those precious degrees are worthy of working on.

You're welcome.
I think those few degrees are worth the effort as well. In a real serious situation, you might get your foods/medications to last a few days longer which can save you having to make multiple trips to forage for replacements. That conserves resources like drinking water, calories, bartering materials, maybe fuel if you still have it.

Being able to avoid spending time foraging might allow you to spend less time having potentially dangerous encounters with nature or other people. More time to protect your own people and assets. Fewer trips to the foraging site means less chance that' you 'll educate others about those resources. Might help you to avoid becoming a predictable target for people (in the foraging environment) who might want to steal from you what they know you'll be coming out to forage. By not being a predictable target, you weaken the predators.

In a way, evaporative cooling can become a force multiplier.
Old 07-05-2012, 08:16 PM
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Living in Phoenix, I am excited to try this out! Can anyone tell me if a breeze is a requirement?
Old 07-05-2012, 08:28 PM
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Evaporative coolers are not much good once the dew point gets above 55 degrees.
Old 07-05-2012, 08:39 PM
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Quote:
Originally Posted by billt460 View Post
Evaporative coolers are not much good once the dew point gets above 55 degrees.
Well that sucks considering we are now in the monsoon season. Thank you for the heads up, now I wont be in the back yard cussing at some clay pots trying to figure out how I screwed up a simple process!!!
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