Evaporator... sort of....

[NoNickName]

http://www.scienceinafrica.co.za/2004/september/refrigeration.htm

[US Iceman]

A clever use of an old idea first used by the Arabians. I have seen similar pictures where they used to make snow on the ground by using night sky radiation and wetting of the adobe walls of buildings.

Thanks for posting that link. I enjoyed reading it. :D

[Dan]

The zeer can also keep water at a temperature of about 15 degree Celsius. "In the camp, it is used as a water pot, to store relief items, and even as a clothes cupboard," he says.

I will abstain from asking what the SEER of a ZEER is... had to say that.:)

But it would be interesting to see this process plotted out on a Psychrometric chart. I am not sure I follow the thermodynamics. Is this simply an advantage of the low wet bulb using a ballast?


A clever use of an old idea first used by the Arabians. I have seen similar pictures where they used to make snow on the ground by using night sky radiation and wetting of the adobe walls of buildings.

Iceman, you are beginning to remind me of the faceless neighbor in "Home Improvement."

How about demonstrating THAT on a psych chart? :)

[Peter_1]

It let us also think about the great poverty still excisting in our world. We must be very happy that we 're born in the 'right' country and that we can take a pint out of the fridge.

[afeef]

interesting artical
so this is refrigeration befor ferion and compressors and electricity
back to nature to solve there problems,
very smart
thanks

[guapo]

till now the province without electricity use this as water cooler, here in the philippines.

[US Iceman]

Dan,

I would refer you back to a previous post on the snow and ice making in warm climates:
http://www.refrigeration-engineer.com/forums/showthread.php?t=4713&highlight=night+radiation

This is not so much evaporative cooling, although it does contribute to the overall effect. On a clear night sky water can freeze even when the air temperature is above 32F (0C). The heat is radiated from the water into the open sky.

Here is an interesting link:
http://www.kilty.com/freeze.htm

I wish I had the pictures to show you this.;)

The Zeer works on the principle of evaporation. The clay pots are porous, so they continually leak water at a very slow rate. My guess is the area where the sand is located between the two pots is filled with water.

The water seeps through the outside pot and cools. I suspect the sand acts as a ballast (more mass) to provide continued cooling throughout the day for the interior clay pot.

If the clay pots were glazed this would not work. The glazing seals the pores of the clay, so no water will seep through.

In areas where the humidity is very low the evaporation process is quite high. So, when water evaporates it does so at the wet bulb temperature.

[jamcool]

Here in the island we have being doing the "sand trick":) and other stuff for years we would also bury ice in the sand at the beach, sand makes a good insulator as was said,another trick :) is to get a drum, fill it with ice and then add coarse salt to your drum of ice place your beers in the drum and if not carefull u can be pulling ice cold beer with ice in it out of the drum:)

[Dan]

I would refer you back to a previous post on the snow and ice making in warm climates:

Thanks, Iceman. I miss a lot of interesting threads. Just saw your post on ice and started to read the article, but work has intervened. I am not good at the math, so I struggle with the explanations. I enjoy pondering the intricacies of refrigeration, regardless.

[US Iceman]

...fill it with ice and then add coarse salt to your drum of ice...

The same way we make homemade ice cream. It's delicious.:D

Dan, some of the math can be a little hard sometime. I have some problems with it now and again. The main thing is being aware of something and just plain old reading about it.

The pictures I wanted to show you are not here yet. I called a friend who took the pictures on one of his "safaris" many years ago. When I get them, they will be posted.

One picture he did not get is their fancy ice removal tool... A burro pulling a wooden scraper across the ground.;)

[Dan]

Thanks, Iceman. If I can get the ice, I know how to do the rest. But...

Radiation, conduction, and convection. Radiation is the mystery for me. Black bodies don't have to be black, emissivity comes into play.... Are what we call radiators really radiators? Why do we use the color black and then reconsider flesh as a black body because some circumstance becomes more extreme?

Also, would I be wrong in saying, after a quick read of some of the articles, that radiant heat transfer can only gain an advantage equivalent to 5 or 10 deg F over and above what dew point temperature can achieve in heat transfer? In other words, that you cannot make ice in 55 deg F air, but it might be possible in 40 deg F air?

Or am I missing the point entirely, as I am wont to do?