Wet towel trick - are we just fooling ourselves?

[olllllo]

Reading about zeer pots and solar cooling...

http://permaculturetokyo.blogspot.com/2006/11/passive-cooling.html

It’s called a zeer pot, or the pot-in-pot and was developed by Mohammed Bah Abba, who realized that he could put the second law of thermodynamics and transpiration to work for him. The zeer pot, is actually two earthenware pots ...

The smaller pot is put inside the bigger pot, and the space in-between them is filled with sand. The sand is made wet with water (twice a day) and a wet towel is put on top of the two pots to keep warm air from entering the interior. As water in the sand evaporates through the surface of the outer pot, it carries heat, drawing it away from the inner core, thus cooling the inside of the inner pot which can be filled with soft-drinks, water, fresh fruit, vegetables or even meat. A damp cloth placed on top keeps the inside pot away from hot air. In this way, fresh produce can be kept for long periods of time without the need for electricity, or camping coolers made high embodied energy.

Tomatoes and peppers will last for up to three weeks, and African spinach, or rocket, which normally would spoil after just a day in the intense African heat, can and will remain edible for up to twelve days. Eggplants will keep for up to 27 days instead of three. It can even be used for storing sorghum and millets for a long time since it protects from humidity, thus preventing fungi from developing.

The zeer will keep water (and other liquid beverages) at about 15 degrees Celsius [59° F] (maybe acceptable for Guinness), and even meat can be kept fresh for long periods.

 

[GilaMinumBeer]

Never worked too well for me.

 

[Stratotankard]

<pedant mode on>

Water vapor transforming to liquid water during precipitation events releases the energy it absorbed while being evaporated and this provides a heat source for clouds.

</pedant>

My meteorology professor used to talk about this. He loved to talk about the 680 calories* per gram of water vapor in latent energy or as he put it "2 Snickers Bars per gram." That's a LOT of energy and one reason why thunderstorms are so powerful.

*I know we're talking different calorie measurements here, but it was a good analogy and helped me remember it for a test.

Terje

 

[Cugel]

My meteorology professor used to talk about this. He loved to talk about the 680 calories* per gram of water vapor in latent energy or as he put it "2 Snickers Bars per gram." That's a LOT of energy and one reason why thunderstorms are so powerful.

*I know we're talking different calorie measurements here, but it was a good analogy and helped me remember it for a test.

Terje

That's right - food calories are different from regular "energy" calories bizzare as it may seem.

One "food calorie" = 1000 calories, or a kilocalorie. Our 2000 "calories" a day diet is actually a 200,000 calorie per day diet.

Try and see what happens if Nestle put "2,000 calories per serving" on a package of chocolate

 

[Schlenkerla]

I think the OP bought into it....

For your amusement......

Whipping a dead horse"

The tribal wisdom of the Dakota Indians, passed on from generation to generation, says that when you discover that you are riding a dead horse, the best strategy is to dismount.

The Federal Govt. management policy dictates that a wide range of much more advanced strategies be employed, such as:
1. Buying a stronger whip.
2. Changing Riders.
3. Threatening the horse with termination.
4. Appointing a committee to study the horse.
5. Arranging to visit other countries to see how others ride dead horses.
6. Lowering the standards so that dead horses can be included.
7. Reclassifying the dead horse as "living, impaired."
8. Hiring outside contractors to ride the dead horse.
9. Harnessing several dead horses together to increase the speed.
10. Providing additional funding and/or training to increase the dead horse's performance.
11. Doing a productivity study to see if lighter riders would improve the dead horse's performance.
12. Declaring that as the dead horse does not have to be fed, it is less costly, carries lower overhead, and therefore contributes substantially more to the bottom line of the economy than do some other horses.
13. Rewriting the expected performance requirements for all horses.
14. Promoting the dead horse to a supervisory position.