# Do the homemade air conditioners with frozen bottled water really work or is it not worth the trouble?

With 10 litres of frozen water you can cool more than 300 m3 of air 10 degrees.So a 100% insulated room with no gear in it of 10 x 15 meters, 3 meters high.

In practice, the room will continually lose cold and you’ll have to cool down all the walls and stuff In it, so if all the ice is defrosted really No 10 degrees colder.

But with a few litres of ice you can actually produce cool air for a very long time.

I propose an extension: spray the melting water into the air flow.That gives more than 7 times (!) so much cooling power!

With a small snake pump on this thing (pair of euros in the Hornbach) instead of the manual control, and a frozen reservoir of half a litre of water where the air is sucked along, you would be able to cool a staggering 130 cuub air 10 degrees!

(If you omit the freeze the effect is slightly less…)

The Heat capacity C indicates the amount of energy to allow a material to rise 1 degree in temperature; The unit is thus Joule/Kelvin.

In formula is the heat that must be fed to allow the material DT to rise in temperature: Q = C * DT [Joule.

Ice 2200 J/kgK

Water 4817 J/kgK

Freezer:-20 degrees

Room temperature: 25 degrees

Water bottle: 2 litres

From-20 to 0 = Delta T = 20

20 * 2 * 2200 = 88000 J

from 0 to 25 = Delta T = 25

25 * 2 * 4817 = 240850 J

In Total, you thus withdraw 328850 J to the room.

Say it takes 90 minutes for the bottle of water from ice to 25 degrees has gone.

90 * 60 = 5400 seconds.

Then you have a cooling power of 328850/5400 = 60.89 J/s = Watt

For comparison, a small air conditioner quickly does 2500 watts so you need 41 2 liters of bottled water to match a small air conditioner.

1 M3 air weighs 1.2 kg and the specific heat of air is approx 1kj per kg K. Say the room 6 meters long is 4 meters wide and 2 high = 48m3

To allow 1M3 1 degree to cool, you need 1200J.So for the air in the room to let cool you need 1200J * 48 = 57600J You need J so you can let the room 5.7 degree cool.

Seems a lot but the room does not only consist of air but also of concrete, furniture and heat sources.So the temperature in the room will not noticeably sink.

Roughly speaking, a human as a heat source is about 100W watts. So you better leave the room than to put a bottle of ice for the cooler;) And then we ignore the fact that the engine of the fan is also a heat source.

It might work but you need a lot of bottles in series switched.And stay low..

The principle seems to me to be reasonably accurate, but in this performance a little bit of a lomp.You can also just put a whole bunch of frozen bottles out of your fridge in your room, possibly blowing a fan against them. Possibly it can be frozen oil too, which works even faster but is worked out before I think. Water takes heat slower or decreases, so also cold.

Moreover, I do not know to what extent this will have a positive or negative effect on the humidity in the room.Conversely, the humidity will in any case affect the efficiency of cooling. Edit: Below my version, so I’m using the current Tropendag to test the principle. I filled five bottles yesterday evening, which I activated around 13.30 with a fan.

My test

I consciously didn’t fill the five bottles completely, kept a little squeezed while tightening the caps, put them in the freezer during the night on their side to avoid chance of popping bottles.About five hours later around 18.15 I conclude that the temperature has not fallen, half a degree higher to 26.5 celcius. I find it difficult to draw conclusive conclusions.

The fan blew up to my bed, which was pleasant last hours, sweating I did only after physical activities, so at rest it was pleasant.But the variables are a lot: natural change, a computer that was running all afternoon, a house that is cool in nature, the degree of air flowing under doors. And and how pleasant was it with just the fan?

I would conclude: do not benefit it then do not harm it.Maybe have some more bottles trying or a smaller space? This was about 20 m2.

Controlled nuclear fusion? Sun and wind? Geothermal?

Answer from Cornelis Zandbergen on how many different FTL systems are there in science fiction?