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willem2
#6
Feb13-13, 02:38 AM
P: 1,398
I think it's supposed to work by evaporation. The air in the freezer is probably 100% saturated at -18C, but the water (or ice) will rapidly evaporate while it's still at a temperature above this. The temperature of the outside of the bottle will probably rapidly decrease to 0C, and this will take longer without a towel, because the air around the bottle doesn't conduct heat well.
Freezing of the water produces heat, but evaporation uses up about 8 times the amount of heat that freezing produces.