can aluminum foil keep things cold and what are the properties that allow it

why is aluminum foil good at keeping things cold
Dr anonymousAsked:
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JohnConnect With a Mentor Business Consultant (Owner)Commented:
You would have to have insulated aluminum foil (3 layers with the middle layer being an insulator.

At best it would be temporary.

"Cool bags" have plastic outer, insulation, then foil liner and they are good to get ice cream home from the supermarket.

When we travel to our cottage we use a cooler that is all metal insulated inside and frozen cold packs inside that. Good for the 3 hour journey.

Anything you purchase that is any good will give you a temperature / time rating.
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Dr. KlahnConnect With a Mentor Principal Software EngineerCommented:
I don't know where you got that information, but aluminum foil is most definitely not good at keeping things cold.  Aluminum is an excellent conductor of both heat and electricity.  As such in a quiescent environment it quickly attains the temperature of its surrounding environment, and if it is in contact with any source of heat it will quickly assume that temperature.

It's true that it is commonly used for wrapping food in a refrigerator, but that's because it is convenient, relatively inexpensive and holds its shape.
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serialbandConnect With a Mentor Commented:
The only way Aluminum foil will keep things "cold" is by working as a shield, if you place it between the object you're trying to keep cold and the heat source, such as the sun.  You can't have it in direct contact.
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serialbandConnect With a Mentor Commented:
The aluminum can work to block radiant thermal energy as one of the layers, but it doesn't work for convection or conduction.  The insulator does the majority of the work at preventing thermal transfer in most coolers, especially since the inner foil layer is in contact with the frozen objects, negating the benefit of the radiant block.

If you have a cooler with metal, It's mostly likely there for structural integrity, no as a layer for insulation.
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JohnConnect With a Mentor Business Consultant (Owner)Commented:
As I noted above, there is insulation in the cooler. The metal is the jacket and yes, keeps it strong. I did not suggest metal was an insulator, rather that the cooler is insulated. The idea with cold packs works very well.
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Dr anonymousConnect With a Mentor Author Commented:
thanx duded
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nobusConnect With a Mentor Commented:
the only way it keeps things cool is by reflecting the outide heat radiation imo
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BillDLConnect With a Mentor Commented:
I completely agree with Dr. Klahn, serialband, and nobus.

In terms of refrigeration you are not "keeping the cold in", you are keeping heat out.  If you want to get technical, there really is no such thing as "cold".  Although you will hear expressions like "close the door and don't let the cold air in", this is not scientifically correct, you are letting the warm air out.  Something feels hot or warm because it contains energy that is a measurable.  You can only measure an amount of heat, but there is no measure of cold.  You are only measuring the amount of energy that creates heat.  Something feels cool or cold because it contains less energy than something that feels warm or hot.  As Dr. Klahn said about heat transfer:
"As such in a quiescent environment it quickly attains the temperature of its surrounding environment".
In nature everything tries to balance itself out, whether it is water or air pressure, chemical concentration, or heat.

In direct context with the question, there are 2 forms of heat transfer: radiated and conducted.  Heat can also be transferred by convection, but it isn't as relevant to the aluminium foil example as the other two.  Other experts have already mentioned that heat will be conducted through the foil when it is in direct contact with an object.  If the object wrapped in foil was warm this would be a more accurate assessment because the heat energy from it would be conducted, but in this case we have an object that is "cold", which is to say that it it contains less energy than the air or other objects on the other side of the foil.  serialband and nobus have covered an important consideration when the foil is keeping out heat.  It will reflect some of the heat away from the object that is wrapped in foil.
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BillDLCommented:
Thank you Dr anonymous
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Dr anonymousAuthor Commented:
no prob
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