thermal radiation question: does aluminum foil wrap keep dry ice colder?

Question

Application: Keeping food in a cooler cold with dry ice, for several days.
We don't want the food getting too cold; we want to insulate the dry ice within the cooler to keep the food below freezing (of water; 0 Celsius), but no colder.
On the one hand, putting the dry ice in cooler with the food after wrapping it in foil, which is an excellent heat conductor, creates a path for heat from hot spots on the cooler's inner surface to the entire surface of the dry ice, to make it sublime faster.  On the other hand, the aluminum foil is a good http://en.wikipedia.org/wiki/Radiant_barrier.  
My feeling is that at freezing temperatures, most energy transfer will be via conduction, and little will be via 
http://en.wikipedia.org/wiki/Thermal_radiation or convection.  I figure at 0, there's very little thermal radiation (see graph on that wikipedia page.)  But that's a gut feeling of an ex-physics student.  Overall energy levels are much lower, so maybe I'm mistaken.  

If no one answers, I guess I could try an experiment.  That would be pretty easy.

Oh, and we'll be using other insulation as well (I'm thinking foam or small-bubble bubble-wrap), raising the cooler, keeping it shaded...

Anonymous · Accepted Answer

what about wrapping the dry ice in paper towels and putting it in a ziplock bag - you don't want condensation from other items touching the dry ice, do you? best way to do it is to experiment for yourself!

Vernalization · Answer

You can use foil however it acts as a conductor rather than an insulator if it is direct contact with the ice and may actually speed up its sublimation... However if you use an insulator such as paper or plastic wrap and then the foil shiney side in it will act like a reflector to the cold and perhaps if the insulator(s) are able to seal the co2 from having the pace to form gas.and or cover the ice adequately it may produce the desired results.. The only way prove this though is to test it by weight with 2 pieces separately in the same container...

My personal experience is wrapping it in industrial quality poly vinyl wrap with many layers with paper bag folded tightly in another plastic bag in a large cooler and in a small one wrapped the same kind of wrap with a special kind of mylar that is very thick heavy duty that I happen to have which works extremely well...One thing  though very important, make sure if using anything airtight that you poke a very small hole to vent it otherwise it will blow  up and pop the bag eventually and can make a mess....

Max · Answer

Hmm, if you want to keep food cool (at about -10C) using dry ice (at -56.4C) for a long period of time i think you can forget it. The dry ice will remain -56.4 defrees (like ice remains 0C when melting). The problem is, if you have a very good insulated container for both food and ice, it will eventually drop the temperature to 56.4 degrees anyway. the temperature of the food will be a function of dry-ice temperature, surrounding temperature, total container isolation and dry ice insulation. My guess is, to find equilibrium at which food is about -10degrees, the heat absorbed by the dry ice is so high, it'll sublimate to fast.

did you get my thought?

good luck

? · Answer

what about wrapping the dry ice in paper towels and putting it in a ziplock bag - you don't want condensation from other items touching the dry ice, do you?  best way to do it is to experiment for yourself!

Anonymous · Answer

I use aluminum foil for just about everything other than microwave. if its something your putting in frig use foil, it gets colder quicker, plastic wrap hold moisture and tends to make food saggie.

thermal radiation question: does aluminum foil wrap keep dry ice colder?

5 Answers