Using dry ice in a cooler
March 6, 2010 4:07 PM   Subscribe

Can I keep canned drinks in a cooler with ice and a layer of dry ice at the very bottom without the drinks freezing?

I have one of those circular standing coolers that you normally see in gas stations that drains into the bottom half with a spout on the side for emptying it. If I put a 1 to 2 pounds of dry ice at the bottom and then a layer of normal ice over it (so the drinks would not be touching the dry ice), would I then be able to keep canned drinks in there without them freezing? The idea was that the dry ice would make the normal ice stay frozen longer. Also, I know it all depends on the setting, but would the normal ice or dry ice last longer? As the normal ice melts will it react with the dry ice to create fog?
posted by Deflagro to Food & Drink (11 answers total) 2 users marked this as a favorite
There's no way of knowing.

would the normal ice or dry ice last longer? Under the assumption of reasonable thermal contact between the two, the regular ice would remain solid as long as any significant amount of dry ice remained.
posted by Chocolate Pickle at 4:14 PM on March 6, 2010

The dry ice will keep the normal ice frozen for a long time quite nicely. You can also put stuff on top and not have it freeze, it's all about the ratio of dry to wet ice and the total amounts of both. I'm not sure if there's some rule of thumb, I'd go with trial and error. You need enough dry ice for the cold air rising up to keep the wet ice frozen but not so much that the temperature at the top is enough below zero (Celsius) to freeze. You can also go with an extra layer of insulation between the ice and the cans, maybe damp newspaper? I've done this with samples I need to keep cool.

I once left a chilly bin with a mix of dry and wet ice outside (could kgs of each) overnight in summer and the dry ice was mostly gone in the morning but the wet ice was still frozen solid, so having the wet ice melt isn't going to be a problem unless it's a really deep layer (in which case the top might melt but will freeze again when it trickles down towards the wet). Dry ice is about -78 degC while wet ice is 0degC, so the water doesn't have much of a chance here.

Also keep in mind that the dry ice will be subliming the whole time, i.e. turning to gas. This is because it's so much colder than even the wet ice around it, you'd need to throw it in a -80 freezer if you want it to stay frozen (in which case everything else would be a rock, heh). This is good because the cold air rises up through everything keeping it cold but can be bad because that's carbon dioxide it's releasing, something you don't want to build up in an enclosed space. When I transport dry ice in my car I have to have at least one window open, several of them when it's more than 5kgs (I generally have 7 or 10kg). The CO2 is the fog you may see, it's very cold so don't stick your hand in it. If you're somewhere even a bit ventilated then a couple of pounds isn't going to be a problem.

Summary: yeah this will work, try different amounts of wet ice until the temp of the cans is correct. And the dry ice should disappear before the wet ice starts to melt just be careful of the resulting cold CO2.
posted by shelleycat at 4:21 PM on March 6, 2010

Oh I should mention that the chilly bin I left outside was wide open. And it rained a bit at one point and the new water froze. Dry ice really does a good job of keeping the wet ice frozen.
posted by shelleycat at 4:24 PM on March 6, 2010

If I keep the dry ice in the plastic bag it comes in, would that cut back on the CO2 gas some?
posted by Deflagro at 4:36 PM on March 6, 2010

I took regular, rectangular ice chests to Bonnaroo (Tennessee in June) with dry ice on the bottom, wet ice next, and drinks/food on top. I raised the ice chest off the ground and threw a blanket over the top. Everything stayed cold and it worked great, except I did use too much dry ice and the food froze. You really don't need much dry ice for a circular cooler, I don't think, so start with a fairly small amount and adjust upward because it WILL freeze the stuff in your cooler. You don't need to worry about the gas if you're outside or keep a window cracked/open in the vehicle.
posted by raisingsand at 4:45 PM on March 6, 2010

I've never heard that carbon dioxide building up in an enclosed space is dangerous. Carbon monoxide is a different story.

Unless the claim is that the buildup of CO2 is so extreme that it drives out oxygen from the space it is evaporating into.
posted by dfriedman at 4:51 PM on March 6, 2010

The danger from CO2 is from displacement of O2 not from a competition with Heme binding like CO - so while not as critical, one should be aware of the increase in CO2 concentration which might happen in an enclosed space. This isn't usually a problem, but as was mentioned when transporting in a car, or working in an unventilated basement it is better to ensure some air exchange is taking place...

Keeping the dry ice in the bag will not reduce the production of CO2 - it needs to go somewhere. If the bag was air tight, it would expand until it popped or a hole formed to release the pressure. A similar effect will happen if the dry ice is placed in another air tight container - pressure will build until something be careful with any containers...
posted by NoDef at 5:11 PM on March 6, 2010

The danger from CO2 is from displacement of O2 not from a competition with Heme binding like CO - so while not as critical, one should be aware of the increase in CO2 concentration which might happen in an enclosed space.

Exactly. This is why I said an area even a bit ventilated is fine, and even than it would have to be pretty small and airtight for a couple of pounds to be a problem. Still worth knowing about though because there have been incidents where people have become groggy while driving with only a few kgs in the car (the guys who sell it to me always look out their window to make sure my windows are open as I drive away as at least one of these incidents was from their store) and it may be that Deflagro ends up with more or has to drive it around somewhere.

I also agree with NoDef about the bag, won't make any difference because the gas takes up more room than the solid and that extra bulk eventually has to go somewhere. The best way to reduce sublimation is to keep everything as cold as possible, so it should be pretty slow anyway with all the wet ice around. For these purposes the gas is good too, nice cold air circulating up through your chilly bin keeping everything a more even temperature.
posted by shelleycat at 5:54 PM on March 6, 2010

When the concentration of CO2 in the air reaches a few percent, it becomes difficult for your body to expire CO2 from your blood and you can suffer from respiratory acidosis. But if you're awake, you'll know there's a problem long before it reaches fatal levels because you'll be panting and you'll feel intensely uncomfortable.

I don't remember the exact concentration needed, but it's like 3-5%. (This has nothing to do with displacing O2.)
posted by Chocolate Pickle at 6:01 PM on March 6, 2010 [1 favorite]

No need for dry ice, check out this instructable for some ideas if your handy, it uses Peltier heat sinks. There's some other working ideas on the site, this one just got my curiosity since it was recent.
posted by hungrysquirrels at 11:13 PM on March 6, 2010

What Chocolate Pickle said about CO2 not being a displacement thing. If you get a burning sensation in your chest, you have a buildup issue. With pure nitrogen or argon, you might never realize you had a problem.

If the cooler is what I'm thinking of (about 2/3rds the size of a 55 gallon drum, the size of the peltier junction you would need for the cooler you're talking about, coupled with the amount of heat they generate and the amount of current they draw makes them not a really good idea for this purpose.
posted by Kid Charlemagne at 11:26 PM on March 6, 2010

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