Dry Ice in freezer to keep cold during outage?
Posted by Sh3rlock_Holmes@reddit | preppers | View on Reddit | 38 comments
If I were to buy dry ice and put it in my freezer a day or two before a hurricane was to come… would it keep my freezer items cold if the power goes out for 2-3 days if I dont open the freezer door? Thoughts?
Mostly prepping for Wednesday.. Tropical storm headed this way.
OnTheEdgeOfFreedom@reddit
Some people seem to be missing basic physics, or haven't worked with dry ice.
A small piece of dry ice in a freezer - like the size of a roll of quarters - will keep the whole freezer cool for quite a few hours. It's not going to sublimate off real fast for the same reason that if you drop a piece of dry ice in a bowl and leave it on the counter, most of it is still there an hour later. (As some boils off it cools the air around it to a very low temperature, and air is a decent insulator.) And yeah, dry ice is less dense than water ice but it's also far colder; it's got about 3 times the capacity of water ice to sink heat by volume.
There are down sides. If you put too much in a freezer, some gas pressure will build up as the dry ice evaporates, which could pop the door open. If your freezer door doesn't close by itself, and many don't, that's bad. But if you open the freezer a couple times a day to take food out, and in a potentially long power fail you do want to start eating your frozen foods, you'll solve the pressure problem.
Personally I'd move the food to a camping cooler, the cheap kind that's not all that air tight, and put the dry ice in there as well. Now there's no risk of anything popping open; and no, a small quantity of dry ice isn't going to suffocate you.
Now, if you have a chest freezer, the usual suggestion is to put the food in and then use water ice to fill it up as much as possible. Water ice is cheap to make in quantity. And chest freezers generally close pretty tight, so a lot of dry ice boiling off really could cause the lid to pop open pretty hard. Water ice for the win in this case. But typical refrigerator freezers don't have much space available, so you want to spend that limited available space on the best heat sink you can get, and that's dry ice.
CarbonGod@reddit
I dunno about that. I lost 10# of dry ice in a -40 freezer overnight. One that was running....(logistics in shipping, I had to get the ice the day before my shipment went out)....
A roll of quarters will NOT keep a normal sized freezer cool for any amount of time.
OnTheEdgeOfFreedom@reddit
|I dunno about that. I lost 10# of dry ice in a -40 freezer overnight.
How? I once used a 3# chunk of dry ice on a ground hornet's nest outside, one New England summer. Drop it on the wasp hole, put a plastic bowl over it upside down, drop a towel over that and wet the towel. I checked the ice 3 days later, after an 80F day. The towel was still frozen to the ground, and there was still a pound left under the bowl.
All I can figure is that you had a lot of air current blowing over the ice. Under the bowl, there was no air movement. and the cold stayed put. That's my best guess.
Jaicobb@reddit
If your freezer was running it was heating the dry ice to 28 or whatever causing it to boil away. If you had unplugged it, I'm guessing, the much much colder air would not have cycled through the freezer and stayed very very cold.
CarbonGod@reddit
But it's based off a thermostat/et al. If it gets below the -40 set point, it will shut off. The dry ice, as you say, would then allow it to get colder. Same with a normal freezer. It won't "boil away" (sublimation dude......), it will just get colder. But the energy density of the dry ice is not as you said it would be. If so, you wouldn't need a giant amount of dry ice to cool an object!!!
----_____--_____----@reddit
Not as well as water would. Fill it with water ice instead of CO2, it has more than twice the specific heat capacity. That means it will withstand over twice as much total heat for the same weight. So fill it with bottles of water or ice packs and stuff, it'll last alot longer.
nayls142@reddit
The sacrificial cold substance needs to be colder than the desired temperature of your food. This is why dry ice can maintain frozen goods, and ice can keep things refrigerated.
If your freezer has a substantial mass of ice plus food, and the whole thing is at 2 degrees F before the power outage, it will slowly warm as heat conducts though the insulation of the freezer. The ice and frozen food will continue to stay frozen as they warm to 32F, then they will begin to melt. Yes the ice will absorb lots of thermal energy as it melts, but it can no longer prevent frozen food from thawing.
Dry ice at -109F will keep the overall temperature of the freezer well below 32F until it's fully melted, so the frozen food actually stays frozen.
I've validated this on numerous camping trips.
----_____--_____----@reddit
No it doesn't. It only needs to be colder if you're trying to maintain that temperature, we are not. We are trying to slow down the warming process, the temperature IS going to rise, but that's fine, it's already considerably colder than it needs to be, probably -30C, and -18C is the recommended freezer temperature for storage. The aim is to slow the warming process, that is most easily achieved by adding thermal mass.
nayls142@reddit
How are you generating -30C ice in a freezer that's at -18C?
----_____--_____----@reddit
Im generalising the standard temperature of a chest freezer
Wise-Fault-8688@reddit
Yeah, I just clean and refill gallon milk jugs with water and use them to take up any empty space.
series_hybrid@reddit
Also, get a top-lid chest-freezer. Cold sinks, heat rises. Every time you open the upright fridge, a lot of the cold drops out and is filled with warm 70F room air.
While you still have electricity, arrange the items in the chest fridge so that the top layer is stuff you want to cook on a propane barbecue as soon as the power goes out.
Take a picture of the items in the fridge and avoid opening it for a couple days. After that, just start using all the fridge items.
Morgue724@reddit
With the added plus of not accidentally suffocating yourself especially if the Frazer were in a basement where it would sink without tp the floor pushing breathable air out, small chance bitcwhy make a bad situation worse.
TheLostExpedition@reddit
Yup freeze water. Its the safest way. Plus you get drinking water when it thaws.
nayls142@reddit
How are you generating -30C ice in a freezer that's at -18C?
AlphaDisconnect@reddit
Big container of water. Frozen. Lots of them.
evilprogeny@reddit
Dry ice would actually sublimate on create a high pressure situation in the freezer the would cause the door to open not such a problem with a horizontal freezer as gravity would close the door again but an upright freezer might be a problem because the door might not swing back and complete the seal which would cause your food to spoil as the temperature rapidly rose in side
DiscombobulatedAsk47@reddit
Keep the freezer full: put 3/4th full water bottles into the freezer. Add more insulation. Throw some blankets over the freezer when the power goes out (do not block the exhaust coils if the power is still on) Do the coin trick so you'll know if your freezer food may have thawed: freeze a container of water, then put a coin or over chip on the ice surface. Place this level in the freezer. If the coin is still on the top, your food has remained frozen. If the coin has dropped into the ice block, your food has defrosted then refrozen. If only partway through then it would likely have had ice crystals and would be safe but texture is off. If the coin is at the bottom, then everything thawed and refroze and should be thrown out.
Beaglerampage@reddit
Not sure about dry ice but the fuller the freezer the longer it stays cold.
MrHmuriy@reddit
Modern chest freezers, even in the event of a power outage, will maintain a low temperature for 40-48 hours (and even longer if you don't open it too often). Even in the event of a longer power outage, it may be easier to plug in a small generator for a couple of hours so that it can maintain a low temperature inside for the next 48 hours.
BentGadget@reddit
Here's an online tool for conversion of grams to tablespoons.
https://www.inchcalculator.com/convert/gram-salt-to-tablespoon-salt/
Two liters of water needs 200g of salt for a 10% solution, or about 12 tbsp.
MrHmuriy@reddit
It's probably better to give quantities in grams - I just measured the weight of a heaping tablespoon of salt - 32 grams. But I use an old standard Soviet steel spoon for such measurements, it is slightly larger than a standard tablespoon in the USA.
WanderingFlumph@reddit
Chemist here.
Dry ice is much colder than regular water ice but it doesn't necessarily have more cooling potential per pound (or per cubic foot if you care about volume) for a lot of nerd reasons. CO2 can also be dangerous if you have a lot of it off gassing in a closed room.
For these two reasons you are better off filling all the empty space in your freezer with water and cranking the temperature as low as it'll go 2 days before you expect power outages. Also as a side note freezers that open on the top (rather than the side) hold their cold much more efficiently when you open/close them and therefore stay a lot colder when unpowered.
Technical_End_7021@reddit
If you have potable water storage already you can add salt to some of the freezer water and mark the bags. Not great for drinking but still good for sanitation and cooking water. Salt will slightly lower the freezing temperature of the water and help keep it a little colder in the freezer.
Spiritual-Bath-666@reddit
The temperature of dry ice is -109.3°F. The typical freezer is kept at 0°F – scorching-hot for dry ice. The freezer will not slow down sublimation – and if you place enough dry ice there, it will create enough CO₂ to pop the door open.
tryatriassic@reddit
Not true. Source: tried this with my-86. You need a -150 for dry ice to keep more than a week
DarkLordMittens@reddit
An interesting side effect of using dry ice in an enclosed space would be that you'd carbonate the items inside. It was quite a surprise when we were traveling with grapes in a cooler.
SumthingBrewing@reddit
I went on a camping trip for 10 days. We froze a bunch of food and dedicated a big Yeti cooler to be our freezer. We put a few pieces of dry ice at the bottom of the cooler (like 2-3 paperback books size). Put a bag of ice on the very top of the cooler.
90 degree daytime temperatures. On day 10 we still had ice. Dry ice absolutely works better than just water ice.
kkinnison@reddit
Nope. Dry ice evaporates too quick
Just use block ice. lasts longer and doesn't evaporate as fast, but you are getting danger close to 32 degrees instead of 0 degrees like most freezers, so the items might not keep unless you got more insulation
I got a few 1g milk jugs filled with frozen water, and a plastic container that is 6x6x12 i can fit in my coolers. basic thermodynamics. You are trying to store "cold batteries" to keep the temp down. I have seen Amish just place a huge block of ice in a disconnected refrigerator and able to keep it cool for weeks
Sh3rlock_Holmes@reddit (OP)
I like that… “cold batteries”
tsoldrin@reddit
i fill free freezer space with gallon jugs of water to help keep it cold. bonus: you can drink it if needed.
ROHANG020@reddit
PUt the dry ice in a good thick foam cooler...then use it if you need it
Rhaj-no1992@reddit
Dry ice can be dangerous in closed areas like cars, small rooms or elevators because it evaporates and forms carbon dioxide.
Honest_Trip_5574@reddit
Use dry ice in a well ventilated room not in underground rooms co2 is heavy enough to push oxygen up and out of basement if enough is used means that you can’t breathe in that room. Use it in a good 7 day cooler like a yeti it will remain like a freezer I use 1 when I go camping in summer 100 degrees or more my food stays frozen over a week.
nealfive@reddit
It’s about thermal mass. I’d echo the freeEr up with water bottles ( make sure to remove some ware so they don’t explode as they freeze)
ProbablyABore@reddit
Dry ice releases carbon dioxide gas as it evaporates. Keep that in mind, especially if your freezer is in a low ventilation area. If your freezer creates an air tight seal it can cause it explosively release, and fill a room with co2.
It's going to cause the thermostat to shutdown due to how cold it is.
You'd need more than 50lbs of dry ice to last 3+ days plus the lead time to the event.
Personally, I'd invest in a small generator to power the fridge with plenty of fuel to keep it running for a few days. Of course, you should have already bought this as finding one this late in the game could be difficult.
traveler19395@reddit
To make an analogy to campfires, dry ice is like gasoline (fast and extreme) and regular ice is like oak (slow and steady).
The dry ice will be much colder early on, but after a couple days will end up much warmer than regular block ice. The best thing you can do is make sure your freezer is as full as possible (without blocking air circulation). Any empty space fill with water bottles, milk jugs, etc. filled with water. If it's a lot of empty space, don't fill it all at once, fill about half then wait 24 hours and fill the other half.
Ok_Midnight_7517@reddit
When camping, we use frozen water bottles as our ice in one cooler and dry ice in another cooler. That 2nd cooler we consider our freezer as everything frozen in there stays frozen for a couple of days. If you put the dry ice on top it will freeze anything under it not already frozen. If you have time, run an experiment before the storm hits. Please report results.