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Keeping items in the refrigerator cool / keeping stuff in the freezer cold


ScienceNostalgia101
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A: In anticipation of future power outages, (last windstorm didn't do it but the next one could) I've been stuffing the top part of my freezer with tupperwaves full of ice. I'm figuring that because hot air rises and cold air sinks, that absorption of heat by melting ice would both preserve my frozen food for longer and double as an indication of how safe the food is by how much of the ice has melted. Would everything below this ice-water mixture be kept at 0 degrees centigrade due to sinking cold air, or is there something I'm missing?

 

B: A little trickier is the question of how to keep items in refrigerator part well enough below room temperature for food not to spoil quickly, but also well enough above freezing so as not to damage items due to severe cold. Would putting tupperwares full of icewater at the bottom create a vertical temperature gradient? If so, how stable would this temperature gradient be?

 

(Sidenote: Why isn't it the norm in apartment design that freezers and refrigerators are installed on the wall, and have one door opening to the apartment and another to the outdoors to keep food cold during a power outage? Presuming some sort of wire mesh on the latter to deter thieves, that is...)

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One trick I’ve heard about is to put a clear container filled with water, then frozen, and a coin placed in top. If the ice melts and refreezes (e.g. while you are away and you have a power outage) the coin will drop to the bottom. But if it’s still on top or only part way down, you know the ice didn’t fully melt.

Filling up space with ice in the freezer is a good strategy because it has a higher heat capacity than air, so things will stay colder, longer.

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  • 1 month later...

Coming back to this thread a month later, with a follow up question I forgot to ask... whether I put in tupperwares full of ice cubes (wherein a flat layer of ice would presumably form at the bottom on partial thaw, and a flat surface on complete thaw) or a coin at the top of a container of ice, that still leaves the question; if something was only partly melted, does that mean that its temperature stayed at 0, and therefore that anything directly beneath it in the shelf below it in the freezer was kept at or below zero? Does it depend on how much surface area of the top shelf the containers of ice occupy, at least compared to the surface area of the bottom shelf occupied by the food items I'm trying to keep frozen?

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3 hours ago, ScienceNostalgia101 said:

Coming back to this thread a month later, with a follow up question I forgot to ask... whether I put in tupperwares full of ice cubes (wherein a flat layer of ice would presumably form at the bottom on partial thaw, and a flat surface on complete thaw) or a coin at the top of a container of ice, that still leaves the question; if something was only partly melted, does that mean that its temperature stayed at 0, and therefore that anything directly beneath it in the shelf below it in the freezer was kept at or below zero? Does it depend on how much surface area of the top shelf the containers of ice occupy, at least compared to the surface area of the bottom shelf occupied by the food items I'm trying to keep frozen?

If there is partial melting then the temperature will not be below zero C. The rest of the freezer will be kept close to zero, but may be slightly above, due to whatever heat leakage there may be through the insulation, which won't be perfect. But I don't think there is any magic about zero C, from the point of view of keeping food from spoiling. Food will keep almost as long at 1C as at 0C.

But it's interesting. It's all about suppressing the growth of bacteria. I'm not sure if this is just like a chemical reaction viz. an exponential function of absolute temperature, or whether here is any sharp "switch on" temperature below which they cease to multiply entirely. I can imagine that if the bacterial cytoplasm freezes, all activity may stop. Perhaps someone else can comment.

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I don't see air rising and falling as a factor inside a freezer stuffed with food - there is little or no air circulation.

The temperature inside the freezer should be between  -15 and -20 C; everything inside should be frozen solid. This is your best insurance against a relatively short power outage. Make sure the door seal is tight, and don't open it unnecessarily. 

Oh, I guess it's an upright freezer. They're convenient but far less efficient than chest freezers. Even so: the more full it is, the longer it takes anything inside to melt. If you don't have enough food to fill it, insert containers of water - you don't need ice cubes; the water can freeze in place - not just at the top, but packed tightly in among the packages of food. The more ice is in there, the more like an old-fashioned ice-box it behaves.  With an upright freezer, the door seal is even more critical. If it doesn't seal tightly enough, put a bungee around the freezer. 

On 1/16/2022 at 7:26 AM, ScienceNostalgia101 said:

Why isn't it the norm in apartment design that freezers and refrigerators are installed on the wall, and have one door opening to the apartment and another to the outdoors to keep food cold during a power outage?

Because sometimes it's summer outside.

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Tactically, I would use plastic milk bottles rather than tupperware. You get a better seal in the lid. And only fill them 7/8 full to allow for expansion when they freeze. Also, I would add a little salt to the water, and allow it to dissolve. That will bring the melting point down below 0 degrees, giving you a better chill effect. And fill every empty space in the freezer with these bottles, so that you have plenty available to replace the used ones as they melt in the fridge. 

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