Freezer Efficiency - Full vs (part) Empty

Qyburn
Qyburn Posts: 2,073
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Hi,

Thought I'd raise this separately rather than derail the other thread. It's often said a freezer is most efficient if it's full. Is that due to the (a) thermal mass of the contents or (b) reduced air space.

Ours is quite big and if we have a proper tidy up there'd be quite a bit of space. So i was wondering if it would be worth padding it out with empty lemonade bottles, to reduce air space. I wouldn't be so keen on using full bottles as that would take a lot of power to freeze, which is then wasted when the bottles are taken out to free up space.

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  • Trace-T
    Trace-T Posts: 44
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    I fill the empty space in ours with puffed up empty carrier bags.
    I once read it improves efficiency if it's not trying to freeze dead space. Scrunched up newspaper was suggested, so you could easily fill the gaps.
  • lohr500
    lohr500 Posts: 922
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    I wonder if containers filled with air will make any difference? I guess it prevents thermal movement of the airspace in the freezer. But is it the movement of air that causes the inefficiency or the fact that there is space not occupied by solid material
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  • Qyburn
    Qyburn Posts: 2,073
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    Assuming an upright freezer, more air space could mean more air is changed each time the door's opened. More air to cool down also means more moisture to freeze and to defrost.
  • Xbigman
    Xbigman Posts: 3,879
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    If your freezer is continually part full the answer is probably a smaller freezer. You might want extra space at times like xmas but if you run everything else down in the run up you should be able to fit everything in. Good freezer management saves money.


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  • Xbigman
    Xbigman Posts: 3,879
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    Qyburn said:
    Assuming an upright freezer, more air space could mean more air is changed each time the door's opened. More air to cool down also means more moisture to freeze and to defrost.

    Every upright freezer I've seen has drawers to stop the cold air flowing out when the door is open. Its probably not a factor that is significant.


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  • QrizB
    QrizB Posts: 13,630
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    Be sure to leave enough air space that air can circulate and chill down any newly-purchased foods (or anything you're home freezing).
    This isn't usually an issue but if it's rammed completely full you might have problems!
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  • Bigphil1474
    Bigphil1474 Posts: 2,254
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    It's partially the air and partially the products. When you open the freezer you let warm air in. The freezer has to cool that air. The less air, the less cooling. However, the products that are already frozen will help cool that air, so it is better to have frozen products filling the gaps than empty bags, bottles etc. , but they are better than nothing. We have 2 freezers, one for longer term storage, and one for the next couple of weeks, as we tend to buy meat in bulk. We only open the longer term one every couple of weeks to restock the other. 
  • Qyburn
    Qyburn Posts: 2,073
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    I thought moisture in the air might be more significant than the air itself, given the specific heat capacity and density of air are both low. Rough calculation suggests 13Wh to cool 1 cu.m of air by 40 Deg.C. I might have a slipped decimal somewhere. Water vapour would need to be frozen as well as cooled, and will then add to the defrosting energy losses.
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