Cooling things: Difference between revisions
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===Super!=== | ===Super!=== | ||
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Terms like '''SuperFrost''' amount to temporarily cooling more. | |||
Terms like '''SuperFrost''' and '''supercool''' amount to temporarily cooling more. | |||
More than would normally be required for a stable temperature. | More than would normally be required for a stable temperature. | ||
Why? Well, for context, freezers are ''slow''. Once they're cold, they don't have to work hard at all, | Why? Well, for context, freezers are ''slow''. | ||
because they're insulated well. | |||
Once they're cold, they don't have to work hard at all, | |||
because they're insulated well. | |||
And since they will spend most of their operation working lightly, | |||
they are optimized to be efficient at cooling fairly slowly. | |||
Yet if you put in a ''lot'' of new groceries, | |||
the average temperature will spend a few hours warmer than the target. | |||
With Superfrost ('''Supercool''' seems to be the same idea but for fridges rather than freezers, but these terms are sometimes brand specific so eh), you make it cool harder for maybe a few hours. | |||
...often still without measuring temperature much, so if you do this without a reason, | |||
you | you might get it to be temporarily maybe 10 degrees colder than usual. | ||
So should you do this before you put the groceries in, or after? | So should you do this before you put the groceries in, or after? | ||
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though also that some things may freeze more than you want. | though also that some things may freeze more than you want. | ||
At the same time or after means less time of other things being warmer | At the same time or after means less time of other things being warmer. | ||
It doesn't really matter, | |||
unless one of your foods is very fragile in some sense - something that really should stay warm too long (suggesting before), or that really shouldn't freeze harder (suggesting after). | |||
In a freezer the same may apply, but is usually less important because a freezer is often -18C | In a freezer the same may apply, but is usually less important because a freezer is often -18C to start, | ||
making it unlikely the temperature the rise will be enough for anything to melt. | making it unlikely the temperature the rise will be enough for anything to melt. | ||
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Most freezers switch back to regular cooling automatically. | Most freezers switch back to regular cooling automatically. | ||
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===On frost=== | ===On frost=== | ||
Revision as of 13:22, 30 June 2024
Physical mechanics of cooling
Passive cooling
Passive cooling tends to mean 'what happens with no moving parts'.
...so whatever amount of conduction, radiation, and/or convection would happen anyway.
Sometimes includes adding a fan, to add to the convection.
You're stirring the air better than just convection would, so heat transfer goes a faster than if warm air just sits around - but the difference is rarely much -- convection always does this at least a little when there is temperature difference (if you're in gravity; this is about density differences).
And you could argue that's technically active cooling (because you're adding work, so using energy), but intuitively it feels like it hardly qualifies.
On the technical side
This tends to mean
- conduction - a good conductor spreading heat throughout
- if any cooling happens, conduction's spreading brings the whole down
- radiation - thermal radiation means movement of charges in materials (anything above 0 K) is radiated as EM at the surface
- (black-body radiation can be seen as a "thermal radiation's real-world math becomes easier if we make some assumptions like that it's not really interacting in other ways")
- convection - fluid flow, in this context often
- air,
- flow caused by heat changing temperatures and densities
- that flow assisting better heat interchange with that fluid, because warmer air moving up tends to draws in colder air from the sides (which technically is an effect that needs gravity)
In practice there's more than one of these happening, but often one that counts for most exchange.