Cooling things: Difference between revisions
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* the '''Seebeck effect''' | * the '''Seebeck effect''' | ||
:: a temperature gradient | :: designs where a temperature gradient leads to an electric potential | ||
:: e.g. used in thermocouples, often to measure temperature | :: e.g. used in thermocouples, often to measure temperature | ||
* the '''Peltier effect''' | * the '''Peltier effect''' | ||
:: an electric potential | :: designs where an electric potential leads to a temperature gradient (at the junction of two dissimilar metals) | ||
:: e.g. used in Peltier elements | :: e.g. used in Peltier elements | ||
You can see Seebeck and Peltier as basically the same thing in reverse, | You can see Seebeck and Peltier as basically the same thing in reverse, so complementary effects. | ||
In terms of things you buy, specific things are optimized for different use of one effect. | In terms of things you buy, specific things are optimized for different use of one effect. | ||
Line 780: | Line 780: | ||
A peltier element you can buy is a whole bunch of individual peltier-effect junctions in series. | A peltier element that you can buy is a whole bunch of individual peltier-effect junctions in series. | ||
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Revision as of 01:45, 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.