Cooling things: Difference between revisions
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==Free cooling== | ==Free cooling== | ||
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Free cooling means "use the fact that it is cold outside to cool inside". | |||
For example, in cold climates, you can cool industrial processes or datacenters just by ''moving'' water or air around. | |||
Yes, you could open the window, but more controlled in terms of humidity but also the actual temperature, | |||
so this often amounts to heat exchangers to cool an otherwise closed system. | |||
If temperature difference are seasonal, you may prefer heat pumps - putting in a little more energy | |||
for a lot more over-the-year guarantees, so just mean part of the system becomes more efficient in some seasons. | |||
This is no longer ''free'' cooling, but still ery useful. | |||
If there is a significant day-night differences in temperature, | If there is a significant day-night differences in temperature, | ||
it may make sense to have reasonably-sided buffers. | it may make sense to have reasonably-sided buffers. | ||
Revision as of 16:26, 24 January 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.