Cooling things: Difference between revisions
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===Windows and windcatchers=== | ===Windows and windcatchers=== | ||
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Houses will concentrate heat, by being closed, without much draft, and being made of materials that absorb more than zero heat. | |||
Isolation lessens the absorption, though not so much other concentration. | |||
Windcatchers, well, catch wind that wouldn't otherwise have gone through your house, | Which means that by the time it's evening, the walls in general, and the air in some rooms, will be warmer than the evening air. | ||
Windcatchers, well, | |||
catch wind that wouldn't otherwise have gone through your house, | |||
and put it through your house. | and put it through your house. | ||
In other words, it's designing for draft, | |||
and to have that happen passively. | |||
Like windows. | |||
But larger effect, and useful when you have enough space, and/or large day/night temperature differences. Which is why you largely see them around desert areas. | |||
It's not hugely efficient, but it's passive so it's free. | It's not hugely efficient, but it's passive so it's free. |
Revision as of 14:33, 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.