Cooling things: Difference between revisions
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Car ACs are refrigeration cycle designs. | Car ACs are [[refrigeration cycle]] designs. | ||
The layout will be different, and e.g. the compressor is driven by the engine via a belt, | The layout will be different, and e.g. the compressor is probably driven by the engine via a belt, | ||
and the receiver/dryer is sort of new, ...but overall it's the same high and low side, | and the receiver/dryer is sort of new, | ||
expansion valve, | ...but overall it's the same: | ||
a high and low pressure side, | |||
an expansion valve, | |||
one radiator outside, | |||
circulate air inside the car over the inside radiator. | |||
It doesn't cool quite as quickly, but that's generally not an issue. | |||
Notes: | |||
* It seems common{{verify}} that there is an added heat exchanger | |||
: so that only a smallish part of the system has refrigerant and the rest of the system is circulating cold water, | |||
: letting you cool more things using simpler components (no need to make them more robust to avoid leaking refigerant), | |||
: and more user serviceability (you can refill the radiator yourself). | |||
* (the receiver/dryer seems to a receiver in that it's an expansion tank for refigerant, and a dryer of moisture that got in during service, protecting the expansion valve {{verify}}) | |||
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Revision as of 13:06, 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.