Technology Connectionslet's learn why Peltier devices are not actually very cool in this new video:
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Legally Distinct Basilisk@TechConnectify I just agreed to take one of these fridges from my parents, who'd gotten one to keep drinks cool while their kitchen was under renovation. If I'd seen this first I would have said "don't bother."
One question I had, though. If Isobutane's boiling point is around 45°C, does that mean that in extreme situations your refrigerator can just get too hot to function?
@BasiliskXVIII Yes but not for that reason.
When the ambient temperature goes up, the refrigerant can't shed heat as quickly which results in the condensing temperature increasing. Since the system is filled with pure refrigerant, condensing temperature and pressure are perfectly correlated so the end result is the high side pressure goes up enough to raise the boiling point enough to keep functioning.
It's only a problem when the pressure exceeds design limits.
@BasiliskXVIII I don't think you'll ever see that happen in a domestic refrigerator, instead the compressor will start to overheat and its thermal safety switch will start kicking in. Enough cycling of that switch will eventually kill it, though.
When it comes to large heat pumps for heating and cooling, there are pressure switches which prevent the system from operating if the pressure gets too high (or in fact too low, depending on the protections you want).
@BasiliskXVIII (left this out)
When the high side pressure goes up, that makes the compressor work harder. So power draw starts going up and more heat is generated in the compressor windings.
That's really the limitation of any refrigeration system. As high side pressure goes up, eventually the compressor is working too hard and generating too much heat to keep working without stuff breaking.
@TechConnectify Thanks for the insight! I'd just been reading about Paradise Nevada hitting around 120°F, and that number being so much higher than the refrigerant's boiling point surprised me.