Heat pumps are amazing. I wonder if you could get a compressor small and efficient enough to run refrigerant around a vest to keep people cool and vent waste heat through a backpack radiator. Getting it light enough would be a problem. So would power. I wonder if you could run the compressor off of walking motions somehow.

@Querral Refrigerated suits do exist! I'm not sure what the main use for them is, but they exist

@Hearth @Querral Space suits? Maybe that's a bit too niche to call a main use

@fudge_the_sphinx @Querral Yeah, I'd call that a bit niche--a more common use is cooled fursuits and sports/themepark mascot costumes, though we're not sure how commonly those are cooled

@Hearth @fudge_the_sphinx A quick search suggests they use simple ventilation fans, chemical cool packs, or dry ice.

@Querral @fudge_the_sphinx Ah, I thought those at least used Peltier cells or something.

@Querral @fudge_the_sphinx Peltier cells are used for some portable refrigerators! They're the only practical way to cool things down without complicated mechanical parts. Which are heavy and prone to failure.

Though they're also far less efficient than mechanical refrigeration.

@Hearth @Querral Peltier heat pumps are some cool physics (pun... mostly intended).

To try and put the (in)efficiency in real world terms, I think the figures I found in brief research were something like 24W for a few degrees C of difference over a 10x10cm pad. Don't quote me on that though, this was ages ago.

@Querral This is something I fantasise about pretty much every summer.

I've still got the parts from the last abortive attempt at building something. I was thinking I'd build a hand-operated pump and rely on a big bottle of iced water lasting long enough to be more practical than an onboard compressor. I built a prototype pump, but the mechanism was too stiff to be useful, and my attention span ran out before I got around to redesigning.

I thought about peltier effect coolers too, but they're so inefficient I don't think they'd be very useful.

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