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Is it possible to operate a heat pump at 450C? Compress a gas until it heats up to 880C; send it outside to “cool down” to 450C; bring it in and decompress it

Is it possible to operate a heat pump at 450C? Compress a gas until it heats up to 880C; send it outside to “cool down” to 450C; bring it in and decompress it where it drops to 20C; and bathe on deliciously cool room temperature air?

gorgoiler 4y ago
(For clarity, this question is more about seeking clarity on my own hazy understanding of how fridges work, rather than some random internet person suggesting “have you thought of this <obvious solution>?”.)
- sbierwagen 4y ago
  Physics-wise, if there's a useful working fluid in the temperature and pressure range you want, it can be done. The problem then is power. Refrigerators are power hungry. Space exploration tends to be desperately short on power-- there's not a lot of sources of electricity that are happy to spend ten years at -100C and then spring forth to produce volts at quantity and with minimal mass. A heat engine is right out. (Where would the cold sink come from?) Batteries are tough. RTGs have terrible engineering challenges-- plus they'll use up a lot of half-life during the coast phase to Venus. Given that design space, a Venus lander (that isn't built to operate at Venus temps) would probably have a battery and a store of internal coolant that undergoes phase change and is dumped overboard. A big block of water ice, or depending on the constraints, something more exotic. >drops to 20C Don't have to get that cold, fortunately. There is a considerable domestic demand for ultrahot electronics for wellhead sensors in oil exploration. (The head of a drill string needs to have some smarts for remote sensing-- figuring out if the rock you're drilling through has any oil in it. If you've got the money, you can buy a microcontroller than can run all day and night at 220 Celsius! https://www.digikey.com/en/products/detail/texas-instruments/SM470R1B1MHFQS/2353584 https://www.digikey.com/en/products/detail/texas-instruments... Fun fact: one of the handful of commercial applications for nuclear fusion reactors, today, is as a source for downbore neutron excitation gamma spectroscopy https://www.slb.com/-/media/files/drilling/brochure/neoscope-br.ashx https://www.slb.com/-/media/files/drilling/brochure/neoscope... )

gorgoiler 4y ago

(For clarity, this question is more about seeking clarity on my own hazy understanding of how fridges work, rather than some random internet person suggesting “have you thought of this <obvious solution>?”.)

sbierwagen 4y ago
Physics-wise, if there's a useful working fluid in the temperature and pressure range you want, it can be done. The problem then is power. Refrigerators are power hungry. Space exploration tends to be desperately short on power-- there's not a lot of sources of electricity that are happy to spend ten years at -100C and then spring forth to produce volts at quantity and with minimal mass. A heat engine is right out. (Where would the cold sink come from?) Batteries are tough. RTGs have terrible engineering challenges-- plus they'll use up a lot of half-life during the coast phase to Venus. Given that design space, a Venus lander (that isn't built to operate at Venus temps) would probably have a battery and a store of internal coolant that undergoes phase change and is dumped overboard. A big block of water ice, or depending on the constraints, something more exotic. >drops to 20C Don't have to get that cold, fortunately. There is a considerable domestic demand for ultrahot electronics for wellhead sensors in oil exploration. (The head of a drill string needs to have some smarts for remote sensing-- figuring out if the rock you're drilling through has any oil in it. If you've got the money, you can buy a microcontroller than can run all day and night at 220 Celsius! https://www.digikey.com/en/products/detail/texas-instruments/SM470R1B1MHFQS/2353584 https://www.digikey.com/en/products/detail/texas-instruments... Fun fact: one of the handful of commercial applications for nuclear fusion reactors, today, is as a source for downbore neutron excitation gamma spectroscopy https://www.slb.com/-/media/files/drilling/brochure/neoscope-br.ashx https://www.slb.com/-/media/files/drilling/brochure/neoscope... )