Space does not have a temperature. Objects in space can have temperatures.
Voyager 2 measured the plasma in the VLISM (very local interstellar medium) to be 30,000-50,000K.
As it relates to air cooling, the densities out 18 billion km from the Sun are very low. Same with nearly anywhere else in vacuum. So it does not heat Voyager 2 much. Similarly, if you are in LEO in shadow where gas temperature is lower, you can't cool much of anything either.
2.7K comes from cosmic background radiation, and that is really a shorthand*. But since space is not matter it can't have a temperature (photons from background radiation don't either.
*that is that an object some place where it receives no other radiation would eventually cool to that temp
I was playing with Stefan-Boltzmann for a 37 x 37 x 3.5mm Ryzen IHS.
Using emissivity of nickel (0.03... very bad), and a temperature of 70C (343.15K), and assuming it is in shadow facing deep space, I get that it could radiate ~0.045W.
Raising the temperature to 105C (378.15K), I get 0.065W. If I lapped it to copper (e=0.052), then it could radiate 0.077W at 70C, or 0.11W at 105C.
Even if it was a "blackbody" (e=1), that is still only 2.2W at 105C, or ~1.5W at 70C.
I need to use heatpipes and connect it to a large flat panel (it is starting to sound like a spacecraft radiator...)
A 1 square meter panel of copper at 70C could radiate ~41W.
If emissivity is raised to 0.8 with coating, then at 0C it could radiate ~250W. That is at the bottom of optimal range for aluminum and ammonia heatpipe radiators apparently. So may make sense to downsize the panel, or maybe use it for the whole system.
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Last edited by hazium233; 01-19-2020 at 08:46 PM.