re: Refrigerators on Venus
Here is a sample mission designed to survive for one YEAR on the surface of Venus:
Power comes from an RTG external to the main pressure/thermal enclosure with independent radiators
Three-stage refrigerant cycles:
R11 from 93 C electronics box to 160 C heat exchange
AlBr3 (!) from 150 C heat exchange to ~500 C heat exchange
Argon from 500 C heat exchange to 750 C external radiator
Total internal electric power - 5.5W
Total electrical power for all stages ~ 260W
Total thermal power of RTG 6,500W (!)
Just for fun, the outer pressure vessel is a Dewar-style vacuum flask with 93 bars outside, and vacuum in the gap!