Every time we check in with [Hyperspace Pirate] he’s trying to make things cold. Really cold. His recent two-part video shows a propane vapor compression system that can go down to -37° C as well as a two-stage system using homemade ethylene that can get to -83° C. He’s trying to get to -100°, so he’s close, and we have no doubt he’ll get there.
The video explains that using two different refrigerants makes the design more practical. At the low temperatures involved, you have to deal with compressor oil freezing. There is a lot of theory required to design an efficient cooler and a lot of know-how required to make gas-tight connections with all the different materials involved.
Using propane in both stages did provide a little additional cooling. But using ethylene in the second stage didn’t work as expected. There were two issues to work through. Part of it was the average temperature of the system, and also, the homemade ethylene needed purification. The ethylene purification setup was almost as complex as the main system and also reminded us, for some reason, of the movie Darkstar. It didn’t work as well as he wanted, which means we have to wait for part two to see it all actually working.
We’ve seen this same guy make dry ice. He’s also tried to make liquid nitrogen, too.