Would this work to replace the compressor and refrigerant for refrigeration? Fridges that last need less repair and have nothing to leak when they do need repair would be pretty neat.
I'll speculate that since it's compression and decompression (as opposed to phase change) that's being exploited, you need a small gas whose behavior is as close to the ideal gas law as possible. Smaller gasses are also more volatile and leaky though, so there is probably some tradeoff.
FTA: Because helium remains a gas until -200 C, we can achieve higher temperatures inside our heat pump core
N₂ boils at −195.8 °C, but that will be higher at 30 bar.
Hard to see how that would be a problem in this application.
Would be interesting to see how much.