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

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. Next question: why do they need gas at lower temperatures to achieve higher temperatures? Do temperatures inside that acoustic wave vary that much?