>>12442487Dude, the butane in your example is starting off well above its boiling point at atmospheric pressure, but is highly pressurized by its own vapors, and therefore is not boiling normally.
When you release that pressure, the liquid begins to vaporize (because reducing pressure also lowers the boiling point of the liquid) and remove heat from the remaining liquid. If you keep releasing pressure the liquid will continue to cool until it finally reaches its boiling point at atmospheric pressure, and from then on boils much more slowly as the energy necessary to boil it must actually conduct back into the liquid, whereas before the liquid already had a lot of stored thermal energy but was pressurized enough that it couldn't boil.
If you stopped venting the butane can, it would stop boiling but as it warmed the vapors would build back up again and re-pressurize the can.
So, the difference between the butane can and the methane inside Starship is that the methane is being loaded in already below its atmospheric pressure boiling point. They could dump a load of liquid methane into an open tank and it would stay at its boiling point. The liquid physically couldn't get any warmer than its boiling point without vaporizing, which is exactly what happens inside Starship, with the excess vapor being allowed to escape. However, if Starship were way beefier and could handle the pressure, they could close the vents and allow methane vapors to build up until it reached a stable equilibrium and no longer boiled even at room temperature. The issue is that that only happens at something like over 100 bar, and also it would exist as a supercritical fluid rather than a liquid and vapor phase.
