why do tanks of compressed air get cold, to the point of frosting over, when the gas is let out quickly?
In:
If you take your finger and rub it quickly against a surface, it will get hot. That’s friction. In a similar way all of the molecules in the air are flying around bumping into each other and getting hot.
If you take all of the air molecules in a room and put them in a small box there’s going to be a lot more bumping and a lot more heat. Just like if you rub your finger on the surface faster.
Eventually though, just like a glass of hot water, that small box is going to cool down to room temperature, and as it does the air molecules run out of energy and slow down, and bump less but it still has all those molecules in it bumping into each other. Only now they’ve slowed down, they’re only bumping into each other with enough friction to keep things at room temperature. Everything is in balance.
Now the box gets punctured, and the air molecules escape. Now there are less air molecules in the box to bump into each other, and so it’s like less friction, they stop making so much heat. Thing is, they were only making enough heat that kept them at room temperature, if they now make less heat then that air has to get colder. If the air is cold inside, it’ll cool down the compressed air tank too.
Latest Answers