History Memes

It works by taking advantage of how gasses become hotter or colder when you squeeze them.

You might be aware of the ideal gas formula from high school: PV=nRT.

This formula is cool and all, but it only works for ideal gasses, and one of the crucial assumptions is that ideal gas molecules don't interact with each other. Of course, this is not true at all in the real world. Gas molecules can have attractive or repulsive forces to each other, which can have some interesting consequences.

The main one is that if gas molecules attract and you spread them out, they will need to absorb energy in order to overcome those attractive forces. In other words, its surroundings gets colder. Vice versa, if you squeeze the gas molecules together, they will release energy, and the surroundings get hotter.

You might start to see where we're going with this. Building a refrigerator just involves smartly squeezing and releasing a gas in the right order. Expand the gas to cool it down, then pass it through the fridge interior so that it can absorb heat. Then, take out the gas, and squeeze to get it hotter. Pass the gas through a radiator to dissipate the heat. Rinse and repeat.

This concept is also why leaks in pressurized gas tanks tend to freeze over - the gas inside is constantly expanding, and is therefore constantly absorbing heat. On the other hand, hydrogen gas, which is repulsive instead of attractive, will get hotter when it leaks, which can lead to an explosion.