ELI5: Explain Like I'm 5

Joule–Thomson effect

The joule-thomson effect is when air (or other gas) becomes cooler when it is forced through a tiny opening. This happens because when the gas is squished through the small opening, it takes extra energy from the gas, which cools it down. It's like when you squeeze a balloon, and it gets cold where you're squeezing it. The joule-thomson effect happens in nature all the time, but scientists can control it and use it to cool things down.