Why Is Compressed Air So Cold

Travelling along this pressure gradient the gas expands and does work and this removes energy from the gas.

Why is compressed air so cold.

A fluid such as water or air that rotates around an axis like a tornado is called a vortex. One hot and one cold. It creates a tornado or vortex of compressed air that separates the fluid into two air streams. The reason the can gets cold after being used is due to a process known as adiabatic cooling a property of thermodynamics.

When you pressurize a gas by compressing it into a container you re putting all those molecules into a smaller volume of space and you re adding potential energy by the compression. In fact it can become so cold that the cans feature frostbite warnings. The cold temperature profile sneaks back towards the can because the air is such a lousy conductor of heat so the heat is all coming from the can. Eventually your hand gets cold.

Compressed air cylinders are required to be kept out of direct sunlight to avoid gas expansion by direct heating and perhaps also due to phase change although no one seems to mention this explicitly. A vortex tube turns factory compressed air into two airstreams one very cold and one hot using no moving parts. This is perhaps why compressed air cylinders feel cold even before use. However that is not true.

Anyone who has ever made use of the compressed air can knows that it can get icy cold. Minutephysics knows the actual reason why compressed air cans become so cold and will explain it.