Why Does Compressed Air Get Cold When Released

The video will explain what really happens inside the compressed air cans.

Why does compressed air get cold when released.

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. This is the principle operation of air conditioners refrigerators and other heat pumps. Then the gas is released through a nozzle the gas expands again and cools. The secret behind this freezing property of the cans is the do not shake warning that is mentioned on the can.

Travelling along this pressure gradient the gas expands and does work and this removes energy from the gas. Metal however feels cold to touch even when at environment temperature due to the high thermal conductivity. When air or other gas is compressed work is done and the gas heats up. Minutephysics knows the actual reason why compressed air cans become so cold and will explain it.

A gas initially at high pressure cools significantly when that pressure is released. There is no reason that the compressed air tank should have a lower temperature in the compressed state when the pressure was not changed for a couple hours. If the container is stored the temperature equalizes to the ambient temperature. Eventually your hand gets cold.

Cans of compressed air get cold while they re discharging because of a thermodynamic principle known as the adiabatic effect.