Why compressed air can cold

This Minute Physics video explores some of the thermodynamics behind that process. Inside the sealed can, this chemical sits in an equilibrium of part-liquid, part-vapor. But when pressure is released by opening the nozzle, the liquid boils, generating extra vapor and cooling whatever remains in the reservoir.

That first equation you see at in the video for isentropic adiabatic expansion is key to what happens in a nozzle with supersonic flow. As the flow accelerates to supersonic speeds, its temperature drops dramatically.

When I was in graduate school, we actually had to preheat our hypersonic wind tunnel in pretty much the same way you would preheat your oven at home before we ran at Mach 6 because otherwise the temperature inside the test section would drop so low that the oxygen would liquefy out of the air! We won't reveal more here. You have to watch the video to understand how liquid gas plays a role in freezing the can.

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But Does It Work? This will probably not happen when you let the high pressure gas out through a common valve into atmospheric pressure. You would have to employ a Maxwell's demon. You are right to better stay safe and not do experiments with the camper gas heater. You could also use a typical hair o deodorant spray container. Show 1 more comment. Farcher Farcher Here's a conjecture which you may verify by doing some simple experiments if you have available an empty cylinder and a cylinder filled with compressed gas: Compressing air sufficiently leads to liquefaction of some of its components, in particular water vapor see this.

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