Why Do Compressed Air Cans Get Cold?

This video is about compressed air cans (aka gas dusters) and why they get cold when you spray them. They cool off because the refrigerant inside (1,1-difluoroethane) is under pressure and boils off when the pressure lowers, and energy lost to the latent heat of vaporization cools the can a lot. Difluoroethane normally boils at -25°C (-13°F), but under ~6 atm (6 bar, 600 kpa) it is a liquid at room temperature. The gas also cools off slightly due to the Joule-Thompson effect of fluid expansion through a throttled valve. Difluoroethane is heavier than air and water soluble, so it is recommended to use it in a ventilated environment to clean your keyboard, etc. Also, 1,1-difluoroethane is a potent greenhouse gas. It is also known as Freon 152a, Ethylidene difluoride, Ethylidene fluoride, HFC-152a, R-152a, and DFE.

Thanks to Tino and Hannah!

REFERENCES

CRC Air Duster Safety Data Sheet

Latent Heat of vaporization

1,1-difluoroethane chemical and physical properties

1,1-difluoroethane on wikipedia

Free Expansion of Real Gases, Goussard, 1993

Joule-Thompson Expansion Course Notes

Properties of 1,1-difluoroethane

Medical Effects of difluoroethane

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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!

Created by Henry Reich

[pratikwase]

minutephysics: what is quantum tunneling? (1 minute 5 seconds)
Also minutephysics- Why do compressed air cans get cold?(6 minutes 12 seconds)

[skydemon]

It's because it's filled with winter air
you have to replace it with summer air

Highschool: Adiabatic Expanison
Undergraduate: Joule Thompson Expansion
Master: Get back to you in 2 years

[EebstertheGreat]

Some dusters on the market use actual compressed air, making them generally safer, though the pressure in the cans is usually somewhat higher (~10 bar) and they don't last nearly as long. They won't reach frostbite temperatures (unless the can explodes I guess), but they do still cool down due to adiabatic expansion.

[MichaelSteeves]

Turning the can upside down is a great way to test for weak points on circuit boards. Intermittent faults tend to show up under thermal stress.

[maheshghorsaine]

Now, we know Kurzgesagt or 3B1B's turn to upload a new video.

[GalluZ]

Can: *100% ozone safe*
Also can: *has potent greenhouse gas*

Balanced, as all everything should be.

[bugjams]

Spraying the can right-side up: *Contributes to global warming*
Spraying the can upside down: *Makes instant ice*

Wumbology!!

[shunyat]

I don't know what to do with this information but I'm glad that I heard it anyway.

[Dulus]

Seems strange, at least for last ~8 years, nearly all gas dusters i bought was basically a proban-butan mix. Much better for the ozone layer, but also highly flammable :D.
And a few of them were R134a ( Tetrafluoroethane is what wiki says is the chemical name).

[clu]

Boo! This video is clearly longer than a minute, I demand my money back!

Oh, wait...

Carry on!

[EEVblog]

We need an upside down compressed air vs freezer spray physics shootout...

[viliphied]

This is also how most modern air conditioners work, though they force the coolant through a closed loop so it gets re-compressed into a liquid rather than going out into the atmosphere. Doing that generates waste heat though which is why they have those big outdoor fans. It’s also why you can’t cool your house by leaving the fridge or freezer open, as the waste heat from compressing the coolant stays in your house. If you were to put the back of your fridge outdoors however... (it would still be remarkably inefficient)

[Ryukachoo]

Oh damn, early for minute physics slowly getting funnier and increasing in production and editing quality.
Also, these cans upside down are NO JOKE, you can get minor surface Frost burns after only a few seconds. Kids blast each other with these as a prank
However this can be used for things like getting dents out of plastic bumpers since it's intense targeted cold

[polka]

It's great in small amounts to freeze wasps that fly out of a nest, freezes the wings so they can only slowly meander towards you on itty bitty legs

[bongobliss]

U cant imagine my happiness when u post a new video

[darkhoodchief]

Why do people use a potent greenhouse gas as a compressed air blower?

[TreeHairedGingerAle]

T_T *"Also a very potent greenhouse gas"* Why we do

[ToxicityAssured]

I agree mostly. The boiling liquid does cool itself and the can. Around 3:00 minutes it's implied that the heat needed to do this comes from somewhere. It's true that more energy can cause a fluid to boil or lowering the pressure works as well. I don't think that's really a good explanation though. Maybe something like this?
A drop in pressure occurs. This decreases the pressure/boiling point and the fluid boils. The most energetic molecules evaporate at a higher rate. Temperature is just the average kinetic energy. If we remove the higher speed molecules leaving the slower ones on average, the temperature drops. Now we have a cooling liquid and heat external to the can can flow to the cool can. The valve closes and pressure builds as external heat from the environment flows into the can. Eventually the vapor pressure is reached and boiling stops. Things are now the same temperature everywhere. Your can is "recharged".
I wonder the differences between full and near empty cans... A larger area of gas compared to liquid (nearly empty can) will need longer to increase the pressure in the larger gas filled area. I think full cans "recharge" faster maybe.

[SpencerSteelman]

me searching this video because i was scared it was gonna explode 👁👄👁