Why Do Compressed Air Cans Get Cold?

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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
docs.crcindustr...
Latent Heat of vaporization
en.wikipedia.o...
1,1-difluoroethane chemical and physical properties
webbook.nist.g...
1,1-difluoroethane on wikipedia
en.wikipedia.o...
Free Expansion of Real Gases, Goussard, 1993
dx.doi.org/10.1...
Joule-Thompson Expansion Course Notes
tccc.iesl.forth...
Properties of 1,1-difluoroethane
www.inchem.org/...
pubchem.ncbi.n...
Medical Effects of difluoroethane
toxnet.nlm.nih...
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[@pratikwase9970]

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

[@rawtrout007]

you channot explain what you do not understand

[@luongmaihunggia]

@@rawtrout007 **cannot*

[@drew4716]

@@luongmaihunggia channot*

[@kyrlics6515]

@@drew4716 schannot*

[@bluesteel7874]

@@kyrlics6515 shallots

[@skydemon3423]

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

[@aurelia8028]

What?

[@roanxx]

@@aurelia8028 woosh

[@aurelia8028]

@Just Cause what? It doesn't smake no snence

[@psychoalert1823]

Real ones know

[@fluffydestroyer5482]

@@aurelia8028 what?syou sdont smake no snence

[@maheshghorsaine6919]

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

[@ohno5559]

3b1b's next differential equations video is supposedly coming this week

[@fattahrambe]

Kurzgesagt already upload couple days ago

[@bored_person]

Didn't they already take their turns?

[@maheshghorsaine6919]

@@bored_person checked after watching this, they are first I think.

[@ingoseiler]

Kurzgesagt uploaded a video on their German channel today

[@clu83]

Boo! This video is clearly longer than a minute, I demand my money back! Oh, wait... Carry on!

[@error.418]

his videos are on the order of magnitude of minutes instead of hours of lecture, he's made videos explaining this because people have made this lame joke for years now

[@carazy123_]

Username I believe the joke they made wasn’t actually about the length of the video, but rather the fact that it is free!

[@bugjams]

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

[@jwoodside68]

well, spraying it upside down also contributes to global warming. It's the same reason this chemical when used as a refrigerant is actually illegal to vent into the atmosphere. So why do we use it in a can that can be vented into the atmosphere? I have no clue. I guess an HFC (Diflouroethane) is safer than an FC (Propane, Butane, ect.), and better for the environment than a CFC (Evil R12) ?

[@michaelweiske702]

@@jwoodside68 wooosh?

[@legitimate8463]

@@jwoodside68 r/wooosh

[@manuelsputnik]

Guys, this is an educational channel. You're being cringy.

[@navyasharma2750]

@@manuelsputnik correct

[@GalluZ]

Can: *100% ozone safe* Also can: *has potent greenhouse gas* Balanced, as all everything should be.

[@aurelia8028]

stfu

[@smugfei6682]

Sure, it is a potent greenhouse gas, but it is definitely the lesser of two evils. I doubt an average family of 4 in North America would use more than one can of compressed air per year. Compare that to the huge amount of CO2 that same average family produces from driving, using electricity from a grid that uses fossil fuels, eating food produced 1000s of kilometers away, and buying/ replacing household items it really isn't a huge deal. Moving towards a 100% renewable & nuclear grid (some states and provinces already do/are close to this, British Columbia for example), phasing out gas/diesel vehicles as EV charging stations become as common as gas stations and improving mass transit, more carbon efficient food production worldwide, and making products more easily repairable and longer lasting should be prioritized first.

[@sinusoidalwave]

@@smugfei6682 i found yanfei in yt comments

[@jamesdinius7769]

Greenhouse gases=\= ozone depletion.

[@The-Devils-Advocate]

@@jamesdinius7769 hence the comment

[@TreeHairedGingerAle]

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

[@GRBtutorials]

At least it doesn’t deplete the ozone layer like CFCs did. Though I don’t know why they don’t just compress air inside the can, as that would also be a lot cheaper. EDIT: turns out it’s because it’s more dense and the pressure stays constant, and isn’t flammable like propane or butane.

[@ShadowDrakken]

"we" don't, I use a hurricane electric blower instead of compressed gas :)

[@gavinkemp7920]

@@GRBtutorials just to clarify a bit the reason we don't use compressed air is their is no conceivable way we could have a significant quantities of air in a aluminium can. So we need something that can liquify. On the other hand we use butane in europe. It not that dangerous we are not using tons.

[@Undy1]

@@gavinkemp7920 Yeah Europe here, I only ever saw compressed "air" with a mixture of propane and butane, never with 1,1-difluoroethane. The key difference is that propane is flammable (not an issue really) and that it boils at -42°C instead of -25°C so it has the potential to get much cooler during operation. Generally "air in a can" is a terrible product - the can gets incredibly cold (to the point of risk of getting a frostbite) and the colder it gets, the weaker it blows (it's not very strong to begin with, but at low temperatures it gets even worse - you can literally blow harder with your mouth. It really sucks if you need to clean a computer - you probably won't be able to do it in one go. And finally it doesn't last very long - it's better to invest in an dedicated electric blower (cheaper but single purpose) or a legit compressor (more expensive but has many other uses including pumping tires and driving a whole variety of pneumatic tools) than continue to buy more and more cans of propane. It's more expensive up front than canned air, but it's worth it because it will blow MUCH stronger and more importantly - indefinitely, so it will pay for itself eventually.

[@kuro13wolf]

@@ShadowDrakken Yeah we should just purchase and install a hurricane electric blower to clean our keyboards like once a month real practical.

[@9034833838]

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

[@travcollier]

So many disciplines are basically... 101: Learn some cool simple laws 201 to post graduate: Learn how everything you were taught in 101 is wrong.

[@anonymeanonyme4047]

and now ????????????????????????????????

[@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.

[@_egg_2933]

“Yah, it’s Rewind time!”

[@johnm5928]

Its also a great way to cause one.

[@AsifAAli]

You want their circuit board to short? Nice try, you evil lithium cell!

[@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.

[@waldolemmer]

I drilled a hole in a long brake cleaner can and soldered a Schrader valve to it. I usually give it about 20 pumps, which results in ~10 bar

[@naswinger]

you actually blew the crumbs into the keyboard at the beginning :(

[@blazewolf9912]

They also blew crumbs off.

[@SpencerSteelman]

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

[@TeamTwiistz]

Finally the hard hitting questions

[@EEVblog]

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

[@anullhandle]

Dave, I never looked at the ingredients label I assume the cold ones just have a dip tube inside like a liquid co2 tank for an environmental chamber? Don't push the button, tear it apaaaart.

[@Dulus0]

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).

[@bobthegoat7090]

At least the principle is the same so you didn't waste any time watching this video

[@Markle2k]

R134a has about 10 times the GWP of 1,1 difluoroethane (1430 vs. 140) edit:wrong number of fluoros

[@Dulus0]

@@Markle2k yes R134a is also a potent green house gas, but as I said majority of cans I bought are propan-butan mix, only a few were R134a, and those were typically bought for some industrial locations, where I guess it was because of the non-flammability.

[@user-by7hj4dj9s]

I have proban-butan mix in my house, bought a few months ago. does not have a pleasant smell.

[@jwoodside68]

Yes, 134A is common. I was about to mention car air conditioning in another comment but googled the chemical before making sure this was the right chemical. Not sure why so many refrigerants are used, or any at all really. but Propane and Butane are just a really bad idea.

[@darkhoodchief]

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

[@nealsterling8151]

Because they're stupid.

[@geilkindfanful]

Because it works good

[@akilw.3360]

They want to counteract global warming by making cold air.

[@geilkindfanful]

@@akilw.3360 xD

[@MarioFanGamer659]

That's because halocarbons have got many useful features (like easily compressionable) which is why they used to were pretty common, though their nasty side effects were found out later (greenhouse effect aside, it's also because they're poisonous and destroy ozone like the infamous CFC).

[@shunyat9023]

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

[@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 but.....yikes However this can be used for things like getting dents out of plastic bumpers since it's intense targeted cold

[@kamalhm-dev]

wait what, how does that works?

[@sakurahonda9245]

When I sprayed one of things, it still sprayed liquid even though it was upright and I did not shake it. Not good when cleaning your computer.

[@jamesmnguyen]

Funny story: I accidently dropped a hairspray can on its nozzle and broke it, causing all the contents to spray continueously. After sometime of freaking out trying to contain the mess. The can was really hard to hold because it was so cold. I couldn't hold it for more than 5 seconds. (I ended up tossing the whole can in the bin, not sure if that was safe or not)

[@anullhandle]

@@jamesmnguyen hair spray cans also double as flame throwers. ...

[@jamesmnguyen]

@@anullhandle I was more concerned with inhaling too much chemicals.

[@3X3Beastsu]

Am I the only one who's watching this instead of studying...?

[@albertholl4836]

We are studying by watching this

[@RprophetOfjesusC]

Youre studying on how not to die, just like me. 🤣

[@athulj9614]

can find more about this in the book THERMODYNAMICS AN ENGINEERING APPROACH 8th edition by cengel pg 116

[@pedrovaz8150]

hi, where can i get that book for free?

[@b2spirit35]

But why is her heart cold?

[@renakunisaki]

Because her blood is boiling and she's under a lot of pressure.

[@gursharanmarwaha3376]

When you go to the DOLLAR store, you spend $6. When you watch MINUTEphysics, you watch for 6 minutes.

[@error.418]

his videos are on the order of magnitude of minutes instead of hours of lecture, he's made videos explaining this because people have made this lame joke for years now. it doesn't say "one-minute physics."

[@polka7970]

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

[@josephpostma1787]

THanks for the brutal idea.

[@bongobliss5795]

U cant imagine my happiness when u post a new video

[@FacterinoCommenterino]

Today's fact: "She sells seashells by the seashore" was written about an actual person named Mary Anning.

[@graphite2786]

Fact#2 A movie about the extraordinary life of Mary Anning is being filmed as we speak. Kate Winslet plays Mary.

[@overestimatedforesight]

This is an unusual Freeze Mage video

[@FacterinoCommenterino]

@@overestimatedforesight it's the fact i'm commenting on this channel today

[@YeppyNope]

Ah, Yes.

[@raykent3211]

Thank you. Can you also inform me about "what noise annoys an oyster"? It keeps me awake at night.

[@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)

[@wolfmobile3693]

If you let some air out of a duster and put the can up against your ear before it gets too cold, you can hear the liquid boiling into a gas.

[@Benedict416]

1:17 Is that why when we say "Hooo~" cold air comes out and when we say "Haaa~" hot air comes out? I think you have just answered 2 question I was always curious about in 1 video

[@bbgun061]

no, the faster stream of air from saying 'hooo' cools your hand faster, so it feels colder.

[@Owen_loves_Butters]

@@bbgun061Even if the air stream is slower, it still feels colder.

[@ha7vds]

the great brian brushwood taught me that a can of air can be used to shatter a lock. now i know why it works. thank you

[@DyslexicMitochondria]

Your videos are so amazing. Informative as well as entertaining. You, sir, are the inspiration behind my channel. Keep up the great work!

[@LaunchPadAstronomy]

Excellent explanation. And thanks for pointing out the fact that it’s a potent greenhouse gas to boot.

[@Cosmic_Ray_]

Minor Avengers: Endgame Spolier About 1 year ago, you did a video on different types of fictional time travel. In the movie Avengers: Endgame, there is time travel that is a bit confusing, so can you do a solo video on this movie or a update video on fictional time travel with this included?

[@MatthijsvanDuin]

3:30 Also, a reflective surface has reduced emission of thermal radiation*. * since any light reflected is not absorbed, and the emissivity at any given wavelength equals the absorptivity at the same wavelength (Kirchhoff's law)

[@basabsardar8733]

Bro his vains

[@SethCWhelchel]

I always assumed there was some sort of endothermic reaction happening, (especially since I could hear fizzing in the can whenever I used it a lot), but I never considered that the gas wasn't actually air

[@vodkainglassofstalinium1221]

Some day this guy's videos will save me in my physics paper

[@gustavogonzalez8648]

No, no it wont

[@leocurious9919]

If that is supposed to save you.... I really hope you fail.

[@jwoodside68]

No, it wont. they very basically cover concepts. If I wanted to grade a paper on HFC's and you never touched on Pressure/Temperature relationships I would have failed you.

[@nickolasdiamond5619]

Everyone in the reply section: r/wooosh

[@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.

[@johnm5928]

Yep, as usual, minutephysics gets something wrong. Agree with your better explanation. As far as recharging when the liquid is low, I would be interested to find out. But one thing I can think of - the smaller amount of liquid is a smaller thermal mass, and therefore would absorb ambient energy faster and therefore regain its pressure faster (i.e., your hand holding the can will heat it up faster with less liquid in the can). Idk, just spitballing.

[@ToxicityAssured]

@@johnm5928 Excellent point, I think you're right. Thanks for commenting.

[@Owen_loves_Butters]

It's not just that the high energy molecules are escaping lowering the average temperature. The process of vaporization is endothermic, as it involves breaking intermolecular bonds (just like how it takes an input of energy to separate magnets).

[@thekrackenx]

4:12 When my mom says don't touch that

[@emmanuelherreraestrada9514]

Wow. Never knew that.

[@manamejeffbeezos]

Dude now I wanna watch a see through compressed air can in slow Mo

[@alvaroparra1411]

If the can is at a very cold temperature, like -273°C (0k), would the can still release air? The video states that the reason it gets cold is because the liquid chemical uses thermal energy to boil. But, what if there is no thermal energy available? Would it still boil and keep the pressure inside the can at 6 atmosphere?

[@ogi22]

Beautiful clip, i would add just 2 things: 1. It's not only Difluoroethane, it's a mixture of chemicals of similar properties. They mix them together to achieve desired boiling points of the gas mixture. I think Cody's Lab had a very nice clip about it. 2. It is HIGHLY FLAMMABLE!!!! Never use it around a heat source. I had a small accident when we tried to remove a stuck bearing... i bought a few canisters of "compressed air" because i knew how cool they can get. I was heating up the bearing from one side using a heat gun and my coworker was spraying liquid "air" on the shaft from the other side... The result was a big ball of fire and a great hair loss of my coworker (i had a cap on my head) ;) I'm so happy it all ended up only with company jokes :D

[@cjpatz]

During rocket launches, is that rapid forming ice you see cracking and peeling off the booster or tanks during launches? And is that the same principle explained in this video?

[@the1exnay]

Clint Patac Probably, liquid oxygen, hydrogen or methane rapidly boiling.

[@android199ios25]

Explain dislikes coz I cant. BTW helium gets hotter due to JT expansion at room temp.

[@DWhite-hg5hp]

It's also highly flammable. Set a toilet bowl on fire by dumping a coke bottles worth of the stuff into the bowl, followed by a match. It also felt like I was breathing razor blades afterwards so, not worth it.

[@Hailmaryy28]

Darwinism at its finest

[@matchstickgameplay]

I see minute physics, I click. It's that simple.

[@ContraHacker1337]

And then you click like. Don't forget that.

[@nameless_monster_]

Bottle : do not shake *six minutes physics : * I 'll pretend that I didn't see that

[@kurtlautenshlager4878]

I appreciate that the walking bassline always resolves right at the end of the video

[@idealoading]

I shake cans with compressed air and i will continue thanks anyway for the info επισης κανω επιστημονικα βιντεο οποιος θελει ας ριξει μια ματια

[@MrNight713]

I’ve always wondered this because at my work we use CO2 cartridges to flush pvc pipes and after we’re done they usually freeze up

[@benYaakov]

If the whole story is of pressure , so it means that we can cook food faster deep inside the earth and oceans :)

[@apkoiv5795]

Because PV = nRT. You lower the pressure, we lower the temperature.

[@IronLotus15]

Not quite. V also increases quite a bit, you have to account for that too. What explains the full effect is a combination of what you said with PV=nRT, the volume expanding, and the energy from the phase change as explained in the video. And of those three I believe the phase change has the greatest impact on the temperature.

[@Hamuelin]

In light of this. Anyone got any good recommendations for mini vacs for keyboards etc.? I don’t really want to contribute to greenhouse gases anymore than necessary.

[@aiellamori]

It really doesn't matter, just use it

[@jerry3790]

If I let out all the information that was compressed into this video, what temperature will it cool to?

[@strangehappenings8961]

Approximately the temperature of your mom. Hahaha 😂

[@Lysergic_]

@@strangehappenings8961 good one buddy

[@renakunisaki]

What's the boiling point of liquid information?

[@g_vost]

So, due to pressure's effect on matter states, does that mean some of our knowledge of freezing, boiling, melting, etc., points are actually false, or at least inaccurate?

[@racimeexe9868]

I think people who doesn't have studied thermodynamics like me have really no clear ideas about these phenomenons, experimenting and deducing things can help thought

[@ChristianJeremyOcaya]

It seems that you've been watching bon appetit Claire's question from the Gourmet Reese's Cup episode

[@VintageToiletsRock]

_Don't use for anything food related... hmmm..._

[@codered6938]

Yea I can only huff them for 1 to 1-5 seconds before my hands get too cold. Thanks for telling me why it happens I’m happy to know! 🙏🏻

[@electronicsNmore]

They aren't real "Air" cans. Almost all these air cans, including the CRC you're holding, use refrigerant to create pressure. Pressing the button down allows pressure inside the can to escape. When the pressure above the liquid refrigerant is lowered, the refrigerant will boil to increase the pressure until it's high enough to keep the refrigerant from boiling(or turning into a gas). As the liquid refrigerant boils(going from a high pressure to a low pressure), it gets cold, just like the refrigerant in your vehicle or home A/C system. Great video, and well explained as usual!

[@inemanja]

Brilliant video again.. No pun intended (seriously).. P.S. I hate how brilliant.org often sponsorship of cool videos, fuck up my chance to use the trem seriously without some kind of disclaimer...

[@shashankambone6920]

This was an interesting video. It's been a while since I've been satisfied from minute physics.

[@beingsentient]

This video mixes up two separate phenomenon, the expansion of a gas and the latent heat involved in boiling. The Joule Thomson Coefficient is associated with the first only. I have a serious objection to the author calling a can of fluorocarbon a can of compressed air, which leads to much confusion, compounded by the fact he's trying to talk about two different phenomenon at the same time.

[@philipberthiaume2314]

This is the same concept that A/C works on, compression and de-compression cycling.

[@Crlarl]

Which is why the same refrigerants are used in both.

[@susahosh]

1:45 - The warning label is telling you not to shake the can...*goes on to shake the can* LOL

[@inzanozulu]

Somebody send this to Claire from BonAppetit

[@annascaligiuri]

inzanozulu I was just thinking the same thing.

[@dgo792]

Thank you

[@consultingmoose]

lolol i was looking for someone to say this 😂

[@riyanraj2043]

can any anybody give me the title to the video of minutephysics where henry mentiones the HISTORY TV EFFECT?? PLEASE

[@sukhrajsingh466]

it's also a potent greenhouse gas

[@JosiahMcCarthy]

Oof

[@heckler73]

Why?

[@jadoei13]

@@heckler73 I know this might not answer your entire question but it has a gwp rating of 124. So releasing 1kg of this should be equal to releasing 124kg of CO2 as far as I understand it. Wiki: Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere up to a specific time horizon, relative to carbon dioxide. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide and is expressed as a factor of carbon dioxide (whose GWP is standardized to 1).

[@cullenl2508]

@@jadoei13 actually according to the government it's 1300 times more potent

[@heckler73]

@@jadoei13 So it hinges on the necessity of the "greenhouse effect" hypothesis being valid. That's pretty well what I expected but wasn't sure. Thanks.

[@BadAssEngineering]

Same effect happens in Cars/Trucks converted to run on LP Propane. The Propane is liquid inside the tank, and it has to be routed to a heat exchanger to heat it up before the engine, because it freezes and clogs parts of it

[@Nuovoswiss]

This was a great explanation of the Joule-Thompson effect and how it relates to adiabatic cooling. The JT effect is something specific to nozzles, and depends on their geometries and the pressure gradient, while adiabatic heating/cooling is the more general case for gas expansion. I've seen many people incorrectly refer to the JT effect and assume that some gasses will always heat up when they expand.

[@the1exnay]

Nuovoswiss If you understand it would you mind sharing- because i watched the video then looked it up and i still have no clue. Why does it matter that in the process of expanding it went through a nozzle, don't most thermodynamic equations just bother with the start and end states? Where does the extra heat come from without breaking the laws of thermodynamics (especially given the fluid is doing extra work to accelerate itself through the nozzle so you'd expect extra cooling- not heating- if anything)? If we measure the thermal energy of the whole system from after using a nozzle or cutting off the top would there actually be a difference in total thermal energy of the system between the two processes?

[@Nuovoswiss]

@@the1exnay Sure thing. At the entrance to the nozzle, the gas is compressed even further since it is being squeezed through an orifice, creating a local hot spot. The energy to do that comes from the heat/pressure of the rest of the gas in the high-pressure container. Away from the nozzle, in the bulk of the pressure vessel, the gas cools adiabatically, as expected. When the gas squeezed through the nozzle expands upon exiting, it also cools adiabatically, but whether that cooling is greater or less than the nozzle heating depends on the details (∆T, ∆P, M, geometry, etc). Thermodynamically, it's like you have some of your pressurized gas expand adiabatically into a small cylinder with a check valve, then compressed that second chamber using a spring to capture the piston's inertia (this is an inertially-driven phenomenon) to heat it up before letting it expand adiabatically once again. The local heating is driven by the expansion of the full volume of gas, but that energy gets dumped locally to the gas going through the nozzle. Does that answer your questions?

[@the1exnay]

Nuovoswiss It makes more sense now. So it's a process by which the air leaving takes thermal energy from the air being left behind. And the total thermal energy is the same at the end for either process, there's just a change in the temperature differential between inside and outside the can? And this heating is just pressure becoming the mechanical energy of moving air which turns into thermal energy via friction and air resistance? I think i might understand it better now, thanks for taking the time to explain.

[@Nuovoswiss]

@@the1exnay That right, for the most part, in practice. The only issue I see is that you're thinking of 'thermal energy' as an independent quantity. If you want to go down the rabbit hole, there is the thermodynamic condition known as 'free expansion', in which any gas can expand with no net ∆T. This does not violate any precept of thermodynamics, but in practice it would require something like a Maxwell Demon, but without any discriminatory capability (and thus, no violation of thermodynamics). Adiabatic expansion (and thus adiabatic cooling) fundamentally assumes that the energy cost to ∆T comes from some work done. If a gas expands without expending any energy to an outside system, no work is done, so it can't change its temperature. What this means for a nozzle is that if the gas goes through it with no opposition (ie, with nothing to push against, even itself) then it will come out the same temperature it started as, when averaged over all its atoms/molecules.

[@the1exnay]

Nuovoswiss Huh, that's really interesting. So in adiabatic expansion it's the work on the environment normally just compressing the air around it or?

[@krlwlfrt]

Thank you so much. I was looking for a good explanation of this effect on KZbin a short while back but could not find any video that explained it this thoroughly.

[@jakeenders7]

You put CRUMBS on an APPLE piece of shi.. keyboard?!? Good luck m9.

[@mattr791]

Did you know that if you spray compressed air into a computer fan it sounds really cool for about 14 seconds then explodes Yea highschool IT class was a lot of fun

[@MyOwnUrl]

3:45 Rip HP users ☹

[@kevingruenofficial]

😮 evaporative cooling. This channel rocks! Awesome elegant and simple explanations as should be. thank you!

[@sachi813]

Try blowing air through your mouth by yawning style and by pouting your mouth and feel the air from both on your hand ...to feel the temperature difference.

[@the_original_Bilb_Ono]

Wouldn't the difference be much more to do with the heat from your hand being pushed off by the fast blowing air? If you slowly let the air out your mouth it feels the same temperature no matter the orientation of your lips.

[@ipsojure2137]

I highly doubt that you can actually create a noticeable pressure difference with your mouth

[@Ifelloutawindow]

They also have a bad taste so when I was a kid and found about the cooling of them, I played with it too much and got some in my mouth. It stayed for almost an entire month. I did it again a week after it stopped and got even more in my mouth. :/

[@طزفيكمياقوكل]

Your explanation of how the cooling is counterbalanced by heating was woefully rushed. Would appreciate your spending some time on it.

[@EpicWink]

I was literally cleaning my PC with compressed air when this vid came out. MinutePhysics part of the conspiracy confirmed :D

[@robmckennie4203]

this is also how air conditioners and refrigerators work, it's not a coincidence 1,1-difluoroethane is also used in those applications

[@jacobras]

Does this mean I should stop shaking my refrigerator?

[@nicholaslau3194]

Well, being a refrigerant isn't exactly why it is used for "compressed air". In refrigeration applications, the low boiling point is needed for cooling (obviously), but for "compressed air", all that is needed is the constant high pressure. Cooling of the can is not an intended feature, but an unwanted side effect.

[@robmckennie4203]

@@nicholaslau3194 i mean, that's true, but i never said that the cooling was a designed feature of compressed air cans? the video explains why they get cold, and i said that the physical effect that makes them cold is the same one used in refrigeration

[@seasong7655]

*SLAPS CAN* This bad boy can fit so much 1,1-difluoroethane inside

[@xnamkcor]

You guys didn't mention global warming. What am I supposed to do with these shots now?

[@brofenix]

Oooooh wow, nice. This was a great explanation and made me want to buy a portable compressor/duster for cleaning dust off my computer rather than using "compressed air" aka difluoroethane.

[@exploding_pineapples]

I didn't know that these air cans could be so interesting

[@jeronimorestrepogiraldo2766]

if these air pressured cans only work upside up, are these meant to be useless in space (0G's)?

[@AlessioSangalli]

What is the sense of the numerous notes that only stay visible for a fraction of a second? It's so frustrating

[@alexwang982]

Alessio Sangalli What

[@RatzBuddie]

I remember nearly freezing shut an airsoft CO2 mag a few times, had to put on gloves to handle it. You have to invert the can to fill the gas chamber and it likes to pool up around the nozzle connection. Super fun, super cold stuff

[@J623L]

Nobody : Science Community: Minute Physics : why do compressed air cans get so cold ??😩😩

[@theemperor1379]

WOW. Thank god i saw this before using it to clean my PS4. But i did broke my fan tho.

[@user-nq6wm1um8f]

Where are those cats😆😆😆 I really miss them

[@proxy1035]

i always flipped the cans upside down and used the liquid to cool electronics down... like my modem

[@isaacorr3180]

TAKE THAT WARNING LABELS! XD

[@joshyoung1440]

SON WHY ARE YOU USING A BACKPACKER'S STOVE ON DRY GRASS

[@ratdude747]

Two things: 1. The stuff in said cans is similar to (if not the exact same thing) as R134a refrigerant. (What's used in car AC systems, other than a select few new models). Hence how R134a can be sold to consumers (and other refrigerants are generally not). 2. The principle that was described here is also how such an AC system works... only with it being a closed system and with a compressor to re-liquify the expanded refrigerant, and a condenser coil to vent off heat (how heat is "expelled" by the system). The rest of the system (expansion valve/orifice tube and evap coil) are the same idea...

[@Monkeymario.]

0:31 I didn't know there were multiple ways of gas expanding!

[@Semi-Addict-Gamer]

A better question is, what is air compressed can? Edit: I knew those cans but not what they are called, I was introduced to them in an old h3h3 video.

[@vpsjdon]

I'll do you one better: Why is air compressed can?

[@skyvenrazgriz8226]

Is that an usualy american thing caned compressed 'air' ? Also sounds like a typical clima killer, if any flourine gas reaches the Ozone layer it will react and dmg it (due to the UV break down)...

[@NetAndyCz]

They are used all around the world, handy for clearing electronics of dust and stuff from hard to reach places.

[@TGPadm]

If you compress a gas it gets hot, then you can stop there until it cools to room temperature, and then release it so it's going to get cold, so you can make a freezer with pump.

[@djame2517]

This is the basis of the refrigeration cycle.

[@mrsteezy1234]

@minutephysics if the canister was to be placed in a perfect vacum and then used what would happen? Assuming the gas expelled is removed as to keep the canister in a perfect vacum.

[@sarlacc66]

I've seen that you've changed your drawing support from whiteboard to paper...

[@masonsilvers6789]

Its always been paper.

[@AravindSagar]

Wow, so these cans maintain a steady output by literally absorbing heat from the surroundings. Nice!

[@TheRationalizer]

I read this in Experimenting On A Small Planet. It's a great book for people interested in science + how we discovered what we know.

[@saosaqii5807]

I always wanted to know why this happen and at first I thought it was because pressurized gas at let’s say room temperature all squeezed into an tiny space heats up because now there is more density and more energy for the same amount of space and entropy cools the air inside off to room temperature again so when it depressurize it becomes cooler.

[@raafmaat]

Now i finally know why i sometimes sprayed freezing liquids instead of air! thanks minute!

[@NetAndyCz]

Yeah, I seriously thought it is just can of air under high pressure.

[@raafmaat]

@@NetAndyCz i thought so too, but then again, never really gave it much thought, as i could probably have realized the pressure would not last so long if it was just normal air