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

[@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 ????????????????????????????????

[@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.

[@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

[@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!

[@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.

[@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

[@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.

[@TeamTwiistz]

Finally the hard hitting questions

[@naswinger]

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

[@blazewolf9912]

They also blew crumbs off.

[@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)

[@shunyat9023]

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

[@LaunchPadAstronomy]

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

[@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.

[@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

[@alexkorinth6459]

Just learned about the Joule-Thompson phenomenon in one of my senior engineering classes, and I'm pumped to see it talked about, even briefly.

[@SpencerSteelman]

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

[@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).

[@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. 🤣

[@kevingruenofficial]

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

[@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.

[@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?

[@bongobliss5795]

U cant imagine my happiness when u post a new video

[@Jesse-cw5pv]

I do volunteer firefighting. When we fill our SCBA bottles we have to fill them slowly otherwise they get a 'hot fill,' then when it cools it won't be as full. It's a bit different than this but some of the principals are the same

[@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.

[@wr2899]

Interestingly, in Europe and Australia normally these dusters contain a mix of butane and propane (LPG gas) which is considered to be less environmentally taxing, the US will slowly get there too. The actual mechanism is the same, just with different chemical properties. LPG has a much lower boiling point so cools more extremely.

[@DyslexicMitochondria]

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

[@hilowize]

The alliteration at 4:38 is beautiful.

[@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."

[@evasuser]

A superb video, almost a physics lecture, ty m8 and keep uploading.

[@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.

[@GhostDrow]

I am so glad that you sprayed an entire can of this stuff out just so you could measure the tempurature of the can and got no real use out of it despite the fact that it is a potent green house gas. So freaking cool.

[@ikerus0072]

Calm down

[@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

[@Dicefinity]

After months of your videos I can now follow through without rewind :)

[@christyhorak2950]

Yash Bhartia so there is hope for me hahaha 😂

[@matchstickgameplay]

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

[@ContraHacker1337]

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

[@cshairydude]

1,1-difluoroethane and other HCFCs are being phased out under an amendment to the Montreal Convention (the original version of which banned CFCs). The compressed air can I have uses propane instead (which apparently is not a greenhouse gas), but I guess the principle is the same.

[@MyOwnUrl]

3:45 Rip HP users ☹

[@sivansharma5027]

5:02 Nah actually I find black holes quite relatable XD

[@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.

[@puyuanzhang9069]

5:27 wandering earth is such a good movie, strongly recommended, it is on Netflix

[@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

[@AravindSagar]

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

[@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.

[@scottstevens7253]

Great video.. kind of crazy a nice metal bottle and strong greenhouse gas is needed for a process that can be done by a regular wall powered air compressor

[@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

[@Ephemeral_Inspiration]

Was literally just wondering this the other day. Perfect!

[@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

[@blazewolf9912]

I was honestly wondering what liquid was inside and why it cooled off enough to allow formation of frost. I looked it up but it didn't really help but now I know. Thanks!

[@manamejeffbeezos]

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

[@OoSweetyman]

I was wondering the same thing while I was huffing my duster

[@thekrackenx]

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

[@YouTubeWhitet]

I like these quick physics videos!

[@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).

[@jasonlameyjkl]

This was infinitely more interesting than I thought it was gonna be. Great vid.

[@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.

[@knzerogaming4665]

My dumb ass thought it said shake, a minute later I’m like why does my hand hurt and feel so cold... frostbite!

[@android199ios25]

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

[@Jop_pop]

Minute Physics: *videos* Me: *is video*

[@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?

[@jordanhenshaw]

Phase change from liquid to vapor results in cooling effect because btu's in outside air get turned into latent heat.

[@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

[@fractal4284]

Cool video you should do a video on high-pressure cylinders how if you feel a smaller cylinder with a high pressure gas one gets cold the other one gets hot

[@nameless_monster_]

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

[@sampleoffers1978]

Cool. If you can pressurize cold and retain or just rig two cans to spray into each other, lowering their temperature, sounds like maybe a freeze engine.

[@exploding_pineapples]

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

[@acerockman3520]

Literally covered this in physics today

[@kurtlautenshlager4878]

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

[@peterandersson3812]

Videos in this channel are always awesome, but this may be one of the awsomest ever. And one can watch it without pausing to think, which you needed to do with the (excellent!) series about relativity.

[@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.

[@Ella-kv9pl]

For anyone who is new to the store channel read this This channel answers questions to things you never knew you were entreated in 😂

[@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

[@seasong7655]

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

[@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?

[@karlavaldez1815]

Came here after using my bottle of dry shampoo and it started running out but i kept pressing to get as much as i could and it subtly began to feel cold and i was confused but also amazed

[@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..._

[@LiborTinka]

You can have instant dry ice by releasing compressed CO2 from a pressurized cylinder into a bag or form. This provides cooling down to -78.5C by means of cooling bath (dry ice in acetone or methanol) for various laboratory procedures (e.g. ozonolysis).

[@shashankambone6920]

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

[@krisanderson5636]

That's an excellent explanation. Far superior to the confused drivel that my old thermodynamics lecturer called "teaching". Although you say that the gas is compressed at the nozzle, which causes it to heat, but surely there is a continuous pressure drop from the centre of the can until the exit point of the nozzle? Isn't the heating just caused by friction from the flow of the gas against the internal surface of the nozzle?

[@b2spirit35]

But why is her heart cold?

[@renakunisaki]

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

[@tuseroni6085]

this also happens with liquid propane, run s bbq or blowtorch for a bit and you will see the propane tank gets cold, this is why. also dont use a blowtorch upside down for the same reason

[@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 😂

[@Andriodacg17]

Thanks for translating the temperatures into Fahrenheit.

[@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?

[@TactileTherapy]

PBS spacetime just uploaded a video. That's the fastest diss-record response i ever saw. I love Physics beef

[@jakeenders7]

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

[@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.

[@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

[@fakjbf3129]

A classmate of mine flipped a can of compressed air upside down and sprayed it against the back of his hand for several seconds. He had to go to the ER for frostbite. We called him "Frosty" the rest of the year.

[@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

[@jamrockpirate]

This video was timely because all week I was wondering about this phenomenon

[@joshyoung1440]

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

[@LasseRonnenberg]

Does this factor in?: The molecules with the most thermal energy are the ones that stay gasseous when colder molecules cool into a liquid. So the molecules with the most energy are the ones in gas form, and when they leave the container, they carry most of the existing heat with them, leaving less overall thermal energy inside.

[@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!

[@moth.monster]

Spraying it upside-down is a great way to get a cooling spray!

[@طزفيكمياقوكل]

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

[@moohooman]

Oh, I usually shakes them, explains why I get a little burst of frost when I sprayed it just after 😅