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Offlinezouden
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Could you cool something with compressed air?
    #10188366 - 04/18/09 05:42 AM (14 years, 11 months ago)

A friend and I were discussing this today at a party. Could you rapidly cool something (say, a 6-pack of beer) by releasing compressed air over it? We know that when gas escapes a bottle it comes out cold.

So theoretically could you build a device which compresses air into a tank, then releases it rapidly across your beer to cool it? Not as a replacement for a fridge, just as something you could keep charged for when you need to chill something faster than your freezer can.

What do you reckon? Does the maths work out?


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Re: Could you cool something with compressed air? [Re: zouden]
    #10188410 - 04/18/09 06:06 AM (14 years, 11 months ago)

Quote:

zouden said:
So theoretically could you build a device which compresses air into a tank




You mean like an air compressor?  :lol:

Episode 29 of Mythbusters, Cooling a Six-Pack, reveals the two fastest ways to cool beer are:

1. Carbon dioxide fire extinguisher = 3 minutes
2. Ice, water, salt = 5 minutes

As CO2 is a good deal colder than compressed air, I don't think you'd get very cold beer.


--------------------
You cannot legislate the poor into prosperity by legislating the wealthy out of prosperity. What one person receives without working for another person must work for without receiving. The government cannot give to anybody anything that the government does not first take from somebody else. When half of the people get the idea that they do not have to work because the other half is going to take care of them and when the other half gets the idea that it does no good to work because somebody else is going to get what they work for that my dear friend is the beginning of the end of any nation. You cannot multiply wealth by dividing it. ~ Adrian Rogers

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Re: Could you cool something with compressed air? [Re: luvdemshrooms]
    #10188469 - 04/18/09 06:55 AM (14 years, 11 months ago)

saying co2 is colder then something doesn't really mean much.  If you want colder co2 then cool it.


Anyways, I don't see why zouden's thing wouldn't work, its basically just standard airconditioner without a closed circuit.  You'd just need a large amount of cool compressed gas sufficient to cool the thing and some means to conduct the heat (could just bubble the gas through I guess though don't think that would be the most efficient)

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Offlinezouden
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Re: Could you cool something with compressed air? [Re: johnm214]
    #10188523 - 04/18/09 07:36 AM (14 years, 11 months ago)

Yeah CO2 isn't natively colder than air. The cooling capacity comes from the ideal gas law, not from any property of the specific gas.

So if a CO2 fire extinguisher can cool beer faster than ice+salt water, then all you'd need to make is a 'reusable' fire extinguisher. I guess that gives a bit of an idea of the scale you'd need.


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Re: Could you cool something with compressed air? [Re: zouden]
    #10188545 - 04/18/09 07:54 AM (14 years, 11 months ago)

If you just want something fast and easy, use dry ice in acetone (or 99% rubbing alcohol, the 70% stuff doesn't work for this).  The dry ice/acetone bath will take something down to -75C very quickly.


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Offlinezouden
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Re: Could you cool something with compressed air? [Re: Seuss]
    #10188688 - 04/18/09 08:56 AM (14 years, 11 months ago)

Yes, I've used concoctions like that in the lab, but it's not exactly practical for everyday use. I was thinking of something that wouldn't require anything except electricity to drive a compressor - dry ice is something that would have to be brought in from elsewhere.


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Re: Could you cool something with compressed air? [Re: zouden]
    #10189523 - 04/18/09 11:53 AM (14 years, 11 months ago)

The problem I see with using an air compressor is that air has a low heat capacity.  If you put your hand in a hot oven, it wont burn; but if you touch the metal or a pot of water in the over it will burn.  Likewise for cold - cold air wont suck the heat out of something as well as cold metal or water will.

But to make this practical for everyday use, you would have to use just air like you said (compared to the usual water/ice).  The water can only get so cold of course, but it sucks down heat very very well.  So to over compensate you would need to make the air very much colder.

So this is a question of the heat capacity of air and water, and how much colder the air would have to be to be more effective than ice water.  Would need to somehow combine the specific heat into newton's law of cooling to find the rate of change of temperature.  I dont quite see how to do that at the moment... hmmm Im gonna think about this.

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Re: Could you cool something with compressed air? [Re: zouden]
    #10189879 - 04/18/09 12:57 PM (14 years, 11 months ago)

> dry ice is something that would have to be brought in from elsewhere.

Dry ice is easy to make.  All you need is a CO2 cylinder and a dry ice bag (along with gloves and goggles to be safe).


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Re: Could you cool something with compressed air? [Re: zouden]
    #10189948 - 04/18/09 01:10 PM (14 years, 11 months ago)

Quote:

zouden  said:
So if a CO2 fire extinguisher can cool beer faster than ice+salt water, then all you'd need to make is a 'reusable' fire extinguisher.



If you think it'll work, why would you "make" anything? If you have a compressor just spray the cans or bottles with the air from it. Or buy one of these and an air gun.
Or maybe this if you can find a place to charge it for you. You can't fill this at home as most compressors available to mere mortals only reach 150 psi or so.

Keep in mind freshly compressed air is hot from the friction of the compressor and if I remember correctly..... just from being compressed. Also volume is an issue. It takes a large compressor to generate large quantities of air.

I think you're kidding yourself but I wouldn't swear to it.


--------------------
You cannot legislate the poor into prosperity by legislating the wealthy out of prosperity. What one person receives without working for another person must work for without receiving. The government cannot give to anybody anything that the government does not first take from somebody else. When half of the people get the idea that they do not have to work because the other half is going to take care of them and when the other half gets the idea that it does no good to work because somebody else is going to get what they work for that my dear friend is the beginning of the end of any nation. You cannot multiply wealth by dividing it. ~ Adrian Rogers

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Re: Could you cool something with compressed air? [Re: Seuss]
    #10189954 - 04/18/09 01:10 PM (14 years, 11 months ago)

Blowing compressed air or co2 will not cool anything unless there is a liquid that is evaporating. Then a fan will work as well. What you want is a compressed gas that is cooled to room temps and then released which causes it to become colder. Ideally the gas is cooled to a liquid but refrigerants are usually toxic to us or to the environment so don't release them. With ordinary air the cooling gained will be very slight when released. A bag of ice anyone?


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Re: Could you cool something with compressed air? [Re: johnm214]
    #10189991 - 04/18/09 01:15 PM (14 years, 11 months ago)

Quote:

johnm214 said:
saying co2 is colder then something doesn't really mean much.




I didn't phrase that well but..... charge an air canister to the same pressure as a CO2 fire extinguisher. Spray one hand with the air, then the other with the extinguisher. Let us know how that works out for you and how long it takes for the second hand to heal.


--------------------
You cannot legislate the poor into prosperity by legislating the wealthy out of prosperity. What one person receives without working for another person must work for without receiving. The government cannot give to anybody anything that the government does not first take from somebody else. When half of the people get the idea that they do not have to work because the other half is going to take care of them and when the other half gets the idea that it does no good to work because somebody else is going to get what they work for that my dear friend is the beginning of the end of any nation. You cannot multiply wealth by dividing it. ~ Adrian Rogers

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OfflineSeussA
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Re: Could you cool something with compressed air? [Re: Stonehenge]
    #10190071 - 04/18/09 01:27 PM (14 years, 11 months ago)

> Blowing compressed air or co2 will not cool anything unless there is a liquid that is evaporating.

Not true.  I've emptied plenty of compressed air cylinders and they get cold from the pressure change.  Ideal gas law, PV=nRT.

> What you want is a compressed gas that is cooled to room temps and then released which causes it to become colder.

Kind of, and you are on the correct path.  For ideal cooling, you want a phase change, from liquid to gas for example.  This is how refrigeration works, known as phase change cooling.


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Re: Could you cool something with compressed air? [Re: Seuss]
    #10190507 - 04/18/09 02:50 PM (14 years, 11 months ago)

"Kind of, and you are on the correct path.  For ideal cooling, you want a phase change, from liquid to gas for example.  This is how refrigeration works, known as phase change cooling."

Not "kind of". What I said is correct and I also made your point about a liquid evaporating. Using fancier words does not make it more correct. Blowing air does not cool anything directly unless the air is already cool. When the compressed air expands it cools slightly but blowing it on something does not cool it below the temp of the air being blown unless it evaps a liquid such as sweat.


--------------------
“A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835)

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OfflineSeussA
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Re: Could you cool something with compressed air? [Re: Stonehenge]
    #10191167 - 04/18/09 04:48 PM (14 years, 11 months ago)

> Blowing air does not cool anything directly unless the air is already cool.

We are talking about a change in pressure... not blowing air.  That is why I cited the ideal gas law.  You don't have to have an evaporating liquid (phase change) in order for a difference in pressure to create a difference in temperature.  This is physics 101, nothing complex.  And yes, if there is a large enough change in pressure, you can cool something below the temperature of the air being "blown".

> Not "kind of".

Yes "kind of".  Your statement "What you want is a compressed gas that is cooled to room temps" is not exactly correct... the part about "cooled to room temps" to be specific.  It is "kind of" close.


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Offlinezouden
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Re: Could you cool something with compressed air? [Re: luvdemshrooms]
    #10191530 - 04/18/09 06:10 PM (14 years, 11 months ago)

Quote:

luvdemshrooms said:
Quote:

johnm214 said:
saying co2 is colder then something doesn't really mean much.




I didn't phrase that well but..... charge an air canister to the same pressure as a CO2 fire extinguisher. Spray one hand with the air, then the other with the extinguisher. Let us know how that works out for you and how long it takes for the second hand to heal.




I reckon they'd be both the same. Why would compressed CO2 be colder than compressed air?


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Re: Could you cool something with compressed air? [Re: zouden]
    #10191610 - 04/18/09 06:27 PM (14 years, 11 months ago)

probably easier to get carbon dioxide to liquify or solidify (whatever it does first at your pressure) then nitrogen due to its increased polarity and weight.  So in that sense you'd have some lower temps from the phase change I guess.  Not inherently though- would depend on your pressure.

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Re: Could you cool something with compressed air? [Re: Seuss]
    #10191624 - 04/18/09 06:30 PM (14 years, 11 months ago)

Actually, Seuss, that is how they do it in an AC or fridge. They compress the gas, cool it to room temps and let it expand. Lets stop quibbling.


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“A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835)

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Re: Could you cool something with compressed air? [Re: zouden]
    #10191696 - 04/18/09 06:46 PM (14 years, 11 months ago)

Quote:

zouden said:
Why would compressed CO2 be colder than compressed air?



I wish I was clever enough to know but have you ever used or seen an extinguisher used? I have. Frost everywhere. I've never seen the like with compressed air.

My dad actually showed me the CO2 / 6 pack trick back in the 70's.

I've been using compressors and compressed air since at least that long ago and have never seen it even remotely chill something as much. Granted I have never tried to cool a six pack.


--------------------
You cannot legislate the poor into prosperity by legislating the wealthy out of prosperity. What one person receives without working for another person must work for without receiving. The government cannot give to anybody anything that the government does not first take from somebody else. When half of the people get the idea that they do not have to work because the other half is going to take care of them and when the other half gets the idea that it does no good to work because somebody else is going to get what they work for that my dear friend is the beginning of the end of any nation. You cannot multiply wealth by dividing it. ~ Adrian Rogers

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Re: Could you cool something with compressed air? [Re: Stonehenge]
    #10191721 - 04/18/09 06:51 PM (14 years, 11 months ago)

Quote:

Stonehenge said:
Actually, Seuss, that is how they do it in an AC or fridge. They compress the gas, cool it to room temps and let it expand. Lets stop quibbling.






Quibbling?  Seuss said something.  You said he was wrong and proffered an incorrect statement.  (I'm not sure what they do in an AC or fridge has to with this, however; since that's a different setup then imagined by zouden here)

as such:

Quote:

Stonehenge said:
Blowing compressed air or co2 will not cool anything unless there is a liquid that is evaporating.


'



You replied to seuss and told him he was wrong and stated an incorrect fact and then when he, quite nicely, explains why your correction was in error, you call it quibbling when it was you who started the exchange.


As Seuss stated: PV=nRT  Temp is proportional to volume so it appears, yes, you can affect temp by changing volume, as anyone who's used a bike/basketball pump or whatever will recognize.

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OfflineSeussA
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Re: Could you cool something with compressed air? [Re: Stonehenge]
    #10191759 - 04/18/09 07:00 PM (14 years, 11 months ago)

> Actually, Seuss, that is how they do it in an AC or fridge. They compress the gas, cool it to room temps

Almost... the gas isn't cooled to room temperatures... some of the heat energy that the gas acquired during compression is dissipated into the surrounding air, but the gas is not cooled to ambient room temperatures.  It is better to think of the system as a heat pump where heat energy is transferred from one system to another.  And yes, this is how an AC or fridge work, as I stated in my post above, "This is how refrigeration works, known as phase change cooling."

> Why would compressed CO2 be colder than compressed air?

Because CO2, in a cylinder, is actually in liquid form (under pressure).  When you release the pressure, the phase changes from liquid to gas.  The phase change pulls heat energy from the surrounding environment, thus it gets very cold.  If you were to use compressed air that was in liquid form rather than gas, it would be much, much colder than CO2 under the same circumstances.


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Offlinezouden
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Re: Could you cool something with compressed air? [Re: luvdemshrooms]
    #10191880 - 04/18/09 07:25 PM (14 years, 11 months ago)

Quote:

luvdemshrooms said:
I've been using compressors and compressed air since at least that long ago and have never seen it even remotely chill something as much. Granted I have never tried to cool a six pack.




But an air compressor doesn't release air nearly as fast as a fire extinguisher. I reckon if you filled an air compressor's tank to capacity, then released it all as fast as possible (with a much bigger nozzle than the standard one) then it would get pretty cold.

But I agree with Seuss, you'd probably need a phase change in order to get some decent cooling capacity.

Though... those little NO2 canisters get really cold. I've frozen a balloon just by releasing all the gas from one canister into it. And I don't think it's held as a liquid.

I haven't been able to find the formula which describes the energy change when pressure drops. I know there must be something, but it's been a very long time since I studied this.

Some rudimentary numbers:

six-pack of beer: 6*330ml = approximately 2000ml
temperature change required = -20 degrees (room temp down to fridge temp)
specific heat capacity of water = 4.2J/ml/k

Therefore the heat lost when cooling a six-pack of beer is 4.2*2000*20=168KJ

So now, assuming compressed air at 10 bar (which is the maximum most air compressors can do, I think) and allowing it to decompress to atmospheric pressure (1 bar) - how much air is required in order to cool the beer? This is the bit I can't complete.


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Re: Could you cool something with compressed air? [Re: zouden]
    #10191920 - 04/18/09 07:36 PM (14 years, 11 months ago)

> I haven't been able to find the formula which describes the energy change when pressure drops

Ideal gas law: PV=nRT

Remember, heat is energy.

> And I don't think it's held as a liquid.

Why not?

Edit: I just looked at the pressure of these cylinders, and you are probably correct.

Edited by Seuss (04/18/09 07:41 PM)

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Offlinezouden
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Re: Could you cool something with compressed air? [Re: Seuss]
    #10192045 - 04/18/09 08:05 PM (14 years, 11 months ago)

Could you find much info on it? I can't. But I know that they don't 'swish' like they've got a liquid inside. I just figured its compressed gas. And I reckon that the CO2 canisters (for soft drinks) are probably the same pressure as the NO2 canisters (for whipped cream / getting high)

edit: not sure how to apply the ideal gas law - does each degree change in T correspond to a degree change in the beer? That seems unlikely, since it's neglecting the mass of the beer.

Do I need another formula to convert T into kinetic energy (by multiplying by the specific heat of air)? Hmmm...


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Edited by zouden (04/18/09 08:08 PM)

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Offlinezouden
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Re: Could you cool something with compressed air? [Re: zouden]
    #10192132 - 04/18/09 08:26 PM (14 years, 11 months ago)

This page here indicates that the pressure in one of those little 8g canisters is 60 bar (900psi) which is considerably higher than what you can do with an air compressor. If that's the sort of pressure required to get a decent chilling effect then my proposal isn't really practical (not that I would pursue it anyway).

But... 8g of 60bar might have the same cooling capacity as 48g of 10bar. If that's true then a 5 kilogram tank (which is pretty small), compressed to 10bar (from an air compressor), should have the same cooling capacity as 100 nitrous oxide canisters.

Sure, it'd take a while to fill a 5kg tank to 10bar, but it'd still be pretty awesome to put your 6-pack into an insulated box and pull the lever to open your tank. I reckon it'd make a huge noise and all this frost would billow everywhere, and your beer would be cold. :awesome:

Keep it in the shed and impress your mates when you have a BBQ :awesome: :awesome:


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Re: Could you cool something with compressed air? [Re: Seuss]
    #10193075 - 04/19/09 12:24 AM (14 years, 11 months ago)

I think what the OP is describing works in theory, but for it to practical, the concept really needs to be adapted to the point where you've got a device thats barely distinguishable from conventional refrigeration and AC cooling systems.

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Re: Could you cool something with compressed air? [Re: Jamz]
    #10193146 - 04/19/09 12:38 AM (14 years, 11 months ago)

Actually there's a few significant differences:

-no coolant loop. The coolant is just air, and it's vented when used.
-the system requires no power when not being used. Compressed air is stored until you need it.


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Re: Could you cool something with compressed air? [Re: zouden]
    #10193773 - 04/19/09 05:12 AM (14 years, 11 months ago)

> not sure how to apply the ideal gas law - does each degree change in T correspond to a degree change in the beer?

Nope... that is a thermal transfer problem; not one of my stronger subjects.  I hated thermal dynamics and didn't do very well in it.  You would use the ideal gas law to find out how much the temperature of the gas changes when  you release the pressure.  It isn't going to be very much.  You now have a thermal transfer problem between the cool air and the warm beer can, and another thermal transfer problem from the beer can to the beer (I would simplify the two; can + beer and assume the can is a perfect heat conductor).


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InvisibleDieCommie

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Re: Could you cool something with compressed air? [Re: zouden]
    #10195264 - 04/19/09 01:18 PM (14 years, 11 months ago)

.

Edited by DieCommie (11/21/16 01:47 PM)

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InvisibleDieCommie

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Re: Could you cool something with compressed air? [Re: DieCommie]
    #10195602 - 04/19/09 02:11 PM (14 years, 11 months ago)

Without actually getting the constants k_g and k_w we can see some behavior.  The volume expression blows up when the temp of the gas approaches the temp of our beer.  That makes sense, the colder the gas is the less you will need. 

For the expression giving the temperature of the gas, if we assume that k_w is more than k_g (since water absorbs heat better than gas) then the temperature of the gas needed gets lower and lower, and then the model breaks down of course when the gas gets non-ideal.

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Offlinezouden
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Re: Could you cool something with compressed air? [Re: DieCommie]
    #10196033 - 04/19/09 03:22 PM (14 years, 11 months ago)

That's a clever way of doing it. So K_w is the cooling constant of beer in ice-water and K_g is the cooling constant of beer in air? That'll be one of the major hurdles, because we know that water is a better conductor than air so it'll be faster at taking the heat out of the beer. The gas will have to be extremely cold to overcome that handicap.


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OfflineChuangTzu
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Re: Could you cool something with compressed air? [Re: zouden]
    #10197540 - 04/19/09 07:25 PM (14 years, 11 months ago)

Of course you can get a lower limit on the amount of gas needed by taking the heat capacity of the gas, the temperature of the gas as it leaves the reservoir, and the amount of heat that needs to be extracted from the beer for it to be cooled to a sufficient temperature.  Any practical device would only approach this, but getting it arbitrarily close is just an engineering problem...

This approach also won't tell you much about timescales.

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InvisibleDieCommie

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Re: Could you cool something with compressed air? [Re: ChuangTzu]
    #10197991 - 04/19/09 08:44 PM (14 years, 11 months ago)

That lower limit would be very much lower than in practice though.  Most of the heat absorbed by the gas, in this method, would be absorbed by the environment and not the beer can.  The amount of heat absorbed by the beer - I would guess certainly less than 10%, maybe less than 1%; pretty small.

Crazy asymmetries in the universe making it difficult to cool things rapidly but easy to heat things rapidly.  :crazyeyes:

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Re: Could you cool something with compressed air? [Re: DieCommie]
    #10199387 - 04/20/09 02:13 AM (14 years, 11 months ago)

You could have the beer in an insulated chamber (like an esky, or whatever you guys call them) and I guess if you had the tank in the same chamber, then quite a bit of the heat would have to be drawn out of the beer.

Although, you'd have to let the air vent out of the chamber, of course, or else it wouldn't work. And that precious air carries most of your cooling capacity.

TBH I would have dismissed this long ago if it wasn't for the Mythbusters apparently doing it with a fire extinguisher.


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Re: Could you cool something with compressed air? [Re: zouden]
    #10203462 - 04/20/09 07:25 PM (14 years, 11 months ago)

Quote:

zouden said:
You could have the beer in an insulated chamber (like an esky, or whatever you guys call them) and I guess if you had the tank in the same chamber, then quite a bit of the heat would have to be drawn out of the beer.

Although, you'd have to let the air vent out of the chamber, of course, or else it wouldn't work. And that precious air carries most of your cooling capacity.

TBH I would have dismissed this long ago if it wasn't for the Mythbusters apparently doing it with a fire extinguisher.




That's why I said it's an engineering problem.  You could have the beer in an insulated box, and pipe the compressed air in from somewhere through a series of ducts which surround the beer in a circuitous route.  Make the path long enough/contact area great enough and the air will extract an amount of heat arbitrarily close to the theoretical max...

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Re: Could you cool something with compressed air? [Re: ChuangTzu]
    #10205253 - 04/21/09 01:52 AM (14 years, 11 months ago)

You shouldn't need ducts though, because releasing that much air that quickly will ensure pretty even distribution, I reckon.


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Invisiblejohnm214
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Re: Could you cool something with compressed air? [Re: zouden]
    #10205368 - 04/21/09 02:55 AM (14 years, 11 months ago)

yeah, but you don't want distribution, you want it localized where it can absorb heat.  You also want something that's better at conducting that heat then air.

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Re: Could you cool something with compressed air? [Re: johnm214]
    #10205396 - 04/21/09 03:27 AM (14 years, 11 months ago)

Yes, but in this case the cooling is from the air itself, so you'd want to minimise the amount of stuff you have between the air and the beer.


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OfflineSeussA
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Re: Could you cool something with compressed air? [Re: zouden]
    #10205694 - 04/21/09 07:14 AM (14 years, 11 months ago)

If I were doing this, I would would take two copper pipes, one that can snugly hold a beer can, and another that is slightly larger.  Place one pipe inside the other and cap the top and bottom, making a copper cup holder (doughnut), more or less.  Drill some tiny vent holes around the top and add a tube to add compressed air in the bottom.  As the compressed air escapes out of the top vent holes, the copper will cool and act as a heat sink for the can of beer.  Don't expect great results with compressed air.  If you were venting in liquid CO2, it would work great.

Be careful of too much pressure as well... depending upon the thickness of the copper and the pressures involved, you could be creating a small fragment grenade.


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Re: Could you cool something with compressed air? [Re: Seuss]
    #10205699 - 04/21/09 07:18 AM (14 years, 11 months ago)

I like that idea. Scaling it down to one can at a time would make things a lot easier, and if it's cooling it as rapidly as we'd hope then you can put another one in afterwards (as soon as the tank is charged).


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Re: Could you cool something with compressed air? [Re: zouden]
    #10206153 - 04/21/09 09:53 AM (14 years, 11 months ago)

I didn't mean that the ducts would place anything between the cans and the air.  They could be half ducts, using the beer cans themselves as the inner walls.

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InvisibleDieCommie

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Re: Could you cool something with compressed air? [Re: zouden]
    #10206478 - 04/21/09 11:12 AM (14 years, 11 months ago)

Another practical problem you would likely have, with any method, is unequal cooling.  I bet you would get ice chunks on the inner wall of the can with warm beer in the middle and you cant really stir or shake the beer.

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Offlinehdang
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Re: Could you cool something with compressed air? [Re: DieCommie]
    #10235162 - 04/26/09 06:48 AM (14 years, 10 months ago)

general stuff, but...pressure and temperature are proportional, that is a change in pressure brings a change in temperature. the problem is when air leaves the compressor its already back at atmospheric pressure and you've missed the boat.

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Offlinezouden
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Re: Could you cool something with compressed air? [Re: hdang]
    #10235171 - 04/26/09 06:53 AM (14 years, 10 months ago)

Have you ever felt the gas coming out of a compressed tank? It's extremely cold. You can freeze things with it.


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