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Thermoacoustic Cooler Means Green-Friendly Icecream
MuddyRiverDoc writes "National Public Radio aired a story describing ice cream
manufacturer Ben & Jerry's sponsored
development of a thermoacoustic refrigeration technology, which uses helium gas
subjected to ultra-loud 173 db sound to chill an ice cream cooler. The NPR interview and
pictures of the Penn State researchers who did the development is
available. There is also a brief description of the technique at the Penn State Live site and at the BBC, and an
over-cute Ben & Jerry's broadband presentation, Sounds Cool!, that
does however provide a useful diagram. Thermoacoustic refrigeration has been a focus of research
for more than a decade at Purdue
and elsewhere,
and has reportedly flown on the Space Shuttle, but this prototype is reportedly
the first that demonstrates the size, efficiency, and quiet operation that
promises successful commercial introduction. Cool Sound Industries,
Inc. is reportedly exclusively licensed for this thermoacoustic technology."
I heard this interview on the radio. Apparently the process doesn't save any energy. It doesn't use ozone depleting chemicals though. Unless it ends up being much less expensive to manufacture I doubt it will go anywhere.
"God fights on the side with the best artillery." - Napoleon, Marshal of France - speaking truth to power
Well, here's yet another link that says..
But from the outside, it's no noisier than your typical icebox. The noise generated by the Penn State fridge can only be reached when the gas is under tremendous amounts of pressure -- 10 atmospheres worth. If the gas escapes, the pressure dissipates and the sound dies down.
Pop Sci had a small bit of coverage on this about half a year ago. Not very informative, but, it can't hurt. Anyway, I'm wondering how feasible putting this in a house is, since the padding required to block the noise would be so bulky (IANAAE) that to make it fit in a standard refrigerator cabinet, you'd have 3 ft^3 of space. :-) Of course, they could just make a small compartment for freezing the foods quickly, and then move them into normal storage. Well, I'll go off to read the article so I have a clue now. :-)
Hurricane Ivan: A 17th century prison collapsed. All of the inmates escaped.
Inside the canister there's 198 Decibels going on... That would shatter your ear drums and make your eyes bleed (possibly) pretty quick I understand...
Outside the container all your hear is a regular humming noise at one frequency...
If you ignore the other uses of a tool, does that make the tool less useful, or you less useful?
Peltier coolers are very inefficient in terms of heat shift. Right now, the best known materials aren't much more than ~10% of Carnot (thermodynamically limited) efficiency. This means that they produce a lot of heat to move just a little. This is why your Peltier block will get pretty chilly on one side but scalding hot on the other and why CPU Peltier rigs virtually require a water block to operate. Standard phase-change coolers are much better, and these new devices (haven't read the article yet) may be even better.
They opperate at 5% efficiency, while top end refrigeration is at 45%. Instead, these guy should be looking at cool chips, which opperate at 55% efficiency.
I prefer the "u" in honour as it seems to be missing these days.
If you suck the freon out of your conventional freezer it will kill you too. If you'd RTFA you'd know the sound waves are contained in the cooling chamber ond only a dull hum (comparable to a normal fridge) is heard.
RTFA
Blaming GW Bush for the Iraq war is like blaming Ronald McDonald for the poor quality of food.
OTOH, one can't convert thermal energy back into microwaves, so the heat must get out of the food by thermal conduction, which isn't very quick in the usual food substances.
Freon
Because Freon is non-toxic, it eliminated the danger posed by refrigerator leaks.
First result when googleing for freon.
Things can brake you know and the sound can get out.
Technology, the cause of and solution to all of life's problems.
Besides the low efficiency mentioned above, there are two other problems with Peltier chips. One is cost. The second problem is that, being made of lead telluride, they aren't very environment-friendly. Lead compounds are rather toxic and do not degrade in nature.
Unfortunately, there's absolutely no way to move heat from anywhere to a warmer place. When one wants to cool something to a temperature that's lower than the ambient we are in, one must first raise the temperature of the medium we want to cool. In both "classical" refirgerators, where a compressor is used, and in these new thermoacoustic chillers, the means used to raise the temperature is by compressing a gas. The compressed gas becomes warmer than the ambient and radiates heat away, through a heat exchanger. When the gas is expanded its temperature drops. Since we let it radiate heat when it was compressed, this expansion will make it drop its temperature to a point that's lower than the ambient temperature.
Reported maximums (research-only included) in terms of Carnot efficiency:
Stirling-cycle (phase-change): ~50%
Peltier junction (solid state): ~10%
Thermoacoustics (standing wave in gas): ~40%
Using a 'speaker fridge' now would be quite wasteful in terms of efficiency, although researchers believe that they can surpass the old CFC-type compressors soon.
The question that comes to my mind, though, is why the focus on the cooling itself. For a non-emissive object like ice cream, better energy conservation may be more easily achieved through better insulation. How about investing in cheaper silica aerogel, hippies? This stuff is virtually as light as air, essentially made of sand, almost as insulative as pure vacuum, and fairly strong. Having a cooling engine without any ozone-depleting chemicals is great, but it's kind of silly if your freezers still have interior styrofoam lining.
First off, the 190db figure is the sound level INSIDE the unit. Acording to the reporter, the sound level outside the unit was no louder then a standard cooling unit.
From the description of given, the tech sounds interesting. They use a powerfull speaker to create areas of high and low preassure in the chamber. In the areas of low preassure they place tubes which run to the cold case. In the areas of high pressure they place tubes which run to an external heat exchanger to vent the waste heat.
I can definately see this technology comeing into widespread use in the future, as stricter enviromental controls continue to restrict conventional refirgerants. I also wonder how well it would work in an automotive setting, where the high level of vibration makes coolant loss more of an issue.
I always liked these - not too hard to make, but also not as effecient as other methodes. Apply compressed air, tube gets hot on one end and cold on the other.
try { do() || do_not(); } catch (JediException err) { yoda(err); }
Basically, they put a gap (of air or other gas) which acts as an insulator between the hot and cold side of the peltier which they somehow get the electrons to tunnel over. This keeps the hot and cold sides completely seperated, which is the real efficiency issue with current peltiers.
'He was a dreamer, a thinker, a speculative philosopher... or, as his wife would have it, an idiot.' - Douglas Adams
Helium is extracted from natural gas, and it's a rare and non renewable resource. You can find it in the atmosphere, too, but it would be way to expensive to exploit. Right now the trend it too reduce the amount of helium used in the industry where possible, or else we'll eventually run out of the resource. You can have a look at : http://www4.nationalacademies.org/news.nsf/isbn/03 09070384
IANWYTIA (I Am Not Who You Think I Am)
Doesn't quite work that way. The reason why you have problems with noise is that speakers are intentionally designed to propogate sound. When sound waves hit your walls the walls resonate and pass along the sound. The refrigerater is quiet to the external world because the compression chamber is designed exactly so that the sound waves reflect and cancel in exacting positions inside the chamber. There is no excess accustic energy left to leave the chamber. This can only be done because the sound waves generated are exactly the wave length that matches the distance inside the chamber necessary to cancel. In other words, if you could "build a wall of it," it would only stop one exact frequency. What you really want is accustic foam that is designed to stop a wide frequency range of sound. This is commonly used in studios to prevent echos off the walls that give the "recorded in a box" sound effect.
Bel, the mostly sane.. "Of course I can't see anything! I'm standing on the shoulders of idiots." -- Me
The key difference between helium and argon is density. Helium is (obviously) lighter than air, and when released, floats to the top of the atmosphere. Presumably some evaporates into interplanetary space, given the energetic environment, there. Argon is denser than air, so it will tend to stay in the lower atmosphere.
Both are fossils of creation, but helium is also generated by alpha decay of radioactives inside the Earth. (Alpha decay particle steals two electrons from an unsuspecting nearby atom and presto, helium.)
If there were enough desire for helium, it might be possible to scoop it from the upper atmosphere. There has been talk of space planes running an oxygen liqufaction cycle for an 'air-breathing rocket'. If we can actually do that, we're halfway to mining helium. Helium would be part of the stuff that *didn't* liquify on the first part of the cycle.
The living have better things to do than to continue hating the dead.
The whole point about CFCs in fridges is that they are sealed in a closed loop {compressor - condenser - evaporator}, therefore, not able to damage the ozone layer until the fridge is disposed of {or you have an accident while defrosting with a chisel .....} The usual way of getting rid of CFCs is to wait until nobody is looking, then discharge them into the atmosphere. Practically speaking, there's not a lot else you can do with them anyway. So if you have a CFC-based fridge and it's still working reasonably well, you should hang onto it -- as long as it's not being abused, it won't be using significantly more energy than a more modern one would, and manufacturing a refrigerator uses up a lot of energy {which also is conveniently forgotten}. If it cost x kWh to make in the first place, and saves y kWh per year compared to the old fridge, it needs to last for x/y years before you have actually made any saving -- if it packs up before that time limit, you actually lose out on the deal {assuming the old one would have survived that long; but older kit was built to last forever, whereas newer stuff is built to pack up after awhile}.
..... so the contacts will stay closed and not spark. If anything does set off an explosion, it won't be the fridge itself.
My new fridge {purchased in a hurry after a defrosting accident last year involving a chisel, the evaporator and a faceful of evil-smelling chemicals} uses iso-butane -- cigarette lighter and camping stove fuel -- as its refrigerant. It's sealed in the pipes, so there is no danger of an explosion. Even if the pipes do start leaking, the thermostat won't be satisfied -- no matter how long the motor runs {trying to cool down the sensor} it won't get anywhere because there is no pressure, so no cooling
Je fume. Tu fumes. Nous fûmes!
As one of the inventors of this technology, I want make certain that readers understand that COOLSOUNDS and Kieth Franklin are NOT licenced, are UNRELATED, and are NOT IN ANY WAY ASSOCIATED WITH THE PSU TEAM !
Even if a fridge isn't the most efficient way to warm the house, it very efficient.
A fridge isn't that efficient in cooling, but it is very efficient in generating heat. Basic physics/thermodynamics.
Like many other devices most of the energy ends up as heat, very little escapes the room/house as light or other forms of energy. In fact a fridge pumps the heat from stuff inside it.
A heatpump can actually be more efficient at heating than a pure 100% heater. This is achieved by pumping the heat from somewhere so you get additional heat on top of the energy you put in.
A fridge is problematic if you don't want the room warmer. e.g. you are airconditioning the room and your fridge is inside the room.
Of you want the fridge to cool more effectively whilst inside an already warm room.