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Refrigerators To Cool With Sound (Cool!)
T-Kir writes "A very interesting report from the BBC where researchers at Penn State University are developing a prototype fridge that cools using metal plates and sound waves. If successful, this technology would help remove the dependance on gases that contribute to global warming. Talk about Cool!"
But it's possible to use ANY compressable gas for cooling. The ones we use now are simply very efficient because they can store a lot of heat. There are several ways to make a cooling system more efficient (at removing heat) assuming you have not already taken the particular step to the maximum.
Of course there are two heat exchange systems in a typical refrigerator; Those inside which are intended to absorb heat, and those outside which radiate it. In a peltier-cooled system the same heat exchanger(s) do both jobs. You also end up needing some kind of heat sink to increase surface area since the thermally active portions of peltier coolers are flat.
By using some combination of these technologies we can move away from environmentally unsafe gases. While this new technology is certainly new and may be superior in many aspects, the only reason we have not moved to more efficient and/or "eco-friendly" designs to date is expense. Welcome to capitalist terra, my friends.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
I wonder what the heat output on the hot side is -- enough to supply a home's hot water needs, perhaps?
Probably not. Best you can do is 100% thermodynamic efficiency -> 40 degF of cooling (taking the chamber from ~70 degF to ~30 degF) would mean about 40 degF heating of an equivalent volume of air. Not enough to heat water for my shower...
Even if you did pick up some heat from friction, etc. you're not going to get the 80+ degF needed for water heating water.
These thinsg have been around for some time. That prototype that flew on the shuttle was from four or five years ago, at least. The main problem with these things is they just aren't as efficient as current refridgerators. Which means the heat output from the back would be slightly more then what the one in your kitchen spits out.
They could be really nice for niches (like the space shuttle) where low maintenence is desired. Another thing about the noise: it's extremely high frequency, and is attenuated very well by the metal that contains the acoustic wave.
By using some combination of these technologies we can move away from environmentally unsafe gases. While this new technology is certainly new and may be superior in many aspects, the only reason we have not moved to more efficient and/or "eco-friendly" designs to date is expense. Welcome to capitalist terra, my friends.
It's not as though expense can be omitted from the equation entirely. Cheap and easily produced refrigeration technology (and air conditioning, which is closely related) have probably prevented more illnesses than any recent development since antibiotics.
On the other hand if the gas is compressed farther it will be able to accept more heat, so you should be able to get a more rapid heat transfer
Sorry, it's been a few years since I had thermogoddamics, but I'm not sure this is correct. The heat transfer uses ENTHALPIC heat, which is given up or absorbed when the material changes state. In other words, Freon (ammonia, whatever) absorbs heat when it changes from a liquid to a gas, and vice versa. You compress the gas JUST ENOUGH to change its state to liquid, compressing it further has no effect (besides, compressing liquids isn't really practical anyway.) I believe what makes the Freon family so suitable for heat exchanging applications isn't it's enthalpic heat capacity, but the temperatures and pressures at which it changes state, i.e. practical in real-world terms. For example a compound that changed from gas to liquid at 2000 PSI at -140C wouldn't really be useful for much of anything. Some substances don't go through the liquid stage at all at practical pressures (carbon dioxide)... they go straight from gas to solid (and vice versa). Hard to pump a solid through a heat exchanger.
Anyway, you made some great points, but the solutions may not be as practical or simple as you suggested.
And I didn't see any mention in the article of what kind of compressed gas was used in the sound chamber.... Freon maybe? haha.
To ensure perfect aim, shoot first and call whatever you hit the target
CFCs and their replacements, HCFCs and HFCs, are all tremendously potent greenhouse gases. They have global warming potentials several thousand times that of carbon dioxide. The ozone problem is pretty much solved because global CFC production has dropped to near zero following the implementation of international treaties to protect the ozone layer. However, the global warming potential of HFC and HCFC replacements is worthy of concern.
Global warming is caused by the sun.
Just as it is true that global warming is caused by the sun, so my body generates most of the heat that keeps me warm. Nonetheless, if I wear too many sweaters, I will get too hot. Taking them off will cool me down, despite the fact that the heat is all coming from my own body. The same principle applies to the atmosphere. The earth's temperature is determined by a radiative balance. We can't change the sun, but we can change the atmosphere (our sweater), and that can cause the earth's temperature to change.
.. bear in mind one thing: cost. Obviously any innovative solution that is ecologically sound is good and all, but the worry is that the uptake in 3rd world countries would be slow.
The new fridge might be more reliable and does not pollute, but the old technology has an army of technicians who can service it, and I believe countries like China are still allowed to produce CFC coolants. In fact, when countries agreed to phase out CFC, China's phase-out was based on its production several years in the future, and as a result its production actually jump in the subsequent years as manufacturers took advantage of the loophole.
More information here
Michel
Fedora Project Contribut