Researchers Pave Way For Compressor-Free Refrigeration 218
Hugh Pickens brings news that scientists from Penn State have developed a new method for heat-transfer that may replace the common compressor-based system used in household appliances. Quoting:
"Zhang's approach uses the change from disorganized to organized that occurs in some polarpolymers when placed in an electric field. The natural state of these materials is disorganized with the various molecules randomly positioned. When electricity is applied, the molecules become highly ordered and the material gives off heat and becomes colder. When the electricity is turned off, the material reverts to its disordered state and absorbs heat. The researchers report a change in temperature for the material of about 22.6 degrees Fahrenheit... Repeated randomizing and ordering of the material combined with an appropriate heat exchanger could provide a wide range of heating and cooling temperatures."
Re:Kind of (Score:5, Informative)
Not at all. Microwave works by emitting electromagnatic waves that exite water molecules, thus making them and (indirectly) whatever they are a part of warmer.
Re:22.6F temperature change (Score:3, Informative)
Congratulations on not even reading the whole fucking summary.
Re:compressionless is new? (Score:5, Informative)
It's still based on compression (and out of Penn State, licensed to Ben and Jerry's, of course), but it's a much *faster* compression, at the frequency of the sound waves used, and it takes advantage of air's intrinsic nonlinearity at high acoustic amplitudes, rather than the much slower effects inherent in traditional refrigeration techniques.
http://www.acs.psu.edu/thermoacoustics/refrigeration/benandjerrys.htm [psu.edu]
Re:Already been done? (Score:3, Informative)
It's pretty vague, but it sounds like it is not continuous. The Peltier effect with thermoelectric material is constant as long as electricity is applied. This new material seems to give off heat and is then able to absorb heat once the electricity is turned off.
It's sound pretty strange and not much better than thermoelectric which already has been around quite a long time. Just wait and see if we can get more technical explanations later.
Re:2nd law says no. (Score:2, Informative)
There, fixed it for you.
Re:2nd law says no. (Score:5, Informative)
There. Fix'd it for you.
When external energy is applied to the system (like, say, electricity), then the system isn't isolated.
Re:One thinks a Uni would not mangle it this bad (Score:5, Informative)
TFA is written very poorly and describes a phenomena involving polymers that is already widely known. There are many examples. Here is one you can try using something far less exotic than the polymers mentioned in the article.
For this example, take a rubber band. Stretch it out. Touch the stretched rubber band to your lips. It will feel warm. Hold it in the stretched position for a few seconds to let it cool down to room temperature. Now let the rubber band relax, and once again touch it to your lips. You should now notice that it will feel cool.
The above process uses exactly the same principles described in TFA. Stretching the rubber band causes reduction of disorder by aligning the polymer chains. It also warms the rubber band because of the work applied. As you hold the rubber band in the stretched state it will cool to room temperature releasing some of the energy needed to heat it. This is equivalent to the step where the electrical field is applied.
Now release the rubber band. The polymer chains now revert back to a disordered state, cooling the rubber. Since the rubber band started in a stretched room temperature state the relaxed rubber band will now be below room temperature. this is equivalent to turning off the electric field as mentioned in the article.
Voila. This is a wonderful new refrigeration system that will replace all existing known cooling systems. NOT.
There are so many issues with practical application of this it is not funny. If these issues didn't exist we would have been using rubber band refrigerators for many decades already.
Also, please note that from a thermodynamics point of view this is essentially how a conventional refrigeration system works (albeit fat far more efficiently).
Re:Efficiency (Score:4, Informative)
you missed the point. polystyrene is flammable, but completely lacks the poly-vinyl-chlorine.
chlorine is an important part of many poison gasses, although 'pure' chlorine is more of an irritant combined with vinyl the chlorine gas is Quite toxic, that's the big problem, in some states it's becoming illegal to use PVC piping, because in a fire when people are trapped breathing fumes, the toxic vinyl chloride gas can kill not only trapped victims but can make onlookers and rescuer crews sick, if they survive.
I know the following link is greenpeace, but they had the most comprehensive page about why Poly vinyl chloride (PVC) is so toxic.
remember, this device is being proposed as a replacement for the compressor/gas phase of a fridge, not the outer housing.
http://www.greenpeace.org/usa/news/how-to-find-and-avoid-toxic-vi [greenpeace.org]
Kind of like kinetic stasis for ferropolymers (Score:5, Informative)
Going by the rough description in TFA, it sounds like electricity's effect on the ferropolymer causes its bonds to strengthen, or perhaps to magnetically align, increasing rigidity, reducing the material's potential for containing kinetic energy.
If the material's new state caps the amount of kinetic energy it can store, it has to move on - first law of thermodynamics and all.
This may be the next interesting bit in applying their discovery - finding a compatible heat conductor, and also learning the optimal frequency, voltage, current etc. at which to apply voltage.
Re:Efficiency (Score:5, Informative)
The fluids go to a condensing unit (compressor) which, instead of going to a coil with a fan directly to outside air, goes instead to a heat exchanger with water. The water runs throughout the building taking heat away from all of the water source heat pumps.
Typically, what I remember, the water will gain 10 degrees from the loop and dump 10 degrees at the cooler. The cooler will either be an evaporative cooling tower or a "fluid cooler" but it is basically always dumping 10 degrees of heat multiplied by however many gallons per minute of flow.
Yeah, the individual space gets a larger than 10 degree F temperature difference, and the SYSTEM gets "just" 10 degrees, but it's apples and oranges, different flow rates of fluids, CFM, BTU's, etc. Energy is energy, the temperature difference is only one part of the equation.
So, my point, and I do have one, is that ~20 degrees C or ~20 degrees F or whatever, it's enough if applied correctly.
Re:Possible practical implementation (Score:1, Informative)
Why complicate things more than they need to be?
Have two layers of the stuff, back to back, with one outer surface exposed to outside and and the other to the inside of the fridge.
Power on both, to dump their heat. Then power off the inner one while the outer is still on; it'll suck heat from inside the fridge. Then simultaneously power off the outer one and power on the inner one; most of the inner one's heat is sucked up by the cold outer one. Then flip their states again; the outer one will dump most of that absorbed heat to the outside, since the inner one is currently rejecting heat. Repeat as necessary. Additional airflow over the outer layer may improve performance, in which case there may indeed be moving parts - a fan - but that's a lot cheaper to replace than a compressor.
Compressors are hard to beat (Score:4, Informative)
I'm not sure how close they come to reverse Carnot in a modern "fridge", but they are very durable. It seems like we had two refridgerators the whole time I was growing up, and the only reason we got the 2nd one was because we were in a different house. It's not exactly like they were being fixed all the time either. In fact, aside from the fact that the fridge we had when I was a kid required manual defrost, I don't think they ever required maintenance. The HVAC unit in my old condo had to be pulled. This was in 2006. When the tech opened it up, we discovered it was build in 1979. These units are essentially refrigerators too, with compressors. Now, that was a good old USA unit, with a steel housing and everything. I'm not sure if the cheapo plastic jobs they installed will hold up as well, but that's an implementation issue, not a problem inherent with the underlying tech.
The point is, can this new technology be as efficient as a compressor, as cheap as a compressor and as DURABLE as a compressor?
That said, perhaps it will find applications outside of keeping your OJ cool and your brow dry. If it does, great; but the current tech is pretty good. I wish they were silent, but even at that, a modern fridge is pretty quiet too.
Re:Adsorption (Score:5, Informative)
1. 12 deg C is a really large temperature change, we have to do with 1-3C. My group would kill for a material like that, $EVIL_GENIUS_LAUGHTER. (With a design like this [iop.org], it's possible to have a much greater cumulative change of temperature than what any single piece of material does, so that's how to cool from +25 to -18 C).
2. The hysteresis [wikipedia.org] is not too high, look at fig. 1 in the paper. This is important, because hysteresis means you're converting electricity to heat inside your fridge. Many materials have great change in entropy and temperature when you put an electric or magnetic field on them, but it's killed for practical purposes by hysteresis.
3. You need a really high electric field. The curves in the paper are done at 100-200 MegaV/m, meaning that you need 100-200 kV to polarize a layer of 1 mm thickness. A CRT uses voltages of around 20 kV, and so it's plausible to use thin layers, or just live with the fact that you'll only get 1-2 C temperature change. (Which means it has to compete with magnetic refrigeration on an even footing).
4. It's hard to polarize and depolarize the material without electric losses. (This is a problem for ferroelectric cooling in general). You're basically charging and discharging a huge capacitor, and you'll lose the charge on the capacitor every round. This could be fixed by putting it as the "C" in an oscillating (LCR) circuit with some inductance, but it's not easy to get an inductance (L) high enough, unless you run at high frequency. This material looks to work at high frequency (the hysteresis curves are taken at 1kHz), but how do you transport the heat into/out of it? If you run at 1kHz, you'll have less than half a ms to transfer heat to the cooling fluid, which means you'll need to use a very thin layer indeed. (Incidentally this will make it easier to get a strong field gradient). Then there's the problem of moving the cooling fluid back and forth over many layers of sub-mm thickness polymer. I'm not saying it can't be done, and there might very well be smart solutions I haven't thought of, but it's not trivial. (And btw, magnetic cooling doesn't have this problem, because we can use a permanent magnet with a several cm gap, and balance material moving into the gap with material moving out.)
Various materials (Score:3, Informative)
"These polarpolymers include poly(vinylidene fluoride-trifluoroethylene) and poly(vinylidene fluoride-trifluoroethylene)-chlorofluoroethylene, however there are other polarpolymers that exhibit the same effect."
It doesn't say what the "others" are, but perhaps there's something that can be used that would be more tolerant of high heat (or less toxic). Alternately, perhaps it could be used in a heatsink type scenario wherein the sink is cooled as it absorbs heat, but doesn't become superheated itself.
Re:Efficiency (Score:3, Informative)
Re:Compressors are hard to beat (Score:3, Informative)
most new cars only have a 2-3% AC penalty (4-5% on max AC setting). With the adoption of variable nozzle compressor technology (called variable displacement), the AC system in most cars only make air as cold as you're requesting it to, and the unit automatically disconnects during acceleration, allowing a smaller engine to feel like it has more power.
In fact, most cars, actually get better fuel economy with the AC than with windows open, when driving over 50 MPH. In stark contract, SUVs actually get less of a benefit than do small cars... 1st, there's already so much drag, opening your windows does not add much more. Also, large engines have ample torque, and have no trouble running larger (and thus more efficient) compressors. http://www.slate.com/id/2194536/ [slate.com].
Older cars, yes 8-10% was normal for AC efficiency loss, but not really anymore.
In other interesting news, they have actually shown that comfortable drivers actually get better fuel economy than uncomfortable drivers. On hot days, drivers tend to be more impatient, and accelerate harder and driver differently than on comfortable days. ventilated seats actually help this further since not only is your front cool, but your back as well is not self insulating and sweating into the seat behind you, and in most cars with ventilated seats, AC use will be decreased slightly (drivers are more comfortable at slightly warmer temps).
Rule of thumb: it varies from driver to driver, ,ambient temp, and with humidity, but if it's over 85, keep the windows up regardless of driving speed. If you're going over 55MPH, keep em up regardless of outdoor temp. It's not only more efficient, but has safety implications as well.
If your car has variable temperature controls separate from the fan speed and vent position controls, generally, use the COLDEST setting, regardless of the temp you want to achieve. (most cars mix warm air with cold to make varying temps, so setting to a warmer temp does not reduce energy use). Use recycled air settings always with the AC. Use the fan speed to control your comfort level. The most efficient system will have automatic temp control (with digital temp readouts) but unfortunately there are typically only available in high end cars. Also note, in most cars, the defrost setting will use the AC unless you are blowing heat, even when the AC is off, so if you've got foggy windows in the summer, you might as well roll the windows up cuz the AC is going to be running one way or the other...