Copper Nanorods Increase Boiling Water Bubbles 3,000%!
by Michael Graham Richard, Gatineau, Canada on 07. 8.08
Copper Nanorods Reduce Energy Needed by an Order of Magnitude
After super-efficient solar panels that are "hairy" on the nanoscale, here come "hairy" pots & pans, as well as computer chip heatsinks and other heat-transferring devices. Researchers at the Rensselaer Polytechnic Institute made the "unexpected" discovery: "by adding an invisible layer of the nanomaterials to the bottom of a metal vessel, an order of magnitude increase in efficiency is achieved in bringing water to boil. [...] The potential applications for this discovery are vast and exciting, and we’re eager to continue our investigations into this phenomenon."
Boiling: Now with More Bubbles!
When using their copper nanotech coating, the researchers "observed a 30-fold increase in active bubble nucleation site density — a fancy term for the number of bubbles created — on the surface treated with copper nanotubes, over the nontreated surface.” Read on to find out how these bubbles help.
Bringing water to a boil, and the related phase change that transforms the liquid into vapor, requires an interface between the water and air. [...] Even though most of the water inside of the pot has reached 100 degrees Celsius and is at boiling temperature, it cannot boil because it is surrounded by other water molecules and there is no interface — i.e., no air — present to facilitate a phase change. [...]Koratkar and his team found that by depositing a layer of copper nanorods on the surface of a copper vessel, the nanoscale pockets of air trapped within the forest of nanorods “feed” nanobubbles into the microscale cavities of the vessel surface and help to prevent them from getting flooded with water. This synergistic coupling effect promotes robust boiling and stable bubble nucleation, with large numbers of tiny, frequently occurring bubbles.
So the water isn't getting hot any faster, but it turns to steam faster. So if you're cooking, you get the signal that it has reached the right temperature sooner (and that can save some energy).
Cleaner Electricity Generation? Better Solar Thermal?
Most power plants boil water to make turbines turn. Could this discovery be useful in making these power plants more efficient? Probably too early to tell how it will be used, but if it makes it easier to produce steam, it should help. We can already speculate that such a material might be adapted to make solar thermal power plants harness the heat produced by the light of the sun more effectively.
Boiling is ultimately a vehicle for heat transfer, [...] This new discovery allows this process to become significantly more efficient, which could translate into considerable efficiency gains and cost savings if incorporated into a wide range of industrial equipment that relies on boiling to create heat or steam.“If the time taken to boil a given quantity of water is reduced by an order of magnitude, that should translate into significant cost savings”
Definitely a technology with lots of green potential. We'll keep an eye on it.
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This could help with water desalination! Awesome!
I thought cooking with copper was risky for one's health, eg cooking acidic foods in unlined copper pots.
And I doubt those nano-hairs could be lined.
it's obviously not going to increase the efficiency of anything by 3000%
( because that would clearly break a few thermodynamics laws ),
it's only going to make boiling processes smoother and more stable: a continuous flow of tiny bubbles instead of a random flow of big, turbulent bubbles.
"it's obviously not going to increase the efficiency of anything by 3000%
( because that would clearly break a few thermodynamics laws ),"
Article says that there are 30x more bubbles. Improvement in efficiency hasn't be given numbers yet by the researchers, but it's promising since they say "an order of magnitude".
I think it's great for power applications that require steam or whatever, but I'd worry about it for food. Would cleaning the pan scrub away the nanohairs, would pathogens find a home amongst the hairs? Would the hairs break off and get lodged in the food? Too risky.
"Would cleaning the pan scrub away the nanohairs, would pathogens find a home amongst the hairs? Would the hairs break off and get lodged in the food? Too risky."
I don't think most people realize how small these things are. Your pan is already all uneven and full of stuff that almost looks like that. It's just not organized so precisely as to have those properties.
But I'm sure that if they can't find a way to make it durable, they won't commercialize it in cooking stuff. The best application seems to be for power generation anyway.
And here we have the big problem: non-technical people reading technical material.
Let's bring it back to thermodynamics...
Not to be a jerk, but there is the simple matter of "latent heat of vaporization" associated with the phase change of water (liquid) to water (gas).
At 1 atmosphere of pressure (ambient pressure) you are going to pay 2257 kJ/kg of water that you are taking from liquid at 100C to gas at 100C. NOTHING is going to change that. You could boil it in a titanium cup, a goat skin bag, an aluminum can, whatever - that is the amount of energy needed to take water from a liquid to gas.
So when they say an improvement in efficiency, they're talking maybe about being able to make a steam converter smaller or being able to make it using less metal. The energy you need to boil the water will be necessarily the same.
No, this isn't magic; you're not creating energy here. You might just be moving it into the water a little quicker.
Tom, you are right, but you are missing part of it.
This doesn't work because it increases the surface area and conductivity (though it might do that also). It works because it creates more interface between the water and air to change phase.
Regarding use in pots and pans.
We all need to extremely, extremely cautious about any device that introduces nanoparticles into the body OR the environment.
I would encourage all readers to spend some time surveying the web-based literature concerning health effects of nanoparticles that get in the wrong place. We only are beginning to get glimpses of the potentially catastrophic effects of taking their safety for granted.
Keep in mind the following:
Unlike some naturally occurring nondegradable molecules (asbestos, volcanic ash) we did not evolve from lifes' beginnings in their presence.
We, nor any organism, can not enzymatically metabolize them. All we can do is hope they clump together into less bioactive clumps.
All they have to do is derange one biochemical process in fetal development and they will initiate lifelong effects for that organism.
I'm not trying to be alarmist or denigrating the great potential that responsible nanoparticle use might offer, but until humans evolve beyond the 'act now, deal with the consequences later' mindset, we will alway be a threat to ourselves and our planet.
Anonymous:
Doesn't matter what's going on... Nucleation sites increase nucleation of boiling, they don't decrease energy needed to vaporize water.
The opposite of this is superheating in the absence of nucleation sites. You can have water at >100C if you carefully heat it in a very clean container.
But when you talk about "efficiency" you're talking about thermo and this doesn't change any of the facts there.
Hmmm, could we just do without the pot and pans? Lets focus on the energy generating applications, this is where it really matters.
Heard of boiling chips or boiling stones? All it does is make the bubbles smaller and more predictable. It doesn't change anything else.
I have to agree with some of the other comments. Carbon nanotubes are not safe in conjuction with food. They're probably not safe in the air or on the ground either. They will have some great future use, but not yet.
Well, guess you'll have to go tell the RPI scientists that they don't know what they're talking about.
Just because someone is a scientist doesn't mean they are right. It means they are more likely to be right about particular questions in their field than any particular outsider, but that is all. Plus, if they are doing RESEARCH (which is their job) then by definition they don't quite know what they're talking about- if they did they wouldn't need to do more research.
As for "efficiency," no device we use in the world achieves the thermodynamic limit of efficiency. Although the amount of energy needed to boil water is indeed fixed, we must consider that some energy is lost to the surrounding air. Slower boiling due to insufficient interface with the air means more time for energy to be lost to the air, and so additional energy is consumed beyond what is necessary to boil the water.
The upshot of this is that, whether for food or for power plants, more of the energy ends up in the resulting steam, and less in the surrounding air. This means we can have more efficient power plants (operating closer to the thermodynamic limit).
Of course, in theory heat engines are a rather bad way of converting energy into electricity. The limit of their efficiency (based on entropy, not on conservation of energy) is strictly determined by the temperatures of the energy source and the place where waste heat is dumped. These temperatures are in practice limited by the ambient temperature and the melting point of whatever is containing your working fluid (here, the steam). The reason they tend to have higher efficiency than other methods in practice is that we've been building them for three centuries, and a LOT of engineers have worked on getting them close to the efficiency limits. Even so, our highest-efficiency power plants achieve 40% conversion of primary energy (coal, oil, nuclear, whatever) to electricity. By contrast, modern wind turbines hit 50% efficiency (theoretical maximum= 59.1%). Solar thermal (making electricity by turning light into heat and using a heat engine) can hit 40% efficiency today, just like any power plant. Current solar PV turns 20% of light into electricity, with a theoretical maximum of 31%. Higher efficiencies are possible, but they require more complicated PV cells (many of which have been demonstrated in labs) such as multiple junctions using different semiconductors, multiple thin films each with different band gap energies, ways for a single photon to excite multiple electrons, ways for multiple photons to excite a single electron, and so on.
It doesn't help for that at all. When you make steam for a turbine you superheat it. They don't care about bubbles - they heat the water till it's all steam and then heat it some more. If anything this would make it worse since it's easier to heat water than steam.
I could see it being useful in desalination plants - except that all the salt will be stuck inside the nano particles (since that's where the water evaporated), so it would clog very fast.
Make for a steam cleaning machine?
Actually if you're talking about thermal efficiency, there are gas turbines that can push 60% efficiency when waste heat is recovered to run a steam turbine in a combined-cycle configuration.
Coupled into a cogeneration facility and you see upwards of 89% efficiency. You can actually create a polygeneration system (electricity, hot and cold) too.
In everyday cooking the object is for the water to reach 100 degrees, after which the heat should be turned down, so that a minimal amount of boiling takes place.
Boiling is generally a wasteful activity that does not increase the speed of cooking since the steam is very close to 100 degrees also.
What this invention does in dramatically increase the amount of nucleation sites, so that with lots of extra (wasted) energy a very high RATE of conversion to steam can occur.
The way to save energy when cooking is to take the water to a boil and then turn the heat down just to maintain that temperature. This device may help in saltwater to freshwater conversion plants to increase rates of production, but not efficiencies
This should be of great interest to Cyclone Power Technologies. They use a "micro boiler" to power their steam engine. Basically, just enough water is boiled for the next piston stroke. Being able to boil the water faster would reduce heat loss (leading to a slightly higher thermal efficiency) and increase specific power.
This is great. I love "unexpected" results like this. So many of the greatest discoveries and inventions come from unexpected discoveries -- like penicillin.
Now, I think some people are missing the point here. With regards to cooking, this doesn't really do anything but let you know more obviously that the water is at boiling temperature. You can achieve that with a thermometer and not have to worry about nanomaterials leeching into your food.
The major benefit of this is that it helps the water turn to steam more quickly. Some people are missing that point in their comments. It doesn't help the water get hotter faster. It just makes it turn to steam 3000% more quickly. So, it actually does end up using less energy to generate the same amount of steam, but you are always going to be up against the limit that is latent heat of vaporization or whatever. Basically boiling large reservoirs of water is now more efficient. It's a great thing.
People who actually cook their own food from scratch on a regular basis will understand the critical flaw in applying this idea: food will have an increased tendency to boil over.
When that happens, any energy savings made will be lost and then some.
Not only that, but I'll bet the energy expended at making and applying the nano tubes is far greater than the cooking savings over design life of the pan
Nice try at marketing the idea to the "man in the street" but on the practical end it is quite ridiculous.
"Not only that, but I'll bet the energy expended at making and applying the nano tubes is far greater than the cooking savings over design life of the pan"
How do you know that, and even if that's true now, why would it be true in a few years?
All new technologies don't seem to be worth it at first, but it's a good thing it didn't stop us with most things in the past.
The principal is the same as 'Heat exchanger' design in quite a few new camping stove pots which doubles efficiency. This nanorod tech will halve much of energy use. It's big.
Google-Images: MSR XPD Heat Exchanger