Charged Superhydrophobic Condenser Surface May Make Power Plants More Efficient 72
New submitter _0xd0ad sends this news from the CS Monitor:
"The activities of bantam water droplets in just one region of a power plant could make a significant difference in the output of power plants, scientists say. ... When a water droplet forms on a sheet of metal coated with a superhydrophobe, the droplet can camp there only so long as it does not merge with another droplet. As soon as it weds with another droplet, the energy produced is so great that the two will 'jump' away from that surface, as if in urgent deference to the surface's severe water phobia. Scientists have proposed that this 'jumping' could be incorporated into power plant design. ... 'To have the most efficient condensing surface, you want to remove the droplets as early as possible,' says Dr. Nenad Miljkovic, [postdoctoral associate at MIT and co-author on 'Electrostatic charging of jumping droplets']. But, in prototypes, this 'jumping' design is not as efficient as engineers believe it could be. Some of the droplets will just fall back to the condenser's surface, recoating it and slowing the process down. ... But a newly discovered component to the 'jumping' process might allow scientists to eliminate this fall back. In an accidental find, the MIT team found that droplets don't just spring from the surface — they also rebound from each other ... because an electrical charge forms on the droplets as they flee the hydrophobic surface. So, if a charge is applied to the condenser system, the water droplets can be electrically prevented from returning to the surface, he said.
So (Score:1)
This allows condensers to have a smaller area.
FINALLY!
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Smaller area means less water means smaller pump means less wasted electricity means higher plant efficiency.
But what's the polarity of the deflector? (Score:1)
Sounds like Star Trek technobabble.
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Nah it sounds like they need an electrostatic deflector array. Just invert the polarity and add in a magnetic flux transducer coil and voila, you'll be able to achieve an efficiency rating of 93.6%, easy.
Sheesh, were you asleep in your engineering classes?
Claification (Score:5, Informative)
The efficiency that is mentioned is water recovery/usage efficiency, not electrical efficiency. In this case a power plant would use more electrical energy to produce the condensation. This is still good news in that it could reduce water usage which is a big issue with power plants in the water starved west.
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Not just water, anything with a HVAC system, assuming this technology worked on other refrigerants.
Re:Claification (Score:5, Interesting)
The way I read this it was about heat transfer. If you can get the water droplets off the "cold" side sooner, you don't have to transfer heat through them. So you want the condensed liquid to go away so you can keep as much surface area in contact with the vapor as possible.
I'm not sure how this makes a closed system more water efficient.
Scale (Score:2, Insightful)
- a chem. eng.
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You know what kills heat transfer? Scale. This system will die (i.e. drop to not so fancy smancy levels) as soon as the scale builds up. - a chem. eng.
Will scale accumulate on superhydrophobic surfaces? I would think the water should move off the surface too fast to evaporate.
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Sub-cooling (Score:5, Informative)
For any particular pressure (or vacuum) there is an associated dewpoint temperature. In this case, it is where the liquid water condenses from the steam. Condensers use cooling water to remove the heat of condensation and subcooling. Cooling water is often cooled by evaporating some of the cooling water in cooling towers, so that fresh makeup water is needed. The steam condensate is recycled to the boiler to be heated and vaporized back to steam to power the generator turbine.
However, the condensed water adhering to the condenser tubes is further sub-cooled below its dewpoint. This means that more cooling water is needed, more condenser surface area, and more energy to reheat and vaporize condensate back to steam.
I speculate that the technology described reduces the amount of condensate subcooling, leading to less cooling and heating duty, improving overall efficiency.
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I agree, no where does it mention that increased condensation is something that will be achieved or water efficiency itself will be increased, its only discussing the efficiency of the heat transport process. I read the article to figure out what he was talking about....and they did talk about a second application that does mention condensation as a power source.
But the finding also suggests another possible new application, Miljkovic says: By placing two parallel metal plates out in the open, with
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If the droplet leaves with a charge, the opposite charge remains and counters the condenser charge, so you need to replenish the condenser charge. At some other point, the surplus charges of the droplets need to be siphoned off. If the movement is supposed to be effective, you will have to maintain a voltage difference, and a current corresponding to the number of droplets. That means that you need to invest power to keep the process running, with a resulting higher temperature of the condensed water. Will it be worth it?
AC with an EE?
That is one of my questions also. In microbiology this type of effect is everywhere. The nature of polar and non-polar molecules is the key to the cell bi-layer and is self assembling in the fact that polar loves polar. The natural process of body cooling incorporates hydrophobic elements in the cooling ducts. I don't see how this is big news. I would like to see some more information on Dr Sadoway's work at MIT [wikipedia.org] on the liquid metal battery. If he is correct it would help more than this b
What? (Score:1, Insightful)
No, sorry OP, you're gonna need to spell out exactly why it'll make things more efficient. Start from the assumption I don't know what a 'bantam' water droplet is, cos, as far as I understand it, powerplants make electricity by heating up water into steam (via coal/gas/nuclear/whatever) then expanding it through turbines to spin generators. Where, in that process, does this efficiency gain come in? Where is this 'sheet of metal' that drops are forming on? What drops? Why are they forming there? How is stopp
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power plant (Score:3)
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Yes, after all these years we're still running on steam. Everything we are and do is based on the interaction between the water and the sun.
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Steam is just a convenie
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and where did the natural gas come from? Dead plants... covered over my erosion caused by weather patterns... all water and sun my friend.
I wasn't denigrating steam. I've a small DIY steam engine myself and take my kid to a steam engine fair every fall. It's a great technology. I plan on building a larger one some day to power a generator as literally any fuel will work to heat it and there-by generate electricity.
Re:What? (Score:5, Informative)
Yea, the OP did make some assumptions about the understanding of the reader and basic heat engine operations.
Most power plants have a boiler that converts the working fluid to a gas. This gas is piped at high pressure though a turbine which drives a generator. This lowers the temperature and pressure of the gas which is then sent to a condenser where the gas is converted back to a liquid. This liquid is pumped into the boiler and the cycle starts over.
What they are talking about is the place where they take the working fluid from a low pressure gas to a liquid by removing heat. This takes place in a condenser. A condenser has cold surfaces that are exposed to the low pressure vapor. These cold surfaces have liquid condense on them that then runs off to be pumped back into the boiler. Apparently being able to get the liquid off the cold surfaces quickly makes the transfer of heat more efficient and faster.
Of course, the real question about their theory here is if the process they claim can be engineered to happen and provide more energy savings than it consumes. So far they have not been very successful doing this on an industrial scale.
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Apparently being able to get the liquid off the cold surfaces quickly makes the transfer of heat more efficient and faster.
You got it exactly wrong. Being able to get the liquid off the cold durfaces quickly stops the transfer of heat to liquid that has already condensated. The warmer the liquid getting out is, the less heat you need to revaporize it. And the less energy you need for cooling the condenser. It has done its job once it produces liquid. Cooling liquid is a waste of energy: its purpose is to cool vapor.
Re:What? (Score:4, Informative)
Another small detail to add to your comment. The faster you turn the vapor into liquid, the lowest is the pressure at the condenser, reducing the work of the pump that creates vacuum after the turbine* and increasing the overall efficiency of the system.
Also, if you have a bigger heat conductivity, you can apply a smaller temperature gradient into the vapour. That could theoreticaly improve the efficiency, but I don't know how that part works in practice.
* Yes, the vapor goes from the turbine into a pump. Seems counterintuitive, but you want to condense it, what is easier to do in a highter pressure, but the turbine works much better with vacuum... In the end big plants gain efficiency by putting some work back into the steam.
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There's more to Christianity than faith-based belief in intangible entities, you know. For example, the whole "peace, love, and brotherhood" thing that the religion is based on.
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And cake sales. I was brought up by Methodist parents.
That doesn't mean I believe a word of the mumbo jumbo. It's the term 'Christian Science' that is choc full of WTFery.
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No, it's your interpretation of the term that's chock full of whatever. The term itself is generic and innocuous.
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No it isn't. Those words have meaning. That's what words are for. To convey meaning.
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No it isn't. Those words have meaning. That's what words are for. To convey meaning.
People have differing interpretations of the same words, based on their individual preconceptions and prejudices. That's what people do - understand the meaning they want to understand.
If things were as simple as your post makes them out to be, there would be no debate as to the meaning of Constitutional Amendments.
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You must be new here if you're going to attack the CS Monitor on its name.
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No. Just flogging a well flogged horse.
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Not dishonest at all. I'm not new here and the subject has come up before.
I was criticizing the name of the CS Monitor for being completely stupid, which it is.
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It's a bit like me starting a serious journal on cryptography and calling it the 'Virgin Prostitute Reporter'.
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I don't discriminate. All religion is nutcase. The difference is just a matter of degree.
Beer connection (Score:2)
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Conversely it would be better if the outside of beer glasses were more hydrophilic, because the longer every drop of water can be delayed from rolling off the surface and leaving more room for condensation to take place, the more time we would have to drink the beer at a suitably low temperature.
Beer cozy?
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You know, most people solve that by using a smaller glass. An insulating one is normaly a good enough second option (but it's nice to feel the glass temperature).
Discovering a more hydrophilic material that's a worse heat conductor than glass looks like a huge enterprize for too small a gain.
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Have a G&T with ice.
The ice keeps it cold and it doesn't taste like beer. Double bonus.
Super-hydrophobic coatings (Score:3)
Super-hydrophobic coatings are now easily available. [homedepot.com] They work very well when new, but customers complain about the coating wearing off rapidly. Something with a more durable bond will be needed.
This is yet another of those materials science articles which jumps from "minor discovery in materials science" to "huge commercial breakthrough Real Soon Now." It's bad for MIT's reputation that they put out so much hype.
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Well, water and dissolved minerals. Those minerals might not know that they aren't supposed to stick to the hydrophobic coating. Scale is a big problem with traditional heat exchangers.
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I've never been good at chemistry (for an engineer), but I imagine that stuff can precipitate out for various reasons. And there is all sorts of weird chemistry going on here - hydrophobic surfaces, electric fields, massive amounts of heat transfer, etc.
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I agree that this is cool stuff. It makes me wish I had a stronger background in chemistry. I went to a really crappy high school and so I was always behind with my chemistry, taking pretty much the bare minimum in college. For the most part I like it (well, maybe not organic), so it's too bad.
You don't need much chemistry (Score:2)
This is very clean water not tap water (Score:2)
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Thanks, that makes sense. What about the other side of the heat exchanger? I imagine that water is pretty filthy. Isn't that side just as important?
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The cooling water can be filthy to the point of having sewage in it at one power station where I did some work (and vast populations of diatoms and algae), or seawater in other places. More than a century of using brass tubing has resulted in tubing that keeps fairly clean and corrodes very slowly, with a bit of help from the occasional lump of magnesium. The corrosion products form a very thin and strong "patina" as you
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Cool, thanks for the info. This is why I hang around here. :)
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Well, water and dissolved minerals. Those minerals might not know that they aren't supposed to stick to the hydrophobic coating. Scale is a big problem with traditional heat exchangers.
No dissolved materials, it's condensing from steam.
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The only thing that will come into contact with the superhydrophobic coating is moisture, so I wouldn't expect the coating wearing off to be as much of a problem there as, say, on your smartphone, which you handle constantly.
For polymer coatings, you have to worry about things like hydrolysis and thermal degradation of your polymer. Since surface geometry is also a major contributor to the hydrophobic character, I imagine there could also be issues with dimensional stability at the microscopic level.
Steam Baloon (Score:1)
Would a coating like this help lower the weight of water clinging to the inside of an insulated steam balloon?