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Charged Superhydrophobic Condenser Surface May Make Power Plants More Efficient

Soulskill posted 1 year,18 days | from the making-water-dance-to-our-tune dept.

Science 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.

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So (1)

Anonymous Coward | 1 year,18 days | (#45038841)

This allows condensers to have a smaller area.

FINALLY!

Re:So (2)

MightyYar (622222) | 1 year,18 days | (#45039561)

Smaller area means less water means smaller pump means less wasted electricity means higher plant efficiency.

But what's the polarity of the deflector? (1)

Anonymous Coward | 1 year,18 days | (#45038957)

Sounds like Star Trek technobabble.

Re:But what's the polarity of the deflector? (0)

Anonymous Coward | 1 year,18 days | (#45039535)

Indeed, I too was wondering if we could get a summary in English.

Re:But what's the polarity of the deflector? (2)

dbIII (701233) | 1 year,18 days | (#45041547)

That's what you get for watching more Trek than reading about science and technology.

Re:But what's the polarity of the deflector? (1)

TemperedAlchemist (2045966) | 1 year,18 days | (#45043347)

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 (5, Informative)

Anonymous Coward | 1 year,18 days | (#45039003)

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.

Re:Claification (1)

mlts (1038732) | 1 year,18 days | (#45039015)

Not just water, anything with a HVAC system, assuming this technology worked on other refrigerants.

Re:Claification (4, Interesting)

bobbied (2522392) | 1 year,18 days | (#45039081)

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 (1, Insightful)

justthinkit (954982) | 1 year,18 days | (#45039465)

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.

Re:Scale (2)

swillden (191260) | 1 year,18 days | (#45039683)

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.

Re:Scale (1, Insightful)

justthinkit (954982) | 1 year,18 days | (#45040245)

All I can give is an intuitive answer -- I think this surface doesn't stand a chance. Surfaces don't stay superhydrophobic or super anything. Things get shut down and serviced but corrosion never sleeps.

Re:Scale (1)

dbIII (701233) | 1 year,18 days | (#45041573)

There's buggerall corrosion on the boiler side of condensers. There so little that tiny amounts of ammonia in condensate dripping on tubes is seen as a massive deal when it happens.

Re:Scale (0)

Anonymous Coward | 1 year,18 days | (#45041279)

You are thinking of the wrong side. There is the condensate side (comes from the steam turbine exhaust) which is chemically treated so it doesn't corrode the boiler at high temperatures and the circulating water side (can come from a filtered ocean or lake). Scale and other shit builds up on the circulating water side. If your chemical treatment is good, you won't get much scale on the condensate side.

But in any case, I don't think this is a big deal, except from a water conservation standpoint. Circulating water pumps operate at low head and don't actually use that much power (even though they push enormous volumes of water). I worked at a half-GWe (1.5 GW thermal) plant that would use 6 MW to power circulating water pumps during the summer. Decreasing their necessary size by 10% or so probably would barely even register on the power plant output. You might save half a megawatt if you are lucky. In the winter you would save even less (less pumps need to be run). There are tons of things you could do in a powerplant that could save more power.

Sub-cooling (5, Informative)

Tokolosh (1256448) | 1 year,18 days | (#45039511)

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.

Re:Sub-cooling (0)

Anonymous Coward | 1 year,18 days | (#45041461)

No, this would increase the subcooling. You can offset this with reduced flow. Subcooling is desired. Without some subcooling and head from your hotwells, your condensate pumps will cavitate. Every power plant controls the subcooling by throttling the cooling water flow so that the plant operates at peak efficiency without damaging the condensate pumps. Too much subcooling is bad because you have to reheat the water going back to and inside the boiler. So you control it in a narrow band.

Re:Sub-cooling (0)

Anonymous Coward | 1 year,18 days | (#45042387)

so -- should we be spraying the condensing coils on dehumidifiers, so they drip water off more efficiently?

Re:Claification (1)

BenfromMO (3109565) | 1 year,18 days | (#45039645)

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 “one surface that has droplets jumping, and another that collects them you could generate some power” just from condensation from the ambient air. All that would be needed is a way of keeping the condenser surface cool, such as water from a nearby lake or river. “You just need a cold surface in a moist environment,” he says. “We’re working on demonstrating this concept.

And I am pretty sure this is what the first poster was mis-reading. The idea behind that second process is that in a MOIST environment with a cold surface, you can achieve power generation in this matter as long as you have the following:

large amounts of cold water AND moist air. The reason the first poster is wrong is that he states that this can be an application in arid regions, which as a rule have neither of the requirements.

Re:Claification (0)

Anonymous Coward | 1 year,18 days | (#45039931)

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.

Wow. No. The plant would not use more electrical energy to flow water through the condenser.

The condensate that is forming here is in a closed system. What it will do is speed up the mass flow rate through the condenser as the water condenses and does not linger on the tubes. This will increase the efficiency by permitting a greater vacuum in the condenser allowing for more energy to be extracted from the expanding steam.

This will not in anyway change the amount of water required within the closed cycle of the system.

Energy balance? (0)

Anonymous Coward | 1 year,18 days | (#45039009)

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?

Re:Energy balance? (1)

moteyalpha (1228680) | 1 year,18 days | (#45039175)

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 by many orders of magnitude.

What? (1, Insightful)

Anonymous Coward | 1 year,18 days | (#45039035)

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 stopping them gonna improve this? What sort of efficiency gain are we talking about here?

Re:What? (1)

lloydchristmas759 (1105487) | 1 year,18 days | (#45039151)

After going through the turbine, the steam is condensated to water, creating vacuum at the turbine "output", and thus increasing its efficiency. That's why improving condensation improves the turbine efficiency as well.

power plant (2)

coyote_oww (749758) | 1 year,18 days | (#45039253)

I just got to tour a power plant - very interesting! The running units were all combined cycle (close to 60% thermal efficiency), and the volume difference on steam in/steam out is really tremendous! The steam was vacuumed out of the LP turbine. And they were complaining about their cooling/condensing system not being efficient enough in the summer to run the plant at full power. Interesting too that the vast majority of the plant was about steam generation/handling/reheating/processing. The turbines and generators are a tiny, albeit critical, piece of the plant.

Also interesting is the sheer quantity of backup and emergency systems. And the generators being cooled with hydrogen and therefore hydrogen lines running all over the plant.

Re:power plant (1)

Charliemopps (1157495) | 1 year,18 days | (#45039395)

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.

Re:power plant (2)

coyote_oww (749758) | 1 year,18 days | (#45039499)

In a combined cycle plant, steam is the mechanism, like gears or levers. The original fuel is natural gas. Burn that in a gas turbine, spin a generator for electricity. Use the exhaust heat to create steam - run the steam through a steam turbine to spin another generator to make even more electricity. This results in very cool steam (barely steam at all), run this through a cooling system to get water which is cycled back into the exhaust stream to be converted to steam, etc etc.

Steam is just a convenient fluid for moving energy around in the process of turning natural gas into electricity.

Re:power plant (1)

Charliemopps (1157495) | 1 year,18 days | (#45040909)

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? (4, Informative)

bobbied (2522392) | 1 year,18 days | (#45039179)

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.

Re:What? (1, Informative)

Anonymous Coward | 1 year,18 days | (#45039305)

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? (3, Informative)

marcosdumay (620877) | 1 year,18 days | (#45039613)

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.

Re:What? (0)

Anonymous Coward | 1 year,18 days | (#45040443)

powerplants make electricity by heating up water into steam (via coal/gas/nuclear/whatever) then expanding it through turbines to spin generators.

The water you're thinking of here cycles through the system in a loop; after the water is expanded and comes out the other side of the turbine it must be cooled to condense back to liquid water and sent around to be heated again.

Condensing the expanded vapor back to liquid water requires a condenser [wikipedia.org] . A condenser must have cold water (or air) pumped through it continuously to provide a cold surface onto which the expanded vapor will condense. This is a heat transfer process; the hot, expanded vapor enters the condenser, encounters the surface made cold by a supply of pumped cold water, and condenses to liquid.

Where, in that process, does this efficiency gain come in?

The cooling and condensing part I mentioned above takes energy. Typically there is some source of cold water, a lake or water off of cooling towers or something that has to be pumped through condensers. Metal tubes or plates or whatever separate the hot vapor and the cold water. Heat transfers from the hot vapor to the cold water inside the condenser. The faster the condensation takes place the more efficient the system becomes; less pumping through fewer condensers.

Where is this 'sheet of metal' that drops are forming on?

Inside the condensers that cool expanded vapor back to liquid water. The 'sheet of metal' concept here has more to do with the laboratory model; real condensers in power plants are typically tubular structures. On one side of the tubes will be cold water, pumped by the power plant from someplace, and on the other side is the hot vapor from the output of the turbine.

What drops? Why are they forming there?

Water drops form as hot vapor is cooled inside a condenser. They form on cold surfaces. This is the same process that happens with a cold drink; water vapor in the air condenses on the container and makes a puddle.

How is stopping them gonna improve this?

'Stopping' is a poor word here. The improvement comes from removing the water from the surface faster, thereby allowing 'new' water to condense. Condensation is a continuous process; the throughput of the process is the rate of condensation. By making the water condense and fall away from the surface faster the process becomes more efficient.

What sort of efficiency gain are we talking about here?

They claim their surface will condense 30% more water than a traditional surface, all else being equal. The net efficiency gain of a power plant will probably be small but noticeable; the condenser pumps are just one of several inputs needed to operate a plant, and this gain will only reduce, not eliminate, that input. A fraction of a fraction, etc....

Water distillation will obviously benefit, making the condenser portion of the system smaller and heat transfer more efficient.

WRT power plants, one can image a system that does not condense water back to liquid and simply exhausts the steam after expanding through the turbine. However, in the real world the water is a purified solution which is mixed to minimize corrosion of the various metals in the system, moderate neutrons, etc. Water chemistry is a big deal in real power plants, so reusing the water is essential.

An example of an open system would be a classic steam locomotive; water is expanded in cylinders and exhausted out through the stack on top, leaving a cloud of steam behind has it moves forward.

Christian Science? (-1, Troll)

TechyImmigrant (175943) | 1 year,18 days | (#45039133)

>news from the CS Monitor

WTF is 'Christian Science'? How does that work?

Is the result of the experiment valid just because you have faith in it?

Re:Christian Science? (1)

CanHasDIY (1672858) | 1 year,18 days | (#45039155)

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.

Re:Christian Science? (0)

TechyImmigrant (175943) | 1 year,18 days | (#45039293)

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.

Re:Christian Science? (1)

CanHasDIY (1672858) | 1 year,18 days | (#45039469)

No, it's your interpretation of the term that's chock full of whatever. The term itself is generic and innocuous.

Re:Christian Science? (0)

TechyImmigrant (175943) | 1 year,18 days | (#45039909)

No it isn't. Those words have meaning. That's what words are for. To convey meaning.

Re:Christian Science? (1)

CanHasDIY (1672858) | 1 year,16 days | (#45058623)

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.

Re:Christian Science? (1)

Anonymous Coward | 1 year,18 days | (#45039171)

You must be new here if you're going to attack the CS Monitor on its name.

Re:Christian Science? (1)

TechyImmigrant (175943) | 1 year,18 days | (#45039301)

No. Just flogging a well flogged horse.

Re:Christian Science? (0)

Anonymous Coward | 1 year,18 days | (#45039959)

No. Just flogging a well flogged horse.

Oh, faked ignorance. Why such a dishonest tactic for someone criticizing others for not accepting science?

Re:Christian Science? (0)

TechyImmigrant (175943) | 1 year,18 days | (#45040107)

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.

Re:Christian Science? (2)

coyote_oww (749758) | 1 year,18 days | (#45039275)

The Monitor is actually a pretty good news source, for the most part. They typically run a single CS article per issue, and are otherwise pretty non-religious. You should take a look before being too critical. IANACS

Re:Christian Science? (0)

TechyImmigrant (175943) | 1 year,18 days | (#45039359)

It's a bit like me starting a serious journal on cryptography and calling it the 'Virgin Prostitute Reporter'.

Re:Christian Science? (0)

Anonymous Coward | 1 year,18 days | (#45039281)

heal the sick, raise the dead, cast out demons, cleanse the lepers.

Do it all with your thoughts, through god!

That is what Christian Science is.

Re:Christian Science? (0)

Anonymous Coward | 1 year,18 days | (#45039495)

The Christian Science Monitor [wikipedia.org] is well known and well respected newspaper that's been around for a very long time. Most Americans are familiar with the name. Even as an immigrant, I'm surprised you haven't heard of it. While Christian Scientists don't meat any reasonable definition of Christian or scientist, none of that has any noticeable influence on the paper, beyond one article per issue.

Re:Christian Science? (0)

BenfromMO (3109565) | 1 year,18 days | (#45039501)

Considering that the scientific method was developed by Roger Bacon ( a catholic) who codified the method about 700 years ago for the Catholic Church and is widely hailed as the father of science....... (this was based on the work of others including the Greek philosophers too) I would almost say that saying science without Christian might be wrong in itself. Of course, I am assuming you are joking, but you never do know nowadays. In other words, even back in the Middle Ages Christians in general who controlled most of the universities and in general were in charge of research were constantly looking for methods to better explain the world through logic and deduction. You see, the entire meme that the bible is literal or that we "have it your way" like Burger King with religion on select bible quotes and ignore other quotes that don't agree with "your belief on what Chistianity is" is an entirely newer thing that yes a small fraction of Americans to this day still believe in. I personally don't get it, but don't confuse a small group of nut-cases who can't think things through logically with Christians in general.

Re:Christian Science? (2)

TechyImmigrant (175943) | 1 year,18 days | (#45039925)

I don't discriminate. All religion is nutcase. The difference is just a matter of degree.

Beer connection (1)

FridayBob (619244) | 1 year,18 days | (#45039203)

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.

Re:Beer connection (0)

Anonymous Coward | 1 year,18 days | (#45039255)

Nobody is keeping you from wrapping your beer glass in wet towels (which are pretty hydrophilic).

Re:Beer connection (1)

Dishevel (1105119) | 1 year,18 days | (#45039351)

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?

Re:Beer connection (1)

marcosdumay (620877) | 1 year,18 days | (#45039649)

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.

Re:Beer connection (1)

TechyImmigrant (175943) | 1 year,18 days | (#45040821)

Have a G&T with ice.
The ice keeps it cold and it doesn't taste like beer. Double bonus.

Confusing (0)

Anonymous Coward | 1 year,18 days | (#45039229)

Your writer seems to be confusing efficiency and power output and power transfer per unit area.

The only thing that this advance might do is to increase the amount of power transfer per area of heat exchanger surface.

The overall Carnot efficiency or power output would not budge.

While it would be nice to be able to use smaller heat exchangers, its not going to have a direct and noticeable impact on efficiency.

Super-hydrophobic coatings (2)

Animats (122034) | 1 year,18 days | (#45039389)

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.

Re: Super-hydrophobic coatings (0)

Anonymous Coward | 1 year,18 days | (#45039441)

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.

Re: Super-hydrophobic coatings (1)

MightyYar (622222) | 1 year,18 days | (#45039619)

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.

Re: Super-hydrophobic coatings (0)

Anonymous Coward | 1 year,18 days | (#45039845)

If the water can't actually touch (wet) the surface, why would any dissolved minerals be left behind on it?

Re: Super-hydrophobic coatings (1)

MightyYar (622222) | 1 year,18 days | (#45040379)

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.

Re: Super-hydrophobic coatings (0)

Anonymous Coward | 1 year,18 days | (#45040479)

For some reason I find it really fascinating. You have a surface that is so hydrophobic that water will form droplets which adhere to each other more than the surface, to the point where the surface tension of two droplets combining will draw them away from the surface into a more spherical shape with such violence as to actually project the droplet off the surface. Add to this the fact that they've discovered these droplets have small charges - is that charge coming from the surface, or is it a phenomena caused by surface tension and rearrangement of ions? The water droplets combine because the energy state of the large droplet is lower than that of the two smaller droplets individually, so that energy has to go somewhere - part of it is kinetic, undoubtedly some small amount is heat, but perhaps some of it generates the charge as well. I wish the article mentioned how much energy it takes to keep the surface charged.

Re: Super-hydrophobic coatings (1)

MightyYar (622222) | 1 year,18 days | (#45041227)

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 (1)

dbIII (701233) | 1 year,18 days | (#45041625)

The chemistry is very simple because there's not much in the water - normally just an additive to scavenge oxygen. All the difficult stuff is taking care of at the "polishing" water treatment plant before it goes anywhere near the boilers.

This is very clean water not tap water (1)

dbIII (701233) | 1 year,18 days | (#45041607)

In power stations a vast amount of work and expense is already devoted to removing minerals from the boiler water, since they are not very good for the turbines. Dissolved minerals may be an issue elsewhere but not in the situation described in the article.

Re:This is very clean water not tap water (1)

MightyYar (622222) | 1 year,18 days | (#45041849)

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?

Re:This is very clean water not tap water (1)

dbIII (701233) | 1 year,18 days | (#45042219)

It's all water on that side not steam so the coating in the article would not be used.
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 get on copper roofs so a few microns of material that doesn't conduct as well as copper doesn't make much difference to heat transfer to the flowing water (I've sectioned, mounted and polished a few bits of condenser tubing and you need a microscope to see the layer). I seem to recall traps to try to get solid stuff to drop out before the cooling water makes it to the condensers but I didn't ever get to see those close up, so presumably mud etc doesn't slow down heat transfer. If fly ash gets in the traps don't stop floating stuff so I saw a bit of evidence of deeper corrosion at tube inlets where the patina was getting eroded away. Little plastic sleeves at the tube inlets fixed that.

Re:This is very clean water not tap water (1)

MightyYar (622222) | 1 year,18 days | (#45042253)

Cool, thanks for the info. This is why I hang around here. :)

Re:This is very clean water not tap water (1)

dbIII (701233) | 1 year,18 days | (#45043865)

Thanks. One other bit of trivia is when that cooling water was especially bad due to drought conditions the inside of the cooling towers looked like the hanging gardens of Babylon with vast amounts of green slime and large amounts of dissolved silicon caused a diatom population explosion (kill those spiky little things and you sandblast through your pipework) - those things made the cooling towers less effective (so less of a temperature difference once it got into the condensers) even if the water quality didn't directly impact on the condensers.
The answer was to put in a pipeline to dam a few hundred kilometres away in the direction of a major city - which resulted in problems due to conduction (earth return so the pipe had to be cut and insulated at many points), tiny feral fish eggs that threatened to get into a different river system (expensive filters that took a long time to obtain were fitted) and then the entire thing was hijacked by local farmers with the help of political friends when it was really needed. Despite the pipeline which took years to finish half the plant was shut down anyway.

Re: Super-hydrophobic coatings (1)

PJ6 (1151747) | 1 year,18 days | (#45045995)

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.

Re: Super-hydrophobic coatings (1)

Guppy (12314) | 1 year,18 days | (#45045581)

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.

Re:Super-hydrophobic coatings (0)

Anonymous Coward | 1 year,18 days | (#45045551)

While polymer superhydrophobic coatings have low life expectancies under harsh conditions, there are also long-lived metallic and ceramic coatings which have been tested in heat exchange applications already. Of course, most of them suffer from high cost of production or cost of materials (especially the rare-earth based coatings), and cannot be applied in any sort of consumer spray-on coating.

Steam Baloon (1)

IdeaMan (216340) | 1 year,18 days | (#45039955)

Would a coating like this help lower the weight of water clinging to the inside of an insulated steam balloon?

Re:Steam Baloon (0)

Anonymous Coward | 1 year,18 days | (#45040139)

The water would still be inside the balloon. It'd just go to the bottom.

What? (0)

Anonymous Coward | 1 year,18 days | (#45042745)

Wtf are they babbling about?

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