Archive for June 2008

Heat Transfer Efficiency For Boiling Water Increased 30 Fold

June 30, 2008

Jeez, here’s still another amazing innovation. Get this. A couple of researchers at Rensselaer Polytechnic Institute have figured out how to make water boil at a 30 fold increase in the number of bubbles created per unit of energy. That means that energy costs to create steam would drop by 30 fold. This process “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.”

Ya think one of them might be desalinaton? Hmm well also there is the Kanzius effect. An efficient heat transfer process there might make the 3000 degree flame net energy for the process. As well you might be able to get more steam for less energy to reduce costs of a kanzius steam reformation process. or efficiently boiled water might be injected into gypsum deposits. imho the salt would play hell on the nanorods that coat the copper sufaces mentioned in the article below. but if you could desalt and heat the water before it hit the nanorod copper plates the steam could be used to drive electrical generation more efficiently to reduce costs of membrane desalination. Finally, a word about pipelines. Maybe an efficient heat transfer material in combination with hydrophobic materials would enable cheaper ways to push water uphill in a pipe. Anyhow check out the article below. Interesting stuff. There’s a Rensselaer Polytechnic Institute Pr

As well as the write up below in PhyOrg.

Anyhow consider the article below.

New nano technique significantly boosts boiling efficiency

 A scanning electron microscope shows copper nanorods deposited on a copper substrate. Air trapped in the forest of nanorods helps to dramatically boost the creation of bubbles and the efficiency of boiling which in turn could lead to new ways of coo ...

A scanning electron microscope shows copper nanorods deposited on a copper substrate. Air trapped in the forest of nanorods helps to dramatically boost the creation of bubbles and the efficiency of boiling, which in turn could lead to new ways of cooling computer chips as well as cost savings for any number of industrial boiling application. Credit: Rensselaer Polytechnic Institute/ Koratkar

Whoever penned the old adage “a watched pot never boils” surely never tried to heat up water in a pot lined with copper nanorods.

A new study from researchers at Rensselaer Polytechnic Institute shows that by adding an invisible layer of the nanomaterials to the bottom of a metal vessel, an order of magnitude less energy is required to bring water to boil. This increase in efficiency could have a big impact on cooling computer chips, improving heat transfer systems, and reducing costs for industrial boiling applications.

“Like so many other nanotechnology and nanomaterials breakthroughs, our discovery was completely unexpected,” said Nikhil A. Koratkar, associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer, who led the project. “The increased boiling efficiency seems to be the result of an interesting interplay between the nanoscale and microscale surfaces of the treated metal. The potential applications for this discovery are vast and exciting, and we’re eager to continue our investigations into this phenomenon.”

Bringing water to a boil, and the related phase change that transforms the liquid into vapor, requires an interface between the water and air. In the example of a pot of water, two such interfaces exist: at the top where the water meets air, and at the bottom where the water meets tiny pockets of air trapped in the microscale texture and imperfections on the surface of the pot. 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.

Bubbles are typically formed when air is trapped inside a microscale cavity on the metal surface of a vessel, and vapor pressure forces the bubble to the top of the vessel. As this bubble nucleation takes place, water floods the microscale cavity, which in turn prevents any further nucleation from occurring at that specific site.

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.

“By themselves, the nanoscale and microscale textures are not able to facilitate good boiling, as the nanoscale pockets are simply too small and the microscale cavities are quickly flooded by water and therefore single-use,” Koratkar said. “But working together, the multiscale effect allows for significantly improved boiling. We 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.”

Boiling is ultimately a vehicle for heat transfer, in that it moves energy from a heat source to the bottom of a vessel and into the contained liquid, which then boils, and turns into vapor that eventually releases the heat into the atmosphere. 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 you can boil water using 30 times less energy, that’s 30 times less energy you have to pay for,” he said.

The team’s discovery could also revolutionize the process of cooling computer chips. As the physical size of chips has shrunk significantly over the past two decades, it has become increasingly critical to develop ways to cool hot spots and transfer lingering heat away from the chip. This challenge has grown more prevalent in recent years, and threatens to bottleneck the semiconductor industry’s ability to develop smaller and more powerful chips.

Boiling is a potential heat transfer technique that can be used to cool chips, Koratkar said, so depositing copper nanorods onto the copper interconnects of chips could lead to new innovations in heat transfer and dissipation for semiconductors.

“Since computer interconnects are already made of copper, it should be easy and inexpensive to treat those components with a layer of copper nanorods,” Koratkar said, noting that his group plans to further pursue this possibility.

Source: Rensselaer Polytechnic Institute

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LLNL Researchers use carbon nanotubes for molecular transport

June 21, 2008

The last time I wrote about the researchers at LLNL was back in December 2006. Their carbon nanotube research is the most promising imho of a half dozen interesting lines of research that I’ve seen. That is, the goal of membrane research is a to have a pipe that ends in in a covered mushroom shape that rises above the ocean floor in 50-100 feet of salt water–someplace where there is a strong coastal current. Fresh water filters through a membrane without extra energy and falls through some kind gas that’s hostile to aerobic and anaerobic bacteria–like maybe chlorine. This research provides a path to that goal.

In the initial discovery, reported in the May 19, 2006 issue of the journal Science, the LLNL team found that water molecules in a carbon nanotube move fast and do not stick to the nanotube’s super smooth surface, much like water moves through biological channels. The water molecules travel in chains – because they interact with each other strongly via hydrogen bonds.

Of course one of the most promising applications for this process is seawater desalination.

These membranes will some day be able to replace conventional membranes and greatly reduce energy use for desalination.

The current study looked at the process in more detail.

In the recent study, the researchers wanted to find out if the membranes with 1.6 nanometer (nm) pores reject ions that make up common salts. In fact, the pores did reject the ions and the team was able to understand the rejection mechanism.

What was the rejection mechanism?

Fast flow through carbon nanotube pores makes nanotube membranes more permeable than other membranes with the same pore sizes. Yet, just like conventional membranes, nanotube membranes exclude ions and other particles due to a combination of small pore size and pore charge effects.

But it was principally charge that did the deed.

“Our study showed that pores with a diameter of 1.6nm on the average, the salts get rejected due to the charge at the ends of the carbon nanotubes,” said Francesco Fornasiero, an LLNL postdoctoral researcher, team member and the study’s first author.

The salinity of the water studied was much lower than brackish water. So work will need to be done to figure out how to increase the charge at the tip of the nanotubes. Might be good to highly charge the filler material. Or put imperfections in the carbon nanotubes to increase their charge. In this blog i mention that charge might be related to something else. Here’s still another take on charge. Might be good work for simulations. Earlier work last fall showed a nice congruence between experimental work and computer models.

Finally Siemans recently announced that they had developed a process that would cut energy use in half. Their method involved removing salt using an electric field. So an interesting way to “artificially” introduce a larger charge for higher salt concentrations would be to create a small electric field along the surface of the carbon nanotube. this of course, costs energy. But it would make an interesting interim step.

As well, its helpful to mention that the study just announced by LLNL was not about how water flowed through the membrane but rather the experiment was designed to more precisely peg the mechanism by which salt rejection took place at the carbon nanotube’s tip. So the animation in the press release is a bit misleading

Some further study of the process by which water flowed through the nanotubes was done by Jason Holt.

He has an experimental project that focuses precisely on the issue of understanding water and ion structure within carbon nanotubes. He has “a paper just published online in Nanoletters that might be of interest (although a little tangential to desalination):”
http://pubs.acs.org/cgi-bin/abstract.cgi/nalefd/asap/abs/nl080569e.html
There is also a review article out that should be accessible to the outside community:
http://www.springerlink.com/content/375433hj6nuj0215/
Here’s a physorg write up of Holt’s work.
Finally, an earlier blog I did on this subject my be helpful.

A while back I asked a member of the LLNL team what the best investment of dollars would be for research in this field. He said that the best investment currently would be “in coming up with scalable (economical) processes for producing membranes that use nanotubes or other useful nanomaterials for desalination.”

Here is a link to the LLNL press release.

Water from Gypsum By Steam Injection

June 14, 2008

Here’s one one interesting idea for getting water to desert regions. Consider gypsum. There’s lots of it in the southwest. The chemical formula for gypsum is CaSO4.2H2O. Notice the H20 on the end? Gypsum is 20% water by weight. Did you know that you can quickly cook the water out of gypsum at 212F degrees 100C . Gypsum occurs in flat planes often not far from the surface–especially in old dry lakebeds. You could cook those planes. Leaving a mineral residue called bassanite–water would percolate up and the earth would subside causing a lake. Think you could find a heat source in the desert? Maybe flared off gas? Maybe solar power? Maybe a coal plant somewhere. 212 degrees isn’t too hot. Hmm 212 is a familiar number. You might use steam.

A Dutch team has already done the initial testing. Holland Innovation Team is planning a pilot study in a desert location. They don’t say where. They don’t say how they’re going to extract the water either. See below

But before you go. Consider. There’s a group of men parked outside of Heartbreak Hotel. Specifically Shell’s experimental in situ oil shale facility, Piceance Basin, Colorado. They climb up to their beds every night. Every night they toss and turn. In the morning they go out to a set of cool tools they’ve developed to extract oil from oil shale using steam injection. There’s several other processes that involve superheated air and others. See the list here. (As well for surface gypsum —concentrated solar might be appropriate.) Anyhow, they’re all revved up and ready to go but congress (specifcally a senator from colorado)is telling them they have to sit on their thumbs and think about it. (For that matter the BLM is holding up a lot of solar development.)

Someone might find these guys and say hey. While you wait. You can can use your cool tools on our gypsum. Funding should be easy.

The water from gypsum looks to be relatively expensive. But certainly it would be fraction of the cost of oil from oil shale since the oil shale requires 600+ degrees heat (vs 212F for gypsum) to cook out the oil and the deposits are usually 1000 feet down (vs at or near the surface for gypsum). And there’s no clean up or refining. For some desert valleys water from gypsum would be a fail safe water source.

Anyhow read the article below and consider.

Public release date: 11-Jun-2008

Contact: Peter van der Gaag
pvdgaag@hollandinnovationteam.nl
Inderscience Publishers

Rocky water source

Water from rock, easier than blood from stone

Gypsum, a rocky mineral is abundant in desert regions where fresh water is usually in very short supply but oil and gas fields are common. Writing in International Journal of Global Environmental Issues, Peter van der Gaag of the Holland Innovation Team, in Rotterdam, The Netherlands, has hit on the idea of using the untapped energy from oil and gas flare-off to release the water locked in gypsum.

Fresh water resources are scarce and will be more so with the effects of global climate change. Finding alternative sources of water is an increasingly pressing issue for policy makers the world over. Gypsum, explains van der Gaag could be one such resource. He has discussed the technology with people in the Sahara who agree that the idea could help combat water shortages, improve irrigation, and even make some deserts fertile.

Chemically speaking, gypsum is calcium sulfate dihydrate, and has the chemical formula CaSO4.2H2O. In other words, for every unit of calcium sulfate in the mineral there are two water molecules, which means gypsum is 20% water by weight.

van der Gaag suggests that a large-scale, or macro, engineering project could be used to tap off this water from the vast deposits of gypsum found in desert regions, amounting to billions of cubic meters and representing trillions of liters of clean, drinking water.

The process would require energy, but this could be supplied using the energy from oil and gas fields that is usually wasted through flaring. Indeed, van der Gaag explains that it takes only moderate heating, compared with many chemical reactions, to temperatures of around 100 Celsius to liberate water from gypsum and turn the mineral residue into bassanite, the anhydrous form. “Such temperatures can be reached by small-scale solar power, or alternatively, the heat from flaring oil wells can be used,” he says. He adds that, “Dehydration under certain circumstances starts at 60 Celsius, goes faster at 85 Celsius, and faster still at 100 degrees. So in deserts – where there is abundant sunlight – it is very easy to do.”

van der Gaag points out that the dehydration of gypsum results in a material of much lower volume than the original mineral, so the very process of releasing water from the rock will cause local subsidence, which will then create a readymade reservoir for the water. Tests of the process itself have proved successful and the Holland Innovation Team is planning a pilot study in a desert location.

“The macro-engineering concept of dewatering gypsum deposits could solve the water shortage problem in many dry areas in the future, for drinking purposes as well as for drip irrigation,” concludes van der Gaag.

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“Mining water from gypsum” in International Journal of Global Environmental Issues, 2008, 8, 274- 281

Public release date: 11-Jun-2008

Contact: Peter van der Gaag
pvdgaag@hollandinnovationteam.nl
Inderscience Publishers