Indian-origin researcher uses copper nanorods to boost boiling efficiency

June 27th, 2008 - 12:15 pm ICT by ANI  

Washington, June 27 (ANI): An Indian-origin researcher at Rensselaer Polytechnic Institute has demonstrated that adding an invisible layer of the nanomaterials to the bottom of a metal vessel may help reduce the amount of energy required to bring water to the boil.

The researchers say that such an improvement in efficiency may have a significant 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. 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 were eager to continue our investigations into this phenomenon, said Nikhil A. Koratkar, associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer, who led the project.

He says that bring water to the boil, and a related phase change that transforms the liquid into vapor, need an interface between the water and air.

He adds that a pot of water consists to such interfaces one at the top where the water meets air, and one at the bottom where the water meets tiny pockets of air trapped in the microscale texture and imperfections on the surface of the pot.

Water inside the pot cannot boil in the absence of an interface (absence of air), even when it has reached 100 degrees Celsius and is at boiling temperature.

Bubbles are typically formed when air is trapped inside a microscale cavity on the metal surface of a vessel, and vapour 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.

During the study, Koratkar and his colleagues deposited a layer of copper nanorods on the surface of a copper vessel.

The researchers observed that the the nanoscale pockets of air trapped within the forest of nanorods fed nanobubbles into the microscale cavities of the vessel surface, and helped prevent them from getting flooded with water.

According to Karotkar, 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. 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, Koratkar said.

He claims that his teams discovery allows the process of boiling to become dramatically more efficient, something that can 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, thats 30 times less energy you have to pay for, he said.

Karotkar further said that his teams work could also help revolutionise the process of cooling computer chips, as boiling is a potential heat transfer technique that can be used to cool chips.

According to him, 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, said Koratkar, adding that his group planned to further pursue the possibility.

The research results of Koratkars study will be published in a forthcoming issue of the journal Small. (ANI)

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