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Help me understand...
By KillerNoodle on 7/27/2010 9:08:01 AM , Rating: 2
The thermal conductivity of Single Wall Nanotubes (SWNT) is aproximately "6600 W/m K for an isolated (10, 10) nanotube at
room temperature,"

This is the thermal conductivity along a single SWNT...So how is 550 W/(cm*cm) an improvement?

RE: Help me understand...
By MrTeal on 7/27/2010 10:10:45 AM , Rating: 2
The numbers you give are completely different quantities. One is thermal conductivity in Watts per meter Kelvin, the other is not really a formal unit, it's just power dissipated per unit area. It's kind of a useless measurement since it doesn't indicate the heat delta.

But yeah, if you assume a 1cmx1cm area, and if you have to move the heat 1cm up from the surface of the chip, that's
[(6600W/mK)*0.01m*0.01m/0.01m], or 66W/k for the number you quoted. IE, you can move 66W of heat per degree of temperature difference. Start adding in some interface losses, and it seems like a pretty good number they posted.

RE: Help me understand...
By MrTeal on 7/27/2010 10:17:25 AM , Rating: 5
I should probably also point out that, if one reads the article, they aren't actually using the CNTs as a bulk transfer medium. The system is basically a traditional heat pipe design, but with a smaller pipe size that's stuffed with copper coated CNTs.

Not that I can blame anyone for not reading the original article, it takes awhile to find the damned thing when you have to mouse over 20 links to find the one that doesn't link back to another DailyTech article. How about placing the original article in the subheading or footer of every post so that we can find it, DT?

RE: Help me understand...
By KillerNoodle on 7/27/2010 10:56:37 AM , Rating: 2
WOW...After reading the original article I understand how they are using nanotubes....They aren't . They are using particles of copper bonded to one another not copper coated nanotubes.

The only mention of nano in the article is the authors' institution of research.

This article seems to be an evaluation of a pore size's ability to evaporate a fluid, in this case water.

RE: Help me understand...
By MrTeal on 7/27/2010 11:13:50 AM , Rating: 2
The researchers are creating smaller pores by "nanostructuring" the material with carbon nanotubes, which have a diameter of about 50 nanometers, or billionths of a meter. However, carbon nanotubes are naturally hydrophobic, hindering their wicking ability, so they were coated with copper using a device called an electron beam evaporator.

The carbon nanotubes were produced and studied at the university's Birck Nanotechnology Center in work led by mechanical engineering professor Timothy Fisher.

My impression was that they actually are using carbon nanotubes in their test setup, not so much for the properties of CNTs as much as their nano-ness. They're just using them to get the small feature size they need to get really strong wicking. It's hard to tell even from the original article, though. You'd probably have to read the actual journal article to get a better idea.

RE: Help me understand...
By KillerNoodle on 7/27/2010 11:22:19 AM , Rating: 2
When you said original article I thought you meant the journal article so that is what I was reading when I commented about not using nanotubes. The last link in the DT article takes you to the published journal article.

RE: Help me understand...
By KillerNoodle on 7/27/2010 11:42:16 AM , Rating: 2
Just read the Purdue press release...

I really am lost now as to where the nanotubes are coming into play.

The press release talks about nanotubes and says that
The findings are detailed in a research paper appearing online this month in the International Journal of Heat and Mass Transfer and will be published in the journal's September issue. The paper was written by mechanical engineering doctoral student Justin Weibel, Garimella and Mark North, an engineer with Thermacore, a producer of commercial heat pipes located in Lancaster, Pa.

But the journal article referenced says nothing about nanotubes.

Are they getting their research mixed up?

RE: Help me understand...
By DanNeely on 7/27/2010 10:12:44 AM , Rating: 2
First guess would be that the macro properties don't scale to match the properties of a singe nanotube.

