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The OCZ Hydrajet cooler, featured upside-down to reaveal the carbon nanotube conductor. (Source DailyTech, Anh Huynh)
The OCZ Hydrojet cooler uses an advanced heatsink material

The first heatsink to make use of directional carbon nanotubes, the OCZ Hydrojet, was on display at Computex 2007. Carbon nanotubes, an allotrope of carbon, are widely regarded as the next major thermal interface material because of their superior thermal conduction properties.  

The contact base of the OCZ Hydrojet is made completely of carbon-nanotubes, which OCZ claims are five times more efficient than copper. Carbon nanotubes have been looked upon as a strong alternative to traditional copper based heatsinks. They are ideal for application in heat transfer products because of their impressive heat-conduction properties.  Carbon nanotube based interfaces have been shown to conduct more heat than conventional thermal interface materials at the same temperatures. In addition, they have shown to be ballistic conductors at room temperature, which means electrons can flow through CNTs without collisions.

Carbon nanotubes are small wire-like structures made out of a sheet of graphene.  The sheet of graphene used to construct CNTs is roughly one-atom thick, and is rolled up into a cylinder. The diameter of the cylinder ranges in the nanometers.

Unlike most other thermal materials, carbon nanotubes are able to move heat in one direction. On the other hand, copper, which is looked upon as one of the more superior thermal materials, moves heat radially. In the case of CNTs, heat is moved along the alignment of the nanotubes.

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RE: Mm,, interesting
By Dactyl on 6/9/2007 5:08:25 PM , Rating: 3
It's not about the temperature of the oil, it's about freezing the permafrost under the pipeline, which normally melts at that time of year, which would destroy the pipeline (if the ground on which it rests melted).

A passive, self-contained phase-change cooling system involving vertically-oriented tubes of ammonia stuck on top of a CPU could theoretically lower the CPU below ambient temperature--especially when the CPU is off! I don't know if it would transfer heat efficiently enough to be useful for cooling CPUs when they are on (or OCed), but it would cause temperatures at the base of the tubes to be below-ambient while the CPU was off.

I think the main reason this approach isn't used is because below-ambient temperatures lead to condensation, which is no good inside your computer case. That's why phase change coolers seal off the area around the CPU completely (also so people aren't injured by touching something at extremely low temperature). There's no reason a passive phase-change cooling solution could not work, except perhaps that it wouldn't cool the system enough to keep the CPU from overheating.

RE: Mm,, interesting
By Goty on 6/9/2007 8:09:38 PM , Rating: 3
*psst* Permafrost doesn't melt. Hence the name perma frost.

RE: Mm,, interesting
By PlasmaBomb on 6/9/2007 9:14:23 PM , Rating: 3
Goty is right about the perma frost.

The system is unlikely to be phase change as the permafrost temperature at the depth of the foundations is unlikely to vary much from -5°C which is well above anhydrous ammonia's boiling point (-33°C).

RE: Mm,, interesting
By dok405 on 6/9/2007 9:59:23 PM , Rating: 3
*pssst* To be classed as permafrost, it only has to be below the freezing point for more than 2 years. I wouldn't quite call that perma .

RE: Mm,, interesting
By masher2 on 6/9/2007 10:08:00 PM , Rating: 5
You cannot cool below ambient without an energy input of some sort...this is the second law of thermodynamics. If this wasn't true, you could easily create a perpetual motion machine.

Ammonia-absorption freezers still use energy. They just use a heat source, rather than electricity. And while a savvy person might ask "why not use the heat of the cpu itself?" a slightly savvier person will quickly realize why this won't allow below-ambient cooling either.

RE: Mm,, interesting
By dajeepster on 6/10/2007 5:16:29 PM , Rating: 3
thank you masher2... I knew that taking second semester physics wasn't a total waste for me :D

RE: Mm,, interesting
By MrPickins on 6/10/2007 12:29:58 PM , Rating: 2
Each heat exchanger is thermally coupled by a heat pipe to the base of the VTM. Running through the VSM, the heat pipe transports heat from the VTM base to the heat exchanger. Since ammonia, the working fluid in heat pipes, has a freezing point lower than the permafrost, the heat pipe works throughout the year, even during the coldest winter nights

The cooling system you are referring to are heat pipes, which we already cool our CPU's with. And no, they don't go below ambient.

RE: Mm,, interesting
By MrTeal on 6/10/2007 12:31:51 PM , Rating: 3
You're both incorrect. There are two seperate systems here, and they're getting confused.

1. When the pipeline is buried unground, there is a refridgeration system in place to prevent the hot oil from melting the permafrost. This refridgeration system does not use ammonia, it uses brine cooled below the freezing point of water.

2. When the pipeline is above ground, to prevent the heat from passing through the metal supports into the ground and cause melting around them, they have a heatpipe system. Nothing is cooled below ambient, but the 50 degree celsius heats up the pipeline, but the heatpipe setup helps keep the supports near ambient temperature, providing a thermal break between the ground and pipeline. This is where the ammonia is used.

RE: Mm,, interesting
By Goty on 6/10/2007 6:08:49 PM , Rating: 2
Wouldn't brine be a little corrosive?

RE: Mm,, interesting
By MrTeal on 6/10/2007 7:39:17 PM , Rating: 2
Depends on what they use for piping. The brine doesn't go through the oil pipeline, it's very possible they use plastic lines.

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