Cooling Next Gen GPUs

[KimB]

Did you read what I said about the AlCu Zalman? Its not a copper base but a Al base and will behave just the same if put aginst the same heatsink that was all Al. I have done test with the same heatsink that was made with all copper, all Al, and copper base Al fin and the Cu/Al was the best and that was on both system test ans test with a 89W TEC. The Cu/Al out did the Cu but 3C to 5C at removing heat for the heat sorce.

This is what a Al fin with forged Cu base is and the same heatsink made of copper would proforem less then this Al/Cu.

This group tested heatsinks of various materials, and found all copper to be the best:
http://powerelectronics.com/mag/power_characterizing_mixedmetal_heatsinks/

 

[KimB]

Conventional wisdom is that although Cu has higher conductivity than Al, it also has higher capacitance. The Cu base/Al radiator designs try to leverage both material's strengths & lower the weight & BOM.

How can capacitance have any affect whatsoever on heatsink design?

 

[stevem]

How can capacitance have any affect whatsoever on heatsink design?

Heh, I thought you were a physics major?
Bob's right. There is a direct relationship between analogous electrical & thermal parameters of metals. When a metal has higher thermal capacitance it becomes a short term store of heat. So in the case where you have a burst of heat there is greater overshoot in its dissipation across a thermal junction. I have not done empirical tests & don't have info on junction or thermal spread angle effects. There's no doubt boundless papers in the literature.

 

[KimB]

Heh, I thought you were a physics major?

Heh, I study cosmology, and few people in physics these days study the thermal properties of materials (most solid state physics is related to low-temperature phenomena like superconductivity, phase change phenomena, and the properties of nano-scale objects). Physics also doesn't do much in the way of empiricism.

Bob's right. There is a direct relationship between analogous electrical & thermal parameters of metals. When a metal has higher thermal capacitance it becomes a short term store of heat. So in the case where you have a burst of heat there is greater overshoot in its dissipation across a thermal junction. I have not done empirical tests & don't have info on junction or thermal spread angle effects. There's no doubt boundless papers in the literature.

I guess I have a hard time seeing how capacitance relates to heat. Electrical capacitance, after all, is more related to the geometry of the conductor, and the material between places on the conductor, than it is related to the properties of the conductor itself.

 

[Junkstyle]

copper is better at thermal conductivity than aluminum. Aluminum is far cheaper than copper though, thats why you see aluminum heatsinks.

btw. good job derailing the thread.

 

[stevem]

Heh, I study cosmology, and few people in physics these days study the thermal properties of materials (most solid state physics is related to low-temperature phenomena like superconductivity, phase change phenomena, and the properties of nano-scale objects).

Undergrad must cover this stuff? Maybe mech/elec eng, I guess.

Physics also doesn't do much in the way of empiricism.

Theoretical work is fine, but at some point a hypothesis must be tested. A bit tough in cosmology, no doubt, but particle experiments are progressing.

I guess I have a hard time seeing how capacitance relates to heat. Electrical capacitance, after all, is more related to the geometry of the conductor, and the material between places on the conductor, than it is related to the properties of the conductor itself.

Not entirely the case. Materials do impact, but the effects may be small in total consideration of the package. Esp in the case of eg corrosion resistance, strength, or BOM. This is only AFAICR, but I believe that Al also has better convection (vs conduction) than Cu.

metal->Cu     vs       Cu->Air
metal->Al              Al->Air

Cu>Al                  Al>Cu

Ultimately, the thermal conductivity of Cu may outweigh any benefits of Al in the context of a HS in a PC case.

Sorry for OT stuff. G80. G80.

(Thanks mods)

 

[Bouncing Zabaglione Bros.]

As we seem to have a thread split, did anyone see this ? Looks quite clever, very intergrated and mainstream. Could be good with a second cooler in the loop for the graphics card.

 

[{Sniping}Waste]

This group tested heatsinks of various materials, and found all copper to be the best:
http://powerelectronics.com/mag/power_characterizing_mixedmetal_heatsinks/

Did you read about the Cu/Al heatsink used? Its not a Au fin with Cu forged in the base. Its Cu plate with Al fins place on it and its not the same as a forged Cu bottom.

The heatsinks tested in these experiments were bonded using a metal-displacement process referred to as swaging. The swaging process, shown in Fig. 1, can be described as a cold-forming process, which is used in the fabrication of high fin-density heatsinks. Currently, this process involves the placement of fins with a tapered base into a slotted baseplate followed by the application of a rolling pressure on the opposite sides of each fin. This process results in vertical and lateral pressure of the base unit material, which tends to push the fin toward the bottom of the groove in the baseplate. This secure connection provides very good thermal contact between the fins and base, and also prevents air and moisture from entering the grooves, thereby preventing corrosion and allowing the heat-sink to be anodized.

 

[hughJ]

Is there a resource online somewhere that shows aluminum to transfer heat better than copper via convection? That's really the crux of this argument.

 

[SugarCoat]

Is there a resource online somewhere that shows aluminum to transfer heat better than copper via convection? That's really the crux of this argument.

its basic physics, the denser a metal is the better/faster its going to conduct and hold heat/energy. Copper is obviously thicker and heavier then aluminum. Aluminum releases heat faster, copper absorbs it faster. Theres nothing else to say.

 

[hoom]

Uhh, Metals don't transfer heat by convection unless they are liquid...

Of course, you are referring to transfer from metal to air by both conduction and radiation, the air then convecting away either forcibly or freely.

 

[Ateo]

Had to register after reading this thread.
This should help answer the question:
http://episteme.arstechnica.com/6/ubb.x?a=tpc&s=50009562&f=77909585&m=106091502

Assuming that a system is constantly outputting heat, the material with the higher thermal conductivity will better move the heat away from the heat source. In the case of aluminum vs. copper, assuming identical geometries, copper will more effectively move the heat away from the point of contact with the CPU and into the extremities of the heat sink. This will give the heatsink a higher average temperature overall.

Aluminum does not 'give up its heat' better than copper! Let me repeat this once more; aluminum does NOT 'give up its heat' better than copper. It is true that, in general, aluminum will radiate heat better than copper but radiation is such a miniscule part of heat transfer in a computer system as to be deemed completely inapplicable.

So why don't the current copper heatsinks far outperform (all tests I have seen show that copper heatsinks do outperform aluminum, just not by much) their aluminum counterparts? In my opinion it is because of a few things; namely poor design, multiple piece heatsinks (remember thermal contact resistance!), impure copper, and difficulty of producing a copper heatsink in the desired form.

I own a pure copper Zalman CNP9500LED and it cools my Pentium D 950(stock) to 24C ilde/45C full load.
Copper > Aluminium...period.

 

[Sxotty]

Not quite. There is a linear relationship between electrical conductivity and thermal conductivity for metals only. See the Wiedemann-Franz law.

Yeah, but he said the reason was that they were both energy which is downright silly. Light is energy and it isn't transmitted real well by copper. Further as you likely know many ceramics that conduct electricity are not particularly good at conducting heat.

Anyway Copper does transfer the heat throughout the copper more quickly, but perhaps aluminum transfers it to air better or something. Maybe the Aluminum oxide film that is always present works great or something.

 

[Davros]

ahh ive got it
copper/aluminium heatsinks have a fan mounted on them
the fan contains an electric motor which contains magnets
the moving magnets produce an electric current
the elctric current flowing through two different metals produces a peltier effect
hence the coper / aluminium heatsink wins


Er ok its bollocks - but it sounded good

 

[Thelacky]

What the industy needs is a new standard for PC cases with build in cooking oil technology and comes with a cup holder to keep your coffee warm.. Everything is cooled by oil pipes, the cool oil sinks to the bottom and the hot oil moves upwards heating the cup holder keeping your coffee hot

If you're going to buy a ATI R600 250W graphic card, it may as well keep you coffee warm.

By the time the ATI R900 comes out, your PC could double as a chip frier.

 

[Davros]

or you could use ion cooling
http://www.beyond3d.com/forum/showthread.php?t=34195