heatpipes are filled with water????

[jjyiz28]

as in the zalman heatpipes for GPUs.
http://www.firingsquad.com/hardware/sapphire_radeon_9800_xt_ultimate/page3.asp


"A gold-plated copper tube connects the top and bottom units; this tube and the heat pipe are filled with liquid. As the RADEON 9800 XT VPU heats up, the liquid in the heat pipe begins to boil, forcing hot vapor to the other end of the heat pipe where it is cooled. From there the vapor condenses back to the liquid phase and returns to the other end of the heat pipe."

i thought the heatpipe was solid copper, plated in gold?>? no??

 

[DannyBoy]

I love this part

"Variations of this heat pipe have been used on Sapphire cards dating all the way back to the RADEON 9700 PRO"

Damn they make it sound like the 9700 pro is REALLY old.

interesting though that it uses a variation of water cooling

 

[Corporate Thug]

wow. never knew that

 

[jjyiz28]

well the 9700 came out like 1.5 years ago, in graphics years, thats a long time. no doubt it still kicks ass even for such an old card.

 

[sandorski]

Liquid, not water. It's something more fancy then water.

 

[sodcha0s]

Absolutely..... the heatpipe wouldn't work if it was just a solid tube. The liquid is actually some type of refrigerant.

 

[VIAN]

Yeah, what that guy said. They should use heatpipes a lot more, it's surprising that they don't.

 

[tallman45]

The liquid may have additives such as Ethylene Glycol (aka: antifreeze/anti-boil) or whatever chemical is used these days.

 

[NickE]

Depending on the operating temperature, the liquid will be some sort of refrigerant, as mentioned above, that will boil somewhere below the maximum desirable operating temperature, and will condense again at a temperature somewhat above (worst-case) ambient. Probably one of the new-generation freons would do the trick without upsetting the environmentalists too much on the effect of all these video cards if they were to one day leak all of their contents to atmosphere.

Adding an anti-boiling agent wouldn't really help things, since you are looking for the refrigerant to boil as it's this that extracts the heat. That's why phase-change cooling is much better than forced convection (air or water).

 

[Jeff7181]

The pipes are under a vacuum so that the liquid boils at a relatively low temperature... I very highly doubt they use freon

 

[NickE]

Originally posted by: Jeff7181
The pipes are under a vacuum so that the liquid boils at a relatively low temperature... I very highly doubt they use freon

Do you know that for a fact or is it conjecture? To have water boiling at 60°C needs a pressure of around 0.3 bara, with this degree of vacuum, there is a risk that air will be drawn in through joints etc. Charging the system under vacuum is a lot harder than pressure filling.

Using an HFC refrigerant would mean that you could run the system at a low positive pressure, avoiding the risk of air being drawn in and getting a good performance overall. R134a is probably no good, that would need a high pressure, even R400's would struggle, but maybe one of the R500 series would do the trick.

Alternatively, one of the hydrocarbons would do, probably butane would be the best choice.

 

[43st]

Originally posted by: jjyiz28
as in the zalman heatpipes for GPUs.
http://www.firingsquad.com/hardware/sapphire_radeon_9800_xt_ultimate/page3.asp


"A gold-plated copper tube connects the top and bottom units; this tube and the heat pipe are filled with liquid. As the RADEON 9800 XT VPU heats up, the liquid in the heat pipe begins to boil, forcing hot vapor to the other end of the heat pipe where it is cooled. From there the vapor condenses back to the liquid phase and returns to the other end of the heat pipe."

i thought the heatpipe was solid copper, plated in gold?>? no??

I agree with you. I highly doubt there's liquid in those. Without a pump device solid copper will transfer heat much faster than any liquid trapped in a tube.

 

[NickE]

Originally posted by: Thera

Originally posted by: jjyiz28
as in the zalman heatpipes for GPUs.
http://www.firingsquad.com/hardware/sapphire_radeon_9800_xt_ultimate/page3.asp


"A gold-plated copper tube connects the top and bottom units; this tube and the heat pipe are filled with liquid. As the RADEON 9800 XT VPU heats up, the liquid in the heat pipe begins to boil, forcing hot vapor to the other end of the heat pipe where it is cooled. From there the vapor condenses back to the liquid phase and returns to the other end of the heat pipe."

i thought the heatpipe was solid copper, plated in gold?>? no??

I agree with you. I highly doubt there's liquid in those. Without a pump device solid copper will transfer heat much faster than any liquid trapped in a tube.

I think you've missed the point of how heatpipes work - they remove heat by evaporation at the hot end, then give up that heat by condensing at the cold end. There is only a small amount of liquid relative to the total volume of the tube, we're not talking about a water-filled pipe or anything close to it.

 

[Jeff7181]

Originally posted by: NickE

Originally posted by: Jeff7181
The pipes are under a vacuum so that the liquid boils at a relatively low temperature... I very highly doubt they use freon

Do you know that for a fact or is it conjecture? To have water boiling at 60°C needs a pressure of around 0.3 bara, with this degree of vacuum, there is a risk that air will be drawn in through joints etc. Charging the system under vacuum is a lot harder than pressure filling.

Using an HFC refrigerant would mean that you could run the system at a low positive pressure, avoiding the risk of air being drawn in and getting a good performance overall. R134a is probably no good, that would need a high pressure, even R400's would struggle, but maybe one of the R500 series would do the trick.

Alternatively, one of the hydrocarbons would do, probably butane would be the best choice.

A heat pipe consists of a vacuum tight envelope, a wick structure and a working fluid. The heat pipe is evacuated and then back-filled with a small quantity of working fluid, just enough to saturate the wick. The atmosphere inside the heat pipe is set by an equilibrium of liquid and vapor. As heat enters at the evaporator, this equilibrium is upset generating vapor at a slightly higher pressure. This higher pressure vapor travels to the condenser end where the slightly lower temperatures cause the vapor to condense giving up its latent heat of vaporization. The condensed fluid is then pumped back to the evaporator by the capillary forces developed in the wick structure.

Here's how it works: the liquid is held under low pressure so that the evaporation temperature is about 30 degrees Celsius.

 

[dxpaap]

cool