What's inside those AMD HSF and ASUS Heat Pipes?

[MisfitSELF]

I recently purchase an Opty 170 and an ASUS A8N32-SLI and was wondering: Just what is inside those heat pipes?

Air? Amonia? Freon?

 

[swifty_morgan]

They are solid

 

[turbo_mcgillicutty]

they are not solid. they are hollow copper (or aluminum) tubes that contain a small amount of fluid that vaporizes under heat. this vapor carries the heat to the part of the pipe that is close to the fan. this vapor then cools and condenses and returns to the hotter part and the cycle repeats.

as for the fluid, im not to sure. someting with a lower vapor pressure and will condense easily and quickly. if the vapor pressure is to high, it will not evaporate and if it doesnt condensate quickly the efficiency of the heat pipe will be reduced.

EDIT: just did some quick googleing and it looks like your guess of freon is close. some use HFC-134a (close to freon), and some sites say a mix of methanol/water (methanol will evap, the water will not unless your system is cooking, by that point, the thing will be dead anyway).

hope i helped!

 

[turbo_mcgillicutty]

p.s. hows the weather in california? im going there for me birthday in 2 days and i cant wait!!!

 

[jap0nes]

hmmmm i dont think it will exaclty vaporize... i guess they have some sort of liquid or gas, but they do not vaporize. they just start circulating from the hotter to coldest part and vice versa, that's how it exchanges heat.

 

[turbo_mcgillicutty]

methanol will evaporate at room temp. freon will do it anywhere above -28 deg farenheit. in order for freon to work in a heatpipe situation, it would have to be pressurized enough to be able to go through the evaporation/condensation cycle. im not sure of the boiling point of HFC-134a.

edit: they are not completely filled with the fluid. there is a very small amount in them. If they were completely filled, the heatpipe would not be nearly as efficient. it is the cycle of evaporation/condensation that gives the heatpipe its efficiency. if the heatpipe was completely filled, the fluid would just heat up until it reached some point of equilibrium. now, this works with water cooling because the warm coolant is continuously replaced with cool coolant. that is basicaly what the evap/cond cycle is doing. replacing the warm coolant (vapor) with the cool coolant (condensed fluid).

 

[Lord-Ilpolazzo]

they are not solid. they are hollow copper (or aluminum) tubes that contain a small amount of fluid that vaporizes under heat. this vapor carries the heat to the part of the pipe that is close to the fan. this vapor then cools and condenses and returns to the hotter part and the cycle repeats.

as for the fluid, im not to sure. someting with a lower vapor pressure and will condense easily and quickly. if the vapor pressure is to high, it will not evaporate and if it doesnt condensate quickly the efficiency of the heat pipe will be reduced.

EDIT: just did some quick googleing and it looks like your guess of freon is close. some use HFC-134a (close to freon), and some sites say a mix of methanol/water (methanol will evap, the water will not unless your system is cooking, by that point, the thing will be dead anyway).

hope i helped!

thats about right. Some also have a wick of some kind inside them, im not entirely sure what thats made of though

 

[turbo_mcgillicutty]

ive heard the wick is made of some sort of metals in powdered form that are fixed to the walls of the pipe. i guess that it could be any material that absorbs the coolant and helps it back to the hot side of the pipe, and doesnt interfere with the heat transfer to much.

 

[jap0nes]

that explains it all

http://en.wikipedia.org/wiki/Heat_pipe

 

[MisfitSELF]

Thanks for the replies Turbo. Weather here is blustery (very windy), but I'm in the Mojave desert. The last couple of weeks haven't quite figured out if it's going to be summer or winter.

I figured there was some sort of liquid in those pipes and they weren't solid because of the way the ends were pinch welded closed. If they were solid, the ends would be simply cut and filed smooth. Also a solid pipe would not be as thermally efficient as filling the space with more thinner copper fins.

Amonia came to mind because it can goes through it's phase change from liquid to gas at close to "room" temperature. (or at least closer to room temp than other gases). Plus it's not a Class I ODC (ozone depleting chemical) like Freon.

Thanks for the explaination as to how these heat pipes work, but I hate to tell you that in a past life, I was an engineer on a satellite in which we used ammonia filled heat pipes combined with a TEC (thermal electric cooler) to cool a CCD array...(-; (although I did get a "C" in thermo, undergrad, so I don't claim to be an expert by anymeans....)-; )

 

[turbo_mcgillicutty]

i should have looked there first and then posted the link. would have saved me a bunch o' typing!!

 

[turbo_mcgillicutty]

no prob on the explanation, it was kinda there for anyone, looks like you didnt need it :lol:. im a biochemist by trade, but i like to dabble in the physical chem and physics realms. 8)

 

[dorion]

You can use water in a heatpipe by having the pressure in the pipe be lower, so the water will reach vapor form at a much lower temperature. Just like how the Freon is pressured to increase it's vapor temperature. Just thought I add that since the Wiki didn't clear it up.