Properties of good video card cooling?

[kevbox]

hey all,

i'm a long time reader but a first time poster on this forum. everyone is awesome on the board and i've really found a great wealth of knowledge here. i was hoping i'd be able to start a discussion to fuel my curiousity about video card cooling.

i've been reading a little bit about video card cooling and i'd like to know a bit more. i'm not interested in which aftermarket video card coolers are better, but i'm interested in why some video card coolers are better than others, and also why some video card manufacturers are able to provide better stock cooling than others. i'm also interested in the physics involved.

so on a video card we only have three features that can improve the heat problem (strictly on-card):
1) fan
2) heatsink
3) thermal paste

that's it right?

is the best solution a combination of all of these? why do certain heatsinks work better than others? passive vs active? is there a certain material that is better? what if the area that contacts the gpu is buffed out? will that improve heat conduction? What about the thermal paste? what chemistry of thermal paste works the best? The fan? plastic blades vs. metal blades? small fan vs big fan? speed? if cooling is such a problem and things overheat so much, why don't manufacturers just slap bigger heatsinks and bigger fans and better thermal paste?

has anyone had any experience with peltier cooling? could that be applied to video cards? i know in the past cpus would be cooled this way. what is stopping manufacturers to use this method of cooling? is it too expensive?

what have you all seen in your past experiences about certain materials in video card cooling construction? if any of you have any references that would be great.

thanks for your help!

-kevin

 

[Fullmetal Chocobo]

The effectiveness of a heatsink (not counting the fan attached) depends upon factors such a material, surface area, and good contact with the processor. As far as materials go, Silver is the best thermal conductor there is, but because of the fact that it is so soft, it isn't very practical, not to mention the cost. Copper is the second best, followed by Aluminum.

Copper (Cu): 4.01 W/(cm*K)
Silver (Ag): 4.29 W/(cm*K)
Aluminum (Al): 2.37 W/(cm*K)
Gold (Au): 3.17 W/(cm*K)

With surface area, this increases the effeciency of the heat sink. Basically the more surface area there is, the more contact with air is made to dissipate the heat. This is where the fins and whatnot come into play. As seen above, you can see why silver thermal paste is so popular. Basically, thermal paste fills in the tiny holes between the heat sink and the processor. Air conduct heat horribly, thus little pockets of air doesn't conduct heat very well.

As for fans, the most important thing (for cooling) is airflow, expressing in CFM (cubic feet per minute). The more air you push over a heatsink, the cooler the heatsink is going to be. Also, the cooler the air (or larger the delta between the cooling air and the heatsink), the better the effects of cooling will be. A larger fan can push more CFM than a smaller fan at the same RPM, so you can effectively slow down a 120mm fan (reducing the noise it creates), and have it as effective as a 80mm fan.

I know very little about peltier cooling, but I'll see what I can find out...
Tas.

 

[kevbox]

thanks for your reply! it is very helpful!

It seems like peltier cooling is not such an efficient way to cool. it requires much too much heat, and the hot side usually needs to be water cooled becuase it gets too hot.

i have a few more quesitons.

at what temperature do most video cards break? how does high heat affect performance? what are video card manufacturers doing to try to solve this problem?

kevin