A question about heat pipe lifespans.

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stigweard
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Joined: Tue Oct 31, 2006 5:11 pm

A question about heat pipe lifespans.

Post by stigweard » Sat Nov 11, 2006 7:31 pm

My new machine is up and running after a few weeks of waiting and everything is running smoothly. It did bring up a question about how long heat pipes are supposed to last. On my old machine, my 6800gt idles at 60c where it used to idle at 45c when new. There is no dust or debris in the fins and the fans work like new. This makes me curious as to why the card now idles 15c hotter.

I have a similar situation with my wife's laptop. It runs so hot now that I have to underclock it in order to prevent it from shutting down. I thought maybe it would be dusty inside so I opened up the laptop and everything was pristine, except the heat pipes were slightly scored from the high temperatures.

Is this kind of thing normal, or do I just have bad luck with electronics?

Tibors
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Post by Tibors » Sun Nov 12, 2006 12:48 am

Heatpipes are supposed to last several years before enough coolant has diffused out of them to influence their performance.

I would sooner suspect cheap TIM between the chips and the cooler. If the TIM has dried out and has become powder it becomes more hindrance than help.

Bluefront
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Post by Bluefront » Sun Nov 12, 2006 2:18 am

Most heatpipes are simply a copper tube filled with some type of liquid, maybe a compressed gas like freon. The tubes are crimped (smashed) on the ends, maybe soldered. This setup could retain it's heat transfer ability for a long time......decades maybe. It depends on the quality of the copper tube, and the seal on the end. There is virtually nowhere for any fluid to escape the tube.

I'd suspect some other problem.......the TIM is the most likely.

Gojira-X
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Post by Gojira-X » Sun Nov 12, 2006 2:54 am

Heat pipes use a very basic principle of thermodynamics, hot fluid will always travel to the area that is coldest.
You would presume that to maximise the efficiency of the heat pipe, you need 4 things,
1. a high temperature "hot end" (the gpu chip),
2. a low(ish) temperature "cold end" (the heatsink/heat spreader at the end)
3. a some airflow over the heatsink/spreader, and
4. some decent TIM to connect the gpu block to the heatpipe and the heatpipe to the heatsink.

The difference between 1 and 2 defines the effiency of the heatpipe with 3 dispursing any hot air from building up on the cold end.

In your setup, clean the heatsink/heatspreader that the heatpipe links to of any dust or debris. This could affect the air flow over it.

If that didnt work, I would look at the temprature of the room, namley "how hot does the get?". It may be that as we are approaching winter, your central heating system may be coming on and rasing the room temp above standard ambient (21 degrees Celsius). By turning room thermostat down you could tip the balence towards cooler running.

Cheak if there is sufficient air flowing over the card. If neccessary make a duct from a known fresh air source to direct air over it.

Finally, if all that does not work. Buy some Arcti-Clean or Akasa TIM Clean and clean off ALL the TIM from the cards. Then apply some new TIM on all the areas VERY THINLY. I do recomend paper towels for the bulk removal as they also lap gpu surface slightly. The Final clean (with TIM Clean) must be done with something lint free.

Remberi that TIM is only there to fill in tiny surface imporfections, not account for machining errors in the heatpipe gpu cooler (the only exception being is where the heatpipes join the gpu block and heatsink, were it has no choice.

You may also get some joy with lapping all the surfaces that need TIM.

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