CPU cooler heat pipe - working or not?

[sorcerer]

Got an Asus X501 laptop in (Win 7 HP) because it's running very slowly. HDD tests ok and the laptop not really overheating at 56C idling, 62C under load as measured by Open Hardware Monitor but, because these are an easy strip-down I opened it up to find that the airways are all clear with no fluff or dust anywhere. Thermal paste had gone dry and crumbly so put fresh on and just thought I'd try the heatsink before putting it back on. Using freezer spray and a no-contact infra-red thermometer I measured the CPU end to be -1.5C but at the first bend it was +16.3C as you'll see in this photo.

Am I just misunderstanding how heat pipes work and expecting too much or can we say that this rascal is faulty?

 

[gadgetfixup]

I believe your cold source doesn't provide enough therms to correctly test with that method. A CPU is essentially a constant fire while running producing an unlimited amount of therms. Your spray while it can frost one end of your pipe isn't producing the quantity of therms to generate the correct results. A better test if you want to use cold instead of heat is to strap that CPU plate to a block of ice or dry ice producing an ample supply of cold units. Although you can see frost on the outside of that place it's acting more like an insulator that cold source. It's surface frost, freezing the moisture on that plate.

The way we test these pipes is to fire up the computer and test the pipe while it has a constant heat source under the plate. There should be a steady heat distribution all the way to the radiator. When these fail, they get very hot near the CPU and down the pipe a bit it will be cool and barely warm.

 

[sorcerer]

Ah right, thank you - that makes sense when you think about it. Cheers my friend

 

[Moltuae]

The heat pipe principle is actually quite a simple one: It contains a liquid that, when heated, vaporises. The vapour travels down the pipe until it reaches the cooler end, where it condenses back into a liquid, releasing heat in the process. The re-condensed liquid returns back down the pipe and the process repeats.

Therefore, to make a heat pipe work, you need sufficient heat to vaporise the liquid.

 

[sorcerer]

Oh, right, so cold shouldn't really work at all then as that isn't going to vaporise the liquid and all I was seeing was just transmission of coldness through the copper. Just for kicks I think I'll try the experiment with a heat gun on a couple of spare ones I've got lying around Cheers sir!

 

[Krynn72]

The heat pipe principle is actually quite a simple one: It contains a liquid that, when heated, vaporises. The vapour travels down the pipe until it reaches the cooler end, where it condenses back into a liquid, releasing heat in the process. The re-condensed liquid returns back down the pipe and the process repeats.

Therefore, to make a heat pipe work, you need sufficient heat to vaporise the liquid.

I had no idea that's how they worked. I thought it was just plain copper drawing away the heat to be honest. Thanks for the info.

So are all laptop heatpipes like that? I remember a couple threads on TN where people found a damaged heatpipe (a nick in the pipe) and I never really understood why it had such a huge effect until now.

 

[Larry Sabo]

Cooler Master has an article describing how it works, and their manufacturing process..

 

[sorcerer]

Cooler Master has an article describing how it works, and their manufacturing process..

Thanks Larry, a good informative article there.

 

[Moltuae]

So are all laptop heatpipes like that? I remember a couple threads on TN where people found a damaged heatpipe (a nick in the pipe) and I never really understood why it had such a huge effect until now.

Most, if not all, will be. You can usually tell by the shape of one end of the pipe, which will often have a squashed/crimped appearance, presumably because of the way in which the pipe is sealed, during manufacture, after filling with liquid. One of the ends will typically look like this:
http://i.imgur.com/eoEF1jb.png
http://i.imgur.com/ObAbhbR.jpg

Have to admit, I once assumed they're were solid copper too -- had never really given it any thought -- until one day, about 15-20 years ago, I tried to modify one. I cut into a heat pipe and recalled hearing a slight hiss, only to find the heat pipe didn't work properly afterwards. That's when I decided to do a little research.

 

[nlinecomputers]

I've been repairing laptops for years but only recently learned about this. Like you I always just assumed it was a heat sink.

 

[HCHTech]

I built a fanless computer back in about 2002, I think. I used a heatpipe that wrapped around the motherboard, then clamped to the solid aluminum bottom of the case. Essentially, the entire side of the case was a heatsink. This thing was kind of a one-off, and there was a bracket on the case that was in the way a bit. I decided for some reason the way to fix this was to take a little notch out of the heatpipe. The second the dremel hit it, it released all of it's gas in a sad little "pffft!". Oh - I thought, that's how that works! ...as I sat down to order another one. :-D

 

[ZenTree]

You learn something every day!

 

[DanF]

Never knew about this tbh.