Heatpipes: The Investigation Begins

[phoronix]

Phoronix: Heatpipes: The Investigation Begins

Since breaking open bottles of beer with heatpipes and other hardware last month at the Intel Developer Forum in San Francisco, we have been cutting open a number of different heatpipes. In this article we have some new details to shed on heatpipes from a numbers of manufactures, including Thermalright, Thermaltake, OCZ, and Abit. These cooling mechanisms are supposed to keep our beloved PCs from overheating, but how does their manufacturing quality differ? With this article, we have plenty of pictures and videos showing you the differing qualities in heatpipes.

http://www.phoronix.com/vr.php?view=11313

[Malikith]

That was cool, I never knew much about heatpipes, learned a bit from this. You should be careful with that saw though haha, I thought you were going to cut your finger off. Now blood is one liquid we don't want to find ;)

[LOLatMS]

Now I admit that I have not read the patents on the heatpipes from the various companies, but fluids include gases as well as plasmas. I think the definition of fluid was something like a substance that moves or flows under shear stress. Perhaps those heatpipes had some kind of gas at some pressure close to 1 atm. In any case, I suppose all is well if the heatpipes perform well. Perhaps a good experiment would be to test a heatsink with one or two severed heatpipes? If performance does not change, it's safe to say that the heatpipes are a scam. In any case, it's good that Phoronix is looking into how the heatpipes are made and whether or not they add value to the various cooling solutions available on the market.

[immudium]

Fine bit of journalism there. It's something that's always kind of bothered me about the hardware industry. They send out these engineering samples to the press who then runs them through the benchmarks and give glowing reviews, but does the average Joe get the same piece of hardware that the press got to review? How would the consumer possibly know if the heatpipe manufacturer took shortcuts to cut costs. The motherboard still overclocks well, just not as good as the press sample. That's only to be expected right? YMMV and all that crap they disclaim at the beginning of their overclocking results. I guess there's not alot you can do other than pick companies that consistently deliver. I have alot of OCZ parts in my systems for that reason so I was glad to see that there was some substance to what they claimed for their heatpipes, though the fact that one of them appeared to have failed isn't promising, but I can give them more of a benefit of doubt than the others discussed in the article.

[cypherpunks]

Sigh.

A typical heat pipe contains a mixture of alcohol and water at less than atmospheric pressure. The pressure is to adjust the boiling point of the liquid and give it somewhere to go when it does boil. Maybe some people have figured out a mixture that can be put in at atmospheric pressure, but it is still important to exclude air from the inside of a heat pipe. Air doesn't boil and condense, so it shouldn't be there any more than it should be in your brake lines or air conditioner's freon piping.

The walls are lined with a wicking material that holds the liquid and carries it back to the hot part, where it boils and enters the lumen of the pipe, travels to the cold end, condenses, and repeats the cycle.

But the important thing is that, in a cold state, ALL of the liquid is held in the wick material. Any excess would be pointless. And it's held quite firmly; remember it's the capillary action that sucks the liquid the whole length of the heat pipe back to the hot end.

If you want to test the build quality of heat pipes, find someone who can introduce a micro pressure sensor into a sealed pipe and check for a consistent temperature/pressure curve. But that's a little more complicated than hacking one open and shaking wet copper braid to see if any drops fall off.

[bdwilcox]

Heatpipes can also contain paraffin wax due to its low melting point and high thermal conductivity. Paraffin wax is solid at room temperature so it wouldn't simply flow out of a broken heatpipe unless the heatpipe was hot enough to melt the wax. This could lead to the false assumption that a heatpipe is empty when it really isn't.

[Wwhat]

I think the braids are most telling, if it was bogus they would not put braids in the heatpipes because doing that just adds a lot to the manufacturing process.
Of course it is possible that due to some mistake while soldering they accidentally lose liquid..
But I think this needs a more scientific approach to find the truth, as previous posters said, there are many possible explanations and the liquid used is of very small quantity and absorbed into the wick to boot.

It's nice that somebody actually tries though, about time too.

[pmorph]

I'm sure those heatpipes are just fine. But if you have doubts, why not drill a few holes in one and see whether it makes any difference in actual use. ;)

[gmeyer]

Where to start? The heat pipes shown in the investigation use a sintered copper powder for the wick structure. This can be seen in the cross section of the pictures. A properly designed heat pipe that uses this type of wick structure will not have any excess water inside and there for no water will run out when opened. All of the water is held in the wick by the capillary action of the fluid. Very much like a wet paper towel.

There is evidence of fluid if you look closely. 1) the slight noise you heard when you cut them open is air rushing back into the heat pipe. The heat pipe is a vacuum device so when the seal is broke it will suck in air. 2) Now that the water is exposed to atmospheric pressure it will not vaporize until it reaches 100 degrees C. 3) If you carefully heat the opened heat pipe to over 100 degrees C you will see the water in the wick vaporize. 4) there is a very simple test for checking if a heat pipe is functioning. Stick one end in boiling water about 2 inches deep and hold the other end. See how long you can hold it? Should be a very short time, about 5 to 10 seconds. Try this with a heat pipe where you have cut the end off.

If indeed these parts functioned as cooling devices before they were cut open it is almost certain the heat pipes were functioning properly.

FYI, I have been in the heat pipe business since the 70's and have learned one or two things about them. Any questions, I would be happy to answer them..

George

[Wwhat]

I must say I DO have the impression it took the industry some time to tweak heatpipes, even with a liquid and a wick you still must find the optimum pressure and kind of liquid, and when heatpipes were new I read some reviews of products where heatpipes were not very functional, whereas now they seem to have gotten them to work quite effectively, most of the time.
And of course it's not unthinkable there are some chinese rip-off fake heatpipe products around.

And don't forget the general heatsink issues reviewers and consumers sometime find, I myself bought sticks of RAM from a reputable manufacturer where the heatsink didn't touch the pads that are suppose to transfer the heat to them, and I had the same once with a graphicscard, as did several reviewers of such products.
Oh and we've all seen the shots of enthusiast opening consoles and such and finding that they had strange issues, like way way WAY too liberal use of heattransfer paste.
Never trust these things if you can check them.

[gmeyer]

I agree that there will always be "knock off" products of questionable quality. By the way, the fluid is 99.9% of the time water and the pressure is set by the vapor pressure of the fluid. By the time heat pipes began to be used by the computer industry the designs had been pretty well established in the military and specialty markets. The wicks are for the most part sintered copper powder (sometimes, grooves, mesh or wires) and all commercial applications use water for the working fluid.

[Wwhat]

I have a sneaking feeling the military weren't communicating their experiences with the chinese, for some reason.
And I know from reading various testresults that regardless of the knowledge in other markets/military the initial computer heatpipe product had some teething issues.
As for your claim they all use water, that's a bit of a daring statement because I'm sure you don't have access to the manufacturing information of the korean/japanese/chinese/taiwanese manufacturers.

Oh and correct me if I'm wrong but it seems logical to me that the liquid used would be tweaked to expected temperatures of the hottest and coolest points, so you would have to consider the ambient temperature, and the rate of cooling of the fins and the maximum/average heat at the contact surface.
Obviously you can pump out air to change the boilingpoint but only up to a point, and that creates its own peculiarities in regards to the movement of the liquid and such I imagine.
Plus obviously water is thicker than say alcohol and would have a different behaviour.

[gmeyer]

I will get into the details later, but I do have contacts with most of the major manufacturers of heat pipes in all the countries you mentioned and have lived there for many years and most of the chinese companies are off shoots of the taiwan companies. So, it is not daring at all to state they use water. I was part of the initial technology transfer of heat pipe technology to Taiwan in the early 90's.

Why water? Next post

Thanks,

George

[Wwhat]

Ok, colour me cynical but now I don't believe you anymore.

About speaking 4 asian languages and being so cozy with various asian CEO's that they tell you tradesecrets that is.

[gmeyer]

Cut me a break! A guy tries to be helpful and you are cynical without doing any research. Not sure it matters what you believe. if you do a patent search under the name of this poster you will find many heat pipe patents.... So, you know more about heat pipes?

[Wwhat]

I'm sure you know plenty (if you are who you say you are, but I'll assume for the moment you are) on the subject of cooling and heatpipes, but I don't buy that on top of that you speak 4 or 5 asian languages and know all those CEO's and they like you so much that they tell you tradesecrets.
That part seems a bit incredible to a seasoned internet user.

Oh and I DID search the name you use and that person certainly knows things aren't so straight-cut and simple and that MANY factors play when designing a coolingsystem, so if you are that george meyer you would agree that the choice of liquid depends on various circumstances and conditions where the heatsink was used for.
And I personally think that person would also be intelligent enough to admit that he can't know the liquid used by all manufacturers.

[gmeyer]

I do admit that I never said I spoke 4 or 5 Asian languages, only that i lived in asia. I struggle even to speak a little Mandarin. I don't understand why you have such an issue with water as a working fluid. There are other fluids used for special applications. For example, if using aluminum you can not use water, it is incompatible. You can use ammonia. Same with stainless steel. If you want operation at very low temperatures then you may want to use an alcohol. If you want high voltage standoff then use one of the FC products. If you want high temperature operation then use sodium or potassium. If you simply want to cool a processor or graphics chips then use water.

Water is in the heat pipe under a vacuum, so it will vaporize at temperatures down to the freezing point. It has very good surface tension and latent heat as well as good vapor pressure at the temperatures electronics operate.

An estimated 300 million heat pipes are used every year and 99.9% of these are either sintered, groove or wire wick structures and use water. They come from Furakawa, Fujikura, YCTC, AVC, CCI, CoolerMaster, Novark or a number of other small companies making heat pipes.

You do not get this information only from knowing the CEO's, you get it through many channels, by having tested and taken their product apart or knowing where they got their heat pipe technology or knowing people who have been through the factories. Engineers and buyers from companies that buy heat pipes.


So, what other fluids would you suggest, maybe I can learn something? You have to consider safety so alcohols and acetone are out for consumer goods. The latent heat and surface tensions of the FC products is too low. Am I missing something?

Cheers,

George

[Wwhat]

Interesting, but no alcohol/aceton for safety? seems a bit weird, it's minuscule amounts in a closed metal tube, acetone is used in abundance by girls to clean nailpolish, and alcohol is used in abundance by common senators and people ;) (also available in any supermarket in pure-ish form for cleaning)
And there are many parts used in electronics that have much more radical chemicals of course, very poisonous and flammable materials.
Anyway thanks for expanding on the water question, now that you explained the logic and how you got the information it all makes sense again.

You can't blame an internet user for getting a little cynical I'm sure you know that from your own experience.

[gmeyer]

Yes, big companies can be a little weird about safety. They are very concerned about some things and oblivious about others. Like the 20 gallons of gas riding behind you in your car. But, that is the way it is! I wasn't making these things up or trying to impress anyone. Just trying to share what few things I do know about.

[MrCanard]

This company http://www.norenproducts.com/Heat_Pipes/what_is.html
was passing out samples of their heat pipes earlier this week at a vendor show.
I been moving the sample back and forth between a hot cup of water and a cold cup of water.
It amazes me how fast the temperature is transferred to the opposite end of the pipe.

[amandpm24769]

Yes, big companies can be a little weird about safety. They are very concerned about some things and oblivious about others. Like the 20 gallons of gas riding behind you in your car. But, that is the way it is! I wasn't making these things up or trying to impress anyone. Just trying to share what few things I do know about.

What Luck i finally found someone who knows about heat pipes....I need some advice if you can spare some:)
I am trying to build my own CPU heat sink with the base material being Fine 99.9 Silver, I have 6mm Sterling silver 925 tubing to use for my heat pipes..(fins will also be Sterling silver 925) Now the questions... how do I get the wick material into such a small Dia. pipe and still have it hollow?
I bought copper screen that i was going to try to put into the pipes for the wick but after all the reading here I am assuming there is a more efficient wick material than copper screen, I just need to know what that material is and where to buy it and how to install it into the tubing.

Also the Sterling tubing I have (6 PCs)is cut into 12 inch lengths...My idea was to bend the 12" tubing in half, the bend would be silver soldered to the Fine Silver base and each side of the base would be a heat pipe, it would look like two heat pipes but it would only really be one bent in half..complete with Wick and working liquid...

Your help would be so good as I am desperate for info to help me with this crazy CPU heat sink idea build.

I have just about everything to build it just need some intelligent helpful information.

Thanks

[mutter]

:o:D:P:P:D