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.
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.
Last edited by Wwhat; 10-30-2007 at 06:34 AM.
Reason: added thoughts on liquid
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.
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?
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.
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?
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.
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.
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.