Cutting Heatpipes

[drcroubie]

Well, i must admit, despite my 10 years of building computers, and few years working on cooling systems for really high power (80kW+) radar systems, i never knew that heatpipes weren't in fact solid.

I recently bought a Noctua U12 to go on to my X2-3800 / m2n-sli/dxe system, purely because it was on special and i thought i could get some lower sound out of my systems. I've been running with the CPU underclocked and undervolted for basically most of its life, and the cpu idles at about 30-40 with an ambient of 20-30 on stock hs and QFan on Silent mode.

After installing my U12, i was not too happy to see that it now idles at 60C, 40 above ambient (nowhere near the 5 degrees i was hoping or expecting). I took it off, wiped off some excess compound, inserted washers under the springs to give some more contact force, and got it down to 35C, same as stock cooler (but still after spending $50).

The only problem was that before i installed it, i had to cut the ends of the heatpipes off to get it to fit inside my case (it _just_ fits with the heatpipes flush to the top fin).
Now somebody tells me that the heatpipes are hollow because they have some kind of liquid inside at low pressure, and i've basically thrown away my money.

So, to the questions:

- firstly, has anyone else ever made this mistake? (just to make me feel better)

- two, i've read up on wikipedia etc, which say that the liquid could be any of water, ammonia, alcohol, mercury, does anyone know which is more likely?

- three, does this sound plausible as a way to fix it?:
Seal up one end of each heatpipe (probably screw into the pipe, maybe glue to vacuum seal).
Mount with pipes vertical.
Run CPU (or bolt to dummy load) to "very" hot.
"Carefully" add a "bit" of liquid to each pipe, then screw/glue seal the other end shut. ('very' hot so that the pipes never explode due to overpressure, when cooler it should be low pressure)
The hard part will be getting the definition of "bit" correct, and not scalding myself in the process too.

Comments/suggestions/answers?

 

[aziraphale]

I don't think you'll be able to fix the cut off heatpipe. You'll have to restore the exact conditions inside as they were before; eg pressure and fluid volumina... But probably someone else has an idea?

 

[Flying-Q]

Firstly, you have made an expensive mistake (one which I heard last year a friend of a friend made so you are not alone).

However (and secondly) you could get really adventurous and try and fix it in the manner you have suggested.

As a starting point I found this which has a nice chart of operating fluids. You need to do some more research to find what the operating pressure is - it may be well below that achieved by cooling from a high temp (using dp=nRdT/v).

Keep us informed if you really try it - even if you fail the attempt is worthy of reporting - and good luck.

Q

 

[mrmez]

Neva knew that abt heat pipes either. Didnt u notice any fluid leaking out after u cut it?

IMHO, the only easy solution is to fill the hollow pipes up with thermal grease as best u can.

As far as i know the paste is thermally conductive, and should help move the heat from the plate to the fins a little better. Any other solution will likely result in u killing yourself or wishing u had.


EDIT........

Nice read on the heat pipes. Tho, doesnt this suggest the best position for the pipe is vertical, drawing on the 'hot air rises, cold air sinks' principal?
Just curious but id like to see a heat pipe showdown with vertical vs horizontal orientation.

 

[T8RR8R]

Google heatpipes before you buy something with them.

Basically a heatpipe is a metal tube filled with a special liquid that vaporizes as a fairly low temp. When the liquid vaporizes it travels up the pipe where it's usually cooled with a fan and/or a multiple fin design. When the liquid is cooled it travels back to the bottom where the cycle repeats. There are 2 basic types of heat pipes, one being capillary and one not. The capillary design allows the coolant to travel to the coolest point of the pipe no matter if it's the highest point or not. The non capillary pipes should not be turned upside side down. Usually these kinds of heatpipes are the ones installed on motherboards because inverted(upside down/right side) ATX cases are not standard there fore are not usually supported by the motherboard industry. Not to say that one performs better, but capillary type heatpipes do allow more options for non-standard installations.

 

[drcroubie]

well, i did also think about using some silicon goop inside the heatpipes too, i'd probably need some kind of solvent to make it a bit less viscous. if i try any fluids and survive the inevitable ex/implosions, i may go for the silicon goop path.

I didn't notice any liquid escaping when i cut the pipes, they were mounted horizontally to cut, my boss suggested that whatever is in there may be in solidish gel form when cold, so only leaks when hot. there is actually a nice stain on the bottom of my case like dried pepsi, but seeing as it's a 7 year old case, it could actually be dried pepsi. it's currently lying on the floor (pipes vertical), so there may be something left if it's non-evaporting stuff.

Another person at work just suggested water-cooling fluid, or even car-radiator fluid (assuming there's even a difference). it'll probably help with the non-corroding of the inside of the pipes at least, which is the only thing i've got against using pure water.
The graph on that link puts air temp right in the middle of the alcohol, benzene, and ammonia range, all of which i'd rather steer clear of, unfortunately.

when i think that i only blew 2 hours wages on it, it doesn't sound too bad, but i'm determined to make it work now, i might try something next week (away this weekend unfortunately).

i'd be interested to hear any other suggestions too.

 

[T8RR8R]

As far as I know it's similar to alcohol and since it's under a small amount of pressure inside the tube it may actually turn into a gas when that pressure is released. I only know so much about these things since I've never actually cut one open.

There are 2 types of glycol used in water cooling. One type is used for your car and the other type for things like PC's, they are different and should not be used universally.

 

[r0x0r]

Completely off topic so everyone else can ignore it but...

Location: c/- Unibar, Adelaide University, South Australia

I go to the Sports Hub three/four times a week, right next door to the Uni Bar. What a small world. :lol:

 

[T8RR8R]

OMG :roll: ...lol

 

[drcroubie]

Completely off topic so everyone else can ignore it but...

Location: c/- Unibar, Adelaide University, South Australia

I go to the Sports Hub three/four times a week, right next door to the Uni Bar. What a small world. :lol:

Completely more off topic then, i'll be there in about an hour, being rowdy on the balcony, and drowning my sorrows for my lamented heatpipes...

(or just getting drunk like i do every thursday afternoon)

 

[r0x0r]

Now I know not to walk under the balcony! :lol:

As for the heatpipes; I would cut my losses and buy a new cooler, simply because if the same thing happened to me I wouldn't have the confidence to try a fix. Maybe on an old CPU but otherwise, no. It's up to you though.

 

[Mugz]

I am occasionally guilty of a tequila or three on a Friday. I live in South Africa, though, so...

Speaking as an industrial engineer, your heatpipes are wrecked, yet you may be able to use them.

Spray 'em out with canned air. If you can get some canned air to collect in the bottom of the pipe while it's still liquid, you're making progress. About one-tenth full should be about right.

Seal off the pipes using whatever method necessary, I like the screw-in plug idea, just add some silicone (or some other suitable sealant) before you screw the plug in.

I've dealt with these little buggers before, just never in a PC setting up to now.

Hope this helps.

Incidentally, I've found pressurised butane (lighter gas) also works for this. It evidently needs something with a very low boiling point. Water's useless at PC temps.

 

[T8RR8R]

I usually drink Whiskey and Coke while I frag some of the un-worthy on BF2142. When I'm at 6 or 7 drinks I usually do alot better...go figger?

I have some of that butane and it should work pretty good. AFAIK all they do to the ends of them are basically crimp and solder, who knows though?

 

[aziraphale]

Neva knew that abt heat pipes either. Didnt u notice any fluid leaking out after u cut it?

IMHO, the only easy solution is to fill the hollow pipes up with thermal grease as best u can.

As far as i know the paste is thermally conductive, and should help move the heat from the plate to the fins a little better. Any other solution will likely result in u killing yourself or wishing u had.

Just forget about what MrMez said here very quickly. He obiously didn't understand how heatpipes work. Thermal grease is the last thing you want in those pipes. A few posts above you can find a link about the compositions of the fluids in heatpipes...

 

[neocristi]

I read a post once of a dude who put some "extra holes" in he's motherboard to fit a socket 775 cooler (obviously he had a different socket). Afterwards, the PC died (no kiddin').

This post today is not as funny as the other I read but still you gotta love this things people do "home made" 8O

That cooler is as good as dead!

 

[jfkillers]

QUEENSLANDERS

 

[aziraphale]

QUEENSLANDERS

huh?

 

[jfkillers]

Queensland won the State of Origin. Just rubbing it in, not that SA should care really.

 

[aziraphale]

aha; interesting...

 

[drcroubie]

Queensland won the State of Origin. Just rubbing it in, not that SA should care really.

yeah, no, nobody cares about league, except queenslanders.

it's nice to come home intoxicated and know that you all still care about me and my overheating athlon (aside: i got an e6420 to 8*437.5 on a Striker Extreme rig i built over the weekend, stock cooler and voltage, idled at 50C, same as my undervolted underclocked athlon currently unfortunately.)

definitely gonna try save it next week though, the "overheat, fill with coolant, then seal" idea sounds much easier after 6 jugs of Pale Ale. but to paraphrase the Pnk Floyd song i'm currently listening to, Careful With That Sledgehammer, Eugene!

ps, i'll let you all know how it goes, assuming i don't get 3rd degree burns from exploding heatpipes all to save a measly $50.

 

[drcroubie]

The best ideas come to me when i'm supposed to be working. so i'm writing it down before i forget it (and so you can all tell me i'm an idiot).

How about this:
Take the top few fins off (to access a few mm on the top of the pipes).
Grab some hoses, clamps, a pump and some liquid, and turn it into a forced-water cooled rig. Surely forcing liquid through the pipes will work better than any evaporative/capilliary passive thing that heatpipes are supposed to do. in theory, it'll just be like a proper radiator/waterblock, but just be attached directly to the cpu.

The other option is to buy a proper waterblock, and mount my heatsink as the radiator in the top of the case. (it's a full tower from back in the good old days when full actually meant "full", plenty of room up there)

what do you all reckon, am i getting ridiculous yet?

 

[bkiserx7]

heat distilled water and coolant (50/50 mix) to near its boiling point, say 250 F. then poor this fluid into the pipes and seal back the top. the near boiling fluid will be nearly as expanded as possible so when you seal it and let it cool the fluid will create a vacuum above it. if you can find some liquid that boils just above room temperature use it instead.

just my 2 cents

 

[SasparillaMayonase]

i had to cut the ends of the heatpipes off to get it to fit inside my case.

Comments/suggestions/answers?

Did you ever wonder why they were called heat PIPES...instead of, say, heat POLES

 

[Polar_012]

Its the biggest and stupidest mistake ever. Why the hell you think you did cut the heatpipes without even knowing whats the heatpipe for. Obviously your temp will suck.

The best you could do is change it to water cooling but the temps will only be slightly better than currently. Get a radiator, reservoir, pump and fix it to the heatpipes. You might need to get few sets of it so that you wont be running the water into the heatpipe simutaneuosly and thus reducing the pressure.

Another alternative is just get a new heatsink.

 

[cb62fcni]

The forced water-cooling idea sounds pretty sweet, if nothing else it would be an interesting experience. You'd first have to ensure that you clean out the heatpipes. A decent pump and some splittlers next. The only problem I can see is that the narrowness of the tubes will restrict flow quite a bit. Still should be interesting though.

DO NOT use thermal greasein the tubes. It's actually NOT very thermally conductive. That's why you only use a thin layer, and too much causes temps to soar through the roof. Some guy measured a bunch of thermal pastes and found that vegimite and toothpaste were both better heat conductors.

What radar system, if I may ask? I'm an old SPG-62/SPY-1B guy myself. Fun stuff.