Heat pipes not containing any fluid?

[Zap]

Originally posted by: thilan29
If there's no fluid it's not performing as well as it could and people didn't pay $50+ to get a cooler that doesn't perform as well as it could.

Well then, why doesn't a company come out with a heatsink just like all the others, and put some liquid inside... BAM, instantly outperform all others!

You'd think some company would come forward and do that, right?

Well, they can't.

That's because heatpipes DO have liquid in them, just usually not enough to pour out since most will be absorbed by the wick. Even the Phoronix article said so:

they didn't appear to contain any fluid but is likely stored in the heatpipe's wick.

As for the liquid in the OCZ Reaper heatpipe pouring out... not too sure because no closeup, but from the pic looks like their heatpipe may not have a wick. All the other heatpipes they cut open had closeups which showed the wick.

 

[thilanliyan]

Originally posted by: Zap
That's because heatpipes DO have liquid in them, just usually not enough to pour out since most will be absorbed by the wick.

If that's the case then I guess there isn't much point in the article. Sorry I didn't know it could be absorbed by the wick.

 

[Zap]

Originally posted by: thilan29
I didn't know it could be absorbed by the wick.

The wick is basically like a sponge.

 

[jagec]

Originally posted by: Bluefront
I'm laughing over this one......anybody ever seen freon in a liquid state? Freon is one substance used in heat-pipes. It's only liquid when under pressure. The very instant a heat-pipe is cut open, whatever freon that was in there turns to an invisible gas......and pours out.

There are electronic devices that can detect freon in a gas state......but you're eves can't. In automotive refrigerant systems a green dye is added to the freon...you can see traces of the dye at the point of a leak. Maybe heat-pipe makers should start using dye in their systems.....make us all feel better.

I really doubt that they use Freon, seeing as that would not be legal in this country. Freon (R11, R12) has been banned from import or production for domestic use, and completely phased out by R-134a, and the only Freon you'll find anymore is in *old* phase-change systems. And you'll have to go south of the border to get an illegal refill.

But yeah, cutting open heat pipes and looking for visible liquid is the wrong way to go about this.

 

[Bluefront]

I use the term "freon" too loosely I suppose. R-12 has been replaced by R-134A......which is a different substance, but mostly interchangeable with R-12. Freon is used as a generic term covering automotive refrigerants....not entirely correct, but usually understood.

Heatpipes without a working fluid hardly work at all. A heatsink such as an XP-120 has a large number of primary fins that attach directly to the CPU base, in addition to the heatpipes. Such a design could conceivably work if the heatpipes were empty.....just not very well. Other designs rely 100% on working heatpipes......and would over-heat the CPU in a flash if there was only air in the pipes.

Now if you only have one empty heatpipe, figuring that out might be difficult. The temp at the far end of the one "bad" pipe might be a little lower than the others. But this difference might be difficult to determine. As to which is the best working fluid.....a toss-up. A leaking liquid heatpipe might short out something. A leaking pressurized gas might be toxic. Either might be flammable. Take your pick......

 

[aigomorla]

Originally posted by: thilan29

Originally posted by: thecoolnessrune
If there is no fluid? What does it matter?

Actually that DOES matter. If there's no fluid it's not performing as well as it could and people didn't pay $50+ to get a cooler that doesn't perform as well as it could.

Plus why call them heat pipes if there's no fluid in it?

okey lets think of basic chemistry now.

Now, as you are aware, as you increase pressure, the boiling point of fluid will become higher.

Think of camping in the mountains when the boiling temp of water is less then 100C due to the less pressure of altitude.

Now think of sub thermal vents where water is like 400C and not turning into steam or gas phase. Because the pressure down there allows the boiling point of water to become that much higher.

Heat pipes. Most of them have a type of gas. This gas is under pressure and heat and will allow the coolant to change phase. Since the average sink will top to around 40-50C a type of spirit or a coolant of some sort with a low evap temp will be used. Otherwise the heat pipe wont make sense.

Now when you cut open that heat pipe what happens? A pressure drop. Then what happens? that coolant which was inside the heat pipe will evap and turn into gas, because of the pressure drop.


Guys sometimes you seriously crack me up with these wierd reasons when all it takes is simple physics and chemistry to solve.

 

[VinDSL]

Originally posted by: aigomorla
Think of camping in the mountains when the boiling temp of water is less then 100C due to the less pressure of altitude...

Heat pipes. Most of them have a type of gas. This gas is under pressure and heat and will allow the coolant to change phase. Since the average sink will top to around 40-50C a type of spirit or a coolant of some sort with a low evap temp will be used. Otherwise the heat pipe wont make sense.

Now when you cut open that heat pipe what happens? A pressure drop. Then what happens? that coolant which was inside the heat pipe will evap and turn into gas, because of the pressure drop...

Um...

Pressure will increase the boiling point - vacuum will decrease the boiling point.

For instance, that's why they put pressure caps on automobile radiators - to increase the boiling point of the coolant (mostly water). And, that's the reason they vacuum down air conditioner systems before charging them - to decrease the boiling point of any water that's present and evacuate it (Freon + water = acid, e.g. rots the AC system).

Soooo, it doesn't make any sense that they would pressurize heat tubes. If anything, they would place the fluid in a vacuum...

You know what? This is all magic, and nobody understands it. Please don't pretend you do...

I can't wait to see how this all ends!

 

[Zap]

Originally posted by: VinDSL
This is all magic, and nobody understands it.

Not magic at all, just applied science.

Fact: A "working" heatpipe (with liquid in it) conducts heat many, many times better than just an empty copper tube (with no liquid in it). I've seen numbers quoted as high as 80x better. Wikipedia

Try this. Get two jars. Put a sponge into one. Pour 1cc of water into both jars. Wait a while. Now, pour out the water. OMGWTFBBQ the one with a sponge in it no longer pours out a liquid!?!?!!

Sponge = wick inside a heatpipe. "The basic idea of the wick is to soak up the coolant."

How heatpipes work - look at the first diagram which shows the empty space as filled with.... "Vapour" and the wick filled with.... "Liquid." If "liquid pours out" then there is one of a few possibilities:
1) The manufacturer put too much liquid inside.
2) There is no wick. This would make it a subset (or relative?) of a heatpipe called a "thermosiphon."
3) There is a wick, but it is not one of the "better" ones.
4) There is insufficient vacuum in the heatpipe.

"Better" is sintered (closer to sponge) while not as good is grooved (simple grooves in heatpipe wall, can't really hold the liquid). "In between" are wire mesh, fiber/spring and other wick designs. The "better" wick designs are better for working against gravity, as in they can be oriented whichever way. A drawback is that "better" wicks actually limits heat transfer, but in most cases it is worth the tradeoff. Note the Vapochill heatsinks which has one large heatpipe (really a thermosyphon) and which requires a certain orientation when mounted. If not mounted in the "proper" orientation for gravity to work, then it basically doesn't work at all. Most normal heatipipe heatsinks don't have this limitation because of effective wicks.

Originally posted by: VinDSL
I can't wait to see how this all ends!

It is ended.

The Phoronix article is IMO misinformed and misleading, and a good example of bad journalism.

Originally posted by: VinDSL
Soooo, it doesn't make any sense that they would pressurize heat tubes. If anything, they would place the fluid in a vacuum...

You are right. The Wikipedia article states:

When making heat pipes, there is no need to create a vacuum in the pipe. One simply boils the working fluid in the heat pipe until the resulting vapour has purged the non condensing gases from the pipe and then seals the end.

An interesting property of heat pipes is the temperature over which they are effective. On first glance, it might be suspected that a water charged heat pipe would only start to work when the hot end reached 100 °C and the water boils resulting in the mass transfer which is the secret of a heat pipe. However, the boiling point of water is dependent on the pressure under which it is held. In an evacuated pipe, water will boil right down to 0 °C.

This also is evidence of why liquid doesn't just pour out of a heatpipe. If it was properly designed to handle temperatures below 100ºC, then the liquid should be in a vapor state except for what is collected in the wick.

EDIT: Fixed improperly closed tags.

 

[thilanliyan]

Originally posted by: aigomorla
okey lets think of basic chemistry now.

I know my chemistry...but I disagree that something like freon would be used (as was mentioned before) as that would require very high pressures. What kind of pressures do you think a heatpipe is under anyway?

I guess unless we know what exactly is used in the heatpipe, we won't know whether it evaporated or there was nothing there to begin with. Also, I suppose not all heatpipes use the same fluid because there was a LIQUID that came out of the OCZ heat pipe.

 

[aigomorla]

Originally posted by: VinDSL

Originally posted by: aigomorla
Think of camping in the mountains when the boiling temp of water is less then 100C due to the less pressure of altitude...

Heat pipes. Most of them have a type of gas. This gas is under pressure and heat and will allow the coolant to change phase. Since the average sink will top to around 40-50C a type of spirit or a coolant of some sort with a low evap temp will be used. Otherwise the heat pipe wont make sense.

Now when you cut open that heat pipe what happens? A pressure drop. Then what happens? that coolant which was inside the heat pipe will evap and turn into gas, because of the pressure drop...

Um...

Pressure will increase the boiling point - vacuum will decrease the boiling point.

For instance, that's why they put pressure caps on automobile radiators - to increase the boiling point of the coolant (mostly water). And, that's the reason they vacuum down air conditioner systems before charging them - to decrease the boiling point of any water that's present and evacuate it (Freon + water = acid, e.g. rots the AC system).

Soooo, it doesn't make any sense that they would pressurize heat tubes. If anything, they would place the fluid in a vacuum...

You know what? This is all magic, and nobody understands it. Please don't pretend you do...

I can't wait to see how this all ends!

shiet... my error...

i thought they were pressurized with a low boiling point liquid. A simular concept to compressors.

 

[aigomorla]

OMG .... double post.

 

[jagec]

Look, I don't know what fluid heatpipes use, but it's not "obvious" that they would be in a vacuum, or pressurized.

That would totally depend on the working fluid.

What you do is find a fluid that has the thermal properties and price you're looking for, and is somewhat near the correct boiling point, and then use vacuum OR pressure to adjust the boiling point to the temperature around which you want the processor to be cooled.

Furthermore, since most enthusiast heatpipe manufacturers are NOT going to be plunking down the money for the best PhD engineers in the world, we can assume that they don't represent "the best possible" engineering solutions...which means that they're going to be using a variety of fluids, and pressures, and designs. The market (also composed of non-PhD engineers) will determine which designs survive, and which do not...and they won't necessarily be the "best" according to all definitions of the word.

 

[Bluefront]

That's correct of course. And it could be the "best" solution would be too costly for the market to bear.

Regarding vacuum/pressure and 134A......in an automotive usage, the system is first put under vacuum before the 134A is added. This is to remove air/moisture, which will eventually contaminate the internals. When the 134A is added, it's under extreme pressure, so the whole system remains pressurized, unless there's a leak. Under pressure, 134A is a liquid, but turns to a gas when the pressure is removed. You can tell this by shaking a can of 134A.....there's liquid inside, which turns to gas released. That would explain why some heatpipes would never pour out any liquid when opened. It wouldn't take much 134A to make a working CPU heatpipe. I suspect a pound of the stuff would make hundreds or more, heatpipes. Cheap solution......but the best?

 

[VinDSL]

Originally posted by: jagec
Look, I don't know what fluid heatpipes use, but it's not "obvious" that they would be in a vacuum, or pressurized.

That would totally depend on the working fluid...

Um...

The whole point of the article was - there wasn't any fluid inside, no pressure, nor any vacuum.

In the absence of any visible or invisible "working fluid", a discussion of vacuum vs pressure becomes masturbatory!

The author just added that information as further evidence that something is afoul with these cheap heat pipes, so called.

In short, the EMPEROR HAS NO CLOTHES...

 

[Zap]

Originally posted by: VinDSL
The whole point of the article was - there wasn't any fluid inside, no pressure, nor any vacuum.

In the absence of any visible or invisible "working fluid"

If the fluid was invisible, then of course those guys at Phoronix wouldn't see any liquid pour out.

What next? Are they going to prove that God doesn't exist because they broke open a Jesus statue and found nothing inside? Maybe belief is what makes heatpipes tick?

Heck, we should all just stop believing in things that we can't see or touch in RL! Yeah, that's the ticket! I'm going to stop believing in the WMC. I mean, seriously, it's just a huge joke posted here years ago. I'm also going to stop believing in the Everywhere Girl. I think she's just a CG image. The virtual sister of Adrianna or whatever that Nvidia girl is called. I'm also going to stop believing that the Governator exists. Seriously, who has ever seen Arnold in RL? Another CG entity. That's why he's been in so many Sci-Fi flicks. Those are mostly CG anyways.

I know... I'll just stop believing that there are good articles at Phoronix. I mean, seriously, I haven't seen any yet, so they must not exist, right?

Maybe Phoronix is trying to be the new TheInq (which was the new TheReg)? After all, computer geeks need tabloids too, ya know.

 

[zephyrprime]

Originally posted by: Zap
First, if there's no air in there, the liquid can't quite evaporate, can it?

Liquids can evaporate even in the absence of air.

 

[VinDSL]

Originally posted by: Zap]

If the fluid was invisible, then of course those guys at Phoronix wouldn't see any liquid pour out.

What next? Are they going to prove that God doesn't exist because they broke open a Jesus statue and found nothing inside? Maybe belief is what makes heatpipes tick?

Heck, we should all just stop believing in things that we can't see or touch in RL! Yeah, that's the ticket! I'm going to stop believing in the WMC. I mean, seriously, it's just a huge joke posted here years ago. I'm also going to stop believing in the Everywhere Girl. I think she's just a CG image. The virtual sister of Adrianna or whatever that Nvidia girl is called. I'm also going to stop believing that the Governator exists. Seriously, who has ever seen Arnold in RL? Another CG entity. That's why he's been in so many Sci-Fi flicks. Those are mostly CG anyways.

I know... I'll just stop believing that there are good articles at Phoronix. I mean, seriously, I haven't seen any yet, so they must not exist, right?

Maybe Phoronix is trying to be the new TheInq (which was the new TheReg)? After all, computer geeks need tabloids too, ya know.

Jeepers! I must have touched a nerve...

It's like I told a kid that the Tooth Fairy doesn't exist...

 

[Zap]

Originally posted by: zephyrprime
Liquids can evaporate even in the absence of air.

Actually... you are 100% right. Doh!

Originally posted by: VinDSL
Jeepers! I must have touched a nerve...

Yes you did... you seem determined in your pursuit of spreading misinformation and that irked me. Now I realized that I probably got trolled. If so, congrats, you win the intarweb award. If not, what is your agenda?

 

[jagec]

Originally posted by: VinDSL

Jeepers! I must have touched a nerve...

It's like I told a kid that the Tooth Fairy doesn't exist...

Next door to this lab is a tank of nitrogen. If I crack it open, I don't see anything coming out! It must be empty! The hissing is probably just my imagination.

The "proper" test for the heatpipe would be to use it on a computer, and wait for the temperature to stabilize. Once you get that temperature reading, cut it open and flush it out with a stream of air to evaporate and remove any trace of the working fluid. Then let the temperature stabilize again.

If you see an INCREASE in temperature...clearly you had a working heatpipe before, which means there was fluid inside.

If you see NO CHANGE in temperature, then yes, the companies have been ripping us off.

But it's ridiculous to look for visible signs of fluid.

There is only a small amount of fluid in any heatpipe,
Most of that will be absorbed in the wick at any given time,
And if cut open, it's very possible that the working fluid will evaporate and dissipate as an invisible gas.

Hearing some sort of "pop" or "hiss" is nice because it shows that there was a pressure differential there, but the conspiracy theorists could just say that it's full of pressurized air, so doing the before/after test is the correct way to go about this.