Cooling Misnomers

[trents]

We refer to air cooling but most good after market "air coolers" use heat tubes filled with water.

We refer to water cooling but all "water cooling" depends on air taking the heat from the radiator.

They are both really hybrid air/water systems. The only difference is one relies on convection in the water component and the other relies on mechanically pumped circulation.

 

[ATMINSIDE]

If you want to be that technical about it, good air coolers are phase change cooling.
Also, those tubes aren't filled with water, they're filled with an alcohol based liquid.

 

[EarthDog]

We refer to air cooling but most good after market "air coolers" use heat tubes filled with water.

There are DROPS of water in heatpipes...which make the transfer more efficient than just solid copper. But its the fin array and the air moving through it that cools it down.

We refer to water cooling but all "water cooling" depends on air taking the heat from the radiator.

But A LOT (a cup to a liter) of water is taking the heat away from the CPU. Yes, the rad needs air to cool itself off, but its water that is taking the heat away (through the block) from the CPU. Versus the heatpipes and fins (then air) that take heat away on a traditional heatsink.

So, I personally wouldn't call it a misnomer..

 

[trents]

If you want to be that technical about it, good air coolers are phase change cooling.
Also, those tubes aren't filled with water, they're filled with an alcohol based liquid.

Whatever. Okay, I'll substitute the word "liquid" for "water".

 

[EarthDog]

This, well something similar, has been discussed quite a bit years ago when AIOs came to market. At that time, some rare birds didn't consider AIOs to be water cooling and only custom loops(they were basing it on performamce). This is a similar discussion I fear.

 

[WhitehawkEQ]

If you want to be that technical about it, good air coolers are phase change cooling.
Also, those tubes aren't filled with water, they're filled with an alcohol based liquid.

Heat Pipe Materials and Working Fluids

Heat pipes have an envelope, a wick, and a working fluid. Heat pipes are designed for very long term operation with no maintenance, so the heat pipe wall and wick must be compatible with the working fluid. Some material/working fluids pairs that appear to be compatible are not. For example, water in an aluminum envelope will develop large amounts of non-condensable gas over a few hours or days, preventing normal operation of the heat pipe.

Since heat pipes were rediscovered by George Grover in 1963, extensive life tests have been conducted to determine compatible envelope/pairs, some going on for decades. In a heat pipe life test, heat pipes are operated for long periods of time, and monitored for problems such as non-condensable gas generation, material transport, and corrosion.

The most commonly used envelope (and wick)/fluid pairs include:

Copper envelope/Water working fluid for electronics cooling. This is by far the most common type of heat pipe.
Copper or Steel envelope/Refrigerant R134a working fluid for energy recovery in HVAC systems
Aluminum envelope/Ammonia working fluid for Spacecraft Thermal Control
Superalloy envelope/Alkali Metal (Cesium, Potassium, Sodium) working fluid for high temperature heat pipes, most commonly used for calibrating primary temperature measurement devices

Other pairs include stainless steel envelopes with nitrogen, oxygen, neon, hydrogen, or helium working fluids at temperatures below 100 K, copper/methanol heat pipes for electronics cooling when the heat pipe must operate below the water range, aluminum/ethane heat pipes for spacecraft thermal control in environments when ammonia can freeze, and refractory metal envelope/lithium working fluid for high temperature (above 1050 °C) applications.

Read full info here Heat Pipe

 

[ATMINSIDE]

Whitehawk, Wiki is great, but I can tell you from first hand experience that all the good heatsinks will be using a media other than water.
Yes, copper with water is common, but I would be absolutely floored if companies like Noctua were using water in their heat pipes.

Ammonia, acetone, methanol, and ethanol are all common in heat pipes as well.
Take a look at this PDF, you'll see that in actual testing that water actually isn't that good compared to other fluids.
http://www.google.com/url?sa=t&rct=...vEdokL6M6jNPUI3gA&sig2=yK9a9yaWR62hMJTiCdP_KQ

 

[HankB]

Almost totally off topic... The application of heat pipes I find most interesting is keeping the permafrost frozen in Alaska.

http://www.polartrec.com/expedition...d-snowpack-interactions/journals/2013-03-30-0

 

[Mr.Scott]

Yes, copper with water is common, but I would be absolutely floored if companies like Noctua were using water in their heat pipes.

I wouldn't. Water is cheap, and it's all about the profit.
The difference in media will not make a noticeable difference in that small a quantity or application.

 

[NiHaoMike]

For high thermal density applications, a "high pressure" refrigerant like R134a is often used to keep the vapor density high enough to allow the heatpipe to be made smaller.

 

[Retrorockit]

As far as misnomers go I call heatpipe coolers "heatpipe coolers", and heatsinks "heatsinks".
I liked the link to cooling medium tests, with acetone at 100% fill the best. Makes me want to cut open some heatpipes and if I find water do something about it.
One factor I don't see mentioned is thht some companies produce heatpipes that are under vacuum which lowers the evaporation point of the fluid.
Also water and alcohol can be mixed to increase the refreshment factor.

I just looked around the web a little and found that water can boil at room temperature or less under a high vacuum, or just about any other temperature needed.
The fluid doesn't need to boil to perform cooling only evaporate (put alcohol on your skin, it cools but it isn't "boiling"). Water can carry/transfer more heat per weight/ volume (not sure which really applies) than other fluids. That and alcohol being soluble in it makes it not only cheap but very versatile and effective.

This has led me to an interesting thought experiment. What if you built a heatpipe with enough vacuum that the water was boiling at room temperature, and condensing and boiling etc. in a cycle with no heat being applied.

 

[EarthDog]

Then it wouldn't help cool anything.

 

[NiHaoMike]

I just looked around the web a little and found that water can boil at room temperature or less under a high vacuum, or just about any other temperature needed.

My friend Brittany Benzaia actually developed an air conditioner that uses water as a refrigerant. The main obstacle is that the vapor pressure is extremely low which means it would be impractical to build a conventional compressor for it. (If you did, you'll need a unit about the size of a car to cool your house.) What she did was develop a switched reluctance centrifugal compressor that more resembles a turbocharger than a conventional HVAC compressor. Combine that with an inverter to spin the rotor at well over 100kRPM and the required mass flow was easily achieved in a practical size. The very low vapor pressure means that a standard "split system" could not be built, so instead the outdoor unit is actually a chiller, circulating water to the indoor unit exactly like how a PC water cooling system works.

 

[Retrorockit]

Then it wouldn't help cool anything.

It would be very cool in and of itself.

 

[Mr.Scott]

It would be very cool in and of itself.

And useless.

 

[Retrorockit]

The truth is it would never happen in the first place. It can't boil and condense at the same temperature. If the vacuum got it to boil at all the pressure would rise and it would quit boiling again, or just go dry. Thought experiments are useful in that they can keep you from making mistakes or help you explore different approaches to things. The idea was useful in that I had to figure out WHY it wouldn't work.
It's like the 100mpg carburetor. Once you know that 1/3 of the heat from fuel goes out the exhaust, 1/3 out the radiator, 1/3 to power the car. I t becomes apparent that the carburetor isn't the problem. Or the solution

 

[EarthDog]

Fuel injection.

 

[Mr.Scott]

Should re-name this thread to 'reinventing the wheel'.

 

[EarthDog]

...to try out square ones...

 

[Nebulous]

...in round holes...