Just another crazy thought experiment... stop in if your curious.

[TuKr]

Alright, ive had these pop up from time to time and my last one was kinda crappy too. It involved mineral oil as an insulator to fight condensation for extreme cooling. Basically a shallow tank that submerged your mobo to keep water droplets from forming on components.

But ANYWAY, the next one...

We know that pressure affects our temperature, Low pressures are usually warmer, high pressures are usually colder. With our radiators its generally the same, by that i mean, if your rad is warm, the air between the fins is less dense. So the reason i am bringing this up and im curious about it is, 1) I dont have a 120mm rad to test with, and more importantly 2) if we turned our static pressure fans to both push air into the radiator directed at each other effectively forcing a higher pressure in the fins of the radiator, Would it effect our temps? same goes for the opposite orientation, both of them blowing out, causing a low pressure(though i think this would raise temps).

yes it sounds crazy and would probably be worthless to even try but if anybody wants to give it a go let me know how it turns out.

 

[EarthDog]

It's not a sealed enclosure so there are no/negligible pressure differences.

 

[TuKr]

were not working within the dimensions of a vacuum. Light a candle and blow smoke over the area above the flame, the smoke will rush upwards above the flame. This is because the air that is warm and Less dense, meaning less pressure, is lighter than the surrounding air. The same applies to the area between the fins on our radiator. If i can evacuate or introduce more air than the surrounding area i have changed pressures. but given that my fans could produce a whopping compound pressure of .25 millibar, i would get a better result simply lifting my computer 10 feet into the air from where it was. I should just sleep on these ideas.

 

[Mandrake4565]

TuKr I have tested this theory, accidentally by installing my fans in Push Push and not realizing it. It definitely does not help temps and in my instance hurt them. I am no scientist but I would have to believe you would need some serious fannage to get the pressure high enough to lower the temp of the fins, even if you sealed it properly.

 

[oldiron]

Unless I am missing something here and feel and free to let me know, even if it were sealed, both fans out would create a vacuum chamber, and both in would basically be a compressor and would be a pressurized tank sort of...maybe another type of heat exchanger could take advantage of that but a radiator is designed to dissipate heat by moving air over the fins...keyword moving.....now using high and low pressure to aid in that air movement would probably be more beneficial. No matter what I think you'd be limited by the surface area of the rad to dissipate heat no?

 

[Dlaw]

You have to also consider that if you had both fans in push on a radiator, the only places that (now warm) air is going to escape is around those same fans. That means that the air sitting in the middle is not likely going to move very much, and is going to continue to get warmer, thus increasing the temperature of the radiator.

The purpose of a radiator is to transfer the heat of the fluid into the air, thus removing it from the loop. If you don't force air through the radiator (not just into it, it's just as important for the air to escape), it won't work.

 

[GTXJackBauer]

Think of the radiators in custom water cooling like the copper heat pipes on CPU air coolers with a fan added to the mix in both examples.

Here's one instance for you. A high FPI radiator will need a high static pressure, noisier and fast spinning fan. A low FPI radiator will need the opposite since its easier to pass through. The amount of pressure isn't needed. If you want every penny's worth, you add a shroud to the mix as well.

 

[TuKr]

well, This was fun. LOL We will stick to moving air across the fins. Thanks guys

 

[EarthDog]

Just an exercise in elementary physics and thermodynamics!

 

[knoober]

In a radiator in your car however this effect is observed inside the radiator. I wonder if that knowledge could be usefull. BTW water loops are beyond me for now. I just wondered if that thought might further the cause

 

[EarthDog]

How does this happen inside your radiator in a car?

 

[knoober]

The water in your radiator will not boil because of the extremely high pressure. This allows the water to stay liquid at a much higher than boiling temperature. Or I should say makes the water stay liquid, I don't think it is an intentional effect.

What I was wondering is if this thermal principle could some how be reversed. By (somehow, I haven a clue as to how really because I'm only vaguely aware of how a water cooler works) lowering the pressure inside the loop you could increase the liquids ability to exchange heat. Maybe. Or something. Just spit balling here

 

[TuKr]

When pressure rises, boiling point does also, that is why recipes need to be adjusted at certain high altitudes. The lower pressure allows things to boil at lower temps. What you mentioned is basically how single stage evaporative cooling works.

Well same general principal.

 

[knoober]

So I'm just going to assume that we don't use a liquid with a low boiling point because the system isn't sealed well enough? What I mean is that if you used a more volatile liquid it might boil sooner but would also condense sooner as well (doesn't this mean it exchanges heat energy better?). So I can only assume that with a more volatile medium you would have more loss due to evaporation (as I've read about happening with water systems) which would lead to constant refills? Anyway I'm still just gabbing for no reason carry on gents, carry on

 

[EarthDog]

Again, there isn't (supposed to be) any air in the loop. So how would we see this happen?

 

[TuKr]

Well, if we increase pressure in the loop we can increase boiling points in the loop, so that says to use something that boils near room temp. Water takes far too much heat to safely use for this purpose.
So wee want something that will be stable at room temp (20 - 25C) but boils above 30C. The most important part would probably be picking something that doesnt boil until its closer to 50C but still effectively cools our loop. Right? The only thing that i can think of that may be safely within our limits is what ever liquid is used in air duster.

I used it in rasberry pi cooling and it only built about 1 maybe 2 psi while capped (quit boiling) at atleast -10C. When i put it under load with ras pi the warmest it got with liquid -7C. We could try it with 1/8th copper and solder joints, tiny loop and see if it pops under load and what results we might get.

 

[knoober]

Well, if we increase pressure in the loop we can increase boiling points in the loop, so that says to use something that boils near room temp. Water takes far too much heat to safely use for this purpose.
So wee want something that will be stable at room temp (20 - 25C) but boils above 30C. The most important part would probably be picking something that doesnt boil until its closer to 50C but still effectively cools our loop. Right? The only thing that i can think of that may be safely within our limits is what ever liquid is used in air duster.

I used it in rasberry pi cooling and it only built about 1 maybe 2 psi while capped (quit boiling) at atleast -10C. When i put it under load with ras pi the warmest it got with liquid -7C. We could try it with 1/8th copper and solder joints, tiny loop and see if it pops under load and what results we might get.

This is along the lines of what I was thinking, but I really dont have the knowledge to back it up. Im seeing perhaps even a gas (dont know what kind of gas) like in a heatpipe. Or at the very least a sealed system sleeved with something that will thwart condensation. For sake of example a 1/4 copper tubing hooked to the cold plate but shrouded in a 1/2 PVC shell. Servicing should be simple enough. Simply replace the copper innards with brand new.... kind of like a non servicable transmission. Its just sealed from day 1 until it breaks --> then it gets replaced. This would theoretically open up all different kinds of mediums to be used inside the copper (whatever is ideal) and the pressure could be fine tuned for performance.

Still just spitballing here, so if cant run with that , Ill do the neccessary research once I clear my plate enough to have the will/time/brainpower. You know in the next few years or so Im certain there is something that precludes such types of mechanics but I dont know what.

Imagination is AWESOME

 

[EarthDog]

Perhaps I am missing something

Again, its a sealed air tight loop, how will it boil?

 

[Dlaw]

I'm not a physicist by any means, but my instincts tell me that using a volatile liquid that boils at just above room temperature for the purposes of cooling a single computer is much more dangerous than the possible benefits (if any truly exist) are worth. If you think about it, what liquids are used in almost every cooling loop (every one that I can think of right now, anyway)? Water and, depending on the intended operating conditions, some form of anti-freeze. That leads me to believe (and I think I've even seen it written here) that water has the best thermal transfer properties of any liquid, or at least any liquid it would be safe to cool with extensively.

 

[knoober]

Well in this case volatile is kind of a misnomer. Volatile not like gasoline but as in boils at low temp. I wont disagree with you, but it would seem that they dont use the more volatile liquids because they would evaporate at a higher rate and leave air in the system. A completely sealed loop would prevent any loss in this way. Once again id have to check with the physics professors, but I think if it boils at room temp, it would transfer heat better than water. The use of water very likely has something to do with availability and not needing special certifications to handle it as well as how reactive it is with the tubing. Im thinking isopropyl though. Iso would take in the heat and give it back faster.

Now its time for me to bow out though, because Im an air cooler after all.

Edit: I seem to remember reading that copper heat pipes on air cooling rigs were sometimes filled with inert gasses. Im just thinking of an expansion of this concept and having the gas move through the radiator.... Im ceertain there are thermal issues to be overcome, but the base concept is (IMO) solid. I do see the problems that could arise though. I really think cost would be the biggest issue though. Each system would have to be custom built, or there would have to be a wide array available for popular case designs.