AOA Forums

AOA Forums (http://www.aoaforums.com/forum/)
-   Cooling & Temperature Monitoring (http://www.aoaforums.com/forum/34-cooling-and-temperature-monitoring/)
-   -   Attempting "Cohesive Air Cooling", will keep u all posted :) (http://www.aoaforums.com/forum/cooling-and-temperature-monitoring/2360-attempting-cohesive-air-cooling-will-keep.html)

e_storm 16th January, 2002 03:18 PM

Attempting "Cohesive Air Cooling", will keep u all posted :)
 
I dunno if anyone on the AOA forums has tried this or if its been talked about before I arrived, but I'm attempting something a guy named Hoot over at OCers.com called "Cohesive Air Cooling".

Instead of loading you case with loud fans and putting a loud fan on your HS, this is just a large Blower, attached to the outside of the case blowing onto the HS. The blower is powerful enough to cool the chip and to take care of the case cooing as well (and then some lol).

Its a 12 Volt, 5 Amp DC blower, so by far the most challenging part is going to be constructing the circuit to control the voltage (potentiometer) so you can slow the blower down (bring the voltage down to about 5 or 6 volts).

I have been, and will continue to, document everything I do in case anyone else sees my results and wants to attempt the same thing. I'll even do an article if the interest from others is there.

e_storm

mrpcman 16th January, 2002 08:52 PM

yeah, a few people have done that here. At the very least, Superman ran a duct to his window. :p good luck.

e_storm 16th January, 2002 09:11 PM

From what I could gather, the people that are doing it are using AC motors with speed control, cause that eleminates the circuit making part of the project.

This is gonna require some electronics/circuit design knowledge, which I don't have yet, but hope to have soon. :)

SteveI 16th January, 2002 09:41 PM

And keep in mind (as I'm sure e_storm knows), that the blower is the key to making this work. Rather than using a traditional fan, using a centripetal (?) blower reduces the turbulance, to create a more efficient airstream. (...if I understand the concept correctly.)

e_storm 16th January, 2002 10:09 PM

You got it brother....

Here's the blower that I have. Its only 176 cfm, but as SteveI points out, its a centrifugal blower... meaning the air comes out in a blast and focused in one direction. Normal Case fans have a radial (?) effect, meaning that they blow kinda in a spiral pattern blowing outward. The further you go away from the fan, the wider the stream of air gets.

In simpler terms, if you put a candle 3 feet or so away from a regular 176 cfm case fan, it might flicker, but won't go out. If you put it 3 feet or so away from a blower, it will blow out right away (concentrated air blast).

I'll shut up now, just turn on one of these centrifugal blowers and you'll understand what Me and SteveI are sayin.

I'll post pics and the whole 9 yards once I get it going...

RudyNg 17th January, 2002 01:09 AM

5 amps 12 volts voltage regulator for controlling this blower? I think there is one over HERE that may do the job.

mrpcman 17th January, 2002 01:31 AM

Quote:

Originally posted by e_storm
You got it brother....

Here's the blower that I have. Its only 176 cfm, but as SteveI points out, its a centrifugal blower... meaning the air comes out in a blast and focused in one direction. Normal Case fans have a radial (?) effect, meaning that they blow kinda in a spiral pattern blowing outward. The further you go away from the fan, the wider the stream of air gets.

In simpler terms, if you put a candle 3 feet or so away from a regular 176 cfm case fan, it might flicker, but won't go out. If you put it 3 feet or so away from a blower, it will blow out right away (concentrated air blast).

I'll shut up now, just turn on one of these centrifugal blowers and you'll understand what Me and SteveI are sayin.

I'll post pics and the whole 9 yards once I get it going...

that's a good analogy....

Pinky 17th January, 2002 01:56 AM

Don't lose a finger dude :p

e_storm 17th January, 2002 05:55 AM

Quote:

Originally posted by RudyNg
5 amps 12 volts voltage regulator for controlling this blower? I think there is one over HERE that may do the job.
Thats good to know....I didn't know things like this were sold. I might still keep going with building my own circuit, for learning purposes and plus it would save a lot of money...

ItHuNkPuNk 17th January, 2002 06:08 AM

Couldn't you stick that thing inside the case and mod it to attach directly to the heat sink?
Only problem is constructing proper support structure to hold it up..
It would look like your case had a hernia otherwise...

Kaitain 17th January, 2002 11:22 AM

Quote:

And keep in mind (as I'm sure e_storm knows), that the blower is the key to making this work. Rather than using a traditional fan, using a centripetal (?) blower reduces the turbulance, to create a more efficient airstream. (...if I understand the concept correctly.)
Um, the airstream will still be turbulent - turbulent flow is inherent to fluids travelling at greater than a certain velocity. (when Re > ~10,000 for gases). It's also more efficient in terms of heat transfer, due to its ability to mix itself.

Centrifugal blowers really only generate a a concentrated air-blast because they do so through a relatively narrow length of tubing. To use your candle analogy: try to blow out a candle from 3ft away yourself and unless you're one bear of a man, or the candle's pathetic, you won't manage. Try it blowing through a drinking straw and that candle's history.

The duct-work gives the air a chance to collect its drag-eddies (the bits going off radially from the tip of the blades) and pull them along with the main air stream.

But before you flame me: centrifugal blowers will deliver more air, watt for watt of motor power than the equivalent propellor-type setup. I can't for the life of me remember why, though! :eek:

Aedan 17th January, 2002 11:45 AM

Quote:

Originally posted by Kaitain
Um, the airstream will still be turbulent - turbulent flow is inherent to fluids travelling at greater than a certain velocity. (when Re > ~10,000 for gases). It's also more efficient in terms of heat transfer, due to its ability to mix itself.
But but but.... Laminar air flow is great for moving air from one place to another. ;) I thought that was the idea - to move as much air through the case as possible... Actually, the best thing about centripetal blowers is the fact they don't stall at relatively low pressures. Perhaps that's why people find they're more effective?

Quote:

Centrifugal blowers really only generate a a concentrated air-blast because they do so through a relatively narrow length of tubing. To use your candle analogy: try to blow out a candle from 3ft away yourself and unless you're one bear of a man, or the candle's pathetic, you won't manage. Try it blowing through a drinking straw and that candle's history.
What's this 3ft business? Presumably, this means enclosing a standard axial fan inside a duct would give a pretty similar effect, not withstanding the fan's ability to stall at low pressures.


Quote:

But before you flame me: centrifugal blowers will deliver more air, watt for watt of motor power than the equivalent propellor-type setup. I can't for the life of me remember why, though! :eek:
But why Kaitain, why?

AidanII

RudyNg 17th January, 2002 12:15 PM

Directing the air flow from the blow is not a problem. All you need to do is to put small pieces of louvers in front of the blower to divert the air flow. This is what we do in real practise. Take a good look at the air diffuser over you head on the ceiling in places that uses central air cinditioning system and you'll know what I meant.

e_storm 17th January, 2002 02:52 PM

Quote:

Originally posted by ItHuNkPuNk
Couldn't you stick that thing inside the case and mod it to attach directly to the heat sink?
Only problem is constructing proper support structure to hold it up..
It would look like your case had a hernia otherwise...

I suppose you could, but it would have to be a pretty big case (wide I mean). The blower itself it 8 inches all. Also, I'm not sure but with it having it that close to the HS might reduce the case cooling effect (chip would be very cool tho lol :cool: )... I guess only the test results would prove that true or not. I guess you could also do it by mounting the blower inside the case somewhere with ductwork going directly onto the HS, but again, some of the CFM and case cooling effect might be sacraficed.

I personally would rather not have my case look like it had grown a tumor either, but the noise is driving me nuts and I'm willing to sacrafice looks for quiet at this point :D.

*edit*..O yea, and also the motor produces some heat from what I'm told, so it would have a negative effect on case cooling and be a lot harder to cool (no HS attached lol)

e_storm 17th January, 2002 03:00 PM

Quote:

Originally posted by Kaitain

Centrifugal blowers really only generate a a concentrated air-blast because they do so through a relatively narrow length of tubing. To use your candle analogy: try to blow out a candle from 3ft away yourself and unless you're one bear of a man, or the candle's pathetic, you won't manage. Try it blowing through a drinking straw and that candle's history.

You make a good point, but I think if you attached the same length of tubing to an equivalent radial (case) fan, the blower would still have a more direct cfm blast at the point of the candle. The blowers are designed for a shot of air, radial fans aren't, they're just made, as said in another post, to move air around.

Quote:

The duct-work gives the air a chance to collect its drag-eddies (the bits going off radially from the tip of the blades) and pull them along with the main air stream.
Ummm...yea what he said. :D

Kaitain 17th January, 2002 03:03 PM

Quote:

Directing the air flow from the blow is not a problem. All you need to do is to put small pieces of louvers in front of the blower to divert the air flow. This is what we do in real practise. Take a good look at the air diffuser over you head on the ceiling in places that uses central air cinditioning system and you'll know what I meant.
Thanks. That's a good tip for case-cooling.

For CPU cooling, the unidirectional blast straight from the blower is probably the best, just for the sheer speed and volume of the air.

Quote:

But but but.... Laminar air flow is great for moving air from one place to another. I thought that was the idea - to move as much air through the case as possible... Actually, the best thing about centripetal blowers is the fact they don't stall at relatively low pressures. Perhaps that's why people find they're more effective?
True, laminar flow suffers less from friction losses, but it's rather slow. The nature of laminar flow also makes it a rather good insulator of heat, which is not at all what you want.

For best results, blow hard, blow fast and don't let too much pressure build up ;)

Quote:

Presumably, this means enclosing a standard axial fan inside a duct would give a pretty similar effect, not withstanding the fan's ability to stall at low pressures.
Yup. Just not as well as a centrifugal blower.

Quote:

But why Kaitain, why?
That's what I've been asking a lot, lately :(

Moving swiftly along, axial flow fans (propellor types) are designed to move high volumes of air with not a lot of pressure increase (only about 0.5psi). And its a very linear trade off between pressure and volume.

Blowing into a poorly vented case, the fan will quickly exceed that 0.5psi and thus the volume it pumps will drop down to almost nothing as it tries to compress to greater than 0.5psi. It also suffers from flowback - the air pushes past the tips of the blades in order to escape making it very noisy. Drop the pressure and it blows more volume. So in the end, the mass of air it can shift per second is fairly fixed.

Centrifugal blowers come in many designs depending on their ultimate goal (high pressure, high volume, best trade off). They will pump at their optimum pressure increase (about 1.5psi) right across the range of flow rates up to their most efficient, and then the decay curve is parabolic. Thus it ends up pumping a greater mass of gas...

more mass = more air = better cooling.

I had to look all that up, by the way ;)

RudyNg 18th January, 2002 12:59 AM

The only way to utilise this blower for cooling computer effectively is to control the air flow of the fan.
With all the back pressure and turbulance that the air pressure from the fan is contributing, the area that need the most criticle cooling ( CPU ) may not be cooled efficiencly.
As such the balancing of the air flow to suit the casing is very important for optimium performance.

dimmreaper 18th January, 2002 01:57 AM

Yuck !!!! Aircooling . . . . :p

Aphex 18th January, 2002 02:45 AM

Lookin good :D, fancy writin it all up for Pc-Critic.com?

Conrad

Daniel ~ 18th January, 2002 02:57 AM

Quote:

Originally posted by Pc-Critic
Lookin good :D, fancy writin it all up for Pc-Critic.com?

Conrad

Feel free to link to the thread! LOL

Would make a good article though wouldn't it, how about one or both of you stretching this out for Conrad?


All times are GMT +1. The time now is 07:00 AM.


Copyright ©2001 - 2010, AOA Forums


Search Engine Friendly URLs by vBSEO 3.3.0