Aluminum fans?

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toozerosickz
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Aluminum fans?

Post by toozerosickz » Sat Aug 06, 2005 9:02 pm

I searched the site and alum fans weren't talked about much. Are they not quiet enough? I was looking at an Evercool 120MM alum fan that has a rating of 84.5 cfm @ 30 db Which sounds pretty good to me. At night I would just use a fan controller to bring it down some.

I would think aluminum fans would blow more air quieter than plastic or am I wrong?

wim
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Post by wim » Sat Aug 06, 2005 9:13 pm

i have 1 Evercool Al. only the frame is aluminium, the blades are the usual plastic coated in a cool silver colour.

regardless i can't see any good reason why the fan blade material would have much effect on noise, only blade geometry. what is your reasoning there?

EvoFire
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Post by EvoFire » Sun Aug 07, 2005 10:44 pm

Wouldn't a aluminum fan resonate more?? Plastic has some degree of stretchiness, on the other hand, aluminum is known to resonate... Would a complete aluminum fan being louder by vibrations?

Straker
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Post by Straker » Sat Aug 13, 2005 5:31 pm

aluminum is just "known to resonate" because most cases made out of it are too light. :P

Evercools are pretty good, hard to mount them vertically because of weight though, and iirc they have solid corners. best to just lie them flat.

dfrost
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Post by dfrost » Mon Aug 15, 2005 1:37 pm

Yeah, but they sure do make a purty mod to a Zalman 7000B-AlCu. And no weight penalty when you cut off all the aluminium.

And yes, the frame corners are quite solid - it would be much harder to cut them away for use on a Thermalright XP-n.

I tried a 92mm example and decided it was too noisy to be worth modifying for my unwindowed 7000B, so used a CompUSA Mad Dog Whisperfan instead. Nice improvement when isolation-mounted on the Zalman, and cooling performance was about 5C hotter then the current XP-120/Papst setup.

Airflow would not be affected by material. Airflow is primarily determined by blade diameter, shape and speed.

mathias
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Post by mathias » Mon Aug 15, 2005 2:38 pm

dfrost wrote:Airflow would not be affected by material. Airflow is primarily determined by blade diameter, shape and speed.
What if the fan was made of teflon?

dfrost
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Post by dfrost » Mon Aug 15, 2005 8:29 pm

Did you think that because teflon is non-stick that it would enhance the air movement? That slipperiness is it's effect on surface tension of fluids (a zero velocity effect), not the drag of fluids moving across the surface.

Surface finish (and blade shape) will be the predominate effect on airflow, and the Sharkoon dimples are an interesting idea from golf balls - not sure if the phenomeon applies, but it might. So teflon wouldn't change the airflow measurably compared to existing plastic fans because the surface finish of the blades are already excellent for the relative air velocities involved.

And I'll bet if somebody thought they could market a teflon blade benefit they would, even if it wasn't real. Hey, maybe here's the chance for you to make some big bucks in the PC market?

mathias
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Post by mathias » Mon Aug 15, 2005 8:53 pm

dfrost wrote:Did you think that because teflon is non-stick that it would enhance the air movement?
No, if anything it would reduce airflow. I heard of teflon coated bullets.

kcarbuncle04
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Post by kcarbuncle04 » Tue Aug 16, 2005 6:15 am

if the blades were coated with teflon it will probably wouldnt help much in it (much like silver wires and audio equipment).

As for aluminum fans (usually aluminum framed, not impeller), IIRC, they're not much different in ratings with the non-aluminum framed ones..
(the panaflos doesnt, IIRC)

mathias
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Post by mathias » Tue Aug 16, 2005 8:09 am

What exactly is an impeller?

hofffam
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Post by hofffam » Tue Aug 16, 2005 9:00 am

impeller = propeller = blade assembly.

I see the word impeller used most often in the context of a pump. The blade assembly in a water pump is usually called the impeller. So is the blade assembly in the jet pump of a personal watercraft ("jet ski").

flyingsherpa
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Post by flyingsherpa » Tue Aug 16, 2005 9:22 am

hofffam wrote:impeller = propeller = blade assembly.
not quite, impellers always have a shroud of some sort. so a small airplane has a propeller since it's operating in free air. jet engines (or your jet ski example) have impellers because they are shrouded. ducted fans are also impellers... it is incorrect to call them propellers. the shroud makes a big difference. ask any r/c airplane pilot... if you take the shroud off a ducted fan engine, it won't provide any real thrust.

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