What is the best 120mm fan?

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poorya_user

poorya_user

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Its about 2 months that I am working to build my own handmade case . until now I could not decide the brand of its fans.
Whole case is about performance and noise is not a big problem.I saw Ultra Kaze 3000 rpm with 133 CFM and 45dB.I think it is too much noise.
I want to know your opinions about 120mm fans.First important thing is Airflow (around 100 cfm) then the noise (20-35 dB).
 
poorya_user

poorya_user

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Ok then what is your suggestion for 100+ CFM? Dont mention the noise.
 
poorya_user

poorya_user

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davcon

davcon

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I would take manufacturers fan specs with a grain of salt
the cfm and decibel ratings are skewed
this fact is revealed on this website
read all you can about fans
they've changed their fan testing methodology
and found that fan cfm is often much lower then stated specs
this is fine since cfm has no relation to a fans cooling capability
http://www.silentpcreview.com/
The best fans are made by Scythe,Noctua,and Nexus(Yate Loon).

"Finally, CFM has no direct bearing on cooling, which is measured not by airflow but by a drop in temperature, usually in a device in the PC. Without the benefit of a thermal engineer's knowledge and detailed parameters about the components and conditions, CFM might as well be APH (angels per pin head). The relationship between CFM and cooling is at least as complex as that between SPL and perceived noise. The CFM value has no real meaning beyond itself. In contrast, with a bit of experience, 30 dBA/1m does have some meaning. Still, DIY computer tech geeks want to compare fans by their CFM rating, and in the SPCR (and other PC tech web) forums, some have gone so far as to specify what CFM rating they believe is needed for their application
. This is a reliance on CFM numbers that has obfuscated the role of airflow in cooling. It's not really a surprise; CFM is one of the very few performance specs that fan manufacturers make available.

Over the years, we have observed one clear phenomenon about fans and cooling: The relationship between airflow and temperature invariably becomes exponential at some point. Increase airflow from nothing to something, and the drop in temperature can be dramatic. Keep increasing airflow, and the cooling improvement becomes less and less significant, until at some point, the temperature hardly drops at all. The trick, for the PC builder who seeks both good cooling and low noise, is to find the point where any decrease in airflow (or fan speed) effects a significant increase in temperature, while only a very large airflow increase effects a significant temperature drop. In other words, once you have enough airflow, additional airflow has very little cooling effect, so all you're doing is increasing noise. "Enough airflow" is not a constant, of course, it varies for each system of components"
SPCR
 
Mugz

Mugz

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Finally other people realise that CFM is not an absolute indicator of a fan's cooling ability. Relative, yes, but not absolute.

Not only does the "enough airflow" variable depend on the system components - I am guessing that refers to component heat output vs exposed surface area of said components - it also depends heavily on the temperature of the cooling medium - in this case, the air.

As an example, we have an item at 80º, which we want to cool to 50º, so with an ambient air temp of 10º, it will need much less airflow than if the ambient air temp was at, say, 45º.

Now if the ambient air temp was 70º, then no matter how much air you blasted at the item, it will NOT reach the desired temp of 50º. It would stay at 70+º.

Watercooling works along similar principles, but because a liquid is much denser than a gas, it has a higher specific heat capacity, so is more effective. This is why a CPU heatsink is so huge compared to a water block.

In essence, enlarging the surface area (i.e. bigger heatsink(s)) and/or dropping the ambient air temp (i.e. air conditioning or moving to Antarctica) with a given set of fans will generally have a far greater effect than upping the airflow (fitting bigger fans) and thus the noise.

Server fans are awesome, especially the double-thickness ones. Pity about the noise...

EDIT to clear up one or two typos. I really need sleep...
 
JofaMang

JofaMang

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I agree, CFM isn't everything, BUT, like the old racing adage goes, Theres No Replacement for Displacement.

Using Polar extremes, even though CFM is not an absolute factor in cooling effectiveness, Zero CFM = Zero cooling. Thus, even though CFM isn't the lone stat, it does have an effect. A 100+ CFM low static pressure fan will still cool better than a 20cfm high static pressure fan. Until the intricate complexities of thermal dynamics are recognized and utilized by the user base to demand better products, the average user will only have a few spoonfed details to go by. Using only CFM (and disregarding sound levels) one can still achieve excellent results in air cooling. Could they do the same work with less noise using fans with much higher static pressure but slightly lower CFM? Yes. Are we currently able to diagnose these factors based on the information fed to us by the manufacturers? No.

There are sites devoted to fan performance, each with their own methodology and agendas, leaving us with even more self-learning and exploration to achieve in order to make the best decisions. One COULD spend a lot of time figuring it all out, and developing an educated opinion on the matter, OR one could just go for the highest CFM fan they can find, and have similar, albeit louder, performance with far less effort required.
 
welshmousepk

welshmousepk

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most reviews generally put them closer to 26dB. but yes, they arepretty damn quiet.
 
Mugz

Mugz

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Having the air flow is important, what is also important is the temperature delta. If the delta is small (warm air on hot heatsink) the cooling will not be very effective, as opposed to a high delta (cold air on hot heatsink).

Unfortunately, like the big-block V8s demonstrate with their massive displacements, displacing large amounts of air through a narrow duct will product noise.

I read a review a while back - cannot seem to find it now - about some kind of honeycomb mesh that fits over the exhaust of the fan. Apparently what this did was focus the airflow into a tighter stream and somehow reduce noise.

Another way of improving the performance of a fan on a heatsink (this does not apply to the twirled Intel OEM heatsinks) is to raise the fan off the heatsink by 1~3cm, what this does is reduce/eliminate the 'dead spot' in the middle of the heatsink that is covered by the fan motor. That makes an extra few cm² of surface that has turbulent air over it, thus increasing the cooling efficiency. Net gain is probably going to be around 2~5ºC, depending on heat loading, heatsink design, and several other factors. That, incidentally, also can reduce noise levels quite dramatically.

In reference to the 'no replacement for displacement' comment: you would be surprised what results you can get by engineering the living daylights out of something.
 
JofaMang

JofaMang

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And when you are done engineering the hell out of an engine, adding more displacement only builds upon those gains. A great example is Fords new 5.0 mustang: 420hp (without direction injection to boot), a net gain of near 200hp compared to the 5.0 mustang that was replaced by the 4.6 unit about 15years ago. There are already reports of stroker kits hitting 500+hp with a simple bump to 5.4 liters without any other modifications. A 5.0 from 1994 stroked to 5.4 would be lucky to see 260hp (from the stock 225) without any other mods.

There is no replacement for displacement. It is a modular upgrade that can only take advantage of, and in no way be hampered by all the other engineering advancements that have increased specific output over the decades.
 
Mugz

Mugz

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Still, with all of the engineering advancements, the displacement doesn't need to be as great for the same result.

Of course, if you want more result... you'll have to increase displacement.

I just had a wonderful thought - a 6.0 V12 revving up to 18,000RPM... now if only we had materials that could take the strain...
 
JofaMang

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We do, its just that the motor would cost several million dollars a pop even if in mass production, hah. The standard piston design internal combustion motor is almost out of tricks to improve efficiency.

I personally would like to see a 6.0 quad wankel running 18,000rpm, or a strategic e85 injected DI twin turbo 1.5l 4 cylinder making 300hp @ 50mpg. Technology has advanced in so many ways, in virtually every single facet of our lives, but we still use the basic engine design that was conceived of over 100 years ago. At this point I will stop myself before dissolving into a oil company conspiracy rant.

Yes, I agree. I have been to the Montreal F1 GP four times in my life, and the howl of the v-10s at 18k stirred the very depths of my soul. My wife said no to a crotch rocket (she likes her husband in one piece TYVM, and thinks I look like a monkey humping a football when I am driving one anyway) so I guess I am stuck living vicariously through others until the 2011 Montreal GP, the next mancation I have planned.
 
poorya_user

poorya_user

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Thanks all you guys .they are all useful informations.
I have a logical question : Who would build a PC-case (Mid-t) with cooper(100%)?
When I decided to build this case I just thought about performance . It was more logical and economic to be aluminum.
Another question : does it makes any difference with aluminum for all component?
The answer is NO. I just want to do it in the best way and I dont care how much money I will spend.I even saw 8000 RPM 220V 80mm fan, but one of my ear now is deaf because of its noise.
 
Mugz

Mugz

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A buddy of mine modified a mk1 Scirocco by fitting a Suzuki Hayabusa engine to it. After rebuilding, modifying, and turbocharging the sucker. What exactly has been done to that engine I don't know, all I know is is that that car accelerates insanely fast, howls like a banshee (in fact, that's what the car is known as), and most people around where I live who have fast cars are terrified of Sciroccos as a result.

In fact, even its driver is scared of it...
 
Mugz

Mugz

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@poorya_user

A completely aluminium case is a pretty cool idea. In fact, since several manufacturers have done that in the past I can think of no reason why not.

Since you are building it yourself, though, you can go anywhere WRT style, colour, and so on.

Are you going to leave it bare metal, anodise it, or paint it? Or some combination?

And by the way, you have inspired me to do a case myself (after I have cleared about seven different projects from my to-do list) using aluminium, carbon fibre, and maybe some leather accents and wood paneling here and there, to give it that 'executive' feel...

There has been at least one homebuilt case on these boards before that I know of, though this guy made his entirely out of wood. It is always cool to encounter someone who has built their own case instead of just buying one of these overly-fancy factory-made jobbies, which are never exactly what the buyer wants...
 
poorya_user

poorya_user

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Actually I am using Cooper not aluminium and about 70% of whole project is done. I am sure about anodise it and no paint.I would love to leave it bare but finger prints covered the whole surface.
 
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