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Fan Sandwich. Good or Bad?

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ezcharlie

Member
Joined
Apr 7, 2003
Location
Philippines
1_909749380l.jpg


i've read and heard for heatsink cooling specially, static pressure is a must.
i'm just experimenting w/ different fan configs.

i have a few fans i'm trying:
silverstone fm121 120mmx25mm
scythe jyuni 1900rpm 120mmx25mm
thermaltake typhoon 2900rpm 120mmx25mm
coolermaster 90cfm 2000rpm 120mmc25mm
delta .9amp 120mmx38mm
nmb .9amp 120x38mm
sanyo denki .58amp 120x38mm

does sandwiching two 25mm thick fans improve static pressure?
does it improve airflow? what are the pros and cons?

trying to get the best comproise for noise/performance.
40dba specs are actually tolerable for me but the lower the
better of course.
example for some reason the nmb runs slower and much more quite than the delta.
the two cm's i have in the picture though i almost can't hear.
i think i might be getting the same performance as the noisy delta.
is it just me or is this really accurate?
thanks.
 
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It would be my guess that it would improve the stability/static pressure of the fans, but I do not think it will improve air flow. The imperfections in each fan would balance out and create a more stable flow, but that is not much more than speculation.

I would imagine, however, that it would be very important to have 2 of the exact same fan. Any variation in speed between the 2 would be counter productive.

All of this is useless if your power supply isn't rock stable too, however, since variations in current to the fans will affect their pressure/speed.

Keep in mind I don't claim to know what I'm talking about, just giving you my input from what I do know. I've never studied the specifics of getting static pressure from fans personally.
 
This is something i considered doing myself, but I never got round to testing it. I use a push pull 2 fan setup on a TrU120E and it is about 2c lower temps for no more noticable noise.
like fa says, get 38mm thick fans, then do push pull aswell
 
so you guys are saying that this sandwich is useless then?

i'm actually trying to find out if sandwiching 2 quiet 25mm fans
will give me similar static pressure as a 38mm fan of equal cfm.

like for example:

is 2 x 25mm 100 cfm fans = 1 x 38mm 100cfm fan in terms of static pressure?
the thicker fan is noisier than the 2 thinner fans together.
as much as possible, i'm trying to quiet down my sys.

of course the best answer is to get a strong and quiet 38mm fan,
but whats the point of being an overclocker if we don't experiment and instead choose the easy way out. hehehe... :)
 
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On the same hand, whats the point of overclocking on air without the noise. They are hand in hand lol. That being said, if that setup is quieter than the 38mm, then by all means that is the answer for your setup. Although I don't know why it would it burn out a fan faster if sandwiched as posted above.

You could always hook the 38mm fans up to a fan controller to keep the noise down. Just make sure you have one that handles the fans. I think a 30w per channel controller should do you just fine if you take that route.
 
not all overclockers want maximum gains :)
as the saying goes, overclocking is an art.
art's beauty is relative. so i've chosen the path of best performance / noise ratio.
doesn't have to be silent, just tolerable and definitely not noisy.
i guess my max threshold is in the 30-40dba range...
(i also don't want the hassles watercooling anymore, even w/ kits, it's definitely more
maintenance than air cooling.)
i've gotten past the days that twice the noise justifies a 10 mhz increase in performance.

i do have a few fan controllers that can handle pretty much any fan i throw at it,
but then again, if you lower the noise of the 38mm fan in my example above to similar levels
as the 2x120mmx25mm fans, then it wont be pushing its 100cfm specs.
 
i've gotten past the days that twice the noise justifies a 10 mhz increase in performance.

thats the wrong attitude mister :D


on the other hand, as much as i like the quiet, i dont mind the noise anymore.. when its noisey i know my computer is working properly :attn:
 
I heard the only way to increase static pressure with two blades is to have the blades rotating in opposite directions.
 
You are not doing yourself any favors with the fans in that configuration. The only way that configuration works is with two counter-rotating fans of equal spec. However, there have been some gains made by using a spacer (ie. gutted fan housing) between two fans that sipn in the same direction. I will try to dig up the thread from a few years ago that has the data to support my statements. ;)

EDIT: some good info HERE and HERE and HERE
 
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I am liking the wind tunnel idea that chev has. Was thinking of something like that for an addition to my case.
 
really?
counter-rotating fans?
thats odd...
aren't blades designed in a way that if they spin in one direction,
they push air and if they spin in the opposite direction, they pull air instead?
but the wind tunnel thing i'm sure i've heard of before.
forgot what it can do though.
 
Chevro1et is correct, they need to be counter-rotating and spaced perfectly for it to work. The configuration you posted above will actually reduce air flow.
 
From time to time, Sidewinder has dual blade, counter-rotating fans in stock. You may want to check them out.
 
ahhh..
after thinking about it, i realized my ignorance.
hahaha...
hmmm...
counter rotating fans.
that would be dfficult to get unless it's sold as a pack.
i'll keep an eye out for those.
at least i already know how one of them spins :)
 
stacking fans is pointless... your going to increase the noise level by A LOT by stacking fans due to the massive amounts of turbulence.

Just stick with a single fan, and if you need better cooling get a better heatsink.
 
indeed!

lol look at that puny nvidia card :)

definately gotta keep cats and small pets away for fear of being triple mulched :attn:

like those airport workers who get sucked into the turbine :cry:

:D
 
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