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TOPIC: Does static p. fan create pressure on both sides?

Does static p. fan create pressure on both sides? 1 week 3 hours ago #15641

  • coolfishsq
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Hello dear friends. So i do understand that the sp fans make high pressure but move less air and the af fans make low pressure but move much more air, but this is on the outlet, what about the inlet? Ive got a case side door with the dust filter, THEN the fan, then a lot of open space inside the case(no grill after a fan, no cages, nothing). So no need for pressure inside. The thing that confuses me is that i dunno if the pressure fans make the air come through the dust filter BEHIND them with the same strong force that appears then infront of them (thus helping the air to come through the dustfilter behind) or they dont work backwards? Because if they dont, the af fan would be much better cus it would move more air through the filter at the same rpm. Wonder if theres any aerodynamics guy that can explain it. Thanks a lot
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Does static p. fan create pressure on both sides? 1 week 1 hour ago #15642

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On the inlet, the SP fan will generate higher pressure inside the case and the AF will give higher air flow.
Same if there's a filter either side of them. The filter will slow down the air a tad though.
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Does static p. fan create pressure on both sides? 6 days 17 hours ago #15651

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well yea but im actually asking whether the sp fan will move the air with more pressure through a filter thats positioned behind it (on it's inlet). Behind. Does it have same good pressure behind it. Or is it same as af fan. Does it SUCK (not push) air with a stronger PRESSURE (not volume) than the af fans
Last Edit: 6 days 17 hours ago by coolfishsq.
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Does static p. fan create pressure on both sides? 6 days 16 hours ago #15653

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whether the sp fan will move the air with more pressure through a filter thats positioned behind it YES
Filters don't make much difference at all - unless they clog up.

Does it have same good pressure behind it YES

Does it SUCK (not push) air with a stronger PRESSURE (not volume) than the af fans YES
Fans push or pull the same.
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Does static p. fan create pressure on both sides? 6 days 16 hours ago #15654

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Short answer: Yes, the fan with a higher static pressure will have higher static pressure. The fan is simply better in creating a pressure difference between in- and outlet. (In the end, a fan is nothing more then an air-pump). Same goes for airflow: More airflow is more airflow, either way. The air can't go anywhere else nor can it simply "disappear" - what it sucks in has to come out at the other end, otherwise it would break the laws of physics (which I highly doubt).

Long answer: That difference between push and pull or af vs sp might not matter.
Due to the design of (most) fans, they are better in building up pressure behind them, on the exhaust side. However, the difference can be really REALLY small and more often then not, bigger differences we observe in benchmarks and tests are a result from the circumstances (fan shrouds, case panels, drive cages, fin density on radiators, fan size, rpm, etc.).

There's also the fact, that because of the higher pressure and the more focused stream of air, an "SP"-Fan will reach deeper into the chassis, blowing directly into a hot spot (for example a front fan blowing to the GPU) - which means, it will be more effective, even though it pushes less air overall. In short: While higher airflow will increase the amount of air (and therefore heat or cool air) that is transported in and out of the case, a higher static pressure might increase the effectiveness of how that air is actually handled, increasing the "heat per air", resulting in better temperatures aswell. In the end, it all comes down to how much resistance the fan has to work against and where it is positioned in the case.

If you want to know more, there's a good article done by Martin that I'll link below, where he tests push vs pull vs fan shrouds. He also points out something important, the difference between laminar and turbulent flow:
we are seeing pretty good gains by going push on the Delta fans instead of pull and it’s not due to more air flowing through the radiator, they measured roughly the same, there is just some sort of other benefit by pushing instead of pulling. I think it has something to do with the air leaving a fan being fairly turbulent and disturbed entering the radiator that creates the small gain there, but I’m not completely sure

Basically, the higher pressure results in a more turbulent flow, increasing the amount of air that touches the hot surface, allowing heat to be transfered more efficiently from the surface into the air.

In reality, many other factors come into play aswell, but to be honest, they may not even matter - because a cpu at 55°C will perform just as good at 60°C.

TL:DR;
Use fans with high static pressure (or ones that have a narrow cone of air, i.e. less dispersion) to direct air to the hot spots, where it's most benefical (like CPU, GPU and Radiators)
and use fans with high airflow to remove the hot air, out of the case (mostly as exhausts on the top and rear).

However, because the difference between the two types of fans can be really small (especially at lower RPMs), I wouldn't worry too much about it if you don't use "the right fan". As long as the temperatures or noise are within your comfort zone, it's not worth the effort of planning, buying and building "the optimal".
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Does static p. fan create pressure on both sides? 6 days 14 hours ago #15656

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There's also videos on YouTube to help explain eg www.youtube.com/watch?v=sh6F2eccMec
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Does static p. fan create pressure on both sides? 6 days 11 hours ago #15659

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well thanks for the help guys, just to be clear i dont have a videocard so dont really need any pressure inside my case, nothing for the air to bump in

The thing that bothers me is that all the people around have different opinions on my issue, see for example the quote from overclockers forum:

hammong
"The only differences between SP and AF fans are on the exhaust side -- if the filter is on the intake side of the fan, you would probably get better air flow with an AF rated fan than you would with a SP rated fan at the same rotational speed"

and you guys say its the same on both sides, really confusing.

That said, its also quite confusing that different dust filter/grill testings show totally different results, for example here www.pugetsystems.com/labs/articles/Effec...rformance-Noise-107/ mesh stops 7 to 11% airflow and wire only 2-3% while in this testing www.silverstonetek.com/techtalk_cont.php?area=&tid=wh12_008 the same kind of mesh (kinda different, but not THAT much really) stops the whoping 59% of all the airflow. And here www.silverstonetek.com/techtalk_cont.php?tid=wh_chessis&area=en the same dam wire stops 29% of the flow (instead of 2-3%) - considering the margin of error and all that kind of stuff the difference is still ridiculous for me.

So i dunno even what to say, still confused...

And the video you posted is about the basic airflow stuff that i wrote in the first topic sentence that i know, doesnt really tell anything about the pressure generated from the intake of the sp/af fan :) but thank you for all that anyway
Last Edit: 6 days 11 hours ago by coolfishsq.
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Does static p. fan create pressure on both sides? 6 days 1 hour ago #15660

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I think you're overthinking things. You don't need to be very precise with case fans. Even positive case pressure benefit is arguable. So AF vs SP is no big deal. Same with filters. Same with push or pull with fans.

Edit - PUSH VS PULL VS PUSH-PULL - www.youtube.com/watch?v=UyC3lZ5WFMk
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Last Edit: 5 days 15 hours ago by i7Baby.
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Does static p. fan create pressure on both sides? 5 days 13 hours ago #15661

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okay sorry then seems to be a wrong place to ask for the things i need.
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Does static p. fan create pressure on both sides? 5 days 13 hours ago #15662

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NEED or WANT or DON'T KNOW?

I don't think you NEED any info to make a decision. As I said - you're overthinking it.

And so, if you can put case fans on without this info, you shouldn't WANT it.

And I think you really DON'T KNOW what you want. As has been said in this thread - what you do with fans, makes a small difference to the temps of the components in the case.
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Last Edit: 4 days 22 hours ago by i7Baby.
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