Airflow, fans and dust

Discussion in 'Overclocking & Cooling' started by daphatgrant, Apr 17, 2019.

  1. daphatgrant

    daphatgrant Moderator Staff Member

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    Hey [H], I've got an older build that I'm trying to tweak the cooling/dust collection on. I've got an Antec Air540 case with a full set of DEMCiflex filters (minus exhaust) and an Arctic Cooling 360 aio. The 3 (120mm) aio fans are in a pull configuration and the 3 non pwm stock case fans (140mm) are the exhaust. With the three 120mm intake/aio fans pulling air through the filter and then the radiator I am losing a lot of cfm's compared to what the three unobstructed 140mm fans are exhausting.

    Intake/AIO fans
    Stock exhaust fans

    I have an older board Asus P8Z68-V Pro that only has 2 pwm enabled fan headers, 3 really but both CPU ones are controlled together. I have the 3 intake/aio (120mm) fans plugged into the pwm cpu header and they are controllable. I bought this pwm fan controller hub with the hopes of connecting all of the 140mm exhaust fans to the PWM chassis fan header and setting them low for positive pressure.

    Unfortunately my plan of using that fan hub isn't playing out. While the 140mm intake fans have power nothing seems to change when I make changes in the bios, they are running at a pretty steady 1,000 rpm.

    I'm wondering if anyone has any suggestions? Worst case I am just going to get some Zalman Fanmate 2 controllers, a sata to (3) 3 pin connector and set all all of the fans to low and see what happens.

    Would I see any real difference if I were to switch to static pressure fans for the intake/aio fans? Switch the exhaust fans out to 120mm's? Remove an exhaust fan?

    Right now I am running the intake/aio fans at 100% 1,450rpm just to not make the case a dust collector
    Thanks for any help,
     
    Last edited: Apr 17, 2019
  2. BlueFireIce

    BlueFireIce [H]ardness Supreme

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    What fans are you using? What are the goals?

    If the stock fans are not the best for rad/HS use then swapping to something like the Noctua NF-A12x25 will indeed help temps etc. Also putting some space between the fan blades the the filter helps if this is not already done.
     
  3. daphatgrant

    daphatgrant Moderator Staff Member

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    I added links to the fans, my goal at this point is to have positive pressure airflow so my case isn't sucking in every bit of dirt around it, lol.

    I have the radiator mounted to the front of the case which has a filter in front of it and the fans are attached to the radiator on the inside of the case. It's filter/radiator/fans.

    Here you can see the front of the case, the filter and the radiator fins.
    2019-04-17 16.44.11.jpg


    Here's the case layout
    Case-2.jpg
     
    Last edited: Apr 17, 2019
  4. BlueFireIce

    BlueFireIce [H]ardness Supreme

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    The NF-A12x25 should pull MUCH more air than the AC fans you linked through the rad. Positive case pressure isn't really possible and doesn't have that big of an effect so long as the largest intake areas is filtered. Pulling in from the top can help as pulling from the front is close to the floor and will tend to pick up more dirt/dust. When my case was setup this way, the underside and front collected dirt on the ground, and the bottom half of the front filter collected lots of dust before the top half. As such I moved intake to the top and exhaust to the front/back. Filter is the same and takes 4x as long to become visibly dusty.

    Best option if the area is very dusty is a proper HEPA filter in the room, and quality AC filters for the house.
     
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  5. daphatgrant

    daphatgrant Moderator Staff Member

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    I "modified" my case so it's on its side so moving intakes/exhausts around won't do much for me in it's current position. I see that the NF-A12x25's are supposed to be released in black this quarter, when they are available I'll look at snagging them, thanks for the recommendation :). My biggest issue is pet har, cat and a golden retriever, roomba runs daily and can barely keep up.
    CaseCoolingFront.jpg

    Another option could be to get a 280mm aio and put it in the "top" so that there would be (3) 140mm intakes and (2) 140mm exhauts... That's kind of an extreme option for a system this old, i7 2600K @4.4ghz. This is the aio I have, apparently Arctic got out of the aio business.
     
  6. VanGoghComplex

    VanGoghComplex [H]ard|Gawd

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    Can you elaborate on that a bit? I'm genuinely curious. Positive case pressure means that you're pushing more CFM in than you're actively pulling out, doesn't it? I'm sure the case doesn't build any measurable pressure in the literal sense, but doesn't "positive case pressure" just mean for us that air is being pushed out of all the little (unfilterable) cracks and crevices in the case as opposed to being pulled in?
     
  7. BlueFireIce

    BlueFireIce [H]ardness Supreme

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    I mean that most air will be pulled through the front filtered area, on most cases you don't have large enough gaps to have any meaningful amount of dust get in. If you can take off the case doors and see streaks of dust from air being "pulled" in that might be an issue, however I have never seen this in anything other than more shop like environments with excess dust or computers that don't get cleaned for years. And yes, pressure will not happen, and pushing more CFM in than out I never saw any meaningful change other than negative impacts on cooling, as in case temps went up, not much of a change on CPU temps, as rad was intake and getting fresh air from outside, GPU/mobo temps however did go up.
     
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  8. VanGoghComplex

    VanGoghComplex [H]ard|Gawd

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    Interesting to hear your experience. I've always heard "positive case pressure" is the preferred method by conventional wisdom because of dust control.

    Doesn't matter much to me personally, with my Thermaltake Core P5... :D
     
  9. BlueFireIce

    BlueFireIce [H]ardness Supreme

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    Yep, same people also swear that you are crazy if you intake through the top and exhaust out the front because "heat rises".

    Which is true mind you, but means almost nothing in relation to the flow of air in anything but a passive system, just like the amount of air that comes in through unfiltered gaps, it is almost unmeasurable by any practical means. I went crazy for a time with stuff like this, boxes of fans I tested, filters, push/pull setups, even using foam and rubber gasketing around the case doors and plastics to stop anything but air through the intake filters. And, needless to say, after all that time spent....It was not worth it. By the end I had figured out that a filter good enough on the intake to make significant reduction in interior case dust meant large impacts in cooling, as well as needing far more cleaning/replacement of said intake filters. It came down to reducing dust in the house over all, through AC filters and room based HEPA filters.
     
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  10. VanGoghComplex

    VanGoghComplex [H]ard|Gawd

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    Yep, that "heat rises" business never held any water with me. A mouse fart moves enough CFM to overpower convection. =D
     
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  11. pendragon1

    pendragon1 [H]ardForum Junkie

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    ditch the filter and clean it more often.
     
  12. daphatgrant

    daphatgrant Moderator Staff Member

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    I would be cleaning it twice a week if not more if I were to remove the filters. It's in somewhat of a corner, I've got a cat and a dog, it's on 24/7 and the intake/exhaust was imbalanced so it's (it was) pulling anything around it into the case.

    I found a balance by going the fan controller route. I installed a fan controller per exhaust fan and slowed them all down to about as low as they go. This allowed me to slow the intake fans (less noise) and after almost 2 days my thermals are right where they were before and I see less dust particles in the case or around seems. This obviously means I'll be cleaning the intake filter more often but that is fine as long as that is now the main collection point for debris. Ambient is 22C, CPU is 27C & GPU is 23C.
     
    Last edited: Apr 22, 2019
  13. pendragon1

    pendragon1 [H]ardForum Junkie

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    I have a dog and cat too, I just clean it when needed. if your happy with how you have it now then good, that's what matters.
     
  14. daphatgrant

    daphatgrant Moderator Staff Member

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    All seems well so far, I'll be watching the thermals as it turns to summer and adjust if needed. I was getting dust and fur stuck to all of the 6 intake filters as well as the mesh pci slot covers. I could also get a small piece of paper to stick to the back and side intake screens because of the airflow imbalance. I do run a roomba nightly in my defense :p.

    Everything now appears to be going through the front intake and pushing out of the case or through the exhaust fans. I'll be cleaning just as much as I was before but it'll primarily be the front intake filter.

    My goal now will be to watch and adjust so that my intake volume is slightly higher than the exhaust volume. Acutely having control of the exhaust fans will certainly help. I'll be watching for the black versions of the Noctua NF-A12x25's that BlueFireIce mentioned and swap out the stock aio fans.
     
    Last edited: Apr 22, 2019
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  15. doyll

    doyll Kyle's Thermocouple is HOT

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    if it was mine I would reverse the airflow so radiator was exhaust with 3x 140mm back and top filtered intakes. Oh, and remove PCIe back slot covers to allow more exhaust area / airflow around GPU so GPU's heated air goes back and out of case with less resistance.

    Here is a basic guide to case airflow and how to optimize it as well as how to setup a basic temperature probe to monitor air temp in specific places inside of case.

    How airflow works
    Airflow is simply displacement; for air to come into case, air must be leaving case .. or .. for air to leave the case, air must be coming into case.
    Think of the air around us as water and we are divers in it and a sunken van is a computer case.
    • We can't move more water into the van (case) through an open window (vent) unless we have another open window (vent) somewhere else in the van (case) moving the same amount of water (air) out through a window on other side of van (case).
    • We can't take any water out of van unless we have the same amount of water coming in at the same time.
    • This means we have to have as many open windows flowing water into van as we have open windows flowing water out.
    • This is exactly how airflow works. Intake fan pushing / flowing air into case is pushing / flowing the same amount of air out of case.
    • Adding an exhaust fan can help case airflow, same as adding a back fan on some coolers.
    • But with good case intake fans we don't need exhaust fans, same as good cooler / radiator fans don't need pull fans. [​IMG]
    • This is why I used to always change stock intake fans. Now some cases are finally coming with intake fans that have high enough pressure ratings to not need 'helper' (exhaust) fans. [​IMG]

    Setting up a case for optimum cooling

    Setting up the case for optimum cooling is often the hardest and most time consuming part of a build... And the most neglected by most builders.
    • There is much more to cooling than good cases and good CPU / GPU coolers. Add the fact that many GPU's make more heat than CPU means getting that heat out of the case and keeping a cool airflow to components can be a challenge.
    • Cases, especially those with filters, usually benefit from fans with higher static pressure ratings than stock fans... "cooler" fans instead of "case" fans.
      Intakes typically have more restricted than exhaust because of air filters, more restrictive grills, HDD cages, etc.
    • I prefer mostly just good pressure rated intake fans and rarely use exhaust fans anymore .. but instead use high enough pressure rated intake fans with exhaust vents being the only other openings in case. This allows intake fans to push air though the case and out. And don't confuse number of fans with amount of airflow... don't confuse airflow with airblow
    • airflow is flowing cool air from intake to component and then flowing component's hot air on out of case without that heated air mixing with the cool air and warming the air going into component.
    • airblow is lots of fans blowing air around, both cool and hot air from components allowing them to mix and raise the air temp going into components .. because basically every degree warmer the air into component cooler results in component being a degree hotterl.
    • Putting in good intake fans in case and maybe exhaust is only the first step. These fans only move air in and out of case.
    • This does not mean heated air is not mixing with cool air.
    • Nor does it mean cool air is going to where it is needed.
    • Getting the air to flow inside of case properly is even more important. We still need to manage where the air flows inside the case. We can do this several ways; deflectors, more intake fans.. & maybe exhaust fans, removing vent grills, removing HDD cage/s, using fans with higher pressure/airflow, building ducts to or from CPU/GPU cooler, etc.
    • Using a remote temperature sensor to monitor what air temps are is the key to finding out where the cool air is flowing and knowing heated air is not mixing into it. By monitoring this we can than make changes to get airflow the way we want it.
    • Keep in mind your case needs to flow more air than components do. It isn't so much how many fans but how well they flow air through the case. If component fans move more air than case fans move through case components are using their own heated exhaust to make up the difference and case heats up. Good rule of thumb is 25-50% more case cfm than component cfm but well tuned airflow can be almost equal equal.
    • Traditional tower cooler exhausting toward back of case must have rear / rear & top back case venting airflow area equal to intake airflow area .. they need to be able to flow more air than components are using .. more cfm than cooler fans have.
    • A duct from back of cooler to back of case (like Thermalright HR-22 uses) is also an option that works very well.
    Example of Cool & Quiet System
    • My Define R2 system has three TY-140 74cfm intake fans. (no exhaust fans) in case while CPU has TY-143 130cfm fan and GPU has two TY-100 44cfm fans
    • Case = 222cfm
    • Components = 218cfm
    • Air temp inside of case going into coolers is never more than 3c above room.
    • 2 front TY-140 1300rpm intake fans match airflow demands of CPU cooler TY-143 2500rpm fans, both PWM controlled by CPU fan header
    • Bottom TY-140 intake fan supplies airflow demands of & GPU TY-100 fans and are PWM controlled by GPU

    It is amazing how much cooler a system runs (and quieter) once the case airflow is setup to keep heated exhaust from contaminating cool intake air. Once we start doing these things, the concept seems like a no-brainer, yet most users seem to think more fans and/or powerful fans are needed to get better cooling. The reality is it's not so much the power and amount of air the fans move. but the currents / pathways the air flows in on it's way through the case that is important. Fan power/airflow only needs to be a little more than the amount the components are using at any given time. Using too many, fan and having too much airflow airblow can be as detrimental to case's flow pattern as not using fans with enough flow .. and if the flow isn't tuned to keep cool and heated air separate the system is not going run as cool as it can.


    How to monitor air temperature different places inside of case:
    • A cheap indoor/outdoor thermometer with a piece of insulated wire and a plastic clothspin works great.
    • Made up with floral wire and tape. We don't want anything to short out with metal. [​IMG]
      LL.jpg
    • Clip and position sensor where I want to check the temp. Make it easy to see what the air temp going into components actually is relative to room temp. [​IMG]
    • Optimum cooling is when air temps going into coolers only being 2-3c warmer than room.. 5c or less is good.
     
  16. honegod

    honegod [H]ardness Supreme

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    I never understood why video card fans push the heated air INTO the case.

    my current setup has 1 exaust fan ducted directly to the CPU cooler.
    With another exaust fan ducted to the vidcard.
    (both are brown & tan 120x25s).

    No current intake fans at all.
    Upper 30s C is where everything pretty much stays.

    The plan is to mount the (on hand)
    140mm 3000rpm industrial noctua to the bottom of the case as intake .
    Drawing input air through a 20"x25" merv 16, 5" thick whole house furnace filter.

    The point being that size of filter area effects the size of particulates the filter can stop without as much pressure drop across the filter.

    The point of positive case pressure is to push HOT air out of the case through all those unsealed gaps.

    Yes Virginia there IS such a thing as case pressure. Normally basic air pressure, but turn on the fans and the case pressure increases or decreases as the fans dictate.

    This is why the fans mmH2O rating counts.

    Air differs from water, so the underwater van metaphor is cool but not perfect.
    The major difference between air and water (for this discussion) is that air IS compressible while water is NOT.

    So a intake fan will Start pumping Air into the case until the fan compresses that air enough to force air out of the case. That pressure continues to rise until the fan runs out of power to further compress the case air.
    That is when 'what goes out equals what comes in' sets in.

    My plan is that having beefy pressure optimised exaust fans ducted directly to the major heat sources will insure that most of the intake fan air will want to go there.

    I want solid cooling in an absolutly (ok, as close as I can get) dust free case with a intake filter that should last at least a couple years before pressure drop starts to noticeably impede airflow.

    Running a merv 15 filter in the central air system has dropped the dust level in the house to imperceptible.

    So the computer filter might effectively NEVER get plugged up !
     
  17. doyll

    doyll Kyle's Thermocouple is HOT

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    Yeah, GPU cooler layout is stupid! Same is true of the pancake / downflow CPU coolers! In order for air cooling to work there needs to be cool intake airflow and in order to have that the cooler and case need to flow the heated cooler exhasut air out of case without it mixing with the cool cooler intake airflow.

    GPU coolers draw air in on bottome side (in most tower cases) and dump their heated exhaust in all directions into case .. meaning all but what little heated airflow moves back and out through PCIe back openings is mixing with cool air and pre-heating it before it goes into GPU cooler.

    Pancake / downflow CPU coolers do basically the same thing .. airflow into cooler and out where it hits motherboard turning away, then hitting RAM, GPU, etc. turning away from motherboard and up along side of cooler and cooler fan and then is drawn back into cooler by cooler fan. I've found that often just reversing these pancake/downflow cooler fans so they draw air up thorugh cooler and dump it into case lowers CPU temps by 3-8c.
     
  18. honegod

    honegod [H]ardness Supreme

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    208002_Case-2.jpg
    So this is a top down photo, aye.

    What I would do is flip all the fans to push the opposite direction.
    So the front rad fans are exausting through the rad.

    The side & rear fans do intake .
    Put a nice big filter on the right side extending past the rear side so the rear fan may be easily ducted to the filtered Air air plenum too.

    Then yank the vidcard fan assembly and run a Duct to the unoccupied riser slots with another exaust fan.

    This A filters all the air and B dumps the hottest Air directly out of the case with no intermixing.
    So the air IN the case will remain much cooler than it is now.